Trying to get an intake on a TSP 408 and dowels on the intake do not want go into the heads. The heads are TSP 317 heads and the intake is an LS1 intake. It fits fine on the LS1 but not the 408. The motor was built for boost and I wouldnt think the heads would have been milled.

 

That's weird, there should be no difference whatsoever in the intake holes on the 317s, whether they're modded or not.

 

Uh huh...Thats what I said fits just fine on the ls1 block but not this block

 

That's what you get for putting a crappy LS1 intake on a 408. lol.

 

Not my motor.. its going in an LS1 GTO with a procharger..

 

Valley cover/bolts too tall?

 

Do you have any other intakes lying around you could try? Any chance the LS1 intake is warped?

 

The valley cover and bolts came off the ls1 the intake came off of. I did pull the bolts out and it still didnt fit. I did measure the distance in the bolts holes across the head and the 408 was a 1/16th of an inch closer than the ls1..

 

how much did they deck the block ?

how much are the heads milled?

they can both bring down the distance between bolt holes from bank to bank .

i recently had to over come this on my 427 , the intake runners needed to be moved out to line up with the manifold bolts , luckily i had a sheet metal intake and i used some exhaust manifold spreaders to separate the runners enough to get the bolts in , in your case you dont have that option. are the bolts to far apart or not far enough ?

 

If the measured distance between the intake manifold bolt holes in the heads are different than the LS1 heads than that shouldn't have anything to do with the amount anything was milled I would imagine. I just can't see a GM casting like that passing QC. Are you certain these are GM castings?