This will fire up some discussions.....!
The original owner of my GT350 replaced the Holley 715 Lemans in early 1975. According to the second owner, and the OO's best friend, someone at the local go fast speed shop in FL told him that the new Holley 650 double pumper was the hot set up for a K code 289.
Car is running just fine with the 650DP, and as of right now Drew is going through the 715 LM to make it fresh and right again.
With all things being equal since I drive my car more than most, which really is the best set up for spirited 3-4 times a month, twisty roads, weather permitting, driving enjoyment ?
Thanks in advance,
Bob
I used to have a 66 289hp car that I put a 600 DP carb and it felt like 50 hp increase, of course it wasnt that much but felt great, a lot may depend on your engine but even though on a dyno you may show an increase with a large carb, for driving around I have found 600 or so carb on a stock type engine feels better especially a double pumper. gas mileage is a different story.
I had several 289 and 302 with the 600 double pumper carbs and what always was a big + that they were really crisp on the throttle with good adjustments they were running like efi. But the original 715 carb is also a great runner with some modifications on the dyno I had better results at real high rpm´s with those but then it was not a stock engine anymore. On a pretty much stock engine I would take the 600.
This might be apples to oranges, but many years ago I owned a 1974 Mustang II that the PO had installed a 351W into. I tried many different carburetors on it back then, being a teenager working at a local speed shop in the DC area. Finally happened upon a Holley 600 DP that a local fellow had been using on a small block Vega that he drag raced. The choke had been removed, including the air horn, it was painted orange and just looked ratty. That carburetor was just RIGHT. I bolted it on, set the idle speed and never fiddled with it again.
On a 289 I'd go with a 4176, a 600cfm double pumper. It will feel crisper.
+1 on a stock hipo.
You should try the 715 when I'm done before making any other decisions.
Quote from: Drew Pojedinec on March 06, 2021, 12:00:54 PM
You should try the 715 when I'm done before making any other decisions.
+1
+2. I have run 3-4 different carburetors through the years and got the best quarter mile times with the 715.
After the rebuild from Pony carbs some 15+ years ago, it runs great with a 715. With old carbs one often overlooked issue is that the throttle plate bores wear. They start sucking in a little more air plus the idle speed is not consistant.
What's great about Holleys is that there is such a variety and you can keep trying different combo until you find the right one. What you like someone else may not.
Quote from: shelbydoug on March 06, 2021, 03:38:52 PM
What's great about Holleys is that there is such a variety and you can keep trying different combo until you find the right one. What you like someone else may not.
+1. Well said.
Quote from: shelbydoug on March 06, 2021, 03:38:52 PM
What's great about Holleys is that there is such a variety and you can keep trying different combo until you find the right one. What you like someone else may not.
Mind you, I am coming from a vastly different place compared to most.
I find the "wheel of carbs" to be annoying. There is a specific reason one works better than another.
I would rather change bleeds and make the fuel curve appropriate for my usage. The 650 double pumper mentioned, it seems like the right choice. Only negative is the majority of them have a tiny PVCR and oversized jets as they were meant for racing. For street car usage you will juggle between having a fat cruise and being underfueled at wide open throttle. The only solution is to drill PVCR's and jetting down, of course this brings us back to just make the carb work for your setup in which case who cares what you started with?
The only benefit of swapping to another carb would be that it being a generic vs a valuable original, you could molest it sufficiently to work perfectly in all conditions.
I simply like the 715cfm as the venturi to throttle bore size is very favorable in regard to optimal tube. (optimal tube being 30 degree inlet, 7 degree outlet, vena contracta being a specified fraction of the outlet).
All of this said, there is a very specific reason that Ford used the 1 5/16, 1 3/8 venturi, 1 11/16 bore combo on so many carbs.
C3-B, CU/CV, BC/BD, 3259, etc. It simply works very well. Not big enough? run two of them.
Bob's 715 probably would have run like poop as delivered to me.
Idle feed is massive, carb was hand made into a double pumper, the details of such are very fascinating to be honest. Someone tossed a newly minted baseplate on it, which aside from hanging the throttle open, it defeated the purpose of the original modifications.
I'll put it back to stock specs and it should run just fine as is.
of course I could be wrong..... :P
Quote from: Drew Pojedinec on March 06, 2021, 12:00:54 PM
You should try the 715 when I'm done before making any other decisions.
Drew, I posted here to get a general consensus from owners/drivers, to see what they had experienced between the two. However, you were still going to get the last say...... I probably should have noted on this thread that when the engine was rebuilt, it was rebuilt to stock specs per the second owner.
BG
Performance preferences are subjective. I do not desire the ultimate power today in one location with just today's fuel. One can tune to chase conditions but I like smooth seamless performance from idle up under a wide range of ambient conditions. A GT350 Holley fills the requirements for me in GT350s and Cobras. Most of the ones I have serviced since the 1970s have been inadequately serviced or modified intentionally or not to work not so well. Last fall I serviced a carburetor for an early 1966 GT350 with really strange jetting and deactivated secondary on purpose. I repaired it to work as designed.
I have used R-3259 and R-3259-1 models on pure stock to seriously modified HP289s. Barring carburetor part failure or ill advised modifications engines do very well cruising slowly in the neighborhood or running 8,000 to 8,500 rpm playing or going down a race tack's main straight. Performance being smooth and seamless from that slow crawl to 160+mph.
The only modifications I found useful were power valve and or jetting changes depending on camshaft, altitude, and or fuel type. No surprise, no stock carburetor covers 0 to 5,000 feet plus or wild camshaft, and or ethanol in fuel without adjustment for conditions.
Quote from: Drew Pojedinec on March 06, 2021, 06:46:27 PM
Quote from: shelbydoug on March 06, 2021, 03:38:52 PM
What's great about Holleys is that there is such a variety and you can keep trying different combo until you find the right one. What you like someone else may not.
Mind you, I am coming from a vastly different place compared to most.
I find the "wheel of carbs" to be annoying. There is a specific reason one works better than another.
I would rather change bleeds and make the fuel curve appropriate for my usage. The 650 double pumper mentioned, it seems like the right choice. Only negative is the majority of them have a tiny PVCR and oversized jets as they were meant for racing. For street car usage you will juggle between having a fat cruise and being underfueled at wide open throttle. The only solution is to drill PVCR's and jetting down, of course this brings us back to just make the carb work for your setup in which case who cares what you started with?
The only benefit of swapping to another carb would be that it being a generic vs a valuable original, you could molest it sufficiently to work perfectly in all conditions.
I simply like the 715cfm as the venturi to throttle bore size is very favorable in regard to optimal tube. (optimal tube being 30 degree inlet, 7 degree outlet, vena contracta being a specified fraction of the outlet).
All of this said, there is a very specific reason that Ford used the 1 5/16, 1 3/8 venturi, 1 11/16 bore combo on so many carbs.
C3-B, CU/CV, BC/BD, 3259, etc. It simply works very well. Not big enough? run two of them.
Bob's 715 probably would have run like poop as delivered to me.
Idle feed is massive, carb was hand made into a double pumper, the details of such are very fascinating to be honest. Someone tossed a newly minted baseplate on it, which aside from hanging the throttle open, it defeated the purpose of the original modifications.
I'll put it back to stock specs and it should run just fine as is.
of course I could be wrong..... :P
I had a bad case of vena contracta one time after I went swimming in the Arctic Ocean.
I'm not arguing for one carb vs the other but it seems to me that this is a disagreement on which carb is "better vs favored sentimentally".
The criteria that Shelby American used to put the 715 on the 289, as well as other modifications, stems from the initial program of making the GT350 a streetable club racer. Not at making it "streetable" in the traditional sense. As such the 65 GT350 was "certified in it's class" to go to Lemans and be competitive vs a 289 Mustang GT. The 66 and 67 GT350 are just carryovers and there is documentation offered in recent discussions here of how even the 600cfm Holley was an issue on some automatic trans equipped cars.
That isn't me, that's the uncovered moments of the meeting in dealing with issues of induction.
IF this is a scientific disagreement and not a sentimental one, I see dyno testing as likely the only way to show how and where the 3259 is "better" then say a specific 1850 which also has it's origins in original Ford applications.
Then it wouldn't be anyones personal preferences that were the data points, it would be what the dyno showed.
There has been scientific data in existence from Holly since before the 3259 was ever applied to the GT350's that clearly show that a 715 on a 289 is WAY too big. Don't argue with me about that, I'm only the messenger. Since some here would like to lean on Holley's data and Ford's engineering, prove that chart is wrong.
Even Edelbrock uses that data to this day as well.
I often have misconceptions that can only be corrected and clarified by scientific data. Sometimes that isn't easy to arrive at as an individual.
I just keep thinking of the review of the "ice and snow tires being the 'best I ever had' by the guy from Miami, FL, in July' ". Exactly what some people perceive as the best and what actually is are not necessarily the same thing.
Show me the data. Not a '63 Ford F150 as a dyno.
You can always have the heads professionally ported, flowed, bigger valves, and then the 715 will work as intended.
My street GT350 sampled a 600-1850, 650-4777 and 715-3259. It liked the 600 best. Best throttle response. No strip work. Just around town and stop light. Seat of the pants, unscientific I admit.
Guys,
I have to apologize.... it appears that the DP on my GT350 presently is a 600 cfm Holley...... List #4776-2
I was going by what the PO said, but something told me to pull the air cleaner and double check..... its not a 650.
Also if it matters, I run 91 octane pure gasoline and occasionally add a few gallons of 110 Sunoco Race to treat it to a little dose of lead.
I certainly appreciate all the comments and information regarding this, and I can assure you I have no sentimental connection one way or another, as I have stated I just want to to what's best for the engine and keep it happy & healthy.
BG
I agree with Drew on the power valve restrictions and the jetting on a stock 4776.
They tend to idle very heavy, which according to Holley is because it is intended to be a 'race carb' with headers and the heavy idle helps the header scavenging.
I THINK what makes it crispy is that the primaries are smaller giving greater signal and you don't need to wait for the vacuum secondaries because of the mechanical secondaries.
I was running a 4779 on a 351c and couldn't get the idle to where the exhausts wouldn't smart your eyes at idle. Of course I didn't know of Drew at that point and probably should not have been using a 5 pound lumping hammer to tune it?
I never asked Drew if he could fix that on the double pumpers? Hey Drew? :)
I can.... but shipping a carb to me for 5 minutes of work is expensive.
Enlarge IAB to .070, reduce ifr to .031
If cam over 245@.050 .067/.033 works better.
Be sure the burning eyes is not a lean misfire, lots of folks head the wrong direction.
Drew ,
I am still AMAZED at how little people REALLY know about carburetors! The FIRST thing they do not understand is the "principal" of how they WORK. MANY talk about "flooding" an engine with a 715-750-850 etc. In truth , a given engine will only flow what the cubic inches , intake and exhaust efficiency and RPM allow. Bolting on a 600 may be an easy way out for some , but I'll take an expertly optimized carburetor any day.
Quote from: gt350hr on March 08, 2021, 12:18:27 PM
Drew ,
I am still AMAZED at how little people REALLY know about carburetors! The FIRST thing they do not understand is the "principal" of how they WORK. MANY talk about "flooding" an engine with a 715-750-850 etc. In truth , a given engine will only flow what the cubic inches , intake and exhaust efficiency and RPM allow. Bolting on a 600 may be an easy way out for some , but I'll take an expertly optimized carburetor any day.
+1
The original formula with the 715 and R model spec heads works perfectly. You can detune with a lesser carb or increase the volume of air. After I had my heads redone it was like turning on a light switch. Not a cheap fix but with these cars values escalating who cares.
Quote from: gt350hr on March 08, 2021, 12:18:27 PM
Drew ,
I am still AMAZED at how little people REALLY know about carburetors! The FIRST thing they do not understand is the "principal" of how they WORK. MANY talk about "flooding" an engine with a 715-750-850 etc. In truth , a given engine will only flow what the cubic inches , intake and exhaust efficiency and RPM allow. Bolting on a 600 may be an easy way out for some , but I'll take an expertly optimized carburetor any day.
To this day, one of my most thrilled customers argued with me about what he needed for months. 350 Chevy with a 600 double pumper, ran like poop everywhere, got horrible economy, etc etc. He finally relented and I sent him a 780cfm carb that I custom tweeked. Better economy, ran better everywhere. He went from ready to sell the car, to wanting to sell his daily driver so he could drive his corvette more. Lol. I mean, the guy was fanatical, sent me all sortsa gifts, etc.... kinda funny actually, tho I pondered a restraining order for a little bit.
Agreed with the flooding comment. You are much more likely to have overly rich issues with a 390cfm carb than you are an 800. I'm not sure how people do not understand what I consider to be common sense, but I also ignore a lot of people. I have one of the greatest books ever written about carburetion, by Walter Larew. I gave a copy to a competitor. With some of the best info in his hands, he misread it and came to mostly wrong conclusions. The same is present here in this thread.
Ohh, Randy, I sent you an email regarding the carb from the Original Poster.... it is super cool, check it out and save the photos for your records.
Drew
Quote from: Drew Pojedinec on March 08, 2021, 10:38:49 AM
I can.... but shipping a carb to me for 5 minutes of work is expensive.
Enlarge IAB to .070, reduce ifr to .031
If cam over 245@.050 .067/.033 works better.
Be sure the burning eyes is not a lean misfire, lots of folks head the wrong direction.
Shouldn't the PVR's be enlarged to a street carb size as well?
When the plugs and the tail pipes are black, it tends to confirm the rich prognosis on the double pumpers. You can also pretty much rig up a generic oxygen sensor and read what is coming out of the pipes.
Got my 715 LM back from Drew a day or so ago..... looks very good. Thanks again Drew......
Now more head scratching. Do I leave the Holley 600 DP on there, or put the 715 LM back on...... ?
I am attaching on old Offenhauser guide from back in the day.
I am leaning on leaving it alone..... I think.
Quote from: oldcanuck on March 27, 2021, 11:18:47 AM
Got my 715 LM back from Drew a day or so ago..... looks very good. Thanks again Drew......
Now more head scratching. Do I leave the Holley 600 DP on there, or put the 715 LM back on...... ?
I am attaching on old Offenhauser guide from back in the day.
I am leaning on leaving it alone..... I think.
I personally think that the 600 dp is more responsive throughout the rpm range BUT the 715 WILL have more top end.
The saving grace is the vacuum secondary. Drew is gonna' jump on me for saying this but others of knowledge have looked at the 715 on a 289 before and determined that as "delivered" new with original design specs, the secondaries never fully open.
The Boss 302 carb is the same way. A 780 on a five liter, generally is too big.
Look, you paid for the 715 to have gone through. Bolt it on and see how it runs. Maybe you'll like it?
The only way you could REDUCE the criticism, not eliminate it, would be to do a "shootout" on your car with the two carbs. A dragstrip would be the most scientific but it isn't necessarily going to give you "everyday" driving advantages and disadvantages.
The double pumpers are way to heavy at idle for day to day street driving but will definitely give a nice showing on a race car.
I won't jump on you. Don't particularly care what you think.
As I said Bob, toss it on and see. Ran normally for me, and I'm fond of the size, but the true test is always on the street.
Quote from: Drew Pojedinec on March 27, 2021, 07:52:13 PM
I won't jump on you. Don't particularly care what you think.
I'm relieved. Thanks. ;D
The 3259 is a derivative of (IIRC) the 2668 designed for a low riser 427. Dan and I have both seen these carbs in prototype form where the original list number was XXXXXXd out and 3259 was hand etched onto them. The major change was the float bowls ( obviously) The -1 revision was a change to the primary metering block.
Use whatever you want or like best. I do. I just don't "push" what "I" do onto others.
Quote from: gt350hr on March 29, 2021, 10:47:24 AM
The 3259 is a derivative of (IIRC) the 2919 ( Dan will correct me) designed for a low riser 427. Dan and I have both seen these carbs in prototype form where the original list number was XXXXXXd out and 3259 was hand etched onto them. The major change was the float bowls ( obviously) The -1 revision was a change to the primary metering block.
Use whatever you want or like best. I do. I just don't "push" what "I" do onto others.
The base design was the R-2668A (Ford C3AE-9510-B) 427 4V carburetor in its 1964 configuration. Delete the square shaped fuel bowl assemblies, create a new version of the "center inlet" bowl assemblies used in the R-2919A 427 4V by changing to 0.110 inch inlet valve seats and DuPont® Viton® rubber resin tipped inlet needles, change the left side fittings to install a transfer tube, and add the transfer tube and presto a R-3259 prototype.
The drawings released December 2, 1964 detailed all the parts including all calibrated orifices for the production R-3259A. The R-3259A was only made in two runs in December 1964. In January the R-3259AAS model went into production; Ford C5AZ-9510-A or Shelby S1MS-9510-A. During the 1966 model year the R-3259-1A (Ford and Shelby S2MS-9510-A) was released and before June 1966 the final production version R-3259-1AAS was put into production.
Holley indicates that R-3259 and R-3259A models were rated at 700 c.f.m.. All the others were described as either 713 c.f.m. or 715 c.f.m. depending on who published what when.
Each new suffix denoted a change in functionality. Most changes R-3259 to R-3259-1AAS were made to improve the air fuel mixture curves and make wide open throttle acceleration of the car quicker. The biggest single functional change was the R-3259-1A that introduced a new calibration for when secondaries started opening and how quickly they opened once opening started. The last change came during the R-3259-1AAS period when a new heavy duty main body went into production circa January 1967.
After all these decades of time many of the family of carburetors have had parts and features mixed around, especially by commercial rebuilders or people making up carburetors by finding one part at a time. It might take an hour to make a list of the common things people have done / failed to do which make their performance decline and or create driving problems.
This family of carburetors had a long development history, years. As designed they work very well puttering along at low rpm through a neighborhood in fourth gear or screaming down a straight at 8,000 or more rpm over and over. Some people make unwise changes that make for miserable driving. Other than float settings, the only changes I have ever found worth the time, and I tried all kinds of going the wrong way "improvements", was changing main fuel jets and or power valve calibration to suit a specific engine build and or altitude. With no racing in mind I leave the power valve channels alone for high altitude as being rich during a wide open throttle sprint at 5,400 feet is better than being any lean at 1,000 feet and less.
The last Ford 'assembly line' variant that I am aware of was the R-3259-1AAS model with some customization of fittings and throttle lever for the GT40 MKIII application.
Three variants I have seen from 3259 to -1 have massively different idle circuits.
OK.... I have made my decision with the help of another SAAC member and multiple car owner.
Instead of pulling the Holley 600 double pumper and installing Drew's freshly rebuilt 715 Le Mans for comparison testing, I thought maybe putting someone with Shelby and Hi-Perf Ford knowledge in the passenger seat as a good litmus. I figured since this member has owned several Shelbys in the past, and currently has a 1967 GT-350 with the original 715, a 1969 Boss 302 and a Ford GT..... I figured his extensive seat time could tell me if I should leave it alone, or put my 715 back on it.
After a brisk drive including a couple of bursts at almost full throttle to 5,000 rpm...... he simply said..... 'I'd leave it alone...."
Case closed.
Good choice Bob, now I can have the 300 cash for the 715 over to you in 5 minutes! LOL!
After you left, I thought I would go out for a short 5 mile spin, my 715 ran great, but then on the way home, I had to pass a truck full of sod, (Knowing that is was going to the house next to mine!!) So on my pass, it was no problem, then as I was coasting back down to the normal speed, I felt that dreaded wanting to stall, I thought, no way am I going to let the guy I just passed see me Found On Road Dead, I put the pedal to the metal and opened it back up again, and the car ran like it never happened, so I got home and I let it run and it showed no sign of any problem....my carb was restored, but by who? Maybe a rebuild is in store for my car, or a nice new 600DP?
Bob, what works works!
67gt350, sounds like a lil trash got flushed out the seat.
Fun story.... so I daily drive a 76 F100 with a 390FE and a holley.
Well, driving to the airport to go to work at 2am. Dark South Georgia road, middle of the swamp. Real dark.
Anyway, cruising at 60mph and I feel the engine wanting to die. I realized a bowl had a stuck float.
Well, if the float drops it normally flushes out the trash, so no cars for miles, I floor it.
100mph and my crappy truck shakes bad.
I hit the railroad tracks at 112mph.
Anyway, no more issues. Rest of the trip was smooth.
Also of note on old Ford downleg carbs. There is no killbleed. The siphon break is in the emulsion tune feed. So can have an issue if blocked.
Fran,
Glad to hear that maybe you have it flushed out...... its telling you, I want to be driven more !
Thanks again for your help yesterday....... I'm still amazed that the Police Officer didn't read us the riot act !
If you do think your 715 needs a going through, Drew is certainly your guy. I have his contacts if required.