[Formulas]

To get a performance expectation based on reality search this site for info concerning your Crower camshaft in a 400 ( more popular build ) and adjust reported powerband RPMS by almost 500 more.... 350s of any brand really drop off in torque after idle with cams 20 degrees more than stock duration.. And because they are small engines to start with they are a bit handicapped to start with.

Even a 068 cam looses off idle power to a 066 / 067 / 254 cams... You get more top end power but what you gain there comes directly from off idle

[ericwoo]

Originally Posted by Formulas

To get a performance expectation based on reality search this site for info concerning your Crower camshaft in a 400 ( more popular build ) and adjust reported powerband RPMS by almost 500 more.... 350s of any brand really drop off in torque after idle with cams 20 degrees more than stock duration.. And because they are small engines to start with they are a bit handicapped to start with.

This is good to know. And yes I was thinking it was just a terrible camshaft selection in the 350 but now it makes me wonder if I have to remove the heads also if replacing the cam.

Originally Posted by Dragncar

The Perfomer was always considered a better intake than the RPM for a 350.

Makes sense. thanks

Originally Posted by Stan Weiss

Now that you have advanced the cam. Have you done a cranking compression test again? If so can you and tells what the numbers are now?

Stan

Yes, I just checked tonight after getting it nice and hot. The psi #'s were pretty high after advancing the cam with the below:

Driver Side:

• #1 : 207 psi
• #3 : 230 psi
• #5 : 207 psi
• #7 : 212 psi

Passenger Side:

• #2 : 220 psi
• #4 : 220 psi
• #6 : 222 psi
• #8 : 204 psi

Is that looking ok?

[Stan Weiss]

Originally Posted by ericwoo

This is good to know. And yes I was thinking it was just a terrible camshaft selection in the 350 but now it makes me wonder if I have to remove the heads also if replacing the cam.


Makes sense. thanks



Yes, I just checked tonight after getting it nice and hot. The psi #'s were pretty high after advancing the cam with the below:

Driver Side:

• #1 : 207 psi
• #3 : 230 psi
• #5 : 207 psi
• #7 : 212 psi

Passenger Side:

• #2 : 220 psi
• #4 : 220 psi
• #6 : 222 psi
• #8 : 204 psi

Is that looking ok?

Looking at those numbers I think the cam and its phasing are fine. What octane fuel are you running and what does you ignition timing curve look like?

Stan

[ericwoo]

Originally Posted by Stan Weiss

What octane fuel are you running and what does you ignition timing curve look like?

Stan

I've been putting in premium fuel which is usually 91 or 93. I thought Kauffman made it sound like they doubt I need it that high so occasionally put in mid grade 89 to test.

I've messed with timing settings dozens of times and nothing really improves performance significantly. Now timing is at about 15 degrees idle and goes up to around 32 degrees at 3,000 rpm.

I did recently adjust the carb mixture again with a richer mixture and seems to pick up a slight improvement. My guess is hp is on par to the 350 HO now which isnt too bad so I am not as disappointed as before but was really hoping to get at least a little more than that.

I'd guess the car probably does have around 320 horsepower like the HO but I have a very hard time seeing it have anywhere near 380 lb-ft of torque like the HO has.

The low end is what I would actually like to work on so I may order the Rhoads lifters that I recently learned about.


If I were to guess, I'd say this car might do around 14.5 secs in the quarter mile. I hope to test in a week or two and will report back.

Other than that, I am kinda hitting a wall with getting this 350 to excel better than the 350 HO. I am beginning to think that is the max possible performance and these engines really are duds

[Schurkey]

Originally Posted by ericwoo

Now timing is at about 15 degrees idle and goes up to around 32 degrees at 3,000 rpm.

And the vacuum advance adds how much at part-throttle?

Originally Posted by ericwoo

I did recently adjust the carb mixture again with a richer mixture and seems to pick up a slight improvement.

HOW are you adjusting the mixture?

I get the sense you're playing with the idle mixture screws, and expecting it to make some global improvement.

[Squidward]

Originally Posted by ericwoo

I've been putting in premium fuel which is usually 91 or 93. I thought Kauffman made it sound like they doubt I need it that high so occasionally put in mid grade 89 to test.

I've messed with timing settings dozens of times and nothing really improves performance significantly. Now timing is at about 15 degrees idle and goes up to around 32 degrees at 3,000 rpm.

I did recently adjust the carb mixture again with a richer mixture and seems to pick up a slight improvement. My guess is hp is on par to the 350 HO now which isnt too bad so I am not as disappointed as before but was really hoping to get at least a little more than that.

I'd guess the car probably does have around 320 horsepower like the HO but I have a very hard time seeing it have anywhere near 380 lb-ft of torque like the HO has.

The low end is what I would actually like to work on so I may order the Rhoads lifters that I recently learned about.


If I were to guess, I'd say this car might do around 14.5 secs in the quarter mile. I hope to test in a week or two and will report back.

Other than that, I am kinda hitting a wall with getting this 350 to excel better than the 350 HO. I am beginning to think that is the max possible performance and these engines really are duds

I am not a tuning guru by any stretch. I think you could get into the 13's with your setup, tho.

Still hoping you can find the performance you are looking for. Just got back from a drive in my bird, and the 350 runs hard. Keep at it!

I had the same question about your carb tuning. You are cammed up, and I can't imagine your idle vacuum is any better than 12-15" max. Hoping your power valve is matched. And your vacuum secondary out of the box settings likely don't match your engine. It has been years since I played with a Holley, so I will step aside on that adventure. Your timing sounds adequate.

[Stan Weiss]

Originally Posted by ericwoo

I've been putting in premium fuel which is usually 91 or 93. I thought Kauffman made it sound like they doubt I need it that high so occasionally put in mid grade 89 to test.

I've messed with timing settings dozens of times and nothing really improves performance significantly. Now timing is at about 15 degrees idle and goes up to around 32 degrees at 3,000 rpm.

I did recently adjust the carb mixture again with a richer mixture and seems to pick up a slight improvement. My guess is hp is on par to the 350 HO now which isnt too bad so I am not as disappointed as before but was really hoping to get at least a little more than that.

I'd guess the car probably does have around 320 horsepower like the HO but I have a very hard time seeing it have anywhere near 380 lb-ft of torque like the HO has.

The low end is what I would actually like to work on so I may order the Rhoads lifters that I recently learned about.


If I were to guess, I'd say this car might do around 14.5 secs in the quarter mile. I hope to test in a week or two and will report back.

Other than that, I am kinda hitting a wall with getting this 350 to excel better than the 350 HO. I am beginning to think that is the max possible performance and these engines really are duds

I assume when you degree the cam you used a degree and found true TDC and zeroed everything. Have you done the same thing with your timing marks, made sure they show zero at true TDC?

Stan

[Formulas]

When a engine is modified to a degree you have to pay particular attention to carburation, .. Timing is a more of a constant based on head design, piston speeds, .. Carburation is different every step in camshaft duration effects low RPM vacuum signal by the time you get on main jets intake tract reversion is down and vacuum is up and the party is over. .... That's why changing just the main jets and power valves usually offers little resolution to a novice tuner

The 600 vac sec. is not a performance carb it is going to be lean before main jets come to play and the IFR is up high and not readily accessible for tuning and a double pumper 750 is the wrong choice for a small street engine.. .. A vaccum secondary 750 CFM carb with a low IFR on a Holley based intake or a good Qjet on a stocker intake would be more preferable than what your dealing with now....

You can take a really great engine put a crappy carb on it and then its all crap

[chiphead]

Originally Posted by Squidward

I am not a tuning guru by any stretch. I think you could get into the 13's with your setup, tho.

Still hoping you can find the performance you are looking for. Just got back from a drive in my bird, and the 350 runs hard. Keep at it!

I had the same question about your carb tuning. You are cammed up, and I can't imagine your idle vacuum is any better than 12-15" max. Hoping your power valve is matched. And your vacuum secondary out of the box settings likely don't match your engine. It has been years since I played with a Holley, so I will step aside on that adventure. Your timing sounds adequate.

I've asked questions about the carb tune before on this one. A 650 should support that engine to about 5400 or so. Shoot for about 67-69 jets primary, .055 PVCR depending on primary HSAB. Secondary should be adequate, it would be good to know what secondary plate is in this 4160.

Please let us know what vacuum secondary spring is currently installed? What is the list number from the airhorn?

Rhodes lifters could be a good option to tame the cam. The issue with those pumping numbers, you may have trouble managing pump fuel if you go with a smaller cam and standard lifters. Advancing the cam makes the intake closing point happen earlier so it builds cylinder pressure and moves RPM range down. If that's not enough to recover torque 2000-3500, you'll need the rhodes.

[Jay S]

The problem this will run into adding Rhoad’s lifters is the engine has a 2700 stall converter behind it, and original Rhoad’s and VPro both are both nearly pumped up by 2700. By 3500 they don’t gain any low end at all. They would gain a little bottom end at 2700, but not much. You would have to do a Vmax Rhoad’s and set the clearance higher to see much for low end power gains when the engine starts out at close to 3000 RPM, and even with a Vmax it won’t help that much at 2700, they are mostly pumped up, probably gain 20 lbs of tq at best. They would help drivability, if that was a concern. It doesn’t sound like that is a concern on this though.


There is still something wrong. I am not very surprised it is still struggling after the cam timing changing, 190 psi was enough before. A 350 can pump about 10 psi more than a 400 on the same octane. Probably even a little more, but even above 200 it could start having issues on anything less than 93 octane.

One thing obvious to most everyone that has chimed in, which have used stock 600 VAC Holley’s in the past ( I have done at least 10 of them), is that is a bottle neck for making much more than 300 HP. There could be multiple problems yet holding the combo back too, unknown problems in the short block, but that particular carb with no tuning is going to hinder any gains in performance in the future..

Could be the converter isn’t holding it either. The 200R4 should spin the tires hard coming out of first gear with its bigger ratio jump going into second. If it can’t do that, something could be wrong in the converter.

[ta man]

Originally Posted by Jay S

The problem this will run into adding Rhoad’s lifters is the engine has a 2700 stall converter behind it, and original Rhoad’s and VPro both are both nearly pumped up by 2700. By 3500 they don’t gain any low end at all. They would gain a little bottom end at 2700, but not much. You would have to do a Vmax Rhoad’s and set the clearance higher to see much for low end power gains when the engine starts out at close to 3000 RPM, and even with a Vmax it won’t help that much at 2700, they are mostly pumped up, probably gain 20 lbs of tq at best. They would help drivability, if that was a concern. It doesn’t sound like that is a concern on this though.


There is still something wrong. I am not very surprised it is still struggling after the cam timing changing, 190 psi was enough before. A 350 can pump about 10 psi more than a 400 on the same octane. Probably even a little more, but even above 200 it could start having issues on anything less than 93 octane.

One thing obvious to most everyone that has chimed in, which have used stock 600 VAC Holley’s in the past ( I have done at least 10 of them), is that is a bottle neck for making much more than 300 HP. There could be multiple problems yet holding the combo back too, unknown problems in the short block, but that particular carb with no tuning is going to hinder any gains in performance in the future..

Could be the converter isn’t holding it either. The 200R4 should spin the tires hard coming out of first gear with its bigger ratio jump going into second. If it can’t do that, something could be wrong in the converter.

I was going to respond as well with possible drive train issues..I've had bad transmissions that seem ok but have held power back. A fun day at the dragstrip would give us some data.

[Jay S]

I had an engine once that gained 10 mph in the 1/4 mile at the track from a converter swap. It went from 98 mph with a brand new 10” 3000 converter to 108 mph using a used 2200 OEM stall.

[ericwoo]

Thanks guys, I will look into modifying the carb. I may pick up a book on that since I am not knowledgeable on that. Was hoping I could buy a carb that gets it at least in the ballpark area.

Just today, I started wondering if my piston rings can't handle the high psi of this build. I don't have any exhaust smoke though. My highest cranking pressure measured 230 psi which is making me wonder if the rings are immediately leaking most of that pressure by when running.

I bought a cheap leakdown tester but as others say, they can't be trusted.

Could my cranking cylinder pressure show high and healthy but it immediately leak by the piston rings?

I may take it to a shop with a professional leak down tester. I am still learning but I've seem to have a lot of bad luck with this build.

Originally Posted by ta man

I was going to respond as well with possible drive train issues..I've had bad transmissions that seem ok but have held power back. A fun day at the dragstrip would give us some data.

I've been questioning this also.

Originally Posted by Jay S

Could be the converter isn’t holding it either. The 200R4 should spin the tires hard coming out of first gear with its bigger ratio jump going into second. If it can’t do that, something could be wrong in the converter.

I questioned this too so that was part of the reason I bought the newer convertor from another brand. Both have less than a few thousand miles on them.

Originally Posted by Stan Weiss

I assume when you degree the cam you used a degree and found true TDC and zeroed everything. Have you done the same thing with your timing marks, made sure they show zero at true TDC?

Stan

Affirmative. I used a piston stop to find the middle. The new balancer was actually off by 4 degrees so marked a new TDC mark.

[Jay S]

I personally would not spend any time tuning a 600 Holley vac for this, and I would not recommend that series carb for a first effort carb tune either. If you have thoughts that you want more cubes in the future, it is one more reason to start with a different carburetor that is a bit larger, calibrated closer and easier to tune for these applications. I can’t say that the other guys are wrong with wanting to use smaller carbs on a 350, but I personally don’t have anything smaller than a 750 on any of my smaller engines.

Many converters are made by larger companies and resold thru different vendors under different names.

With the compression the engine pumps, it should at least run good at the lower RPMs below 4000 even with fairly significant cylinder and ring wear. Moving the cam timing around 8* with not a lot of change in how the engine performs suggests there is another troublesome issue someplace that is yet to be found. Bore taper can knock a bunch of top end HP off, but I would expect it could still perform decent at lower RPM’s. A leak down test is a starting place, but mostly it is just going to tell you what you already know (that it isn’t a new engine anymore).

[Schurkey]

Originally Posted by ericwoo

I bought a cheap leakdown tester but as others say, they can't be trusted.

It's not that they can't be trusted.

The problem is that the results need interpretation that only comes from testing known-good engines of similar bore diameter, OR using a "master orifice"--a calibrated leak of similar volume to a borderline-high-leakage "good" cylinder. In other words, the maximum allowable leakage.

Either method gives you a leakdown number on YOUR leakdown tester that you can compare results to when testing an unknown engine.

[Formulas]

" Thanks guys, I will look into modifying the carb. I may pick up a book on that since I am not knowledgeable on that. Was hoping I could buy a carb that gets it at least in the ballpark area. "

I wouldn't worry about buying a book, All the information you need is already at your finger tips, Also no book or web site can tell you exactly what size to make any given calibration point you will only get ball park information, ...
The gem in a internet search will be where the calibrations are at in a carb and where in a engines operating range they effect, ...
Key search words,

Air bleeds high speed low speed HSAB / LSAB kind of need an AFR meter. for them,

Bypass air and effect on transfer slot exposure,

Idle fuel restriction = IFR. Holley carbs did this high and low points in a metering block mainly effects idle and off idle transfer slot richness, Low IFR more easily to tune thus more desirable... Your 600 is most likely a the high point

PVCR restriction points and effect..

Acell pump cams and nozzles.

Transfer slot restrictor in some cases for aftermarket carbs with big slots.

Of course main jetting

Fundamental to have a steady good fuel pressure and float height from the get go

Im sure i left something out but this will give you a start

[chiphead]

Here's the thing. A carb that is too small should provide really good response at low RPM then start to be a restriction at high RPM. Heck, I disconnected the secondaries on my 750DP for tuning, and the car didn't slow down until over 3500 RPM.

But what the OP is reporting is the opposite. It's sluggish at low RPM and then starts pulling hard from 3500-5000.

What does this tell us? If you do the fishbone diagram of contribution, you'd get the list below

Carb related:
Idle circuit too rich or lean before mains start at 2500 RPM (typical pullover RPM for holley)
Too weak a secondary diaphram spring (will cause a big BOG when secondaries come open too early)
Primary float height way off
Improper gasket or assembly?

Intake
Too much plenum volume or insufficient port velocity?

Heads
large runners result in insufficient port velocity at lower RPM
Improper compression for engine size and camshaft (too high or low)

Timing:
Too little base timing or timing coming in too slow? Should hear/see detonation if timing is coming in too fast.

Valvetrain:
Cam installed retarded or too tight valve adjustment
Camshaft duration too large for application

Transmission:
TV cable adjustment issue
Internal tranny failure, starting in 2nd or dragging
Torque converter insufficient stall speed
Torque converter clutch engaged/dragging in low gear

Rear end
Insufficient gear ratio
brakes dragging

[NeighborsComplaint]

If advancing the cam didn't make a night and day difference, then you have created an engine with "lazy port flow due to small displacement, huge intake runners and ports. In a high winding small block Chevy, steep rear gears offset the loss of low-end torque by getting the engine into the power band faster and utilizing the engine's higher RPM power potential (6500-7,000RPM).

This "Chevy Pattern" doesn't work on a Pontiac 350 which shares same stroke as the 400/455. The 455's displacement results in better volumetric efficiency at lower RPM due to displacement but is RPM-limited even with forged internals. The 350 displacement has lower volumetric efficiency despite the longer stroke and the same long stroke RPM limitations. Adding large cross-sectional intake runners and bigger ports results in lazy port flow and loss of power production at low to mid-range RPMs further exacerbated by increased camshaft overlap. In effect, you have created a 450HP capable Chevy Small-block with a 5,000RPM redline. The low end power loss isn't offset by upper register power production due to the RPM limitations.

My gut says go "back" to a stock or Performer intake, #48 /#18 heads and an #067 /#068 cam combination transfer the intake and heads you have to a 400 shortblock for better torque production and resulting street performance.

[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.

[Squidward]

Originally Posted by Formulajones

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 feel ya. I don't want to spend any more of the OP's money speculating wildly. I just know that my cam a few degrees smaller than his ran a 14.0. And his KRE heads are no doubt better than my mildly ported iron heads. I'm a fan of what he is trying to do, just out of answers besides stuffing a Summit 2801 in it, which is what I would do at this point.