[steve25]

At a port volume of 185 CCs that 17% bigger then the stock 154 CC intake port.

The minimum valve bowl diameter of the KRE heads is 12% bigger than the stock factory size.

This all adds up to less port velocity and throttle response until the motor gets up to the rpm where it can make use of the added air flow offered by the KRE heads.

With his now far better 200 psi of cranking pressure Rhoads lifters can not be used.

[Formulas]

There is a lot of squirrel chasing going on, That's partly from asking a crowd a question, everyone in the crowd has a different depth of experience and understanding of their experience...

That said i have played with a vac sec 1850 holley (600 vac sec) they have no place on a engine where a decent level modifications have taken place and some performance is expected.... They are at best a replacement for a 2bbl intake and carb with everything else 2bbl spec.

My 1850 was given to me from a chevy guy it ran previously on a stock 327 i rode in the car very unimpressive i later put it on my 350 that i ran many other carbs on and it was very unimpressive.... I even had a 450 4bbl. holley on it which had animal acceleration up to the point it was to small CFM.

You can buy a 20k stereo and put ear buds on it and its going to sound like a 20k walkman

Caveat .. the actual OP list number has not been provided but there isnt to many 600 vac sec holleys

[Jay S]

The 350 needs more converter than its big brothers if you want to keep up with the larger CID engines. If more power off the line is the biggest goal, a higher stall(especially a lock up converter) in a 200R4 could help also.

With regard to port volume being to much, it is generally known to affect the engine after valve lift hits 20% of the intake valve diameter. This 350 has 2.02 intakes, so the port volume starts to affect the engine above around .4” lift. With barely over .5” lift, the port volume probably never becomes much of a factor on this, especially considering stock KRE volume is really not big, it is probably closer to 180 cfm with the smaller 2.02 intake valves (roughly 13% over stock?). We usually add compression and under cam the engine a bit when dealing with extra port volume for smaller CID’s. With the pumping compression up above 200 lbs both those things should be pretty much covered. If port volume is a concern, you also generally want to be on the rich side on the mixture, certainly not on the lean side. That carb has to go or make major mods to it. Exactly what Formulas’s said….

It could be building a bigger engine better suites the desires for the car, even could add stroke to the 350 if trying to keep in somewhat original. Pumping a high of 230 psi with a stock short block with OEM cast pistons will probably come back and bite you at some point. But there should be more power to be found yet as it is.

[chiphead]

If you guys think it's the carb, then find an ebay special 3310 750 vac sec, throw a heavy secondary spring in it and go to town.

If its the cam, set the current cam straight up and install rhodes lifters, or throw in a Summit 2801.
I ran a XE256 cam in a P-350 with 75CC 670 heads, RPM intake, Q-jet, a stock converter, TH350 and 3.23 gears. It wanted a little more converter, but would easily do the dairy queen burnout. The small stock cam was the 254, the garden variety P-350s usually had small duration cams.

[Stan Weiss]

With what this engine has for cranking compression and that the OP said he has been able to run 89 octane gas. I would add a degree of time at a time and see how the engine responses.

Stan

[srmmmm]

Originally Posted by Formulajones

You guys do realize the Kauffman d port head out of the box is only a 180 or 185cc intake runner at best right?

That's not a big head by any standard. Hell I put 195's on a little 327 and it still made 447 ft lbs on the dyno and over 400 ft lbs. The entire pull from 3000 where we started the pull all the way to peak HP.

So there is no reason a Pontiac 350 can't make low end torque with a smaller 185 head, especially considering it has a 3.750 stroke in it!! If it's weak down low you guys are doing something wrong, and it isn't the heads.

I don't know what your answer is, I'm not there building the engine, so all we can do is guess, but I can tell you from my own experience I routinely use heads much larger than yours on my builds and have no issues with torque production.

I know guys here are trying to help but unfortunately you've been sent down a rabbit hole with pages of suggestions and no end in site.

I agree. I'm running 6X-4 heads on a 350 block with ample bottom end torque. Granted, I've got a 4.25" crank in it, and a cam with .502/.510 lift, but it was pulling over 400 Lb Ft@3000 rpm to a peak of 442 Lb Ft@4300 rpm.

[Formulajones]

I doubt it's the carb either. There were quite a few performance engines back in the day that were factory with small 600 cfm carbs. In fact the L79 that we ran in the nomad for decades was factory with a little 585 cfm Holley and I routinely spun that thing to 6500 all the time. It pushed that boat of a car to mid 14's with just a 3.55 gear on street tires. If a 585 works on a 327/350 HP spinning 6500 rpm I dont see why it wouldn't work on a 350 that might turn 5000 or 5500. Might have to jet it but I doubt it's a huge flow restriction at that rpm.

The op is complaining about a low end problem anyway and that's not where a small carb would be an issue really.

We can throw all kinds of math equations at this but they typically don't take other factors at play into account. So it's a ball park reference at best.

[Jay S]

I agree the extra lack of low end power with the drive train behind this Pontiac 350 is a mystery even with that 600 Holley.

There should be more quite a bit more power with a bigger carb though, the 600 vacs are set up to go on basically stock engines with 4 bbl. I had one we shift at 7000 RPM on a 318 mopar. With no tuning the factory settings pulled the entire power curve down pretty quickly. Out of the box we use them on anything from stock 300 to 360 cid small blocks in cars a pickups to bigger engines in pickups and big trucks. They are all jetted lean enough from the factory you can drop them on a bone stock low compression 350 SBC, 351 Ford, or 360 Mopars and not do any tuning.


Richard Holdener did some work with dyno testing the factory SBC’s that had similar cams the the Crower in this 350, except the SBC cams are single pattern cams. If I recall correctly, his L79 327 made 340 ish HP with 750 holley and open headers at 5400 RPM. With the factory 580 carb IRC the L79 in true stock form was closer to 310 to 330 HP with manifolds. This 350 Pontiac engine with the mods it has should have potential to be closer to almost 400 HP. It is clearly not performing like it should.

https://m.youtube.com/watch?v=Tz7CM9_0QJU

[steve25]

His usage of those heads and that intake is flat out not necessary to make 400 hp and is in fact a handy cap to his motor’s performance in the rpm band that it will be mainly called upon to run in.

Tomorrow I will post up an article done by Jim Hands in a 1995 issue of Pontiac Enthusiasts magazine.
To this day and to me it’s still the best empirical evidence for what a 455 needs to run low 12s in a 4000 plus lb car.

Basically without going into the deep details he ran those times with a 9.6 comp.

Ported iron heads flowing 237 cfm@ .500” lift @ 28” along with a port volumes of a mire 160 CCs.

Rpm intake and shifting at 5500.

RAIV cam
Rhodes lifters
1.65 rockers.

3.55 gears.
Custom 2700 stall converter.

Here’s the bottom line .

If you think for one second that a motor like the OPs of 90 less cid and .460” less stroke then a 455 is going to even run 75% as well with 180 CC heads regardless of what they flow then you are flat out mistaken period.

[Formulajones]

What Jim hand did was cool but it's honestly outdated 40 year old material. In the 80's and early 90's an 11 second car was getting it done. Today it's nothing too impressive anymore. We can make 500hp at the drop of a hat with bolt on parts these days now that we have so much aftermarket support, and 600 isn't much more difficult.

At the end of the day I would only expect so much from a Pontiac 350 anyway. Don't know what the op is expecting to accomplish with it but it's not going to be a power house no matter what head is on it.

One thing I noticed if I read it right, I don't know for sure because I'm not going back through 10 pages but I believe this is a stock untouched short block. So pistons are probably in the hole .025-.030" so that's not helping matters. Stock pistons with a big ring pack and a bunch of other things that are not going to help the cause. So like I said I wouldn't expect a miracle here.

[Jay S]

I was racing at the track in Kansas City on Wednesday nights when Jim Hand did the intake testing. I even lined up next to him a couple times.

[Jay S]

We had an engine that was under performing and it turned out the stock heat range spark plugs were too hot. A worst case once a newly built engine would only idle until we changed to a colder plug. It can be a night and day difference. Just offering things to try.

[steve25]

I fully disagree,
It’s not outdated at all for a motor that can run those numbers , using a lot of stock parts and not costing over 6k even today.

[Stan Weiss]

Yes, I know it is a SBC and not a Pontiac. Dyno sheet in post #3

AFR195 Heads and XR276HR

https://www.corvetteforum.com/forums...ocker-cam.html

Stan

PS - OK Find the link I was looking for - Running a Holly 6210

https://www.corvetteforum.com/forums...ew-engine.html

[Formulajones]

Originally Posted by steve25

I fully disagree,
It’s not outdated at all for a motor that can run those numbers , using a lot of stock parts and not costing over 6k even today.

It gets outrun by crate motors these days so yeah it's an outdated recipe.

Not saying it doesn't work but it's not super fast anymore

[Formulajones]

Originally Posted by Stan Weiss

Yes, I know it is a SBC and not a Pontiac. Dyno sheet in post #3

AFR195 Heads and XR276HR

https://www.corvetteforum.com/forums...ocker-cam.html

Stan

PS - OK Find the link I was looking for - Running a Holly 6210

https://www.corvetteforum.com/forums...ew-engine.html

That's kinda weak for a 327 with 195's and a hydraulic roller that should be 11:1 compression too.

The 327 we just built used AFR 195's as cast out of the box, a bullet hydraulic roller that's 227 @.050 and is 10.7 compression. Ran it on 91 pump and it made 489hp and 447tq
Now my son daily drives it. Very docile

[Jay S]

I recall someone running bigger port RA4 heads on a 350 racing dirt track. As I recall all it had was a RA4 cam. I recall it had stock forged type pistons, and won over 40 main features. Hmmm…

[Stan Weiss]

Originally Posted by Formulajones

That's kinda weak for a 327 with 195's and a hydraulic roller that should be 11:1 compression too.

The 327 we just built used AFR 195's as cast out of the box, a bullet hydraulic roller that's 227 @.050 and is 10.7 compression. Ran it on 91 pump and it made 489hp and 447tq
Now my son daily drives it. Very docile

I posted that up because of how similar it was to the OP engine.

I believe it is 10:1 and also had a 650 cfm Holley

XR276HR 276 282 224 230 .502 .510 110

60916 278 289 221 229 .455 .470 112

Stan

[HWYSTR455]

Smaller displacement engines do need more SCR for low-end power, it can be at times a dance trying to get there for a street engine.

Spread bore carbs usually work better too for smaller displacement engines, since once you start turning RPM, they need more than what same-size square bore carbs can offer.

Multi-carbs work similar and is an option, but adds to the tuning puzzle.


.

[besserspat]

I have a 360P in my 73 bird, it was the OP that got the original 350P rebuilt by CVS machine shop.

It has a small cam, 670 heads with roller tipped CC rockers, some 15/8 hooker ceramic coated headers and a Eddy RPM intake with edelbrock carb and a triangle foam job air " cleaner" .

I've replaced the air induction hood for an original flat hood, so I removed the Eddy RPM and carb which I sold to someone here and put on a 68 iron intake with a rebuilt QJet and a real air cleaner.

The car has a 1968 4 pinion N diff with 3 36 gears and a TH350..

It lights up the tires at will and sounds great, its not fast by any mean but its peppy enough that I have been post-poning its engine/transmission/rear end swap for the last 5 years now....

I have a brand new 461, SD full CNC ported iron heads, OF cammed , with new built Th400 and Continental JH special 10" and new 8.5 3.08 posi for it sitting on the shelves waiting to go in that car.

Funny how the little 350P makes me smile everytime I drive it. Proof that we dont always need big displacement.

Good luck with your 350 ...