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normally I am pro milling heads, but this application might see boost. At that point I can swap gaskets (probably get rid of the +4cc pistons as well) and keep the same heads. I admit that milling is a better way to increase compression, but I just didn’t want to buy another set of heads down the road. my other n/a setups have had milled heads.
I doubt you're reducing strength much by milling. LSA heads are also made out of a stronger alloy, iirc.
 

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Mill .020" and use a .040 or .045 cometic gasket. Stupid expensive way to do it, but next time around you can swap to a thicker gasket if that's what you want.
 

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Discussion Starter #25
this is just my preference, I like the responsiveness of higher compression when out of boost, I'm trying to manage IATs during all this, As it does get high at the top of 5th, My end goal is a more efficient setup, the less boost I need, the less cooling I need, the less work I have to do.
 

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Why bother keeping the compression up? ADD MOAR BEWST
this is just my preference, I like the responsiveness of higher compression when out of boost, I'm trying to manage IATs during all this, As it does get high at the top of 5th, My end goal is a more efficient setup, the less boost I need, the less cooling I need, the less work I have to do.
[/QUOTE
i didn’t know it was already boosted, it makes a lot more sense to run lower compression and turn up the psi haha
let me reply to my own reply haha. It makes sense if you’re going for peak hp. i guess if your goal is responsiveness or simplicity of tuning, i can also see how a little more compression miiiiight help
 

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this is just my preference, I like the responsiveness of higher compression when out of boost, I'm trying to manage IATs during all this, As it does get high at the top of 5th, My end goal is a more efficient setup, the less boost I need, the less cooling I need, the less work I have to do.
just out of curiosity, what is your elevation? how many lbs i’d boost are you pushing? and what compression ratio are you at?
 

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this is just my preference, I like the responsiveness of higher compression when out of boost, I'm trying to manage IATs during all this, As it does get high at the top of 5th, My end goal is a more efficient setup, the less boost I need, the less cooling I need, the less work I have to do.
Top of 5th? 180mph on a 28in tire on the stock 3.46?

Roughly 8cc per compression point worth ~4% power. The head you want to put on is only half a compression point less based on those estimations. Thats not a lot of power loss.
 

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Discussion Starter #31
Top of 5th? 180mph on a 28in tire on the stock 3.46?

Roughly 8cc per compression point worth ~4% power. The head you want to put on is only half a compression point less based on those estimations. Thats not a lot of power loss.
188 on 27", I don't have a gto. Just happen to have a LS2, so figured might find some data on it over here.
 

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So this is a boosted setup? You are wasting time with all this head swap, milling, thinner gasket nonsense if it’s boosted. Ls9 head gaskets have been used successfully to 1200 rwhp and heads don’t gain that much on a boosted setup. If you want more power add 3 psi and you will gain more without fussing with heads/milling/etc. Also cathedral port heads are more responsive out of boost than square ports if that’s a concern at all.

A buddy of mine ran LSA heads worked by tea on his 408 and started pushing water at 1200 rwhp. He switched to a 6 bolt setup and makes 1700 rwhp now. If iat is a concern run a better intercooler or switch to an air to water or add meth injection. So many options don’t do it the hard way milling heads and using inferior head gaskets for a little compression when it will actually cause you more issues with big boost.
 

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Discussion Starter #34
So this is a boosted setup? You are wasting time with all this head swap, milling, thinner gasket nonsense if it’s boosted. Ls9 head gaskets have been used successfully to 1200 rwhp and heads don’t gain that much on a boosted setup. If you want more power add 3 psi and you will gain more without fussing with heads/milling/etc. Also cathedral port heads are more responsive out of boost than square ports if that’s a concern at all.

A buddy of mine ran LSA heads worked by tea on his 408 and started pushing water at 1200 rwhp. He switched to a 6 bolt setup and makes 1700 rwhp now. If iat is a concern run a better intercooler or switch to an air to water or add meth injection. So many options don’t do it the hard way milling heads and using inferior head gaskets for a little compression when it will actually cause you more issues with big boost.
I get that, that's the typical logic on a drag built, that gets undivided attention and only does A to B maybe twice a month. That's not what I have or what I do, Besides It's already near perfection for me, I'm less interested in re-fabbing anything or wiring in addition pumps and relays, that's more work to me.
Not concerned about pushing water. Had that issue with another TT build and been remedied.

My post is about clearance, not how to build a fast car :)
 

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I get that, that's the typical logic on a drag built, that gets undivided attention and only does A to B maybe twice a month. That's not what I have or what I do, Besides It's already near perfection for me, I'm less interested in re-fabbing anything or wiring in addition pumps and relays, that's more work to me.
Not concerned about pushing water. Had that issue with another TT build and been remedied.

My post is about clearance, not how to build a fast car :)
If not building a fast car why change what you have now? If wanting more power for a toy then the answer is still the same...more boost is the easier way to do it.
Regardless of what you think you’ve remedied milled heads with thinner head gaskets will increase the potential for pushing water with boost. If wanting more response out of boost switching to square ports from smaller cathedral ports is a step in the wrong direction as you will lose response even if you keep compression the same or even slightly higher.
Nothing you say makes sense it seems more like you came here wanting to argue. I don’t build drag cars either my cars can be daily driven so everything I’ve said applies to a street car. Not sure why you think it could only go a to b a couple times before needing work just because you add a few psi.
 

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Discussion Starter #37
why bother switching then? leave stuff the way it is.
Near perfect isn't perfect. And I feel I can do better, is that ok?
If not building a fast car why change what you have now? If wanting more power for a toy then the answer is still the same...more boost is the easier way to do it.
Regardless of what you think you’ve remedied milled heads with thinner head gaskets will increase the potential for pushing water with boost. If wanting more response out of boost switching to square ports from smaller cathedral ports is a step in the wrong direction as you will lose response even if you keep compression the same or even slightly higher.
Nothing you say makes sense it seems more like you came here wanting to argue. I don’t build drag cars either my cars can be daily driven so everything I’ve said applies to a street car. Not sure why you think it could only go a to b a couple times before needing work just because you add a few psi.
the argument here isn't even about my original question, but others claiming how they would do it or how thier friend did it. I've already done the "add few psi" thing, I'm not downplaying other peoples builds, but they typically aren't at wot long enough to be concerned with adding a few more psi, as their A to B typically ends in 3rd or 4th gear. And will never see 5th or 6th and/or knows what happens up there.
 

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Near perfect isn't perfect. And I feel I can do better, is that ok?
wtf is your definition of "better," staring at a different casting number on your heads when you have your hood up?

the only reason most rational people would swap out 243's for rectangle port heads is for better flow. In doing so, you already have to put more money in for the heads, gaskets, and whatever machine work you want done. but you said your post isn't about having a fast car.

so it's about that casting number, right?

as far as clearance specs, if you don't already know, please learn how to measure valve drop on a set of heads or measure PTV clearance yourself. we're not going to do the work for you, and frankly it should be done individually for every setup and not just with some generic numbers googled off the internet. you can find those answers yourself if you put forth the time and effort.
 

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Discussion Starter #40
I was able to filter through it, I've gathered .030 mill isn't uncommon on this head/block combo. So switching to a .040 gasket and a clean up isn't too aggressive, gets me closer to my goal. But yes I'll double check clearance.
 
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