97 grand prix head gasket job

[Fishbo]

i just replaced head gaskets and intake gaskets on my 97 3.1 L. it now wont start easy and back fires out the intake line above throttle lever while cranking over . when it starts it barely runs. what could it be? ive put new plugs and wires on it too.

[Mickey#1]

Double check that all the spark plug wires are connected to the correct coils.

[Fishbo]

did that when i put new wires on. im going to do a compression test this after noon just to check cause this car ran great before i took it apart. it just pushed antifreeze. thanks for the help

[Mickey#1]

Compression check was going to be my next suggestion. Are the intake & exhaust push rods the same length on the 3.1?

[Fishbo]

i hope so cause i didnt really pay too close to that when i put it together i just tried to lay them out in order i took them off and return them to same spots when i put them on, but one fell on floor and i didnt know which spot it fell from.

[Mickey#1]

I changed the LIM gaskets on my daughter's 3.1 Lumina a couple years ago & thought they were different but wasn't 100% sure. I just looked them up on Rockauto and the exhaust pushrods are over .300 longer than the intakes. You may have bent some valves if they're mixed up.

[Fishbo]

Thanks alot I'll check on that

[tblake]

Yep in GM's infinite wisdom, they made the exhaust pushrods longer than the intakes on the 3100. Good motor, bad design. I also do not like how the pushrods on these motors aren't 100% parallel with the lifters. Seems like whenever these motors are cold started there is some valvetrain noise untill it gets warmed up. Only reason I can think of is how the pushrod is seated on the lifter as the noise.

When you first started your motor, did it knock? I have a feeling one or more of your lifters are pumped up causing it to hold the valves open. This has happened to me once and I just left it sit for a while and started it later. I have heard of guys even haveing to pull the valve covers off, start the motor, loosen the rocker arm bolts on the lifters that are pumped up as the motor runs, and then slowly tighten them untill they bleed some oil off.

In your case though since you said you dropped a pushrod, I would run a compression test, find the bad cylinders, and make sure the pushrods are in the right spot.

When I have to replace LIM gaskets or anytime I have the pushrods out of this motor, Before I start it, I will put a socket on the crank pully and turn the motor over a few times slowly by hand just to feel for any contact between the pistons and valves. Even though I always make sure the pushrods go back into their exact same spots, anything can happen.

[Fishbo]

yeah it only ran for 30 seconds or so but knocked a little. i thought i had a couple of collapsed lifters but id bet i swapped a couple of pushrods. that sucks but i cant see it being anything else. would that cause it to backfire when cranking it over?

[Fishbo]

o.k. i checked the pushrods and i had 2 mixed up. so that was the problem. thanks everyone for the help.

[tblake]

Nice job!

[Mickey#1]

Is it running?