I have just rebuilt the top end of my engine with Vortec heads comp xe268 cam, air gap intake, and edelbrock 600cfm carb. I am having alot of trouble making it run right. I can't get it to run without like 16 degrees advanced timing and then it will nock when i try to drive it. Plus i have to set the idle screw really high in order to keep it running too. I put 93 octange and i have .041 head gaskets to try and lower the comp. Do u think it could b a manifold leak at idle i get a very erratic reading at about 10 in. any ideas? thanks

Jono

It sounds like you may have installed the timing chain a tooth or two off. It's also possible, though not likely, that you installed the distributor 180 degrees off. The distributor would be something to check before tearing the timing cover back off, but I don't think it would run as good as it does if it were 180 out. Check it anyway to be sure.