considering returning to the 240z world after 35 years. my 73 had a 100k and was running strong when i sold it. how many miles do these engines and transmissions last and at what point is a preventative rebuild recommended. i realize that driving tendencies, oil changes , preventing overheating and general maintenance all factor in. Just looking for some guidelines and advice.thx.

If you are talking all the L motors up to 83? I'd say the bottom ends( short blocks ) are good for 250k+ with proper care.

Heads are a bit different. The older the model, the shorter the life. Newer heads have the better seats and guides . Then you factor in FI engines burn cleaner which is easier on the parts.

Accessories are very good as long as they are OEM

With marginal care - the L24's were good for at least 250K miles. Even then, most of the time they only require new rings/bearings. The cylinder walls spec. out to within factory guidelines in 8 of the 10 L24's I see torn down.

Blue is right - if there is a problem - it's usually head gaskets and then warped heads. At 80/90K most L24's could benefit from a fresh valve job. A lot of engines wind up getting a complete overhaul - just because the actually just needed a valve job.

One young lady put over 350K miles on her Z - before her mechanic pulled it for overhaul - This was after she lost a head gasket and over heated the engine. In that case the block had to be over-bored because the cylinder wall tapper was out of spec., but there actually was no excessive wear on the cylinder walls.

This was back in the early 80's and she put a lot of miles per year on the car. Drove it reasonably and had her mechanic service the car regularly.

Type "A" transmissions in the 70/71's could be problem at 100K or less - the Type "B" in the 72/73 were in good shape up to 150K miles...

The truth is - now 40+ years later, with who knows how many previous owners a car has had - if you have to pull the head for any reason - most guys will go ahead and do a complete overhaul.

FWIW,

Carl B.

My goal is to find a well taken care of 240 with body, original paint z with no rust. as you all know not an easy task and many of those cars have 200k. I'd rather rather rebuild and replace mechanicals than those dreaded floor pans , frame rails and all the other cancer. i have a line on an original owner car but while it appears nice, i do not believe there have been any major updates other than routine maintenance so i recognize their are lots of mechanicals that will need to be performed. it is a 71 series 2. what would a fair price be for such a creature?

How many miles on it and what shape is it in ? A lot of info missing but a rust free Z is worth a lot for the reasons you stated. Carl might jump in here and give his 2 cents, he is a better market judge. I know I might pay up to 7500$ for a rust free 1 owner even if most of the mechanicals needed some love.