Bronze valve seats?

[madkaw]

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.

Yeah, we went from a bit over .030 to shaving .050- big difference.

[Jeff G 78]

Correct, but we are talking two different things. I would never take 0.030" off an E31, let alone more. That's a tiny chamber and a really high CR number depending on head gasket and final head thickness. I was simply speaking to the need for tower shims at 0.030". If it were me, I would have scrapped or sold the damaged E31 and started with a P79 head to get a better chamber shape. For a stock street engine, I'd just pick up an E88 and be done with it.

[madkaw]

Correct, but we are talking two different things. I would never take 0.030" off an E31, let alone more. That's a tiny chamber and a really high CR number depending on head gasket and final head thickness. I was simply speaking to the need for tower shims at 0.030". If it were me, I would have scrapped or sold the damaged E31 and started with a P79 head to get a better chamber shape. For a stock street engine, I'd just pick up an E88 and be done with it.

Come on- where's you sense of adventure.

Probably looking at 10.5 to 1 . With right cam(bigger) it might be okay with proper tuning.

Make sure you I shroud the chamber as much as possible

[Eddy67]

So one last idea for you guys, I also have an n47 head which I hear is the least desirable, it has never been machined down and its only .003" out, which is still in spec.

What are your thoughts on this head? I really only need to be able to drive this car 2500 miles where it will be restored and I can then think about which option to go with on my e31 heads.

Edited January 29, 2014 by Eddy67

[Jeff G 78]

There is nothing wrong with the N47. It got a bad rap before there was flow testing showing that it flows just as well as any head. It has the large valves and steel seats, but it just doesn't have the heart shaped chambers that the P79 and P90 heads have.

[Eddy67]

So performance wise is it better than a stock E31?

[madkaw]

Doesn't the 47 have round ports?

I thought you weren't worried about performance?

2500 miles for a resto- whoa!

[Eddy67]

Well I am not to worried about the performance, but if one option gives me a little more I will go for that.

The car is heading back home to Canada with me after being here 16 years. We cannot get these cars up there any more, they were already scrap 25 years ago when I bought my first one all very badly rotted out.

As far as the ports on the N47, both intake and exhaust are round, whats the difference between them?

[Jeff G 78]

Again, flow data shows that the N47 is just as good as the N42 with square ports.

[Eddy67]

Awesome I think this may be the way to go for now.

[Zed Head]

So far I've been ignored but what the hell...

Eddy67 is looking to find the head that will give him a performance boost over the stock E31. Seems like the bigger valves of the N47 should provide more flow, giving more potential. Whether or not the rest of the parts can realize that potential is unknown. The carbs would need some work, I assume. The cams are similar, if not the same grind. The round ports will be dumping in to square exhaust ports, so should be okay.

But, the important question of valves hitting the edges of the cylinder seems to be in play. If he can avoid or fix that problem, and is ready to retune his carbs, then the N47 seems like the way to go.

BUT, it seems that the round N47 ports might be larger than the square exhaust manifold ports of the manifold used with the E31 head. Another thing to fix. Carbs on N47 - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z

Everything still leads back to just using the bronze valve head. It's not going to die in 2500 miles.

Edited January 29, 2014 by Zed Head
Clarity - Got my N's and E's and numbers crossed up

[Eddy67]

So I did order the valve seats a few days back, any idea how much they are to put in? I guess if I do this it will make for a reliable head that should go for a long time.

The bottom end is very tight, no play in the pistons, no ridge ring at the top of the cylinder either.