Diseazd

My machine shop said they just did an engine exactly like mine (73 pistons in L24 block). Evidently 73 pistons need to be milled .030 inch for 0 deck height. They can mill the pistons with rods attached. I'm going to have them mill .025 inch for a positive .005 inch deck height ( most experts I've talked to including Dave Rebello say .035 to .038 inch clearance is minimum), so you could actually have plus .015 inch and still be OK.( gasket is .050 inch when torqued). As far as material available to mill......the valve fly-cuts are a lot more than .030, so that shouldn't be a problem. Looks like I'll be zipping it up shortly.....I'll update when I get the pistons back from the shop.

Green should be perfect.

When I build my engines (and I've built a lot of them), I take the crank to a machine shop..... get it checked for straightness and make sure it mics to standard....I also have them polished. If the crank checks out, I install Clevite standard bearings and just bolt her up. I've never had a problem. Datsun engines don't wear unless really abused. In 20 or so engines, I've never turned a crank or rod journal and you usually can't feel any wear on the cam lobes or at the top ridge of the cylinder. It's always prudent to check things though.....let us know what your clearances are and if you have other questions as you go forth! Good Luck.....Guy

My How to Modify book gives .0025-.0028 inches (rod) and.0025-.0034 inches (mains). The 240Z factory manual gives .0008-.0028 inches (mains) and .0006-.0026 inches (rods). Why don't you plasti-gauge your bearings and see what you come up with. .0026 on the rods and .0028 on the mains would be in the ballpark. The How to modify numbers would give you a little looser engine but if your crank is standard, they're always pretty much on the numbers. Oh by the way.....I don't think your number one main journal has two holes(either would the bearing shell for that journal)......let me know if I'm wrong. Thanks Guy

The answer to your question is main bearings are .0025-.0034 inches. Rod bearings are .0025-.0028 inches. Use plasti-gauge.

Gumby.....Did they mill your piston with the rod attached?

Thanks Fred....seems the 73 flycut pistons are a slight different size than the 70,71 or 72. From what I extracted from the knowledge bank at the Mitty was that there's enough clearance on a street driven Z (no rod stretch) to bolt her up and run. I seem to have about .020 clearance and it's only around the outter edge of the combustion chamber. Andy (70 Cam Guy) found a .020 soft copper shim at NAPA if needed. Thanks Guy

Talked to Carl Beck and Jim Frederick at the Mitty.......The 73 pistons come out of the block by .030". It's not the block! The .020 clearance should be plenty for a street car......They are currently building one in Florida with 73 pistons also. I'll build it onward and post pics of the finished product. Oh...by the way....we had breakfast with John Morton, Pete Brock and Les in Atlanta. A world of engine knowledge at that event. Guy

He's not only my son but my partner......someone has to make a living while I knock out drinks with you Ron! Guy

12 foot lbs. to max of 15 foot lbs.........no more or you'll strip the aluminum head.

I just talked to Z Doc in Roanoke. He brought up a good point. The machine shop should have attached the front cover when decking.......otherwise the block and front cover will not match up to the block deck......learning is fun!!!!:stupid:

As I understand it you can have the flat top of the piston out of the block by .015 with the stock gasket which crushes to .050 inches. The clearance needs to be .035 inch minimum. I believe that the gasket that MSA sells is for a bored out L28 and is 2mm. If anyone knows where I can get a 2mm gasket for a .040 over L24 I sure would appreciate your help. 2mm would be .080 less .035 out of the block would be .045 clearance. Thanks Guy P.S. It's a P30 block

You're right about that! The number on the crank is E3141. I pulled a piston.....both rod and piston were L24 (long rods). I'll pull all pistons and dump this block in the garbage!!! It's beautiful with it's new paint and brass freeze plugs. What a shame! Guy

Which means that the engine block must have been decked before......but .035 of an inch? .......WOW!

That'll help. The reason I ask, is because I'm building an L24 (72). I bought the motor used, so I don't know the history. I put the bottom end together assuming all was original ( it didn't look like it had ever been apart) and when I installed the .040 over 240Z Nissan pistons, they came out of the deck by .035 inches. The machine shop decked the block .008 of an inch and assures me no more, but the piston is out .035 of an inch. I pulled a rod and they are 240Z rods. Is it possible someone had installed (by mistake) an L26-L28 crank?

If you have an L series crankshaft by itself, how do you determine whether it is an L26...L28 or an L24 without measuring the stroke? In other words, are there any marks or numbers to simplify the process?

You don't need it......just use 2 metric wrenches!

Absolutely beautiful!!!!!.....Put some original seat covers along with the steering wheel IMO.

I remember slobbering over those body parts.....Called the guy, but he wouldn't sell separately. I think he shipped it overseas, and if I remember correctly, he wanted $5,000.00.

ZLADY......We're proud of you!!!! Guy

It costs me more in time and gas to drive to the dealer than shipping. :stupid:

MSA has them.

Undoubtably the best bang for the buck that you can install in your Datsun! This thing really does what's it supposed to. The bump stop is the way to go as far as simplicity. Use both the original and the bump stop for best results (damps the unit). Dave ......your product as usual is superb! Guy

Maybe Bruce "screwed up"!

Looking forward to seeing your car Ron ...........I'm sure John Morton will enjoy it too. I was sitting on the back Esses at Road Atlanta when he won the Road Race of Champions back in the 70's!