Thread: chevy 350 build problems

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Would appreciate intelligent input regarding ongoing problems after allowing 2, yes 2 engine shops to rebuild engine in the last 6 years.
Ongoing problems have included mismatched timing and carb setup with tuning an everyday task with no end to driveability issues. Have had so many "experts" advise me what to do that I am ready for a create engine replacement to end this saga. Am told that with the cam I have the ign. timing should be between 12-14 deg and an idle of 1000-1100 rpm. Using 91 grade fuel. If I retard timing to 10-12 deg idle speed is so low around 450-500 rpm the negine stumbles all over the place. If I advance idle speed I get preignition and run on after engine shutdown. I still have light pinging at moderate acceleration. Vacuum is direct to manifold. If I connect to timed carb port forget it the whole car is all over the place at idle. Main complaint is the lack of overall performance. After last engine rebuild was told the transmission should be changed to 700R4 which I did at trans performance shop. No problem with the trans but no improvement in performance. Next I was told to change out the cruiser rear end from the 2.29 to a 3.42 which I did. Still no improvement in performance. DO I just have a dog or what. Hate to have to spend out on engine again.
Wonder if the cam is the wrong type for a street car it's calssed as a bracket racer cam. Most driving rpm range is from idle to around 2500 rpm unless you floor it for get up and go. Am looking for a strictly street car, NO RACING, but one which goes when it should, especially from a standing start. Currently I can run faster myself. I also notice there seems to be unburnt fuel coming out of the exhaust with the smell. No idea what's causing that. I NEED INFORMATION, CREDIBLE ADVICE and HELP, or a NEW CRATE ENGINE.

chev 350 block
OE iron chevy heads
J&E forged pistons
Lunati cam 2000-5500 rpm
Edelbrock intake
Edelbrock carb
dual exhaust with cats

I'll give you some info, but you'll need more I'm sure.

First, find a new way of meeting and evaluating "mechanics". Anyone who would suggest a trans change or a rear gear change to correct an engine operating problem is clueless.

Second, by your own description you usually operated in the 0 - 2500 range, but the Lunati cam you listed is intended for 2000 - 5500. I'd say you are definitely over cammed, which is probably contributing to a vacuum problem, which will affect your advance. Those things may be what's contributing to pinging, I doubt you're having preignition. The run on is probably caused because the idle linkage screw is in too far leaving the butterflys slightly open at shut down. Cam specs would be helpful, e.g. duration, overlap, etc.

Third, if you're getting rich fuel condition out the tail pipe your cats are wasted. Since it sounds like you've been wrassling with this for some time, they've probably been overwhelmed with HC and are spent. Could be your carb is set up wrong, but with the other issues you need to approach this one problem at a time and avoid the "change everything" approach. (similar to the trans and gear thing).

A little more info is probably required to diagnose your problems:

Type of car
compression ratio
Valve size on heads
Specs on cam (lift and duration) and wether cam is straight
up or advanced/retarded.
Which Edelbrock intake
Which edelbrock carb (CFM)
What ignition system are you using

Originally posted by ROC
Would appreciate intelligent input regarding ongoing problems after allowing 2, yes 2 engine shops to rebuild engine in the last 6 years.
Ongoing problems have included mismatched timing and carb setup with tuning an everyday task with no end to driveability issues. Have had so many "experts" advise me what to do that I am ready for a create engine replacement to end this saga. Am told that with the cam I have the ign. timing should be between 12-14 deg and an idle of 1000-1100 rpm. Using 91 grade fuel. If I retard timing to 10-12 deg idle speed is so low around 450-500 rpm the negine stumbles all over the place. If I advance idle speed I get preignition and run on after engine shutdown. I still have light pinging at moderate acceleration. Vacuum is direct to manifold. If I connect to timed carb port forget it the whole car is all over the place at idle. Main complaint is the lack of overall performance. After last engine rebuild was told the transmission should be changed to 700R4 which I did at trans performance shop. No problem with the trans but no improvement in performance. Next I was told to change out the cruiser rear end from the 2.29 to a 3.42 which I did. Still no improvement in performance. DO I just have a dog or what. Hate to have to spend out on engine again.
Wonder if the cam is the wrong type for a street car it's calssed as a bracket racer cam. Most driving rpm range is from idle to around 2500 rpm unless you floor it for get up and go. Am looking for a strictly street car, NO RACING, but one which goes when it should, especially from a standing start. Currently I can run faster myself. I also notice there seems to be unburnt fuel coming out of the exhaust with the smell. No idea what's causing that. I NEED INFORMATION, CREDIBLE ADVICE and HELP, or a NEW CRATE ENGINE.

chev 350 block
OE iron chevy heads
J&E forged pistons
Lunati cam 2000-5500 rpm
Edelbrock intake
Edelbrock carb
dual exhaust with cats

ROC, I'm going to post your email to me here for all to view in an effort to get you as much exposure to the informed minds here as possible. Mike had a couple specific questions you should try to get the answers to to help reply to these latest questions. The kinds of heads you currently have may help fill in the blanks. If you don't know exactly (other than the iron part) get a casting number from the heads (make sure both are the same too). Your objective of 300 hp is not unrealistic, just takes the right combo.

"Appreciate your response which sort of confirms what my suspicions were. I must be a glutton for punishment. Am a novice re most of the drivetrain components and their EFFECTIVE match between each other. I agree the first issue is with the cam as the car is normal street car driving range between idle (600 rpm) to approx 2500 rpm at highway cruising speed. Only time that high end goes up is flooring accelerator where it is reaches around 3500 rpm max shift point between 1st and 2nd gear.
Was also suspicious of the OE iron heads. If I changed out to loaded aluminum units can you advise on products? Am also concerned about the correlation of the distr. cam, weights and springs as contributing to the performance issue. Any thoughts on this or is it a waste of time for street car. Think that is where most confusion is. I want a street car but the shops must be advising on a race car.

Am searching for a power train that will provide me with minimum approx 300HP at the rear wheels with min of 300+ Lb ft of torque across flat band again for street/hway driving.

The following 2 cams I am considering using as replacement. Your comments please??? If I go with roller cam #2 what will it require as far as fundamental changes if any to heads etc??? What would you suggest?

Also is there a point at which you must go to HiPo drivetrain and use prem grade fuel 91/93, or is it still possible to get the numbers I want from a drivetrain using reg grade fuel 87.

Greatly appreciate your insight and help in directing me to where I should have been 6 years ago. Would it be worth my while to just dump the rebuild and invest in ZZ4 crate as all my friends with camaros have advised? Drop it in and go.
Will also check on cats. Fortunately the car no longer requires emissions testing so I could dispense with these altogether.

Thanks again.

Extreme Energy Hydraulic Flat Tappet---Recommended

RPM Operating Range
1300-5600
Duration Adv. at .50"
In Ex In Ex
262 270 218 224
Valve Lift Lobe
1.5" rocker Separation
In Ex Angle
462 .469 110 deg

ROLLER CAM
RPM Operating Range
1600-5400
Duration Adv. at .50"
In Ex In Ex
270 276 218 224

Valve Lift Lobe
1.5" rocker Separation
In Ex Angle
495 .502 110 deg


CURRENT LUNATI CAM
Duration @ .50 ins Advertised Duration
224 deg 290 deg
224 deg 290 deg

Open/close @ .050 ins Gross Valve Lift
04 deg
BTC
40 deg .460 ins
ABC .460 ins
48 deg
BBC
04 deg
BTC
Lobe Separation Valve Lash Adj.
112 deg .000 ins INT
.000 ins EXH


LUNATI advised me that the 112 deg would provide plenty of vacuume even for power brakes."

Well i also ran into so many problems with my motor i wanted to blow it up but i didnt, I had a slight bigger lunati cam the 515 lift one and had plenty of vacuum. I went with an even bigger cam and still have good vacuum. I doubt cam is ur problem, i would look elsewhere, maybe distributor, are ur weights kicking back all the way? i asked everybody and they all told me different things, a little sandpaper on the posts is all i needed so they kicked back. I would get rid of the cats too, no need. What kind of carb do u have, how built is this motor of urs? i also have iron heads with small valves and can pull off some good timeslips. How did u adjust ur valves? are they too loose?, too tight? bent pushrods? What kind of intake do u have? I think everyone will want more info on ur motor. It could be lots of things, is this a stock 350 with a cam change? I really think you need to share more.

I asked for more specific information because diagnosing a problem from distance is an iffy proposition at best.

Personally, it sounds like you have a mismatched engine parts combination (if you have been fighting this problem for 6 years, I suspect you have covered the simple basics several times by now).

The problem could be any number of things from compression ratio (to low?) to intake ( trying to use a single plane intake with large runners) to carb (too big/too small), to heads ( Chamber size producing too much/too little compression, extensively ported, too big or too small valve size), to carburator (too big/too small correctly jetted?) to cam (it has to match the rest of the componets, AND has to be timed properly) to exhaust (it sounds like that may be plugged, and I would correct that first before I did anything). You transmission and rear end ratio sound pretty good, but what is the stall speed on the converter, and does it match the RPM range on the engine.

If you have a mismatched combination and put a new engine in but use the same mismatched componets (i.e. intake, carb exhaust etc) you will have the same problems you have now.

Now personally, from the RPM range and type of driving you indicate you are doing I'd concentrate on torque and let the HP numbers take care of themselves.

The combination I'd recommend building is:

8.75 to 9.1 compression,
Stock 1.94 heads
Cam in the 4.50-4.80 lift range with around 2.80-2.90 duration
(flat tappet cam, maybe a littler hotter on a roller)
A free flowing exhaust (good rams horn type manifolds, or if going with headers no bigger than 1 5/8 primary tube size)
A dual plane intake with reasonably small runners and a carb in the 600-650 CFM range.
A stock HEI giving about 36 degree total advance at about 2800 RPM shoud be a good starting point for the iginition.


It's not a real glamorus combination of parts, but it is proven and works very well.

Heads: Edelbrock E-Tec or similar, in ALUMINUM - weights less and dissipated heat metter so you can run a bit more compression on pump gas. The Vortec style heads in aluminum would be great choise too. WIth alum heads you can do 10:1, with iron heads stay at 9:1.

Higher compression willl give more power and better throttle response.

dist timing: you can have your unist (or buy one done) that will have the total advance in by 2500 or 3000 RPM. 36 degrees is about right to start for TOTAL timing. You DO want a vac advance unit as you'll be on the street.

650 or 750 carb. 750 will give a bit more top end at the expense of bottom end. generally, vac secondaries with auto trans, mech sec with manual.

If you go vortec style heads your choice of intakes is somewhat limited, but will achieve your goal.

as to 300HP at teh rear wheels - pick your transmission carefully - you can lose as little as 25 HP with a manul ot powerglide, to nearly 80 HP with a TH400. 700R4 is a better choice than a TH350, but either on will need some work to hold up to 300HP if you beat on it much.

Originally posted by 71nova
Well i also ran into so many problems with my motor i wanted to blow it up but i didnt, I had a slight bigger lunati cam the 515 lift one and had plenty of vacuum. I went with an even bigger cam and still have good vacuum. I doubt cam is ur problem, i would look elsewhere, maybe distributor, are ur weights kicking back all the way? i asked everybody and they all told me different things, a little sandpaper on the posts is all i needed so they kicked back. I would get rid of the cats too, no need. What kind of carb do u have, how built is this motor of urs? i also have iron heads with small valves and can pull off some good timeslips. How did u adjust ur valves? are they too loose?, too tight? bent pushrods? What kind of intake do u have? I think everyone will want more info on ur motor. It could be lots of things, is this a stock 350 with a cam change? I really think you need to share more.

Thanks to all so far who have given advice. Most of the specs I have posted as responses to Mike P. I think I know where the biggest problems lie and your inputs have basically confirmed this. Last engine job was done while I was living in N. Carolina. Thought I was in the home of performance and engine specialists. Was I wrong.

I know of quick fixes to distr. weights and springs including slight reshaping of ears. Before I get there I think there are fundamental changes to be made. I cannot agree more in the statement that all components must match each other throughout the drive train to allow a cohesive peroformance objective to be met. I only wish the engine shops/machine shops knew this and advise their customers accordingly instead of sticking in anything that fits. I realize now I have a mismatch screwup of engine components fighting against each other. The car is no better now than the original 305/350turbo trans/2.29 rear end.

Will review info given by all parties to date but I must stress that I am looking for a performance street car. Should I stick with iron heads with lower comp. or replace with alum. to increase to around 10.1 as long as I am OK on prem fuel 91/93 oct.
For a street car the Lunati cam is no good. I listed 2 options in past response wonder if anyone has used either of the 2 described. The Lunati cam currently installed is not suitable for a street car. The iron heads are basic OE units. Have no idea if they were a matched pair will have to check.

If I go to roller cam would I have to replace heads with aluminum units or not?

Thanks to all. ROC