Thread: Need some small block help

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In a nutshell:

I'm working with an 86' Pontiac Pariesienne, originally equipped with a carbureted 305. This motor packed it in (jumped timing chain, rear main leak) so rather than repair I went and bought a GM crate motor P/N 12499529. I also bought an eledbrock 3701 performer intake. I've re-used the stock rochester Q-jet carb from the original 305. I transferred all the pulleys, fuel pump, etc installed the new motor went to start it up and it will start then die. If I hold the throttle so the motor starts and revs at 1500rpm or higher it will keep running, as soon as I let off the throttle it will come down past 1500 and shut down. When it's running I can hear what sounds like a belt squeaking sound, but it seems to be coming from the rear passenger side of the engine. (Hard to pinpoint location of sound) I have found tdc re-wired the distributor about 4 times now but each time it dosen't make a change. I've got new plugs, new cap rotor and coil. I've tried another Q-jet carb from a running engine and it has the same problem, making me suspect an issue with the intake. I went to try using the stock 305 intake from the old motor, but I found the exhaust crossover is completley carboned solid and I don't know if it's a good idea to use this intake in the condition. Does anyone have any ideas?

Not familiar with that part number. Is it a roller cam motor? If not, how did you break it in?

Don

It's hydraulic lifter cam. I have only had it running for about 10 minutes total on the driveway, trying to get it to idle. So no break in time to speak of.

This is a GM crate replacement 290hp, flat tappet motor used as a standard replacement. It's a great choice and should run well and give you a lot of trouble free miles.

I suspect you have a vacuum leak - might be the squealing sound. How did you install the intake? The Performer is a good choice but must seal well. I use gaskets on the sides - with Gasgacinch on both sides. With Edelbrock manifolds, you must use RTV high temperature silicone sealer instead of gaskets. Apply a 1/4" thick ribbon of sealant across each end seal surface set the manifold straight down and work quickly to get the bolts in working in a zig-zag pattern across the manifold and torque to 12-15 pounds.

Good Luck,
Glenn

Sure does sound like a vac leak.Tell ya what.Get someone to start it and keep it running.Spray that of the intake with carb cleaner and if you see it raise in RPM,you have a leak.

Here is my concern and the reason I asked about the engine. If it is a flat tappet hydraulic lifter motor it needs to have the cam broken in the right way. The right way is not to start it and let it idle, you need to run it at 2000 rpms or so for at least 20 minutes and add some zinc additive to the oil or you run the risk of wiping out a cam lobe. Even with those measures lots of cams still get wiped.

That squealing might not be a simple vacuum leak, but something mechanical inside from not breaking it in the right way. I'll also bet it was never prelubed before start up.

Don

I took the advice and removed the intake, went out and bought the proper edelbrock intake gaskets and gasgacinch glue. I scraped and degreased the heads, and ends of the block plenum. Applied gasgacinch and the edelbrock intake gaskets to the heads, and 1/4" of black rtv to the cast plenum ends. I overlapped 5/8" up the intake gasket on each corner, quickly laid the intake and torqued in the proper order each bolt to 20 ft lbs.

I installed everything ontop of the intake and let it sit about 15 hours to dry/seal up. I started the motor, this time it seemed to run much smoother over 1500rpm, it almost sounds normal, it will start to come down to idle but now when it drops past 1000 it seems to just die, it wants to go, it will puff and cough as it's dying, then just shut off. I checked my idle mixture screws on the rocherster q-jet and I found them turned out almost 8x. I read online to turn them in all the way gently, and begin calibration at 1 1/2 turns out. So thats where I am at.. also very frustrated. HALP!!!!

I think you're headed in the right direction. Turn out 1-1/2 turns and see what you get. I know this may sound silly, but are all of the vacuum hoses hooked up? There are typically three vacuum ports at the base (in the front) of the carb - all must be hooked up or plugged.

I removed the edelbrock, hot tanked the original cast 305 intake from the dead motor. Installed it with new gaskets, put it all back together and tried again. Same problem. I researched breaking in this engine and standard method is to start it and hold it at 2000 rpm for 25-30 minutes. This is going to drive my neighbors crazy so I am going to do it tomorrow just before lunch when most of them are at work. I will then mess around with the idle mix screws and see if the break in made any major differences.

What do you have the timing set at? Should have a light on it that will read the degrees of advance when you do the cam break in run... For the run in, at 2500 RPM the timing should be around 28 to 34 degrees total. At 2500, all the vacuum advance and most if not all of the mechanical advance should be in so you will be reading total advance. Timing needs to be close during the run in so that you don't overheat the engine... As Don mentioned, you also need to have a zinc additive in your oil!!!!

i would not have recommended reusing the mechanical fuel pump! wouldnt be bad ideal to check mechanical advancer. adjust both mix screws the same. and if its automatic check the vacum line on the transmission it may need replacing

Originally Posted by Itoldyouso

Here is my concern and the reason I asked about the engine. If it is a flat tappet hydraulic lifter motor it needs to have the cam broken in the right way. The right way is not to start it and let it idle, you need to run it at 2000 rpms or so for at least 20 minutes and add some zinc additive to the oil or you run the risk of wiping out a cam lobe. Even with those measures lots of cams still get wiped.

That squealing might not be a simple vacuum leak, but something mechanical inside from not breaking it in the right way. I'll also bet it was never prelubed before start up.

Don

Yep , My thoughts too Don , Don't let the motor idle at all , until the cam is run in !

1986 ? that would be a computer controlled quadrajet. Not a problem as long as you have all the sensors,wires and grounds in place. If not it'll never run right.
If you don't have everything in place and set up as it came from the factory and if you don't have the knowlege to set it up like it should be,then you need to find a pre 1980 distributer and carb.

I'm still at it.. I've been through 6 new carburetors from my poor local Lordco store. Each and every Rochester rebuild I've gotten from them has had some sort of rebuild defect be it a leak, missing part, or improper assmbly. I have now got the car to the point where it starts and runs well, very well infact, but I'm down to an idle problem. If I don't have the idle turned up a good amount, when you put the car into gear, the engine bogs and dies. When I turn up the idle to the point where the engine won't bog and die, it lurches into gear and you really have to hold the brake down to keep it from rolling away. I have to find the happy medium here. What should I do?

Not sure it would have to be a carb issue... As Howard mentioned months ago, if the car still has the computer controls for the carb in place then everything else in that system has to be correct.... Howard is a lot more knowledgeable on that stuff then me, I've never had good luck with that system and usually done away with it and either gone back to a regular carb or gone to a more modern EFI system. These in-between years when cars had the partial electronic controls and hadn't quite progressed to electronic systems that work quite well have always been "problem children" for me!!!!