Hi, any initial setup and tuning tips when setting up the factory dual carbs on the 428.. i started with just cracking open the butterflies on the rare carb, then using the front carb to set the fast idle and set all idle mixture screws 1 3/4 turns out.. Car runs ok, but would like to know how others have done their initial setup..
There was some good information on the old forum, but that's long gone..
Thanks
Both cars have idle circuits so both need to have the idle mixture screws dealt with. "I" try to set both throttle blades open the equal amount so the fuel distribution at idle is as consistent as possible. Same for the idle mixture screws.With the factory progressive linkage, the front carb is in use most of the time (obviously) so fine tuning it is important.
Randy
Hi 67gt500,
I am currently also trying to tune a SBF dual quads with the Holley carb's from June 1966, LIST 3360 and 3361. They were concourse restore before I purchased and installed around eight years ago. Up until last year, the car had been running great, even drove to SAAC 35, 2000 mile round trip with no issues. Last July the car starting running bad, blowing black smoke at start up and not liking to start when hot. Something changed inside the carbs and the Ethanol fuel I had to buy for the return trip home from the Seattle Historic Races I am sure did not help. I try to run pure fuel as much as I can.
So I have since rebuilt and put back on the car. If I understand how the systems is suppose to work, the secondary carb should not be working at all when at idle. (If the secondary throttle blades are open, this will not be the case.) You should be able to completely choke off the air horn with a towel and have no impact to the engine running. The primary carb adjustment will be completely independent of the secondary. Set the fuel mixture screw, float level and idle screw, etc. Then set the secondary to match the primary and you should be good to go.
You may also want to run a vacuum gauge for the best setting for the fuel mixture screws. If I understand correctly at idle you want the max vacuum. With the gauge you can dial right on the mark. You will also need to adjust the idle screw as needed to maintain your target idle RPM.
Now this is in conflict with what Randy said with the throttle blades open equal. I found when the secondary carb throttle blades were open at all, I could not get the idle down because fuel was being drawn in from the secondary carb. Soon as I got the blades closed tighter I was able get the idle down and adjust the carbs.
Bottom line, fine tune primary carb and then match settings in secondary carb.
That is my experience. I hope this helps
Cory
I run the 2x4 Holley set up on two of my cars. One is my 67 GT500. The other is my 68 GT350 (347).
I can tell you what I do with them. Others may disagree. Power to them? ;)
What I do is get the engine to only idle on ONE carb. The idle throttle positions do not need to be the same on the two carbs. You want the secondary carb throttle as close to fully closed as you can get it.
There will always be some idle flow through both carbs and that includes the secondaries of each carb.
In my view you MUST use a vacuum gauge procedure to adjust the idle. The idle mixture screws do not lean the mixture. They increase or decrease the volume of atomized fuel traveling through the idle slots.
In order to be atomized, fuel must be mixed with air. Thus an air jet and a fuel jet. Those control the mixture ratio.
The a/f mixture is set by the size of the idle air restriction and the size of the idle fuel slot. Those are the "jets". You can't change that mixture ratio.
You can in fact lean the idle by closing down the idle mixture screw to about 1/2 turn, then increase the throttle screw to open a little more.
The reason that you are leaning the idle by doing that is that when you open the throttle you are idling on the mains, which have a leaner mixture then the idle circuit does.
So you are mixing down the idle mixture by using the idle throttle screw.
As far as adjusting the throttle linkage, all that matters is that you are not holding open the secondary/primary throttle with it AND that you want the secondaries to start to open at about 50% of the opening of the primary throttle AND that when the primary carb is 100% open, so is the primary throttle on the secondary carb AND you are not over centering either carb to get that relationship.
In this manner, the two carbs act like a 600 double pumper Holley with a HUGE secondary vacuum operated throttle/booster.
Since the secondaries are going to be opened by engine vacuum/load demand, they really can't flood/bog the engine.
The reason that the vacuum secondary 2x4's were taken out of the road racing cars was that the vacuum secondaries under race conditions had the TENDENCY of not closing the secondaries fast enough.
If you notice, the carbs are mounted backwards. The main reason for that was this is a "street" set up and the primary throttles are centered in the intake as much as can be done.
Some of the small block 2x4's had the carbs mounted forward with the primary carb in the front.
Depending on who you talk to, some think (including me) that this makes a fuel distribution problem in the manifold until the secondary primaries are fully opened.
In Trans-Am racing, the cars were run virtually with WOT all the time. Trust me. If you never actually saw this in person, it more closely resembled death wish racing and everyone involved seemed to be the first one that wanted to die in combat.
If I could post, I'd offer the pile up of cars at St.Jovite as evidence. Death wish.
My small block runs the exact same set up as the 427/428's with the carbs backwards. It simply runs fantastic that way. It's WAY different then my Webers on my Pantera and each is definitely a treat to drive. They put you in a special place and the biggest problem is you can't find a big enough, wide open enough road to drive them like you want to AND you have to go home eventually.
Also on the tuning. You have to get the automatic choke set up operating correctly before you can set up the throttle linkage. If you don't, the choke will have you on too high of a setting.
Best to try to do this with (the choke) with the engine hot. That's where you set the choke to be wide open at full operating temperature. Then you set the choke on "index".
Now bear in mind, that you CAN NOT use the universal HOLLEY choke thermostat. You MUST use the FORD thermostat. These things are marked and they have different opening rates.
The original Ford Master Parts book showed that choke thermostat for the 2x4 FE setup. My SB is using it also. It takes a while for it to fully open. About the same amount of time to heat up the oil +/-.
IF you live in a southern climate of the US, then it probably doesn't matter too much which thermostat you use BUT here in NY, when it cools off, if you use the fast thermostat (HOLLEY being the fastest) you are going to stall the engine which will set off a syndrome of pumping the carbs to start a stalled engine and as a result, you WILL wind up fouling all of the plugs.
Again, trust me on this one, YOU DO NOT WANT TO FOUL up the plugs on the FE. If you were Elvis, you'd take your gun and shoot the car...and it would deserve it too! Mutha effin hore!
OH, almost forgot, it is IMPERATIVE to get the fuel level correct. IF you were an intellectual and did your dual diligence and went to HOLLEY to get the procedure, you're in trouble. You need to drop the level about 1/8" lower then the instructions will deliver you or else, YOU WILL FLOOD with gasoline to the level you will think you hear GOD and think he is telling you this is the "great flood" and you need to build an ARK.
It seems to be related to the ethanol in the fuel? Something about it expanding when warm?
So that's my story and I'm sticking to it. I hope you can find it of some redeeming value?
;D
I loved having dual quads on my CJ but opted for stock 735 cfm years later.
Acceleration a tad less but running much leaner and stock under the hood looks great!
On a forward facing application ( small blocks) the primary carb should be in the rear as opposed to the big block's backward facing carbs and primary carb in the front. How you make them idle is your choice because there is more than one way.
Randy
It is interesting that this subject was brought up. I just got my 347 running on the stand with the Holman Moody 2x4 Boss 302 manifold and 600 Holley vacuum secondary carbs. It does not have progressive linkage. I noticed the idle mixture screws do not have much effect. It idles at about 1,000 rpm. The throttle plates do not seem like they are open too far but I did not take the carbs off and look to see how much the idle transfer slot is uncovered. Both carbs have the throttle plates open the same amount. I am not really using either one as a primary carb at this point.
Quote from: 1109RWHP on June 20, 2018, 09:58:19 PM
It is interesting that this subject was brought up. I just got my 347 running on the stand with the Holman Moody 2x4 Boss 302 manifold and 600 Holley vacuum secondary carbs. It does not have progressive linkage. I noticed the idle mixture screws do not have much effect. It idles at about 1,000 rpm. The throttle plates do not seem like they are open too far but I did not take the carbs off and look to see how much the idle transfer slot is uncovered. Both carbs have the throttle plates open the same amount. I am not really using either one as a primary carb at this point.
I need clarification on understanding this. Are you using Boss 302 heads or Windsor heads? Again, it would be great if we could post pictures in this thread to help illustrate what is going on.
I don't know what the Holman Moody Boss manifold looks like but I do know what the SHELBY version looks like.
Your idle rpm may be more related to the camshaft that you are running? What are the Holley carb list numbers you are using?
Quote from: 1109RWHP on June 20, 2018, 09:58:19 PM
It is interesting that this subject was brought up. I just got my 347 running on the stand with the Holman Moody 2x4 Boss 302 manifold and 600 Holley vacuum secondary carbs. It does not have progressive linkage. I noticed the idle mixture screws do not have much effect. It idles at about 1,000 rpm. The throttle plates do not seem like they are open too far but I did not take the carbs off and look to see how much the idle transfer slot is uncovered. Both carbs have the throttle plates open the same amount. I am not really using either one as a primary carb at this point.
Your idle characteristics are common for that intake/cylinder head combination and idle speed. Non progressive linkage ( in your case) is a plus. The only way to get back into the idle transfer slot is to drill a hole in the primary plates OR adjust the secondary stop to keep the blades open enough ( air wise) so the primary can be closed some. My race car doesn't idle for long periods so I just set the idle speed and leave it at that..
Randy
It is a Windsor style block with Trick Flow 225cc aluminum 351 C style heads. I will have to look at the list# to see what they are.
(https://i.imgur.com/TwulcLym.jpg)
(https://i.imgur.com/wq25GQOm.jpg)
(https://i.imgur.com/q1ayWabm.jpg)
Here is a video of it I took with a potato phone.
https://www.youtube.com/watch?v=zb9bLhDpni4&feature=youtu.be
I think that is the cam rather then the carbs. I have Webers on my Pantera with Ford A3 aluminum high port heads. The heads came off of a circle track race car as the guy was upgrading to the C302 versions. Those are 225+ ports so it is similar to your set up.
With the Webers though, it is set at about 825 but it does sound like a marching band with the 180 headers at idle with that cam. That's ok because the racket is behind me and is quiet in the cabin.
Those heads were shaved .030 by the original race engine builder (Danbury Competition) but the ports and pockets were left alone. They show 630 330@ 600, so why look for more?
I've got a lot of cam in it for a street car and it idles similarly to yours. Compcams solid 246 @ 50, 73 overlap, 606 lift.
I got tired of messing with the 1850 Holleys on the Shelby. Idle was too heavy. Almost like a double pumper.
What I did was take two 85-6 Mustang GT carbs and switched them over to look like 1850's. The benefit to that is that the idle is so clean, but that hazes the ceramic coating on the headers because of the heat BUT it got rid of that, smarting your eyes at idle just about everything else did.
Those carbs are factory set to idle at 14.6 and they do but that is JUST idle.
I'm still screwing with them on the idle air bleeds to fatten that up a little so that I will still have some ceramic coating left on the headers. The dam things cost enough from Bittle and it took them two years to get them to fit the chassis right.
That engine idles right at 800 hot but it doesn't have as much cam in it. Compcams solid, 236 @ 50, 63 overlap, 528 @ 1.6, 561 @ 1.7.
The iron heads just crapped out so is in transition to AFR 185's. Idle will probably be a little different when that set up is finalized?
If those are the headers you are going to run, stainless with no coating, I'd suggest that you try them. They are worth the time to convert them. I definitely have the 347 idling on the one carb.
As far as the linkage goes, it depends on you. On how you feel about it but for me the 427/8 backwards stile works for me particularly since it is using all of the Ford linkage. The Ford linkage is progressive and in reality runs on the front 2 barrels to about 3,000 rpm.
The progressive linkage definitely helps the feel. With throttles just tied together all that means is you are running on the full 600 cfm all the time. That's just a torque killer.
Ironically, the issue I am having with the 2x4's is the single choke. If it doesn't fire up at one pump I have the tendency of holding open the throttle enough to cause the engine to backfire through the non-choked carb. That has made issues on more then one occasion.
I'm considering putting a choke on both carbs maybe with just the Holley choke thermostat on the secondary carb to make it open very fast?
Seems like everything is ALWAYS in development around here.
Just my perspective
Quote from: shelbydoug on June 22, 2018, 07:01:26 AM
Those heads were shaved .030 by the original race engine builder (Danbury Competition) but the ports and pockets were left alone. They show 630 @ 600, so why look for more?
I hope this isn't suggesting 630 CFM @ .600" lift. That is Blue Thunder Big Block Thor head intake flow.
Quote from: 2112 on June 22, 2018, 10:31:26 AM
Quote from: shelbydoug on June 22, 2018, 07:01:26 AM
Those heads were shaved .030 by the original race engine builder (Danbury Competition) but the ports and pockets were left alone. They show 630 @ 600, so why look for more?
I hope this isn't suggesting 630 CFM @ .600" lift. That is Blue Thunder Big Block Thor head intake flow.
It isn't suggesting anything. It is stating the facts from the flow bench. It's actually at .630 lift.
Iron 4v Cleveland heads with just a nice 3 angle valve job showed just under 300 (299) @ 600.
Look at the flow numbers out of the box on the current Windsor heads. The AFR 185's are 296 @ .550. They flow more at .200 then the stock iron heads do at 500. Amazing stuff but to give credit where credit is due, Ford Motorsports was making the Cleveland aluminum "high port heads" in 1981 and if I show you the "hot CHI" Aussie heads, they are just copies to a large extent.
The Windsor heads took a while to catch up.
Quote from: shelbydoug on June 22, 2018, 10:34:45 AM
Quote from: 2112 on June 22, 2018, 10:31:26 AM
Quote from: shelbydoug on June 22, 2018, 07:01:26 AM
Those heads were shaved .030 by the original race engine builder (Danbury Competition) but the ports and pockets were left alone. They show 630 @ 600, so why look for more?
I hope this isn't suggesting 630 CFM @ .600" lift. That is Blue Thunder Big Block Thor head intake flow.
It isn't suggesting anything. It is stating the facts from the flow bench. It's actually at .630 lift.
Your flow bench is defective
Quote from: 2112 on June 22, 2018, 10:37:55 AM
Quote from: shelbydoug on June 22, 2018, 10:34:45 AM
Quote from: 2112 on June 22, 2018, 10:31:26 AM
Quote from: shelbydoug on June 22, 2018, 07:01:26 AM
Those heads were shaved .030 by the original race engine builder (Danbury Competition) but the ports and pockets were left alone. They show 630 @ 600, so why look for more?
I hope this isn't suggesting 630 CFM @ .600" lift. That is Blue Thunder Big Block Thor head intake flow.
It isn't suggesting anything. It is stating the facts from the flow bench. It's actually at .630 lift.
Your flow bench is defective
That's ok...so am I. ;)
Doug,
Your post says 630 it should be 330 IMHO. NO Cleveland head on this planet will go over 400. 630 is beyond the best Pro Stock heads out there at the moment. Joe's good but not that good LOL.
Randy
Quote from: gt350hr on June 22, 2018, 10:48:46 AM
Doug,
Your post says 630 it should be 330 IMHO. NO Cleveland head on this planet will go over 400. 630 is beyond the best Pro Stock heads out there at the moment. Joe's good but not that good LOL.
Randy
Correct. 330. I already admitted I was defective? So? ;D
...oh...and not that I can actually USE that kind of flow? Never said that ;)
No problem.
It's also important to mention that different dual quad intakes have their own "quirks". There are some significant tuning differences between the early Ford 289 dual quad and the later T/A - SHELBY letterd version. The early manifold is not as finicky on tuning. Guess how I know.
Randy
Quote from: gt350hr on June 22, 2018, 11:09:56 AM
No problem.
It's also important to mention that different dual quad intakes have their own "quirks". There are some significant tuning differences between the early Ford 289 dual quad and the later T/A - SHELBY letterd version. The early manifold is not as finicky on tuning. Guess how I know.
Randy
I would think there was no consideration on the T/A manifold for any idle quality considerations at all? IF the engine happens to idle with a .650 lift, 300 something duration cam to begin with, that would be shocking.
"It's the manifold. Yep, let's blame the manifold!"
I'd like to see a side by side comparison of those two manifolds on a dyno with a "street engine".
As per our discussions I'm really shocked that the new aftermarket windsor heads are getting these kind of flow numbers with these small ports. Maybe the better manifold IS the street manifold?
Also, I can swear that this Blue Thunder version I've got has had it's runners finagled with from the original? Somethin' a little funky with it? 8)
Doug , In order,
No manifold except the lousy "fuel economy" ancient Edelbrock stuff is designed for idle quality. That is carburetor calibration/tuning.
Certain manifolds/ spacers/cams etc. , make tuning for a good idle a challenge to say the least
About 15-20 hp on a semi stock street engine with a significant loss of low rpm torque. ( until 3,000 rpm)
The street manifold ( Blue Thunder ) is a restriction on a head that flows over 220cfm . The T/A manifold is best with 240-270 cfm and will not support 300+ even with substantial porting.
It may be funky but not a bread winner in the flow department over the original Ford manifold. No measurable performance difference "out of the box".
The above is purely from my experience and yours may vary.
Randy
As you once pointed out the iron GT40 heads were at best 250cfm and Joey pointed out that the AFR heads were at 296 at .550. That is better then iron Boss 302 heads.
So my rational is that I am putting them on for less weight, my iron heads crapped out and anything I get over and above that is icing on the cake.
You put 800hp in a Mustang and it's still a 12 second car.
You do bring up the subject of intake flow on these 2x4 intakes though which is why a while ago I asked you if you had experience with the SHELBY 2x4 BOSS 302T/A manifold? The runners do look bigger on them and I KNOW you messed with the Tunnel Ports which definitely are bigger.
To me, all of those SB T/A manifolds look like the same core/runners, just changed to mate with the intended ports on the heads, that being where the restrictions come in?
Aside from the port mismatch, I think physically the Boss 302 will bolt up to a Windsor head. That's what I was thinking when I asked you about that. Are you going to say that one only flows 250 as well?
See. I get these radical thoughts that just peculate up out of nowhere like the volcano in Hawaii. Once it starts, you can't stop it and the magma runs all over everything.
You talk about restrictive intakes. How about carbs? No one ever considered that a 48ida with a 42mm choke is restrictive on a 289 (that's 300cfm), but it is or that there is no way a 289 can use a 715 Holley. I'm ok with all of that. Don't tell the carbs though, ok? They get very upset sometimes. ;)
How's a 300cfm carb restrictive on a head that at best flows 250? Oh no...stop the magma please.
Complaints are all relative though. Any way I look at it, I'm over 400hp on the dyno and starting out at best at 250, I'm doing ok.
Doug ,
I've run about 70% of the dual quad intakes produced for the Boss 302. It's easier to say which ones I haven't run most of which are owned by Gus Tarrab. The dual quad Cross Boss ( for regular Holleys)` , the ''variable runner" dual dominator , and a "box" plenum dual quad are about the only ones.
Near 300 cfm flow in a wedge versus a Boss head is a very different situation and doesn't compare well with the same being said for the tunnel port. "Flow" is a number and by itself doesn't relate to the efficiency of the port. That is a common mistake of those who only pay attention to flow. Same for Webers. They are designed to be run as "IR" or one barrel (isolated) for each cylinder. IF yo put Webers on a dual plane ( or common plenum) manifold you would be looking at almost 2,000 CFM because each port "could" draw from any one of the eight venturis.
I put 800 hp in a Mustang and it would NOT run in the 12s unless it was the HALF mile , or it was running 6.95x14 blue streaks! You might but not me.
Boss intakes need larger volume runners than does a 289 , pure and simple. H&M cobbled up some intakes ( with allot of welding) to fit a Boss head , but they were poor on performance.
The ports on the Trick Flow heads are smaller than a Boss head so the intake needed some epoxy work to make it match. Plus I think Ray Charles ported it at one time.
(https://i.imgur.com/PCN0ibTl.jpg)
(https://i.imgur.com/WK7hnpxl.jpg)
(https://i.imgur.com/6bopm1Jl.jpg)
(https://i.imgur.com/jP1lfjsl.jpg)
(https://i.imgur.com/YCkPHR7l.jpg)
Your manifold was a "predecessor" of the SHELBY lettered Boss intake. This was a common thing H&M did with Buddy Barr. Manifold designs that Ford chose not to use or a project was cancelled, often got an H&M logo or Holman Moody spelled out and sent to them to sell. This saved them ALL of the development costs ( Ford already paid that) and gave them finished parts in the $30 a piece range , delivered. Most sold for over $150 through H&M so the profits were excellent.
Quote from: gt350hr on June 22, 2018, 05:37:29 PM
Your manifold was a "predecessor" of the SHELBY lettered Boss intake. This was a common thing H&M did with Buddy Barr. Manifold designs that Ford chose nit to use or a project was cancelled, often got an H&M logo or Holman Moody spelled out and sent to them to sell. This saved them ALL of the development costs ( Ford already paid that) and gave them finished parts in the $30 a piece range , delivered. Most sold for over $150 through H&M so the profits were excellent.
Tony Carey tells me he never paid more then $50 for a manifold. I asked him for a T/A and he said $2500 BUT he'll take trades. ;)
Yes, I'm aware of the different aspects of an IR vs. a 180 intake. My point was about the flow numbers also.
2400cfm is what a set of Webers will flow. You need to adjust that for the size of the chokes. That number was for a 42mm which is what the Shelby Team cars were credited with running.
The only way to answer many of these questions scientifically is side by side on the same engine with the various combinations. Since in this day and age that's about as likely as me cloning a Tyrannosaurus rex. So the next best thing is to pick someone's brain while they can still remember before it all fades into the mist?
Guess who won out as the source? ;D
So basically what you are telling me now, again, is that PROBABLY the best match for me is the T/A with a wedge head. Then another $4500 to replace the hood that the engine just sucked in?
I gotta' plan this out better? ;D
GREAT PICTURES! THANKS!
What effect does changing the firing order to the 351 order have on the manifold?
2400 cfm is the "capability" of the carbs. If you put a low meter on each individual "throat" you will find less than 100 cfm per cylinder
actually" flowing. ( more like 75) Reversion , lack of a common plenum , etc hurt the flow . BUT if the carb was any smaller , it would hurt horsepower. Ford realized in '62 that 48s were too small for high rpm use at Indy for the 255 pushrod engine and switched to 58s. 48s on a 427 was like a 750 single four , so some manifolds were made for 58s though there weren't enough carbs to go around. 58s on a SOHC was a loser too. Not enough cfm because of the lack of a common plenum for all the cylinders to draw from. IR sucks , literally. Your Pantera would go faster with 58s too. Just about the right size. Modern sprint car guys now use 3" butterflies ( or more) on their fuel injection systems and make 900 hp.
Two Webers on a "common plenum , non IR" manifold would be what Ford was trying to do with the Autolite Inline. I plan on switching my 331 to a Vic Jr single four to see how much faster it is than the old school dual quad.
Changing the firing order is not a big deal power wise on a dual plane intake.
Randy
Quote from: gt350hr on June 25, 2018, 12:16:37 PM
2400 cfm is the "capability" of the carbs. If you put a low meter on each individual "throat" you will find less than 100 cfm per cylinder
actually" flowing. ( more like 75) Reversion , lack of a common plenum , etc hurt the flow . BUT if the carb was any smaller , it would hurt horsepower. Ford realized in '62 that 48s were too small for high rpm use at Indy for the 255 pushrod engine and switched to 58s. 48s on a 427 was like a 750 single four , so some manifolds were made for 58s though there weren't enough carbs to go around. 58s on a SOHC was a loser too. Not enough cfm because of the lack of a common plenum for all the cylinders to draw from. IR sucks , literally. Your Pantera would go faster with 58s too. Just about the right size. Modern sprint car guys now use 3" butterflies ( or more) on their fuel injection systems and make 900 hp.
Two Webers on a "common plenum , non IR" manifold would be what Ford was trying to do with the Autolite Inline. I plan on switching my 331 to a Vic Jr single four to see how much faster it is than the old school dual quad.
Changing the firing order is not a big deal power wise on a dual plane intake.
Randy
Go faster? I need to hold on now!
I know of only 4 sets of 58's. Bob Gingold has one of them still in the original wood case, all serial numbered concurrently. They came in what looks like a display case all lined in velvet like a Proof Coin set does from South Africa.
The "Pantera" manifolds are "tuned" for 51mm. Lots of graphs with all sorts of bright colors all circle and intersect right at that point BUT the consideration is for a 6,800rpm max.
What actually flows through an engine, I personally don't know.
According to one of the formulas, my A3 heads would need to see 11,000 rpm for the engine to be able to pump that much air with 357 cubes. Whenever I see Joey he asks about them. All I know is "they work good". They work better then the iron heads. That's what I tell him. Hey. They were $400 bucks. How could I turn them down? No doubt he regrets that sale? ;D
12 seconds 1/4, 197 @ 6,800 in 5th is at my limit if I'm lucky. Depends is making some really nice designer type adult diapers. Reasonably priced to.
Hey Mike Cook went 9.6 at 130 somethingin Gary Hall's GTS Pantera by just changing to 5.36 gears. No fancy Webers, just a 4779 Holley.
I gave up on drag racing because the tire shake hurts my neck. Blurry vision from it is too spooky. I can't see where I'm going. I need a tracer light that I just point at. Detached retinas. Attached rectum. The smell from all of that smoking rubber turns my stomach too? Plus I'm sensitive to the spectators. They give me the finger and one guy "mooned" me? How insulting? ::)
At least if Jungle Jane would flash me just once! That would help. 8)
At some point flow numbers do mean something, probably a lot? I have to remember that not only am I the driver, I'm the pit crew and the sponsor.
At one time the Dodgers wanted to talk to me because I threw 100mph. That's fine. Do you know how fast the ball comes back when the batter hits it? Don't ask. You don't want to know. Your eyes can't focus fast enough to see it but if it gets you, you likely won't remember a thing...IF you survive that is? ;)
Aluminum heads. They're just there to save weight an polish up with Mothers.
So far, I haven't found anything that sounds like Webers or pulls out of high speed turns like them. It is easy to show on a dyno how EFI eight stack pulls better on the average but it doesn't pull harder in key spots.
Plus, it doesn't throw flames through the stacks in the dark at cold start up. That one always draws crowds. ;D
Here's a curve Doug. IF you had a two inch tall "box" made to bolt onto your Weber manifold you could run two Webers and make more power than you do now with four. The ability for all eight cylinders to "feed" off of a common area makes a huge difference.
Quote from: gt350hr on June 25, 2018, 04:32:59 PM
Here's a curve Doug. IF you had a two inch tall "box" made to bolt onto your Weber manifold you could run two Webers and make more power than you do now with four. The ability for all eight cylinders to "feed" off of a common area makes a huge difference.
Stop it. You will push me over the edge. I've been dangling there for years.
Would my combination work better using two 390 cfm carbs instead of the 600's? I was wondering about this before I spend a lot of time messing with the 600's. The only thing I have done so far is install the secondary diaphragm covers with the vacuum fitting to tie them together and replaced the secondary metering plates with ones you can install normal jets in.
Quote from: 1109RWHP on June 25, 2018, 09:49:19 PM
Would my combination work better using two 390 cfm carbs instead of the 600's? I was wondering about this before I spend a lot of time messing with the 600's. The only thing I have done so far is install the secondary diaphragm covers with the vacuum fitting to tie them together and replaced the secondary metering plates with ones you can install normal jets in.
Depends on what you mean by better. I don't think so. I think the 600's are just about right. How hard it pulls depends on the gearing. I'm running a Richmond 5 speed, 3.27 first gear, 3.50 rear.
I don't know about the flow numbers but it makes one heck of a racket and its hard to see over the hood until the nose comes down. It pulls very hard from any rpm in seemingly every gear. I do not think it is over carbed.
It's a perfect example of how you can do everything wrong and turn out so well. Pulls very much like a big block.
Actually Randy presumes that my Pantera never ran anything but Webers. Not so. It ran the Ford Motorsports version of the Edelbrock Torker, aka, the 341-a, and a Holley 4779, 750 dp. It wasn't even close to the Webers. Kind of like an electric golf cart going up hill by comparison.
Sometimes I think things like flow numbers are just for the nerds to argue over and just load into their data forms? As Randy points out, no one races a flow bench. So of the results just seem to defy logic at times?
I bet throttle response will be better with 2 smaller carbs but top end numbers may take a hit.
Quote from: 2112 on June 25, 2018, 10:17:57 PM
I bet throttle response will be better with 2 smaller carbs but top end numbers may take a hit.
It will be all done by 3500
Ok, I will go with what I have.
I have a 347 with dual quads that are 390 cfm and I could not be happier, it doesnt stumble or hesitate and pulls like a frieght train cleanly past 6k, i have the carbs mounted backwards like 67 gt500. Mustang and Fords issue a few years back got the highest HP with the 390's over 460's. I didnt think they would work that good but I was wrong.
Quote from: 2112 on June 26, 2018, 01:38:09 AM
Quote from: shelbydoug on June 25, 2018, 10:30:01 PM
It will be all done by 3500
Nope
By comparison to 600's it will.
This all depends on what your set up is. Size of engine. Type of transmission. Gearing. Camshaft, not to mention type of linkage and is about the same discussion as selecting any of that criteria.
Run what makes you happy and how you like it.
As far as relying on what some of these magazines investigate I've taught more intelligent and insightful high school tech classes. I haven't seen one yet where they can even select a matching camshaft for what they are going to test.
They are good reading for filling your spare time in study hall.
If you want to argue, go tell your wife that her hair cut sucks and slug it out with her. I'm not interested. I learned not to do that 50 years ago.
NO ONE is going to write a prescription for what you should take. This is largely what you like.
I am not arguing. You made a blanket statement and I responded.
I have compared a very similar small carb combo to a big carb combo on a common plenum intake (very high end build) no other changes were made and my experience was greatly improved throttle response with a small hp loss at 6500rpm. It certainly didn't fall off at 3500.
Not unless its a 6 banger... ;)
Quote from: 2112 on June 26, 2018, 11:11:38 AM
I am not arguing. You made a blanket statement and I responded.
I have compared a very similar small carb combo to a big carb combo on a common plenum intake (very high end build) no other changes were made and my experience was greatly improved throttle response with a small hp loss at 6500rpm. It certainly didn't fall off at 3500.
I don't care if you are arguing or not. I'm just not going to. I too am not a novice on this and am just offering guidance.
This is like offering $20 to the homeless guy and he kicks you in the balls because you are a cheap bast ard.
Simply put. It don't matter to me. Figure it out yourself. ;)
Quote from: 1109RWHP on June 25, 2018, 09:49:19 PM
Would my combination work better using two 390 cfm carbs instead of the 600's? I was wondering about this before I spend a lot of time messing with the 600's. The only thing I have done so far is install the secondary diaphragm covers with the vacuum fitting to tie them together and replaced the secondary metering plates with ones you can install normal jets in.
The factory T/A "regular" Holley intake used 720 cfm center squirters. ( 660s weren't invented yet) Going to a 390 carb is a waste of time. When I ran the Shelby intake at the drag strip ( back in the late 70's) , I ran 1850s and just a jetting change up to 70s in the primary but I had Eelco plates in the secondary and used regular Holley jets ( 71 by my note book) I had the diaphrams connected too. It was worth about a tenth of a second and 1.5 mph in trap speed over the H&M manifold and 850 DP I normally ran. Yours should be similar jet wise. Quick Fuel makes secondary jet conversion plates now and they are superior to what I ran.
Randy
Quote from: jerry merrill on June 26, 2018, 12:51:30 AM
I have a 347 with dual quads that are 390 cfm and I could not be happier, it doesnt stumble or hesitate and pulls like a frieght train cleanly past 6k, i have the carbs mounted backwards like 67 gt500. Mustang and Fords issue a few years back got the highest HP with the 390's over 460's. I didnt think they would work that good but I was wrong.
Jerry,
Every engine is different and the same goes for carburetors and manifolds. Your combination works well for you no doubt but it would hurt the performance of my 331 drag race engine. I know because I have tried them.
Randy
I have the secondary plates already and the vacuum units connected.
Ok, for the idiots like myself. I sent my carbs off to be restored on the 67 GT500. I have done lots of single Holleys but never a set up with two. I need to set them back up from scratch. Any tips?
My reply #1 . You can set the idle mixture screws at "one turn out" from bottoming. ( all four screws) Then "crank in' some throttle opening on both carbs. Start it up and adjust the idle speed back and forth until adjusting one or the other changes idle speed , effectively making them even. While all of this adjustment has been happening the engine should come up to temperature so you can set the idle mixture screws ( some guys hook up a vacuum gauge and go for the highest vacuum reading ) and tune them to the smoothest condition. This may take a few "rounds" . Your idle speed may have increased so you may have to lower the speed screws. at that point , "I" would go for a drive , come back and re check all my adjustments . Yes it is a tedious process but that's the price you pay for the power you get from dual quads.
Randy
Got some time today to mass with the carbs again. I opened the secondary plates with the stop screws 1/2 turn. I removed all of the choke parts from the one carb also. Checked the fuel pressure and it s 6 psi at the regulator. Got it warmed up and it still idles at 1,000 rpm but the primary idle speed screw is all the way out now. I can however adjust the mixture crews though. I used a vacuum gauge to set them to the highest rpm. It has about 8-9' of vacuum at idle. Set the float levels lower so it is just below the sight plug opening. I will have to adjust them again once the motor is in the car at it's normal angle. I have this trick adjustable billtet pcv valve that I want to mess with but I need to do it once everything is in the car and plumbed the way it will be for good. I have a oil separator can to go on it also. Idle is good and it sounds pretty crisp.
Quote from: 1109RWHP on July 08, 2018, 10:28:07 PM
Got some time today to mass with the carbs again. I opened the secondary plates with the stop screws 1/2 turn. I removed all of the choke parts from the one carb also. Checked the fuel pressure and it s 6 psi at the regulator. Got it warmed up and it still idles at 1,000 rpm but the primary idle speed screw is all the way out now. I can however adjust the mixture crews though. I used a vacuum gauge to set them to the highest rpm. It has about 8-9' of vacuum at idle. Set the float levels lower so it is just below the sight plug opening. I will have to adjust them again once the motor is in the car at it's normal angle. I have this trick adjustable billtet pcv valve that I want to mess with but I need to do it once everything is in the car and plumbed the way it will be for good. I have a oil separator can to go on it also. Idle is good and it sounds pretty crisp.
8-9" isn't much vacuum. It doesn't matter terribly IF you don't need vacuum for accessories. I get uncomfortable under 12".
I would think it is MOSTLY the cam but I have no experience with the idle characteristics of that intake manifold/head combination. Randy does. I'd guess 85% is cam, the balance is the runner configuration of the intake?
All considered, 1,000 is livable. More of a Pro Street type set up. I've seen those not being able to idle under about 1,400 rpm though and the things just spit through the exhaust because of the amount of overlap.
The Cleveland in my Pantera idles at 12 to 13". It was a lot of finagling to get it that high. Normally 10-11 would be about what to expect with the cam, head, carb combination.
After MUCH time and effort working on vacuum, I gave up and just installed a CompCams vacuum pump. It gives me a stockish 17" for the brakes. The trade off is you can hear the compressor running which annoys me. Such is life. That's much about compromises of what you can live with and can't?
Normally the Webers alone will drop you to about 11 to 12" at idle.
By the same token my 68 GT350 idles at about 800 hot, with about 14" BUT it has a milder cam and uses the "street" 2x4 intake and not the T/A that Randy is running.