I just got my heads cam swap done today. This is what I put in as far as modifications go. Comp Cam 224/224/ 581/581 112 LSA, LSX 78 mm trottle body, SLP LT's No cats, Stock Ported and Polished Heads w/2.02 and 1.60. milled 10 thousandth Stock Length Pushrods. I started the car up. There was a valve train noise. Then the car shut down after about 30 seconds and will not start up. I eliminated the Air pump, EGR, and and cats. So I know the computer might be a little confused to top it off with the other modifications. I cannot get the car to start up anymore. The 3 back cylinders on the passenger side are getting spark but the rest aren't. The only thing I can think of since the heads are milled and I have the stock length pushrods I may have a case of valve/piston slap which may be sincing knock with the knock sensors then shutting down the engine to avoid anymore damage that may have already occured. Anybody's advice would be greatly appreciated.

 

Check the ground wires on the back of the heads.

 

does it still turn over....if so probably a bad oil pressure sending unit. It will allow the motor to run until is sees no oil pressure

 

The car has oil pressure. The ground wires on the back of the head are secure. I looked into the heads a little more and they were milled 25 thousandth. The car cranks over but will not fire.

 

Did you turned the motor over by hand to make sure nothing was binding before starting the car?

 

Yeah the motor was turned over by hand several times before actually firing the engine up. Nothing seemed to bind and everything seemed perfectly normal.

 

check compression, that will tell you if you bent some valves..

 

This is what scares me; you didn't know how much your heads were being milled! Milling the heads is a major modification, just like porting and polishing them. You should have known exactly how much the heads were going to be milled before you even decided on cam specs; I am sure others will agree with me. Not compensating enough milling the heads can easily make the decision of buying new shortblock a very easy one. Pull the heads back off and check for contact between the valves and pistons.

 

Speed Inc. told me that they use this heads/cam setup on alot of cars and they always use stock length pushrods. The guy who machined my heads told me not to go any higher then a 550 lift with as much as these heads are milled but he told me this after the fact. I think I'm going to put shorter pushrods in and check compression and I'll hope that I have compression and the shorter pushrods will fix the problem. Does anybody know if valve/piston slap will sence knock from the knock sensors?

 

dude,
Pull the heads back off and check them, go from there.

 

first things first.. don't go tearing the engine apart as suggested above... Check the compression.. It's going to be like sitting on the couch with your girlfriend, waiting on the pregnancy test results, but after you get it over with you'll feel much better. If you come up good on all the cylinders, at least you know you didn't tweak the valves. After that, it could be a simple as missed wiring connection, chafed wire, overlooked ground... If you come up ugly on a cylinder or two, tear down the front cover and see where you made your mistake. The heads are coming off at that point, but at least verify there is a problem with cylinder sealing before you go tearing engines down... some of the suggestions in here are fuggin frightening


People pretty frequently mess up the order of the wiring harnesses on the coil packs. They get spark, but not in the correct firing order. Just another quick thing to check.

 

I only said what I did due to the after the fact info on how much the heads where milled.............

ANd it sounded like you had check all of the wireing already.