Thread: Rebuilt engine will not run

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I rebuilt a 62-327 block and the internal parts are new. The heads are cast 202/160(?) breathing through Hooker headers and 2 1/2" pipe. On top is a Edelbrook manifold with a Holley 650 duel feed line dbl pump. The disitributor is 63 ventage with Mallory elcetronic guts and a stock coil. The 62 block has a hole for the crank case vent tube/road draft tube. I placed a plug in the hole when I preped the block for rebuilding. A PCV is on the right valve cover and feed into the intake manifold. The other valve cover has a breather filter. Crank and cam timing were set by the rebuild shop. Timing is set at 12 degrees BTDC.
Symptoms: Engine runs rough for approx 5-8 min when first started and after warming up she will stall. Bottom line is, the motor does not run smooth and stalls after being warmed up.

I'm having similar problems with a sbc that I rebuilt so my advice may not be worth much.
I don't think you should be using a breather with a pcv valve. It should be a closed system. Try plugging the hole in the intake where the pcv goes in or plug the hole in the rocker cover where the breather is.
If that doesn't help I would pull the distributor and replace it with a HEI unit. If that makes it run smooth you can rebuild the old dist and put it back. It may be the original 63 distributor bushings or the gear are worn out. If it runs the same with HEI you'll at least know it's not the dist causing the problem.
There are some guys on here who know a lot more than I do about troubleshooting an engine so they may have more advice when they check in.

The manifold is a edlebrook performer/duel plane. the pcv enters the manifold on the backside of the runner going to the right rear side of the motor. the holley is new and it sits on a 1/2" spacer. the rear plug at the base of the carb is vac and it is pluged into the brake booster. the tube on the rightside of the carb is a vac line for the distributor advance. i have not been able to ck for vac leaks as i'm in the desert in kuwait/army sand warrior. the motor was just put together and i don't want to send it back to the shop because they have not got it right over several attempts/they're done!

I would switch your PCV and Power brake vacuum lines. The PCV should go to the carb and the brake booster to the manifold. You do need a breather on the opposite valve cover. Some factory cars have a breather tube running up to the air cleaner, but they serve the same purpose. If you are sucking air out of the crank case through the PCV, you need to let it in somewhere.

What sort of choke set up do you have, and what fuel pump?

I agree with those who suggested you check for vacuum leaks. Just for test purposes you can try plugging the vacuum ports to the brake and PCV to see if that makes a difference. I would do one at a time so you know which one makes a difference, if any.

When you say it stalls, does it just quit running as it idles, or does it stall when you open the throttle?

Pat

THE CHOKE IS MANUAL AND THE FUEL PUMP IS NEW, A MANUAL HIGH FLOW HOLLEY FUEL PUMP. I DON'T KN THE FOWL RATE, BUT IT IS ONE STEP BETTER THAN THE STOCK PUMP. I HAVE PRESURE GAUGE ON THE FUEL LINE NOW, I DON'T REMEMBER THE PRESURE READING, BUT IS CORRECT.
AS I DROVE THE CAR,THE MOTOR WAS HOLDING BACK. WHEN I STOPPED THE ENGINE DIED. IT STARTED UP AND AGAIN IT FELT LIKE IT WAS HOLDING BACK. WHEN I STOPPPED THE SECOND TIME IT STALLED.

Originally posted by Stu Cool
I would switch your PCV and Power brake vacuum lines. The PCV should go to the carb and the brake booster to the manifold. You do need a breather on the opposite valve cover. Some factory cars have a breather tube running up to the air cleaner, but they serve the same purpose. If you are sucking air out of the crank case through the PCV, you need to let it in somewhere.

Pat

I agree with switching the pcv and power brake lines Pat but not on the breather. The pvc relieves the pressure created by blowby. If you have a plugged pcv valve on a sbc it will blow out the front or rear intake gasket. That can't happen if you have a breather. The breather would vent the blowby into the atmosphere and that's what the pcv is supposed to eliminate.

Al, on the PCV - Breather. This is how I understand and envision it. The PCV system Positive Crankcase Ventilation, is set up to relieve pressure in the crank case as you said. It replaced the old road draft tubes that use to just vent into the atmosphere. The idea was to pull any blow by into the motor to be burned in the normal combustion process, but I am sure you know that.

The system creates a suction at one point in the crank case, usually a valve cover, but I have seen them in valley covers and other locations too. This connection is sucking air out of the crank case, in order for it to work effectively you need to let air into the crank case some place else, usually in an opposite valve cover to create a cross flow of air through the crank case. The breather is designed to let air into the motor, not vent it out. If you look at most stock air cleaners, they have either a metal tube or a hose that goes to a valve cover. Inside the air cleaner is a small filter right where that tube connects. That filter is to clean the air being pulled into the crank case. On aftermarket air filtration systems the need still exists to let air into the crank case so people put a breather on the opposite side from the PCV connection. I hope I have explained this correctly, if not please refer to my signature line

Pat

I may be all wet (been known to happen), but I think even after correcting the PCV and brake booster connections you might still have the same problem. Sounds like to me that you have a leak either in the hose going to the booster or the booster itself has a Vacuum leak. JMO.
p.s. Should be easy to check. Pull the Hose and plug the fitting. If it runs then, back track the hose and if no leaks, you'll need to replace the booster.

Check out this picture of an open system (breather on the valve cover) and a closed system (breather inside the air cleaner). Also check out the reference material here:

http://64.78.42.182/sweethaven/MechT...Num=4&modNum=6

They explain it much better than I can.

Pat

Originally posted by csf03716
oh the endless possibilities....by chance, do we have a situation where there is insufficient vacumm based on too much cam shaft?......it gets better every post!

Yeah, Charlie, and he can't even trouble shoot this til he gets back from the Giant Sandbox. I base my answer on a problem I had years ago with the same exact symptoms as he has described. But that doesn't mean that that is the answer for sure.

I don't think this pcv debate is helping 1warrior solve his problem. I may be wrong. I disqualified myself as an expert in the first line of my reply.
I know that a stock Chevy has an oil filler that screws on like a radiator cap and it has a gasket to keep it from drawing in air. Taking the cover off while it's running will change the idle speed but probably not cause it to run rough.
I just thought it was the easiest thing to check first as it doesn't require any tools to check it.
He does have the power brake and pcv reversed. perhaps taking them both off and plugging them with his thumbs will eliminate both of these things as the culprit.

Why is it that so many things can go wrong to make an engine run worse but I don't know of anything that can go wrong and make it run better?

I could go on forever but I have to go beat a dead horse.

Originally posted by Stu Cool
Check out this picture of an open system (breather on the valve cover) and a closed system (breather inside the air cleaner). Also check out the reference material here:

http://64.78.42.182/sweethaven/MechT...Num=4&modNum=6

They explain it much better than I can.

Pat

i agree with you on the pcv systems stu. im glade you came up with those diagrams.

I had a Problem like this once with a rebuilt Exchange motor.
They did'nt Pre-pump up the hydraulic lifters and snugged the rockers down. Need I say the the car would start, run ruff then
die. I did this a couple of times then pulled the valve covers to find three bent push rods.


~ Vegas ~

I guess you could say that. Just the same the new motor was broke and would'nt run, just glad it did'nt flatten any of the cam lobes.

~ Vegas ~

Dang I'm really glad that did'nt happen to it.

~ Vegas ~