Head shim availability

[slipnfall]

Hi there! FYI, I'm still in the planning stages for rebuilding my '91DE. I stopped at a local machine shop to ask questions and get some general information. The machinist I spoke to told me that Nissan will no longer sell individual shims - only as a set. He said their shop sends customers to a local dealership to have their motor re-shimmed, due to the cost of a shim set. Since I mistakenly lost track of the 16 buckets' placements, I'll need a re-shim eventually. Are single shims available online anywhere?!? I would rather have my machine shop do this adjustment due to $$$.

Thanks!-Jamie

[deviousKA]

If you still have your full set of shims, you can get them installed properly it will just take some time. Ok before i go on, if you plan to get this head rebuilt (valves ground, etc..) make sure your machinist matches the installed valve stem height to oem. When valves are ground, they sit deeper in the seats > valve stem is also moved. This should be checked, and stems may need to be ground down for correct height.

Ok back to the first comment, you can get all the shims in correctly (with stock valve grind, or lapped valves). You will be spending some time torqing and untorqing the cams, and using a feeler gauge to check tolerance for each 16. Just keep swapping them untill they are all within spec (.013-.016" iirc). If you have the valves/seats machine ground on this head, the stems will need to be checked/ground to get them back to what they were oem. The stock shim arrangement should still work properly. I have been able to get this done, with stock shims, on 2 japan de heads and 3 mexicos.

On that note, be aware that japan de heads (240sx), mexico de(altima, truck) and US de (altima, truck) all use different thicknesses of shims and are not interchangable. Good to know if your out looking for a shim.

BTW. If the head is rebuilt for performance application (arent they all?) and the valves are sitting deeper in seat, unshroud them for better flow.

[slipnfall]

Devious, Sorry for the delayed response - busy week on my end. Thanks for the response - my concerns are greatly alleviated Re: shims!! I only misplaced the position of 4 buckets, and the shims have stayed in each. So this doesn't seem as bad as it could have been(16 buckets, 16 positions, lots of re-torqing!). Anyways, that's good news.

Yes I do plan to have head work, although I am still sorting through all my options. The machinist said other 240 owners have had a 5-degree valve job(?). I'm confused, because I was under the impression that there was only one angle, located on the valve seat... But hey, thanks for all the tips and good info!

Respectfully,-Jamie

[eddiec]

yes the valve seat angle is generally a 45deg cut/grind. for better airflow/performance a 3 angle can be done. this cuts above and below the seating surface to better blend the cuts and allow for smoother flow. a 5 angle is just 2 more cuts above and below what a 3 has.

i would think a 3 would be sufficient.

[chandler]

a 3 angle valve job is standard, 5 angle is the best performance job. me personally I want my valve to be ground to 44.5deg, and the seat at45.5 deg that way when they meet the form a tight seal that when it wears it gets bigger =)

[Ubernoober]

Sounds like a recipe for disaster to me. Exaust valves dissipate thier heat through contact with the seat. By reducing the contact area, you are increasing the wear (which means a change in seated stem height) and reducing the valves ability to get rid of its heat.

[chandler]

no, on start up the seat wears to a perfectly even matched set of angles just like a normal seat, And as for lapping the valves with compound? not in my engine, sorry but machinist bluing with tell me if I have the contact patch right , and ill roll them by hand to make sure they fit no place for sand in my engine