Head swap on N/A?

freakintiger · Oct 1, 2005

Hey all!
As some of you may remember I began collecting parts for a turbo mill, but it seems that in these parts, they are hard to come by...
So I have this nice oval port turbo head sitting in my garage.
My question is this: If I were to port/polish this head, 3 angle valve job with some larger valves and maybe add a more aggressive cam and use just one bank of plugs and one coil pack, would I see an appreciable power gain?
I know I would have to obtain the older manifold(port as well)and use the older style TPS with an adapter pigtail, so it would be esentially replacing the top end of the motor...
Worth it?
Thanks for the input!

bhuff30 · Oct 1, 2005

sure, you would see some extra power from porting and polishing that head. It would be mostly above 3k, and it would feel a lot nicer at 5k. Still, if you want to make descent power NA, you gotta get the compression up.

ratrapp2 · Oct 2, 2005

what kind of parts do you need?i've got a lot of turbo stuff laying around i'll sell fairly cheap.

freakintiger · Oct 2, 2005

bhuff30 said:
sure, you would see some extra power from porting and polishing that head. It would be mostly above 3k, and it would feel a lot nicer at 5k. Still, if you want to make descent power NA, you gotta get the compression up.

bhuff, would I be able to raise the compression ratio sufficiently just with head milling? Or are you talking domed pistons?
Thanks, you are the NA guru...

bhuff30 · Oct 2, 2005

freakintiger said:
bhuff, would I be able to raise the compression ratio sufficiently just with head milling? Or are you talking domed pistons?
Thanks, you are the NA guru...

Ohh yeah, milling would be fine. You can mill it up to .120", which gives you something like 12:1 on flat tops. I think dan'l milled his 93 lx .060, which gave him nearly 11:1 compression which needed mid grade. Going .050 should give you 10.5:1 which would probably work alright on 87. I was running 9.7:1 with no problems on 87, but you have a dual plug head which is good for detonation resistance.

freakintiger · Oct 2, 2005

If I can go 9.7:1 on mid-grade, how much on 93 octane premium(I run this already)and how much beyond .060 would the head have to be milled? Is 12:1 compression sustainable on 93 octane? I had thought 11:1 was the max.
I am planning to swap in the oval port TURBO head, so I won't be DP anymore. I want to outflow the DP head...

Thanks bhuff!

bhuff30 · Oct 2, 2005

freakintiger said:
If I can go 9.7:1 on mid-grade, how much on 93 octane premium(I run this already)and how much beyond .060 would the head have to be milled? Is 12:1 compression sustainable on 93 octane? I had thought 11:1 was the max.
I am planning to swap in the oval port TURBO head, so I won't be DP anymore. I want to outflow the DP head...

Thanks bhuff!

Hmmm, with the oval port head, you should probably keep it to 11:1 for 93 octane. That still might be pushing it, depending on how much ignition timing you try to run. No way to know until you try it.
Since you are running and oval port, which has a larger combusions chamber, .060 would give you 10.1:1 and .100 would give you 11:1.

Dan'l · Oct 4, 2005

This one caught my eye at work, so I figured I'd chime in. .060 on a dp head was ok with 87 octane at wot. However, the partial throttle would "re-teach" it's mapping and the computer had to be shut down @ every 2 weeks to send it back to the base maps for partial throttle or it would start to knock at partial throttle. I don't think your flame travel will support that kind of compression in the other heads(non dp). Your timing is not adjustable, so you have to build your heat through compression. Also, unless you need it, you're slowing yourself down by having too much octane. The lower the octane rating the faster the fuel will burn...ie...faster quench time and more of the fuel will be burned in a given cycle. Later, Dan

freakintiger · Oct 4, 2005

OKAY...so I have a brand new DP head in my garage also, would I be better off just hogging that one out, stuffing bigger valves in and milling it for compression...

...also, I believe things are a bit hotter in my compression chambers than stock, that JET-HOT coated header is heating things up, I think that is why my idle is funny. I think it cooked my motor...

tjm73 · Oct 4, 2005

freakintiger said:
OKAY...so I have a brand new DP head in my garage also, would I be better off just hogging that one out, stuffing bigger valves in and milling it for compression...

...also, I believe things are a bit hotter in my compression chambers than stock, that JET-HOT coated header is heating things up, I think that is why my idle is funny. I think it cooked my motor...

Jet-Hot should run cooler, not hotter.

freakintiger · Oct 4, 2005

tjm73 said:
Jet-Hot should run cooler, not hotter.

For the engine bay yes, but since the stainless steel ranger header is coated inside and out, it itself cannot shed nearly as much heat as it used to. Therefore the head cannot lose the heat it would have through the manifold originally, or now the header. The heat is forced either to stay in the head and dissipate from the head itself and through the aluminum valve cover, or be blown out through the exhaust. I think my year old catalytic convertor is dyiing out due to the inntense heat thrown at it...

Head swap on N/A?

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