what compression should I choose.

[Aproductions]

Alright so I went to the machine shop today to see the progress on my motor and find out what headgasket to get.

So I am going with a Cometic MLS .020 over.

Also, I am running a Holset H1C from 20-25lbs.

Running 94oct plus the AEM meth kit 50-50.

tune= Ecuflash and evoscan.

Most important, is it safe to go with a thicker headgasket if I want to lower my compression?

here is what I am told.

if i went with the .051 regular Cometic MLS I would be at 9.6:1 compression. (I have 9:1 pistons in).

So it breaks down something like this.

.051=9.6:1
.063=9.0:1
.070=8.7:1
.075=8.6:1

and the list continues.

So for a street car that I want some bottom end on, is it safe to go with a .070 thick headgasket?...remember its MLS

 

[gst96spyderman]

I lowered my compression replacing my HG. Went mls 1.6mm though. Minus timing belt breaking after 400 miles, I'm satisfied. Only problem is I run a sleeper 16g setup and the lower compression makes boost buildup at lower rpms a little longer.

 

[cookmeup272]

I would run 9:1 compression, Thats what I will be aiming for and if we dont get E85 here...then ill be running 93.

 

[Aproductions]

you think it is safe to do the 20-25lbs with a holset with higher comp?

remember I don't have link....I use ecuflash

 

[cookmeup272]

I will be running an hx40, but im not sure how much boost i will be running on 93...and I have dsmlink, so I dont really know what to tell you there. I never used ECUFlash and havent really been keeping up on it.

 

[LiquidX]

This Shoukd be in "bolt on tech" not the newbie forum. You have been on here long enough to know this and your post count shows that.

 

[MrBoxx]

Alex, at Liquid's recommendation, I moved your thread to the Tech section, Cylinder Head and Short Block sub-forum. You'll get more high-quality, in-depth answers here than in the Newbie forum, where you'll get mostly uninformed opinions. If you feel differently, let me know.

 

[Aproductions]

no thats cool, thanks.

I only did it to get some quick answers fast. sorry.

 

[Aproductions]

so which shouold I choose.

.051=9.6:1
.063=9.0:1
.070=8.7:1
.075=8.6:1


Is it safe to go thicker?

 

[codeofdastreets]

compression im going on the next motor will be wiesco 10.1.1.. on e85

 

[Aproductions]

How safe is it to go like .070 on a mls headgasket?

That would give me around 8.8:1 compression.

or should I do like .080 for like a 8.4:1 compression?

 

[DSMer541]

Got me wondering what my compression is... I went with a 8:1 piston and a Mitsu 4-layer MLS, so im probably at around stock 6-bolt compression( 7.8:1 )..... Im able to run 14* peak timing at 24 psi on a E3-16g and 92oct pump gas so far ( still pushin it ), when I do 3rd gear tuning and I throttle it at 3,200 rpms I see full boost by 4k..... I've heard lower compression can handle more boost and more timing easier which is why I went with a low compression build so when it comes time to strap that monster turbo on I know I can push it.... It is a street car too, and I dont mind a little lag

I guess the question is what are your HP goals and do you think you will ever run more boost or a bigger turbo? If your gonna eventually go for big power, like more than 550hp, and lots of boost, you may want to get that compression down...

 

[Aproductions]

I will stay with the holset h1c and I am thinking 25psi but not more.

also like i said I have aem meth and 94 octane.


I could probably do 8.8:1 with a .070 gasket but it is safe to go that thick?

 

[DSMer541]

I dont see why not..... just make sure you torque everything down properly and in sequence and it should be fine..... but Im not really a expert in the headgasket department so dont take my word for it....

 

[Aproductions]

would anyone else like to chime in and tell me if it is safe to run the thick headgasket like .070 or .080?

 

[Aproductions]

I could really use some help with this.

Is .070 too thick for a mls headgasket, I don't want it to blow out.

Also would the 8.8:1 compression be okay for my car or should I go a little thicker/lower comp?

 

[BigBeans]

I could really use some help with this.

Is .070 too thick for a mls headgasket, I don't want it to blow out.

Also would the 8.8:1 compression be okay for my car or should I go a little thicker/lower comp?

If you always plan to use pump/meth, 9:1 is fine.

If you want to run decent boost and have the option to do so on pump alone, get under 8.5 so you can keep some timing in it and make good power.

I run 30psi with straight 93 pump gas on a .066 Cometic MLS with no issues. Overall compression is about 8.3 in my setup. I never had a problem with the .066 HG i've been using. I kicked the snot out of the car on the dyno without even re-torquing the head, no issues.

I wouldn't hesitate at all to run a .070 MLS.

 

[bastarddsm]

If your running pump gas, run the least compression you can.

Also, are you sure those numbers are right? 1 cr point for 0.02" sounds like a lot.

 

[Aproductions]

thanks man,
I think I will go with the .070 gasket...giving me about 8.8:1 comp.


so I will run about 25lbs with 94 and 50/50 meth.

I know I could do 9:1 but I want more flexibility. I also found a .080 gasket but that is getting thicker and my comp would be like 8.3:1 or something.

the machinist told me to do 8.6:1 which would be a .075 gasket.....would that give me that much more timing and boost?

 

[BigBeans]

thanks man,
I think I will go with the .070 gasket...giving me about 8.8:1 comp.


so I will run about 25lbs with 94 and 50/50 meth.

I know I could do 9:1 but I want more flexibility. I also found a .080 gasket but that is getting thicker and my comp would be like 8.3:1 or something.

the machinist told me to do 8.6:1 which would be a .075 gasket.....would that give me that much more timing and boost?

You're not going to see much difference between 8.6 and 8.8. Higher compression is good for off boost power and MPG, so with the higher octane from meth i'd go for the higher side, the 8.8.

 

[DSMReviver]

9:1, and meth is great combo.

my future plans, and also you dont have to boost the crap out of it.

 

[Aproductions]

well from what I hear the h1c doesn't start flowing alot till 25psi.

 

[DSMReviver]

well from what I hear the h1c doesn't start flowing alot till 25psi.

You sure can boost to what ever you desire, long as you have bottom end support, like me, i have eagle rod, and wiseco pistons. good to handle that much or more. and with E85, it will handle 25psi with ease.

But even with 6bolt rod, i am sure there will be no problems. just look at the guy that did 6++hp on a stock 6 bolt. oyster motorsport i think with E85.

 

[Aproductions]

their comp is 7.8:1

I am gonna do 8.8:1 and yeah I am just worrying about knock

 

[BigBeans]

my future plans, and also you dont have to boost the crap out of it.

High boost is the only way to run a big turbo on a small engine.

their comp is 7.8:1

I am gonna do 8.8:1 and yeah I am just worrying about knock

You'll be fine, just tune it safely.