Bronze valve seats?

[Eddy67]

So adding .030 shims or what ever it takes to get it in spec is ok to do? what it the most you can go or am I at the limit now?

[madkaw]

Most you can go for what?

You need to study up on the L motor.

What block are you using?

[Eddy67]

Its the L24 motor, what is the most you can take off the bottom of the head and the thickest cam shims that can be used. I ask because I would like to have this machined flat so it will remove a little more off the bottom of the head. That said it is only out by .006" maybe it does not need machining this may still be in spec. I read that .002" per cylinder on an aluminum head was ok not sure about the 240z head

[Eddy67]

Anyone,,,, I really want to send this head out and have it pressure checked and ground if I am still within limits of doing this. It could be when all is said and done I may need up to .040" shims is this doable?

[madkaw]

Get it flat unless you want to change HG's a lot. Take the minimum off and then shim with some .030 shims to get it close.

This will pump up your CR, so detonation will have to guarded against.

It's doable. Buy te book on "how to modify datsun engines" and read .

Should make for a hot L24 with planning.

[Eddy67]

Cool I will take the head to the shop for pressure testing and to have it machined flat

[Jeff G 78]

You don't have to use tower shims. My endurance racer P79 head was shaved 0.050" and I don't run shims. I get to the correct timing with the offset cam gear bushings as described in the "How To Modify..." book. Runs like a champ.

[Eddy67]

Wow .050? I will have to find the book you are talking about. Thanks for everyone's input

[madkaw]

You don't have to use tower shims. My endurance racer P79 head was shaved 0.050" and I don't run shims. I get to the correct timing with the offset cam gear bushings as described in the "How To Modify..." book. Runs like a champ.

True. But if you go with a performance cam and you actually want to degree it, it will be MUCH easier having the geometry close. Shims are 60$ .

P79 has a much bigger combustion chamber so .050 on it is not as much as a e-88 that already has small chambers.

In the end- your head should be fine, but some homework will pay dividends

[Jeff G 78]

Agreed Steve. Getting the timing spot on wasn't very hard with the offset bushings.

Edited January 27, 2014 by Jeff G 78

[Zed Head]

You can tell things are slow when you're trying to convert a guy who just wants to replace his excellent shape valve seats for something more durable in to a race engine owner.

Not that there's anything wrong with that.

He could probably run the bronze seats for 20k - 30k miles while he works on the other head.

[Diseazd]

Wow .050? I will have to find the book you are talking about. Thanks for everyone's input

Jeff is talking a P79 head with deep chambers. Don't think for a minute you can shave .050 inches off of an E88 or E31. You don't want to contact the valves against the pistons. Like Steve suggested.....get a copy of "How to Modify the Datsun 240Z and 510". I believe (but not sure), that you don't want to take off more than .030 inches with a stock gasket.