If I put heads of a 1972 429 on my '90 460, do I have the same compression afterwards? I think the '90 has about 8.5 to 1.

 

No and it won't work, the EFI manifolds will not work on the carbed heads. But if you are wanting to put it on then most likely you wil lower your compression (unless of coarse you have the PI heads) if you have the D2VE open chamber heads, the combustion chambers are approx 100cc, adn they are very prone to detonation (your 90 heads are approx 93-95cc). Basically the D2VE heads are considered to be good door stops and not much else.

 

I know about the manifold and the exhaust flanges. But my efi heads now make 10:1 compression( modified) and I need around 8-8.5:1. I'm putting a turbo on it. A friend of mine has the '72 heads laying around since he got himself some D0VE-C heads.

 

Just look for a set of E7TE heads, they will be the bigger chambers, and be EFI heads to bolt up to your manifolds. If your friend has a set of D0AE heads then those would be good if you can get them to work as they are about the best heads you can get. (and quincidently if they do happen to be the PI heads and your friend swapped them out for DOVE heads he is crazy) but any other 72 head is junk and just barely worth the price of scrap iron and have virtually no place on any engine let alone a performance engine.

 

I'm just gonna keep my heads then, I'll just get a spacer plate cut to bring the compression down.

 

Not sure how that will work?

Can one just buy a thicker head gasket or will that not be enough?

 

running a spacer plate can be done but it would be cheaper to buy aftermarket alum heads. Before the advent of taller deck aftermarket blocks, that was one way to get more cid but you have to put the spacer on then bore the block and sleeve all 8 cylinders, then you have to buy custom length head studs, and built up the intake manifold to match the higher deck hieght etc, etc. I don't know all the specifics just the basics on doing it and it's not a simple project. Just get a new set of heads and start from there if you need to drop the compression because too much was milled of you current heads.

 

actually, it's a very simple thing to put a spacer on the block. You don't have to change anything else, just put the spacer on. All I need is an 1/8in spacer. Everything will bolt right back up. I know that because my current heads were machined down 1/8in to get the higher compression. And after machining them down, everything still bolted right up, manifold and all. So by putting a spacer plate on, I'm just going back to stock

 

no your not, contrary to what someone has told you. first off when you mill hte heads you are only cutting down the combustion chamber but if you increase the deck hieght your cutting down the entire bore so the CC difference will not be the same. Second off putting a spacer in the way you are saying would require 2 head gaskets so adding .125 (1/8") would not be adding the same amount but would be adding .166". Next milling .125 off stock heads on a stock block will not net you 10:1 compression more like 9:1 as you are only dropping the chamber size by about 20-22cc which is about how much of a dish is in the pistons (if they are stock) if not stock then putting dish pistons will drop your compression back down. Next milling that much off the heads DOES require milling hte intake, it WILL NOT FIT and even if you got it to fit then the ports will have a major misalignement problem. Anything over about .030 off the heads starts requiring you to mill the intake to keep alignment problems to a min. And lastly you are wanting to put a turbo on and talking about running 2 head gaskets and a spacer, well let us know how that works out for you.
your really going about this the hard way but hey it's your money and engine do it anyway you want.

 

dont stack head gaskets or do the spacer thing... they will ruin your quench... itll increase its tendency to knock... something youve really got to watch if youre turbo or supercharging a vehicle.. if i were you id go get some 100cc blue thunder heads- way better flow numbers and plenty low enough compression for turbo... also make sure you put a proper cam in for your application

 

The quenching was/is a bit of a concern. That's what I wanted to find out from some turbo guys. I know they sell plenty of turbo kits for higher compression cars and they come with spacer plates for the block, but they may have a different head design.

And Monsterbaby, if you take 22cc's of the combustion, you end up with about 10:1 compression. And the intake fits just fine. I didn't have to make one hole bigger to bolt it down. And for the alignment of the ports, first off, have you ever checked stock heads and intake alignment? It's not even close. And on mine, I took the time to match the head ports to the intake ports and opened them up as big as the gasket holes are.

 

well that is true if you take 22cc out of a 8.50:1 compression 460 you do end up with slightly over 10:1 problem is a 92 460 may say it's 8.5:1 but probably more like 8:1 max. Do the math on it, to achieve 8.5:1, the chambers have to be 92cc (they are more like 95) , and the pistons must be at zero deck, the factory number is figured on everything bieng exact and they aren't.
But hey you got it all figured so I will just leave you alone. After all, I don't believe in superchargers anyway so your right I should stay out of this.

 

BTW just because I was curious since you mentioned some turbo kits for hi compression engines came with a spacer plate, and I have never seen that and wouldn't trust anyone that suggested it I did some searching. I couldn't find one single turbo kit that had that listed so could you please give us a link.
But what I did find was the use of spacer plates on some type of 4 cylinder engines, and how they manage to do that without blowing out head gaskets, and all I can say is have fun cause I sure wouldn't want to put that sucker together. you have to oring every single water passage, oil passage and each cylinder on both sides of the plate and have to machine the block and heads for orings in each and every one of those positions, so by my count off the top of my head without going and looking at one of my blocks that adds up to around 60 orings per cylinder head. Thats gonna be real easy to keep them all aligned and real cheap on the machine work.

 

I don't really have any links to kits with spacer plates, although I haven't searched for them either. A cpl of yrs ago I read some articles in the turbo magazine. One kit I remember was for a VW VR6 engine. It had a spacer plate. I don't remember anything about o rings though.
Right now I'm just getting the parts for the turbo conversion together ( turbo, blow through carb, fuel pump, blow off valve etc.) I have experience in turbo cars, but haven't converted a non turbo into a turbo yet. I'll probably just end up getting some used heads and rework them a bit and keep the stock compression.