Author Topic: Trans Am Intake Port Sizes  (Read 3598 times)

427heaven

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Re: Trans Am Intake Port Sizes
« Reply #15 on: June 19, 2020, 09:52:41 AM »
That's the one- I figure if it was good enough for the Factory COBRA race cars 55 years ago its good enough for some spirited street car driving. I have a couple of small blocks with 750 dp carbs that will run circles around this set up but that's not vintage looking or running vintage parts. Most of the time I try to look period correct.

shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #16 on: June 19, 2020, 10:30:07 AM »
I don't think they were used on race Cobras?

The 750dp Holley, r-4779, was my first disappointment.

I think of the Holley 2x4 as a 600dp with an unlimited vacuum secondary booster to it.

The mechanical secondary Holleys were developed for the T/A set up. In competition, the vacuum secondaries would hang open or were too slow to close.


The Carters don't get good until the "Thermoquads" arrived.


Dual Carters were used over at GM and on the street Hemis, so I'd need to reserve judgement until I tried the set up.

I'm not a fan of mid 60's Carters at all from my GM days.


I will admit that dual Holleys is not an easy setup to work but I think the Ford linkage helps once you get the kinks out and the manifold design is superior.

Just my perspective based upon my experiences.


As a matter of fact I'd say that getting Webers to work right is a whole lot easier then this frickin' dual Holley thing. I always liked a challenge but when does it stop?  :o
« Last Edit: June 19, 2020, 08:02:00 PM by shelbydoug »
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gt350hr

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Re: Trans Am Intake Port Sizes
« Reply #17 on: June 19, 2020, 11:24:50 AM »
    '66 was single four. Ported COBRA. For '67 dual fours were allowed. The early dual four was a turd so a new version was designed. I can't answer the reason why changes to the castings were made without looking at the blueprint itself as the original design engineer of that intake has passed.  Maybe I misled you in saying the part number was changed for the SCCA. The SCCA did "suggest" a Mustang based part number , and a "revision request" ( some minor change to the casting or machining of it) allowed the C6ZZ to be assigned to it. You are correct that the part (casting) number could only change due to a revision. You will also note that Z as the last letter is uncommon for a casting number.  A and E are the most common suffixes used in cast engine parts.The C6OA was distributed in many of the over the 2 4V induction kits which were very popular at the time.
      Both of my manifolds had "smoothed" entries , not port matched. "I" port matched #9 to my VicJr heads and saw NO improvement on the ET slip.

What was the "turd" manifold?

I thought I had a T/A manifold in the C60A? I'll need to stop referring to it as that. It's not.  :(

The implication is to leave the ports alone as cast. What does the intake port look like on the GT40 head? It's too bad that cameras didn't exist back in the day in the SA Race Shop. Maybe they did and the mechanics kept breaking and throwing them around?

The lack of documentation from it is surprising. Was the information too proprietary?

        The "turd" IMHO is the first design dual four Holley like you used to run. The manifold was only 20-25 better than the single four Cobra manifold and 715. It WAS good for gas mileage with the original 465 carbs. You had to drop the jets down 3 or 4 but it actually got better mileage than the single. The port sizes were tiny. I purposely didn't mention the Cobra /Carter manifold for the same reason. The manifold you got from Mike is the T/A version with completely revised runners and port sizes matching the C6FE (GT 40-T/A)heads that the manifold was designed for. The intake port is slightly bigger than the 351W head.
    When I make changes to something on my engines . I measure the changes by the ET slip. "I" saw no change after spending about 10 hours reworking one of my T/A intakes. That tells me that I may have improved it but it wasn't the area where the engine was lacking.
    55 years ago this stuff was cutting edge so it was somewhat guarded information. You can buy new C6FE heads from Cobra Automotive , they are reproducing them with several CRITICAL structural improvements to stop them from cracking externally which was a serious issue with originals. This is a small undertaking so they are understandably expensive due to the "short run" costs.
    Randy
Celebrating 46 years of drag racing 6S477 and no end in sight.

shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #18 on: June 19, 2020, 11:57:16 AM »
My AFR 1388's match EXACTLY the Mr.Gasket 302 intake gaskets. ("Joey" recommended them. Said I had to see the flow numbers out of the box)

When I layed those on the C60A (no longer the T/A) the ports on the manifold were 1/8 smaller all around. That is a BIG difference.

I don't presently have a set of gaskets for the 351w 4v here. So I couldn't compare them. I would have no idea how anything would match up to the GT40 heads. I've only seen pics of them. Neither could I tell from pics that I saw if those ports were as cast or gasket matched to "something" else?


Again, I'm not arguing, just trying to learn now what was proprietary information back then.


When I first layed up the gaskets, I remembered thinking that the ports were the same size as the "Blue Thunder" 2x4. That one I port matched to the gaskets and I was running the 68-302 4v heads (massaged as they were).

The ports on that manifold after gasket matching them left very little on the top of the port to seal to the manifold. MAYBE 1/8"?

Since this C60A was virgin, I elected not to go there with gasket matching.


This is probably all just academic anyway? The car is not going to be vintage raced and as it stands will be fine on the street and open tracks.

There is no way I am going to race "hole shot" Gillis under any circumstances. I got the dimples out of the roof and I don't want them back.

Do you know what dimpling the roof sounds like in the driver's seat? It sounds like the car is one big oiling can. I was confused. Never heard anything like that before. Don't want to hear it again.


It had only occured to me that with out of the box flow numbers on those heads around 300 cfm @ only .500, how much of a mismatch the intake ports were.

I've done a few Edelbrocks port matching and if anything, I thought that was detrimental to the overall performance. I seem to recall a note in the box from Edelbrock saying "leave them alone!"


Now let me also say that the nearest "legit dragstrip" used to be Englishtown in NJ, but that was converted to something else. Probably a golf course like Bridgehampton was?

So the locals here, I need to be careful with. They are liable to report me as testing a vehicular battering ram intended to attack "protesters" with? They're kinda' funny that way. One guy threw a garbage can at me because he thought I was gonna' patch out in front of his house. 

Wheel stands are absolutely out of the question. :o
« Last Edit: June 19, 2020, 12:18:04 PM by shelbydoug »
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gt350hr

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Re: Trans Am Intake Port Sizes
« Reply #19 on: June 19, 2020, 03:09:38 PM »
   The Blue Thunder uses the original patterns for the first dual four Holley . It is not a "high performance" manifold but it "does" improve power. Your "port matching made a difference on that Blue Thunder manifold because the case in ports were SO small.
      My point in answering your question of port matching is that "it did no good" in my development program. Often times having an intake port opening smaller than the cylinder head is a good thing. The mismatch has been proven to help curb reversion which is present to a certain degree in EVERY "poppet" valve engine. As I recommended leave the mismatch because the advantage comes from the increased runner volume from the revised ports.
    "In the day"  SAI was no different as far as security as any modern day professional race shop. My fortune has been from being a "local" to SAI and finding many who worked there willing to help a kid "wet behind the ears". Back then "name dropping" opened many padlocked doors. I don't have this information because I read it in a book. I played detective and went to places like Engle cams , Valley Head service , Mondello's , Doug's etc. trying my best to improve my racing effort. In the 54 years I have been playing with the Ford engine line , I have learned a few things that were a waste of time , money , and effort that are still recommended by those more familiar with other engine brands. Do what ever you like.
Celebrating 46 years of drag racing 6S477 and no end in sight.

shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #20 on: June 19, 2020, 04:28:19 PM »
Thank you for the time you have taken to reply. I appreciate it. Hopefully there may be others that find this thread helpful?


Considering the initial intent of the C6OA, I suspected that the smaller port match up was intentional and likely significant?

The BT was a different story. The ports were much smaller then the 302 ports BUT upon examination it was clear that the runners match the "gasket matched" ports. So what the heck?



As I said, this C60A isn't going to be ground on AND I do appreciate your personal efforts in sourcing it and thinking of me. I value it highly.

At night I keep it in it's own bed alongside mine. It has it's own pillow, mattress and blanket. I was thinking of giving it a reading lamp but I only have one book anyway?

My greyhounds sleep on the other side. They're retired x-racers but still stubbornly competitive and don't like anything faster then them.
Everything is fast here. Some faster then others?


I will eventually test it with the carbs forward as well. I don't like the linkage and the proximity of the fuel bowl to the distributor cap in that configuration. "We'll see?"  ;)
« Last Edit: June 20, 2020, 06:53:08 AM by shelbydoug »
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JMobley

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Re: Trans Am Intake Port Sizes
« Reply #21 on: June 19, 2020, 07:05:23 PM »
Thank you for the time you have taken to reply. I appreciate it. Hopefully there may be others that find this thread helpful? 

Hanging on every word!  These kind of threads are amazingly helpful to guys like me




shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #22 on: June 20, 2020, 06:58:15 AM »
Thank you for the time you have taken to reply. I appreciate it. Hopefully there may be others that find this thread helpful? 

Hanging on every word!  These kind of threads are amazingly helpful to guys like me

Glad to have helped and entertained.

Here's a pic of the ports of my C60A. You can see how much more margin they have over the BT which was port matched to 302 intake gaskets. It's about 1/8" more, or smaller (.120") all around the port.

You can see the shadow line of the gasket if you look closely.

Manufacturers of manifolds typically do that with their castings expecting the "builder" to fine match the port to the gasket. Leaving the extra metal gives the builder options.

This one I am leaving alone. As Randy states, gasket matching it shows no improvement and may have some advantages?


When you examine the runners on it you will notice that they are of equal length and that they will act as a tunnel ram at WOT.

The runner diameters are round and match the carburetor bores in the carb mounting flanges of about 1-3/4" each and transition to a rectangular port. That's the real differences between the T/A manifolds and the "turd".  ;)



I know that the distance from the throttle plate and opening of the valve is significant to maximum flow velocity on individual runner manifolds.

The Pantera Weber manifold is a case in point. On that manifold the number happens to be about 4-1/2" and the diameter, 51mm.



This manifolds runners are a bit longer (I didn't measure it before installing but I should have), look to be about 8", but it is "tuned" to a 289 which needed more torque added to it then a 351.

That considered, the 289 Weber manifold runners could have been taller for more torque but are probably a compromise to get the assembly under the hood of a COBRA?

Those runner lengths are now determined on a dyno. Back then, probably with a slide rule and theory?



The idle ports are added much like my C7ZX intake is and maybe is a Ford exclusive to 2x4 intakes. Other manufacturers manifolds are almost like single big plenums.

Sorry for the extra large picture. The computer has a mind of it's own and took it upon itself to post it enlarged. It does show gasket shadow lines on what was thought to be a virgin manifold? Must have been mounted and vapor blasted at some point in it's life?

Those of you with numbered manifolds can probably use this picture to determine if the port size is original or not?
« Last Edit: June 20, 2020, 07:32:42 AM by shelbydoug »
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JMobley

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Re: Trans Am Intake Port Sizes
« Reply #23 on: June 20, 2020, 08:20:55 AM »
Here’s my C60A with 3360/3361 carbs.  The intake was in very bad shape when I found it so I sent it to Jim Cowles for clean up. I’m gonna rebuild the carbs this week and hopefully have it in the car by mid July.  Been reading all your previous threads on tuning and such.  You, Randy and others have dumped a ton of great info into this forum and I for one totally appreciate all of it



« Last Edit: June 20, 2020, 08:38:34 AM by JMobley »

shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #24 on: June 20, 2020, 09:50:57 AM »
Looks like it was vapor blasted. Beautiful.

I'm glad to see that I had some small part in corrupting you the right way.  ;D
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427heaven

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Re: Trans Am Intake Port Sizes
« Reply #25 on: June 20, 2020, 05:56:24 PM »
My earlier TURD version will still run circles around most similarly equipped early SHELBYS, and look great doing so. Aaahhh over indulgence from the swingin 60s is still most gratifying.

shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #26 on: June 20, 2020, 08:05:15 PM »
My earlier TURD version will still run circles around most similarly equipped early SHELBYS, and look great doing so. Aaahhh over indulgence from the swingin 60s is still most gratifying.

I agree. I found it a very satisfying setup. Significantly more fun then a single 4v.

And the carbs are just like PACKED in there like, like...nothing else! Way cool!  8)
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TA Coupe

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Re: Trans Am Intake Port Sizes
« Reply #27 on: June 20, 2020, 08:42:42 PM »
Looks like it was vapor blasted. Beautiful.

I'm glad to see that I had some small part in corrupting you the right way. 

And I am glad that Randy and I may have corrupted you into turning your carbs around to face the right direction also.🤣

   Roy
If it starts it's streetable.
Overkill is just enough.

shelbydoug

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Re: Trans Am Intake Port Sizes
« Reply #28 on: June 20, 2020, 09:24:29 PM »
Looks like it was vapor blasted. Beautiful.

I'm glad to see that I had some small part in corrupting you the right way. 

And I am glad that Randy and I may have corrupted you into turning your carbs around to face the right direction also.🤣

   Roy

 :-*
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