356B T5 engine rebuild question

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David Jones
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Re: 356B T5 engine rebuild question

#46 Post by David Jones »

I will believe you CJ as I have seen the difference. I was just surprised that the part number listed is the same for all the manifolds. None the less I thought they are all the same externally and the only difference internally was the port matching. How much difference will it make on a street car anyway?
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Re: 356B T5 engine rebuild question

#47 Post by Ken Tuvman »

Marc Walz wrote: Tue Aug 02, 2022 12:15 pm Cam is ordered from Elgin, had a nice chat with Dimitri today. Cam should be here in Germany next week.

Also had a chat with Candace Delaney from 356 Carb Rescue. They have a set of fresh overhauled Zeniths ready to go for 1800 bucks. Don't know if this is a good price, as the restauration/overhauling itself is already 1200 bucks.
Marc - I toured 356CR facility- they’re good people & put out outstanding product!
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Re: 356B T5 engine rebuild question

#48 Post by C J Murray »

David Jones wrote: Tue Aug 02, 2022 2:13 pm I will believe you CJ as I have seen the difference. I was just surprised that the part number listed is the same for all the manifolds. None the less I thought they are all the same externally and the only difference internally was the port matching. How much difference will it make on a street car anyway?
If you carefully match the ports to the manifold things should be ok but steps in there are not good. The bore size is less critical on a street engine but no steps.
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Re: 356B T5 engine rebuild question

#49 Post by Marc Walz »

Has anyone a picture of a set of C manifolds? Are the diameters only bigger on the head side or also on the carb side? Also, are the C manifolds the same as the 912 manifolds?

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Re: 356B T5 engine rebuild question

#50 Post by Doug McDonnell »

912 manifolds are different and for Solex Carbs. If you look at the Online Porsche Classic parts catalog the intake manifolds for the C are 616.08.035 and 616.108.033.01 for the SC with Solex. And on page #164 of your Pellow book he discusses that the C intake has a larger port where it mates to the head and he goes on to discuss that this is why a C with a milder Cam than an S is the more potent engine. Or to paraphrase Cliff Murray - with its low end torque of the Normal and high end power of a Super the C was Porsches best street Cam. Of course he understood but left out the intake change which Pellow mentions.
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Re: 356B T5 engine rebuild question

#51 Post by Marc Walz »

Doug, Stoddard reffers that the number 616.08.035 is a 356A manifold:

https://www.stoddard.com/61608035.html

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Re: 356B T5 engine rebuild question

#52 Post by Doug McDonnell »

I do not have a parts manual for a 356A but I do have one for 356B with the T6B supplement and the C supplement and that part number is the same. But I agree with Pellow that the port where it mates to the head is larger on the C Manifold. So perhaps the casting was the same but port size was enlarged just on the C? Someone like Cliff, Dick Weiss or Vic Skirmants who build a lot of engines would know for sure.
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Re: 356B T5 engine rebuild question

#53 Post by Marc Walz »

This is what the guys from Carb Rescue wrote me back:

For your Normal engine UPGRADED to the mentioned specs, we would recommend a Super Set up, with C style manifolds.

C manifolds allow a little better air flow than the regular Normal/Super style manifolds which are probably what you have on your engine now.

As previously noted, Super and C carbs are interchangeable performance wise. C's have a very slightly smaller main air correction jet, and a very slightly larger idle jet. When you get your car up and running, if you should want to change your jetting to C spec, it is easy to do. You might also find that you may want to step down on your mains. Everything we are talking about here is "by the book". In practice, you will tune to your specific needs.

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Re: 356B T5 engine rebuild question

#54 Post by David Jones »

All the Zenith carbs have the same base throttle body. 32 mm ports on all, only difference is in the carb bodies. This means the carb to manifold porting is the same on all. Just match the intake ports on both. Usually laying the head to manifold gasket against both will make any difference very obvious.
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Re: 356B T5 engine rebuild question

#55 Post by Vic Skirmants »

The C manifolds had a simple cutting operation at the head end. You can easily see it on a stock C manifold.

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Re: 356B T5 engine rebuild question

#56 Post by Steve Douglas »

IMG_1620.jpeg
IMG_1621.jpeg
IMG_1622.jpeg
Here are photos of a A/B manifold and a "C" manifold, you'll notice the diameter is slightly bigger and tapered to match the larger intake ports on the C/912 heads. Also the standard gaskets as sized to fit the A/B manifolds. I use a Dremel rotor tool with a drum sander attachment to match the gasket to the port size. Bottom manifold in the pictures is a C, the other is from a 60 Super. The gasket overlap can be seen in the 3rd photo

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Re: 356B T5 engine rebuild question

#57 Post by Marc Walz »

Thanx Steve for the photos!
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Re: 356B T5 engine rebuild question

#58 Post by Marc Walz »

So that should be a correct set, right?

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Re: 356B T5 engine rebuild question

#59 Post by Vic Skirmants »

Yes

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Brian R Adams
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Re: 356B T5 engine rebuild question

#60 Post by Brian R Adams »

What's the actual size (in mm) of the longer oval dimension, A/B vs the C?

Harry Pellow claimed in his Little Spec Book that there was a slight difference between the A and B intake port dimensions (Zenith manifold).

Edit: Correction: Pellow claimed difference between A/B Zenith Super and Normal (see my follow-up posts below).
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Last edited by Brian R Adams on Sun Aug 07, 2022 12:03 am, edited 1 time in total.
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