What am I doing wrong to get decent power out of a 350?
 

I've spent countless hours researching online over the past year and several thousands on parts and my car is still kind of sluggish IMO.

I have a hard time seeing my 350 producing much more than 300 horsepower. The below is what is on it:

• original stock block with 65,000 miles
• Crower 60916 camshaft with hydraulic lifters
• Kaufmann KRE 65 cc D-port heads- they are supposed to be milled down further to get compression around 10.1-10.5 but I never confirmed it was actually done. Valves are 2.00/1.66
  
• 1.65 roller rockers
• Edelbrock RPM Performer intake manifold
• Hooker headers with 2.5" Pypes exhaust system
• 600 cfm double barrel Holley carb (I tried putting a 750 double pumper and it was bogging down the engine)

Any idea of what I can look at that may be wrong with this set up? Or what upgrade I should do to get this thing to over 350 horsepower?

I was expecting some decent power but boy this thing is kind of a dog. I have a hard time seeing it do less than 15 seconds in the quarter mile but I haven't tested yet. When I asked Kaufmann what kind of power he thinks it can produce, he said I may be around 375-400 hp.

Glad to see you are giving it a run. You have a build that on paper sounds similar but better than mine.

Cam: your 60916 is just a couple more degrees more than my 10510702 Voodoo cam, same LSA. The lift is slightly less than mine, but very close.

Heads: your KRE d ports undoubtedly flow better than my 2.11/177 mildly ported #12 iron heads.

I run FiTech for fuel system. It's likely not faster than a Holley, but might be easier to tune.

What is your ignition setup and timing curve?

My best et was 14.04 with awful air and embarrassing 60 foot times. I think mph was something in the 100 ballpark. This was during my last track trip years ago, where I had just got into data logging my runs and adjusting afr settings for best et/mph. I have no problem admitting I suck as a driver. But I have no doubt I could've had 13's.

The rest of the package was th350, 2000 stall converter (more stall would've helped), and 3.73 in a 1st gen. Stall and gears with a cammed up 350 really helps. The power band really comes in above 2000 rpm.


As a point of reference, I broke out of the 15's with a 69 350, stock 47 heads, Summit 2800 cam, same trans/2k converter, and 3.23 gears. I can't remember if I was running a qjet or Holley then.

The point of telling you what I ran is not to peacock on my setup, but that I think you are selling yourself short, or something is off in your tune. I am really not that good at this compared to many people.

Dare to be different! Btw, welcome, congrats on post #1.

Have you done a cranking compression test? If so what are see seeing.

Stan

As was mentioned above, steeper rear gear and some stall will allow the engine to perform in its power band. Start with ignition curve and timing. Most aftermarket camshafts require 16 to 18 degrees initial as a starting point. Then knowing your timing advances coming all in at specific RPM allows for fine tuning. Example: 36 total all in by 2,800 RPMS……

Several things are wrong with your combo!
1)
The larger port volume of those aftermarket heads or any of the available aftermarket heads only serves to harm throttle response and torque in your CID motor below 4000 rpm.

2)
You want more then 300 hp you say, well stock heads are more then capable of producing that along as a stated above. Producing superior throttle response.
You only need 175 cfm@28” to make over 350 hp.

Good port velocity in the motors average rpm range is just as important or more then cfm if the motor will not run above 5500 rpm.

3) your choice of intake manifold is harming the motors power production just like your choice of heads is.

4) if your cam is not producing at least 175 to 180 psi of cranking compression then that’s a issue also and a big issue at that!

In short and in my opinion everything you have bolted on above the deck of the block is fully counter productive to your stated goals.

I agree do this. Engine should work pretty well. What gearing convertor and weight of car?

Cliff always said that the Crower cams always need 4 to 6 degrees advance to get to correct 108 or 109 centerline. If its retarded it will be sluggish.https://forums.maxperformanceinc.com...ighlight=60916

HP is in the heads,start there.Tom

In the Nov 2000 issue of muscle car review a stock rebuilt RA3 400 fitted with long branch Firebird exhaust manifolds and the 068 cam was dyno tuned on race fuel ( just to be safe ) to 368 hp @4700 rpm and 448 ft @ 3500 rpm.

So you should have no problem making 350 hp with stock heads with your 354 cid motor if your cylinder pressure is up where it should be.

Which 600 and 750 Holley’s were you running? We have had a lot of trouble with new Holley stuff make decent power without an extraordinarily amount of tuning. OTB they have been 50 HP short of a well prepped carb. I can’t imagine a newer 600 DP running well at all on that combo without and insane amount of tuning. The bogging on the 750 DP is easily fixable. It could also be a sign you have some issues with the timing and carb tuning.

This….the 2802 cam dirt motor 350 took 8* to get it to a 108-109.

The smaller the cubic inch in any engine brand the more you have to rely on the RPM factor to make HP / Speed ... The 350 Pontiac spent most of its life in fuel mileage and emissions era... So they were paired with bad rear gear ratios, low compression and old school transmission tech a;; of which are counter productive to fun..

I always find it funny how every Pontiac guy will admit our stock head flow suxx but the minute you bolt on a flowing head OMG that's not the way to go

To have fun with a smaller N/A engine you have to make it easy and in a short time to get from idle to a productive torque output

A 462 engine is a no brainer with its almost linear torque curve

That cam isn't really that big but in a 350 it will noticeably soften the off idle response and while the engine is loafing around trying to get out if its way the clock is ticking

I will try to check that this week and report back

I've adjusted the timing probably several dozen times by testing and never really seen a huge difference in performance with adjustments. Right now I believe I set it around 15 degrees initial and around 32-36 full around 3,000 rpm.

The 600 is a Holley Model 4160 vac secondary. The carb was rebuilt because it was dumping fuel in it and running rich. I put a lighter vac spring and really doesnt seem much faster.

This is very helpful. It was installed dot to dot. I am not an advanced engine builder and really only know the very basics. I believe I can take the timing cover off with the engine block in the car and check this

The gearing is 3.55 in a 68 firebird which I believe is around 3,300 lbs. It has a 200-4r transmission. I had a TCI saturday night special convertor (1,600-2,000 Stall) but just changed it to a TSI Race convertor (2,800-3,200) this weekend. It performs a little better but still not an impressive improvement for the time put into it.

I could be selling myself short and plan on seeing what the 1/4 mile time will be at the track this summer. This is very helpful and gives me a reference to see if I am matching up. Part of me wonders if I am just use to the low end torque when I built a 302 67 mercury cougar- that seemed to perform a lot better than this 350 engine which has a mid to upper power band camshaft. However, I've read that pontiac 350s are suppose to have a lot of torque so that has me scratching my head.

What transmission, torque converter and rear gears does it have?

Interesting. I appreciate the numbers for me to check. I was wondering if I should change out the intake manifold from the RPM Performer to the standard Performer. I read that somewhere online and then another place said to go with the RPM :confused:

The heads were a little bit of an investment so I would like to see if I can get those to work. I thought about taking them off to port them but you're suggesting I should definitely not do that?

I kinda get the impression that the engine isn't really flowing well. I did recently stumble on the suggestion of checking the pushrod length and that if they are too short, the valves won't open to its full potential. I do not believe I checked that and hope to get to that today.

200-4r with TSI race 2,800-3,200 stall. Correct me if I am wrong- I believe that means small blocks like mine would stall around the lower end of 2,800.

Rear gears are 3.55

The standard performer can make well over 400 hp with superior drivability up to 5500.

Here are Edekbrocks own recommendations for there intakes and as you can see the performer rpm has a power band of 4500 to 6000 rpm.

If your motor is not Camed and you do not have a converter to flash up to 4000 rpm then you have simply put yourself behind the 8 ball.

Don’t advance the cam until you have done an across the board compression test so you have a base line to refer to .

To save yourself a mess jack up the ass end of the car after you have drained the rad and before you pull off the lower hose.
This will get the water level in the block below the water pump holes and keep coolant out of the nose of the pan.

This is easier then removing the 1/8” pipe plugs each lower side of the block when you have headers.

The motor has the same stroke as a 400 and is only a mire 13% less in total CID.
I had a 350 in a 4 door Tempest with a 2 speed trans.and 2.93 gears.

Once I put on a stock 70 intake and carb , stuffed in a used 067 Cam and swapped out the Super Turbin 300 for a TB 350 I was very pleased with what it had for low speed power and mid range power up to 4000 rpm.

Basically your motor is suffering from too little power in too narrow of a rpm band.

That all sounds great! Who assembled the top end, installed/degreed cam, determined pushrod length, etc? As mentioned already, hopefully a compression test (engine hot) will shed some light on dynamic compression. No sense in pulling anything apart until you've done some testing. A factory 68-72 iron intake should be better than the RPM in your combination, but even so, at high RPMs that engine should be screaming. What does the fuel system consist of? fuel line size, mechanical pump, etc?

Here’s another opinion but since you’ve asked for things to check….
Personally I’ve never ever owned or seen a vacuum secondary Holley carb that would fully open on at WOT. Put a small screw and nut in the slotted secondary linkage and go drive it. I didn’t realize the cam specs until I looked it up. The cam, heads, and intake would work well on a 400. It’s just too much for a street 350.