shmark

Ok so given I'm pulling the cam towers, it's a short trip to pull the heads too so I might as well. That gets me thinking...which is dangerous. I'd like to get another set of US 16v heads to play with, so what would you do?

Flycut?
Modify to accept larger Chevy valves?
Multi-angle grind?
Cooling improvements?

I'm betting I can take a set of US heads and upgrade them for less than the price of decent euro heads. Anyone got a set they want to get rid of?

BC

I do. US heads already cleaned up and disassembled. Would you like them for 150 dollars for both?

hacker-pschorr

I'm going to assume you are able to do all of the necessary machine work yourself?

The last set of EuroS heads that sold around here went for $500.

123quattro

Those heads needed machine work too though.

shmark

True, but if you're going to rebuild the heads (and it doesn't make sense NOT to) the cost goes up. US heads are cheap, Chevy valves < $100 for a complete kit, basic machine work wouldn't be that expensive and I know a couple guys. Which is why I'm wondering what's possible. Are we stuck with the Porsche valves/seats/springs/etc., or is there a cheaper alternative? I know someone else has to have done this.

Brendan - I would but the shipping would probably kill it.

BC

Shipping won't be bad. They are not super heavy and I have an account with fedex. How about we do it and we can work together on shipping if you are in for the 150 for the heads themselves. I'd like to move them.

BC

No, you can get chevy valves, ford springs, aftermarket retainers. The basic shape and size of everything is very "domestic"

shmark

So I have a line on a set of '79 heads. Does anyone know if there are any issues fitting them to an '83 4.7? And perhaps more importantly, what would be involved in installing a set of euro S intake runners?

Abby Normal

Mark,

Just wanted to say hello and that the Shark looks fantastic!

123quattro

I just bought a set of heads/cams/carriers. They weigh 80 lbs.

BC

Just a set of heads is 50 pounds. It was 40 bucks to ship them.

BC

I think 79 is somewhat different. Seat materials, etc.

LT Texan

Mark, the 78-79 heads have some big combustion chambers resulting in the 8.5:1 compression ratio.

Not a good base to start with if your going normally aspirated.

shmark

Thanks Abby, good to hear form you! Looks like I'm not going to make it to Mike's TB party, at least in the shark. Will you be there?

And on topic, I'm getting the 79 heads and we're going to see what's required to play with them. According to DR's engine spec page the 79 was 8.5:1 while my '83 is 9.3:1. I wonder how much of that is the chamber vs the piston design. Anyone cc'd the different year heads?

https://www.928gt.com/t-928engine.aspx

So am I going out on a limb here, or has anyone else gone down the road of modifying the 16v heads? The more info I find, the more I think this can be done very easily. Chevy valves are slimmer than the 9mm 928 valves, which means more air and fuel. With a larger/slimmer intake valve, higher pressure springs and a little machine work we ought to be able to get some good numbers. Even if the overall compression is a bit lower...and that's not necessarily bad if there are other mods in the future.

shmark

Also, my last dyno numbers put me at 180rwhp. I know that doesn't mean much relative to the factory rating of 234hp, but on the same day and conditions a '79 928 dynoed at 179rwhp. Now my car should be making around 15hp more than the '79 and that means I'm down on power. I know for a fact I don't have a full seal around the air meter and there could be other places I'm losing as well, hope to find out more when I pull the intake.

So with some head work, intake updates, new cams, smog pump delete and y-pipe, I'm thinking I'll be seeing at least a little improvement.