On 7/22/2025 at 6:37 PM, zspert said:

Don't know if this is old ground but there was NO effort, none, to keep engines and transmissions with the cars from which they came.

@zspert , do you know if the heads for the program cars had hardend valve seats installed as part of the rebuild? What I'm really wondering is, should I be running lead-free additive in my car?

Good morning deanhuff,

Can't answer your question as I just don't know. However, if you're like the owners of the vast majority of old cars and only put a few hundred miles on your Z per year it isn't really an issue. Of course if your comfort level requires a lead additive by all means feel free.

If you've recently acquired a Z I strongly suggest

1 - cold and hot valve adjustment

2 - cold and hot cylinder leakage test

3 - new valve cover gasket (the absolute best is Nissan which is still available from your local dealer under P/N 13270-Y7010)

Cheers

I think that the fundamental question is about how much and what kind of work was put in to the engines. Were they completely rebuilt, or were they just evaluated for function like a rebuilt alternator?

Is there documentation out there about any engine work? If the valve seats weren't replaced then the new owner is in the same boat as if it was an original 240Z.

It would be interesting to see the "work orders" for a Nissan Vintage Restoration Program car. I've only seen anecdotes and old publications about the program, but not the official communications from Nissan.

From what I understand the fist batch of rebuilt engines were rejected and returned to be rebuilt. Metal bits from machining were found in the engines. Everything was done to time and budget constraints, quality may have suffered because of this.

1 hour ago, Zed Head said:

I think that the fundamental question is about how much and what kind of work was put in to the engines. Were they completely rebuilt, or were they just evaluated for function like a rebuilt alternator?

Is there documentation out there about any engine work? If the valve seats weren't replaced then the new owner is in the same boat as if it was an original 240Z.

A couple of pages from period Japanese magazines which covered the 'Program' show engines and engine parts (see attached).

Clearly - and fairly obviously - the engines were rebuilt and warrantied. It's not like overhauling an L24 was rocket science or anything. No rare earth elements involved. Putting forward the idea that that they were just given a spruce up and a coat of paint is fairly, er, out there...

1 hour ago, Zed Head said:

I think that the fundamental question is about how much and what kind of work was put in to the engines. Were they completely rebuilt, or were they just evaluated for function like a rebuilt alternator?

Is there documentation out there about any engine work? If the valve seats weren't replaced then the new owner is in the same boat as if it was an original 240Z.

It would be interesting to see the "work orders" for a Nissan Vintage Restoration Program car. I've only seen anecdotes and old publications about the program, but not the official communications from Nissan.

AER Manufacturing in Carrolton, TX remanufactured the engines.

Williams Technology in Summerville, S.C. rebuilt the transmissions.

(Williams Tech was bought by Caterpillar circa 2004/5)

Both were existing suppliers to Nissan.

https://www.aermanufacturing.com/

https://www.ame.org/sites/default/files/target_articles/92Q6A4.pdf

1 hour ago, HS30-H said:

It's not like overhauling an L24 was rocket science or anything.

There are different levels though. Sometimes valve seats are checked for wear and just recut, or if they look okay they might just be lapped. Sometimes they are removed and replaced. That's the question at hand. If they were all removed and replaced as part of the rebuild, and the program was done after hardened seats were introduced, then they probably have hardened seats.

An old AER document probably has the information.

Here are two descriptions showing the possibilities.

https://gaynors.com/auto-repair/engine-rebuilding/

"Valve seats are replaced with hardened seats..."

https://www.budgetenginerebuilders.com/

"Cylinder heads reconditioned with new bronze guide liners, valve springs, valve stem seals, resurface of valves, seats and head gasket surface area..."