E-31 Rebuild

[seerex]

I just got an e-31 , wanted some suggestions on what not to do or any suggestions for the rebuild of it , right now gonna strip it down and have it cleaned and ported and polished for a new cam , should a 3 angle or 5 angle valve job be done or thoughts any aspect . just don't wanna mess it up , it gonna be with a F-54 basicly stock block , thanks all:geek:

[26th-Z]

Nissan specifically does NOT recommend removal of the cam towers for reasons of the cam bore alignment. If you surface the head or repair a warped head by surfacing, the cam tower alignment will need to be adjusted. Shims are available to raise the towers to the proper height after surfacing. Goodson Tools and Supplies #DHS-60 Head Saver Shims.

You may have bronze intake valve seats and want to replace them to run unleaded gasoline.

A 45 1/2 degree cut is specified for the valve face. Be sure to check for the correct margin on the valve - 0.4mm+ and 0.8mm for intake and exhaust respectively.

The valve seat is cut at 30 degrees, 45 degrees, and 60 degrees top to bottom. The 45 degree cut corresponds to the valve face angle.

The manuals I have discuss all of this over several pages. Aside from the Datsun engine manual, a really good source of info is "How to Rebuild Your Nissan and Datsun OHC Engine"; Tom Monroe, 1998, 2001

[JMT240KGTR]

Never had issues with removing cam towers/re-alignment issues.

All you need to do is ensure when re-assembling the towers and cam is as you progressivley tighten down that the cam is moving freely. Now to determine what freely is remove the rockers whilst the cam and tower are still in (before removal), rotate the cam and you'll know what to feel for when re-assembling.

Also, during re-assembly of the cam and towers, ensure the rockers aren't in; place these in after you've aligned/tightened cam and towers.

I know someone who placed the rockers in, then the cam and towers; wasn't able to determine "true feel" and ended up re-building the engine.

As for shaving the head if you're leaning that way, .030" is max according to the books before shims are required on towers, however, I've done up to .050" with a new chain, guides, tensioner etc etc and haven't had issues. I would recommend using shims/new rocker/lash pads if shaving more than .040" though for peace of mind.

I've found by being a little adventurous and creeping over what "the bible says" doesn't hurt; it's when people go too far over recommendations they stuff things up.

[Walter Moore]

I just got my E31 cylinder head back from the machine shop last week. As was mentioned earlier, they came with brass seats on the intake valves.

Not that it is likely to be a big deal with you, since you intend to port the head anyway, but the original valves were smaller, 42mm, than the valves in the later engines. So far as I have been able to determine only the larger intake seats, 44mm, are available now.

The machinest who reworked my E31 said that it wasn't really possible to install the small seats anyway, because the brass seats have to be cut out of the head, with the result that the seat opening will become slightly larger.

(Steel seats are easier to remove. Just head the head to 300 degrees F, and they fall out, or so he claims...)

And of course, larger valve seats will require larger intake valves...

For some reason the exaust valves in my car were smaller as well, 33mm versus 35mm. Happily for me, I found a bunch of valves on Ebay cheap and was able to use those rather than buying new ones.