Question : '95 3.4 camshaft and timing chain installation

[Jegliebe3]

Quick question hopefully someone will have an answer to: Putting a rebuilt 3.4 together. Crank in, cam in with rear seal and was flush with front end of engine as expected. New sprocket installed on crankshaft....all the way back to the slightly larger diameter on the front end. installed chain and it pulled the cam out about 1/4" or so. Looking at the old cam, sprockets, and chain, it looks as if the old cam was slightly forward, maybe 1/8". Can anyone tell me if this makes sense, did I do something wrong.....eagerly awaiting!

[geoffinbc]

The back of the cam gear has a thrust surface and it should ride on the corresponding surface on the block. Flat tappet cams have a slight taper to the lobe and the lifter rides off center this makes the cam walk to the back of the block and the gear provides the thrust surface to keep it in the right spot.

[trotterlg]

I know exactly what you are talking about. Same problem on a 3.1, the alignment pulled the cam forward about .050, so when it was pulled back by the lifters it caused the chain to be out of alignment. I figured this was wrong so my solution was to chuck the bottom sprocket in my lathe and take .050 off the back side. This made every thing line up right. Not sure is there is some small differences in the crank noses or the sprokets or what, but I am sure the chain should be aligned when the cam is pulled all the way to the thrust bearing on the rear of the top sprocket. Larry

[geoffinbc]

Yes the chain should be straight. What brand of chain was this? Were the sprockets both the same brand? Was the bottom sprocket on the right way?

[trotterlg]

Don't recall the brand, but both sprockets and chain came as a set. Bottom was on correct, but I had to machine some off the back side to get the chain straight. I am sure there are little differences in some sets and chains, but I did notice this and fixed it durning install. I should note that this is on a 3100 block and crank with a 2.8 flat tappet cam with the proper chain and sprockets for a 2.8. Larry