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Sun Jul 06, 2025 3:18 pm

ive seen a few threads here and there on the stock DP end castings and a lot of differing opinions. So i was wondering if anyone ever ran any flow test on them and came to any definitive conclusions?
And if so stock compared to ported, or to the aftermarket larger endcastings ?

Sun Jul 06, 2025 5:13 pm

Consensus seems to be that bone stock end castings max out around 88-90 HP.

Consensus is that the aftermarket “high flow “ castings are too big for anything but truly large engines or turbo applications.

There are a few people in the world who know exactly how to get more out of the stock units, or cast units that work in mid-size engines. I’ll stand aside and let them speak for themselves if they so choose.

I’ve tinkered with one by cutting one in two and altering the split but never got around to testing to see if i’m on the right track. Maybe on the next engine.

Or I’ll just go to someone who knows what to do to build out a set, whatever it costs and however many NDAs I have to sign, and call it a day.

But I am interested, and next time around will be building a smaller displacement engine with a modified PICT-3 and as much cam as it will handle.

Sun Jul 06, 2025 9:15 pm

I was getting about 105 HP in a 1971 bus with stock 1600 dual port castings. I ported the heads, backcut the valves, and made sure that all turns were radiused properly. I also made sure that any areas in the 34 pict 3 that had rough castings, uneven mold seams, protrusions etc,. were flowed so that everything from the air cleaner to the cylinder was a smooth path - meaning no sharp edges. The surfaces were generally kept with a light roughness to stop any laminar flows. Used an extractor type exhaust for minimal backpressure. They used to call the cam a RV cam but I think it was the equal of what is the Engle 100 today. The only issue is that the engines were not originally made to handle the stress and heat created in a VW bus so the longevity of the engine is less than stock. With a stock exhaust the HP fell way back to slightly faster than walking but the life span of the engines was greatly increased. There comes a point where it is no fun working on a car when there are other things one would rather be doing.

Sun Jul 06, 2025 9:30 pm

I tested about 6 sets, was finding 115-130 cfm at 25" on a head that flowed 150
ID about 31mm-31.5
Suits 35.5-37.5 intake valves
The end castings are best designed part of the stock intake, IMO
as VW built them.....the heads are meh, center section is crude, carb is crude, but the end casting just need a little clean up, tho IMO they don't need to be made of aluminum, (steel ones heat soak less)

"The problem" is more to do with the qualities of the whole intake manifold itself, what it just naturally does. It is what it is.

Best use of the the stock end castings IMO, is to put a turbo it.

Guido Wensing (sp?) has made larger stock type aluminum end castings, which is neat, but I have yet to see them used in an application where they could truly shine.

Sun Jul 06, 2025 9:32 pm

I am not convinced that there would be enough advantage to warrant the cost of bigger ported end castings on a boosted engine. If running a single carb, the turbo will more than take care of any low flow short fall. I see guys running them here and making anywhere from 140 to 200+ HP on stock-ish engines.

If you are going for HP higher than that you will be going large displacement, blow through with dual Webers or 4 throttle bodies and EFI so you won't be using end castings anyway.

Modoc, I was not aware that the end castings have a heat soak problem. How does that manifest itself? Deterioration of the intake boots possibly?

Sun Jul 06, 2025 9:46 pm

With steel manifolds you will notice the difference, less HP loss when hot.
It's just that very rare to see, few steel end castings are ever paired with a center section that actually works well.

Sun Jul 06, 2025 9:49 pm

I looked in my notes, and my results are about the same as Modok.

I tested them on a Mofoco 40x35 head. I test at 28”. I did a stock end casting, a German Winsing larger end casting, and an IDF manifold for comparison.

Here are the .500” lift numbers.

Stock end casting
113cfm

Winsing
131.2

Untouched CB offset IDF manifold
137.9

Brian

Sun Jul 06, 2025 10:08 pm

Seems about right.
I had a higher flowing head and a bellmouth velocity stack on the manifold.
Some flowed more one side or the other, some just flat out flowed more than others.
Testing a pile of them and choosing the best pair was a very fast way to gain 10CFM or better, with no real work.

Mon Jul 07, 2025 1:04 am

I/we measure a little less, but that can be the calibration, or that the ones we tested were less efficient
If you want a stock like idle there is a definitive upper limit on overlap. So unless you go radical, yes 88-90 hp through stock castings. If you accept a choppy idle at 1000-1100 rpm the hp can easily increase about 10

Wensing castings can, with a little detailing, support 140 hp through a modified Solex carb

Mon Jul 07, 2025 5:41 am

modok wrote: With steel manifolds you will notice the difference, less HP loss when hot.
It's just that very rare to see, few steel end castings are ever paired with a center section that actually works well.
Ah! The same could be said about the heated center section too. It's a drivability vs flat out HP thing then. A compromise the factory found necessary to make.

Mon Jul 07, 2025 6:29 am

Sounding a little ignorant here, but I assume ya’lls numbers are for one end casting ?

Alstrup, I assume you’re referring to removing or at least shortening the divider?

I can definitely see the heat soak thing too, those end castings have been hotter than I expected a few times I touched them. Some carbon fiber ones would be pretty cool but not sure how well they’d hold up. I’d considered 3d printing some back when I started messing with printing but from my experience there’s nothing available (yet ) that will hold up to the heat and fuel both.

Mon Jul 07, 2025 8:11 am

These end castings are ported. I didn’t use them on this version of my turbo. But, plan too. See the pipe welded to the inlet? Sorry, only pic of them. I can dig them out if needed.

Mon Jul 07, 2025 8:44 am

BFB wrote: Sounding a little ignorant here, but I assume ya’lls numbers are for one end casting ?
.

Modok said he tested about 6 pairs.

I only tested one because I had no desire to spend more time on it.

Brian

Mon Jul 07, 2025 8:45 am

NJ John wrote: These end castings are ported. I didn’t use them on this version of my turbo. But, plan too. See the pipe welded to the inlet?

This is what the off-road guys do to their end castings.

Mon Jul 07, 2025 9:25 am

One sided of one end casting at a time.

Mon Jul 07, 2025 10:30 am

Would a setup like this on a 2332 benefit from highflow end castings?

Mon Jul 07, 2025 10:37 am

modok wrote: One sided of one end casting at a time.

Yeh that’s what I meant.
So for the two of them together we’d be talking 225 - 250 cfm -ish?
Which really is quite a bit for a N/A vw engine. and as far as boosted , boost doesn’t really care it’ll just shove it through regardless ( up to a point ).

Mon Jul 07, 2025 2:42 pm

BFB wrote: modok wrote: One sided of one end casting at a time.

Yeh that’s what I meant.
So for the two of them together we’d be talking 225 - 250 cfm -ish?
Which really is quite a bit for a N/A vw engine. and as far as boosted , boost doesn’t really care it’ll just shove it through regardless ( up to a point ).

On a 4 cylinder 4 stroke engine ,only 1 cylinder is on an intake stroke at one time . so the flow is still 100 to 130 cfm .

The friends that build 1600 FV engines spend a lot of time looking for the best matched flowing castings .

Mon Jul 07, 2025 3:23 pm

I asked this question before about increasing flow and was told to check out the Formula Vee forums, but couldnt find anything helpful

I have run a flex ball hone thru them but cant measure any results. They look better but the flow bench is the only way to know. I do think 10 to 15% increase is reasonably possible

Mon Jul 07, 2025 4:19 pm

Wreck wrote: BFB wrote: modok wrote: One sided of one end casting at a time.

Yeh that’s what I meant.
So for the two of them together we’d be talking 225 - 250 cfm -ish?
Which really is quite a bit for a N/A vw engine. and as far as boosted , boost doesn’t really care it’ll just shove it through regardless ( up to a point ).

On a 4 cylinder 4 stroke engine ,only 1 cylinder is on an intake stroke at one time . so the flow is still 100 to 130 cfm .

…

Im not seeing how that correlates to the capabilities of the end castings.

According to my mathing, with he help of some online calculators , a N/A 2276 turning 5500 rpm at 100% VE flows 220 cfm. If your running a single center mount carb then you have 2 endcastings, each capable of flowing minimum of 110 CFM to as much as 130 CFM.
Even if you only counted the flow per cylinder at a time, each one only flows 55 CFM , which is half what the endcasting is capable of.
Tell me if im missing something here?