I had my 400 block align bored. I believe it was bored and not honed b/c I now have a special rear main seal. What do I do for a timing chain? Do I need to worry about my transmission alignment with the crank centerline? Thanks

 

There are timing chains available from Comp and others for that situation. Check their catalog at www.compcams.com on the Timing Set page.

There are offset dowel pins to raise the trans. Either Moroso or Milodon makes them.

I can't imagine what sort of a special rear main seal you'd need. I've had lots of blocks align bored, they always used the same seal as any other block would.

 

I will have to dig up my paperwork but I think it was the same one for an aftermarket quality crank.

 

reguardless of what or who's crank you have the journal diameter is going to be the same and the seal will be the same.

 

Naw, the shop probably just kept his block and gave him somethin different, maybe a new block (305) with the 1 peice seal.

 

actually......

400's are weird when it comes to align boring. Fel pro makes a special rear main for it - #2909.

Read here: http://home.wi.rr.com/montecarloss/rearmain.html

 

That's not a 400-specific thing, it's for all 2-piece RMS small blocks since they're all the same. Whoever wrote the page evidently didn't know that.

In all my days I've never had to use one. But then about the most I've ever had to take off of a block to get it to align was about .005", not enough to screw up the seal.

 

I think what they are getting at, is as follows:

the "ridge" that supports the rear main seal, on a 400, is smaller than the journals without the bearings installed. hence even if you align bored it only 0.001, it is going to open the "ridge" way up to the 400's journal size.

on the other hand, the non-400 blocks have a much smaller journal - small enough that the unbearing'd journal is smaller than the "ridge" that supports the rear main seal, so when align bored, the boring tool fits within the "ridge" without cutting it.

You can find the same story on federal mogul's website http://www.federal-mogul.com/felpro/...ets/pg_54.html :

 

Now that we have established that I do have a different rear main, do I really need to worry about alignment of the trans and such? I am assumming that the tolerances are fairly large? Thanks

 

Have your machine shop stop their boring bar before it gets to the rear main seal. That's all I can figure; I've never had to use a special seal in any align-bored 400 block I've built, including some with the splayed4-bolt caps added, which obviously requires an align-bore.

The tolerances as far as trans lineup are fairly large, but not trivial. If your block ends up with the crank moving more than .005" or so, you should get the offset dowel pins, to prevent side loading on the pump bushing, which will cause leaks and premature failure of the bushing.

 

You need to talk to the machinist to see how much was removed, what spacer bearings they used (to check the validity of the first response), and how much offset (if any) was cut. If they look at you oddly, you may have selected the wrong machine shop. Most times a case can be align-bored or honed without changing the centerline one stinkin' bit, especially if the machinist knows anything about proper set-up and indicated the piece in correctly - even with new main caps. If it was done correectly, the timing chain and transmission mounting issues will be irrelevant. The only issues then left would be the seal size, and what color you're going to paint the inside of the case.

It's just an engine - it ain't rocket science. Then again, rocket science isn't rocket scinece any more....

 

My machinist is good. He said he had honed my mains. He removed .002 just because I have studs and that changed the torque on the caps slightly. He mentioed that on an align bore would not need a new seal. B/c of the method in which a hone and a bore is done differs. I am not exactly sure. He also said that the seal on my block is the same as the donovan or rodeck blocks he machines. This is a felpro 2909 that I purchased for my block. He said that timing and trans tolerance will not be an issue. Thanks for the input.