Cam tower alignment - L28

[Ttiger]

I'm putting my L28 back together after replacing the rings, bearings, valve stem seals, etc. The engine had two bad rod bearings which is why I pulled it apart.

I had removed four of the cam towers to get my valve spring compressor into position. I kept track of where they went for reassembly.

I've got the towers back on and the cam in place. I left the towers loose while I slipped the cam into position. I can tighten all the towers, except the back one (#5). If I tighten #5, the cam wont rotate. If I leave it loose and tighten the 4 others, the cam rotates smoothly.

I played with feeler gauges and found that if I put a .04 feeler gauge under the #5 tower and tighten it, the cam will rotate freely.

The thinnest tower shim I've found is .15. I really don't want to try and shave .04 off the other 4 towers.

Ideas? Thoughts?

Thanks

[olzed]

Odd.

Have you removed them to make sure the tower bases are spotlessly clean?

Assuming you have them in the right positions, you should be OK. Tap them around a bit near the base, as you tighten them down.

I have had success like this.

If all else fails you could easily make a 4 thou shim I suppose.

[240260280z]

I concur.

You can you try tightening the first 4 a little more and #5 a little less.

As well,it may not necessarily be height; the cam could be tilted front to back or left to right.

Try to seat the towers with a rubber mallet (or hammer and block of wood) after cleaning and deburring both mating surfaces as olzed's excellent recommendation.

Also clean and inspect the alignment keys and holes as binding or debris there will also affect alignment.

You could also get a new set of towers from a donor head and try.

Edited June 25, 2012 by Blue

[Diseazd]

I wouldn't put a shim under the tower under any circumstances. Are you sure you put them back in the same order? I always permananely mark the numbers on the towers before removing them. If they are in the proper order, they will work. Loosen all towers and very slowly tighten all together in very very small increments while turning the cam each step. Also, make sure the alignment pins are installed for each tower.

Edited June 25, 2012 by Diseazd

[emptech]

I'm assuming those numbers on your feeler gages are metric? I don't have a mic handy, about

how thick is aluminum foil? But like others have said, if nothing has changed, debris under one

or more of the other cam towers?

I'm sure you marked your towers with something like a center punch, one tick for #1, two ticks

for #2, etc. If they all got mixed up, how about trying different orders until you get one that

fits right, not the right answer, but might work. It worked for me one time when I had my head

milled and the towers didn't line up, swapping them around worked.

Jim