You have to have really flat surfaces for a metal hg to seal.

97-gst said:

mods are all up to date in profile. Running 93 octane tuning on dsmlink, not gonna crank it up to 30 right away, but was planning on going to 25 and cheackin for knock then 28 and so on. heres the headgasket Cometic Multi-Layer Steel Head Gasket (DSM) - Modern Automotive Performance

Click to expand...

You can use a felpro head gasket and arp head studs and run 25 psi all day from what I have read. also pretty much what the guy above me said the surfaces of the head and block need to be perfect to run a metal head gasket or your going to have leaks. where as the composites can form to the slight imperfections better.

oem composite with arp head studs.

Yea, the metal HG's are picky about how well the surface is cleaned, machined andkept perfect right up till installation. Personally i would like one but don't want to mess with it until i'm forced to. Currently i run normal ARP's and a Felpro composite HG and run 30psi on ethanol daily. doing it on pump gas isn't much different except there's littleroom for error with the detonation that can soeasily occur on pump gas.. Just keeptiming low and AFR's proper and you should be ok

30psi on a evoIII running pump gas

^^^
+1, how is this possible? i did not know they would really do 30psi. anyway, your on stock internals correct? maybe more experinced people can chime in on that. i would think you may be pushing the limits of the rods/pistons at 30psi. just a thought.
i have the cometic mls, seemed great for the 330 miles the car was actually running. no need to retorque with arp's. i did just to see but they did not budge.

I think 30psi on stock internals is to much.

was gonna get some cams too while the head is off, what would yall recommend? i mean i was just sayin in the general 30 psi range. Im on completely stock seven bolt running 24 psi right now with no knock. Is there anything else I should try and get for it while its apart?

There is no good answer to this question, contrary to all the answers that get thrown around every time it's asked. The Cometic MLS and standard ARPs may work for years at 33psi on one car, and let go at 28psi on another.

In relation to the OP's question, the limits of the HG, head studs, and engine internals are determined by actual cylinder pressure...and boost is just one piece of that equation. Fuel type, AFRs, timing, knock, airflow, and other factors all contribute to the total pressure exerted on the HG and other engine components.

On a related note, people get WAY too hung up on boost. Horsepower is made with air flow (the volume or mass of air flowing through an engine)...not the pressure felt at the IM. You could get 40psi of "boost" flowing through a steel drinking straw, but you aren't going to make a lot of power with that much air.

I run mitsubishi MLS and Maperformance h11's to 43 psi on pump meth with no problems. I had regualr arps, but a little bit past 30 psi the head studs started to stretch. If you plan on going further eventually just get the h11's and call it a day

jpmxrider489 said:

I think 30psi on stock internals is to much.

Click to expand...

My friends car just got off the dyno today on a stock bottom end 7 bolt with 86,000 miles on it they ran it to 30psi then backed it back down to 28psi only, because the car wasn't making more power due to head setup. Ostar runs around 40 psi on stock internal bottom end. So I think everything will be fine depending on tune.

i wouldnt boost 30 until you do your internals and bearings and everything.

Calan said:

There is no good answer to this question, contrary to all the answers that get thrown around every time it's asked. The Cometic MLS and standard ARPs may work for years at 33psi on one car, and let go at 28psi on another.

In relation to the OP's question, the limits of the HG, head studs, and engine internals are determined by actual cylinder pressure...and boost is just one piece of that equation. Fuel type, AFRs, timing, knock, airflow, and other factors all contribute to the total pressure exerted on the HG and other engine components.

On a related note, people get WAY too hung up on boost. Horsepower is made with air flow (the volume or mass of air flowing through an engine)...not the pressure felt at the IM. You could get 40psi of "boost" flowing through a steel drinking straw, but you aren't going to make a lot of power with that much air.

Click to expand...

AMEN!! it comes down to lbs/min from what i know of forced induction engines. thats why im sure a t25 at 15psi and a 20g at 15psi would have an enormous difference in power. psi plus actual airflow, just like u said.

97-gst said:

was gonna get some cams too while the head is off, what would yall recommend? i mean i was just sayin in the general 30 psi range. Im on completely stock seven bolt running 24 psi right now with no knock. Is there anything else I should try and get for it while its apart?

Click to expand...

272's seem to be a very popular choice. cant speak from personal experience....yet. theyre at the machinist. womp, womp

i run 25lbs on a stock head and bottom end all day long pushin 400hp

I would do the mitsubishi metal multi layer head gasket.

If your using a mls i would have the head and the block decked.

pyanac711 said:

i run 25lbs on a stock head and bottom end all day long pushin 400hp

Click to expand...

The stock longblock is a heavy mix of aluminum and iron, so it should be able to support substantially more than 25 lbs of weight before causing deformation or damage. Although, I'm not sure the hood would close correctly with a 25 lb. object resting on top of the the longblock like that. And I'm still trying to figure out why it's relavent to know how much weight an engine supports...

^

jpmxrider489 said:

I think 30psi on stock internals is to much.

Click to expand...

We all have our opinions some are right some are well... .

For the majority of people on here yes... But some people do know how to get away with it just fine


bottom-line this all has been discussed many times... .

99gst_racer said:

The stock longblock is a heavy mix of aluminum and iron, so it should be able to support substantially more than 25 lbs of weight before causing deformation or damage. Although, I'm not sure the hood would close correctly with a 25 lb. object resting on top of the the longblock like that. And I'm still trying to figure out why it's relavent to know how much weight an engine supports...

Click to expand...

I can only applaud at this. Very classy.

As Calan touched on, the amount of pressure makes little to no difference without the proper variables set before hand. There are several, several factors to how your engine makes power, pressure being one of them. You are forcing air into the combustion chambers to make more power. The density of the air, temperature, timing of the ignition, how efficiently it's being compressed, evacuation, etc. all factors into the ultimate power making process.

Now, for this question you are more worried about the common boost level you can run without lifting your head. We'll make it simple - A T-25, stock turbo on a 2G turbo'd DSM is a paper weight and flows very little comparatively to the rest of the turbos that we are used to. It's the 'baby'. A 16g, however, flows much more efficiently. 10PSI on a T-25 is different than 10PSI on a 16g. Same goes for any other turbo. Where you may be able to run 25psi with one turbo, at 22psi you might lift your head on another turbo due to the efficiency differences between them and how much they actually flow.

Now an experience with my old GST as an example - I was able to run 19ish PSI on my 14b. When I switched over to a 16g I was hitting fuel cut by 15psi. After a fuel pump rewire I was able to run 16psi without leaning out or hitting fuel cut. So, if you want a proper answer - explain what turbo you're going to be using.

Edit - Via your profile I'm seeing your turbo as a Evo III 16g. With the proper tune, fuel delivery, those ARP's and Headgasket, you could likely run that turbo to it's full efficiency. Just look up the map for that turbo to find it's most efficient level and work from there.

wvturbo2 said:

I run mitsubishi MLS and Maperformance h11's to 43 psi on pump meth with no problems. I had regualr arps, but a little bit past 30 psi the head studs started to stretch. If you plan on going further eventually just get the h11's and call it a day



My friends car just got off the dyno today on a stock bottom end 7 bolt with 86,000 miles on it they ran it to 30psi then backed it back down to 28psi only, because the car wasn't making more power due to head setup. Ostar runs around 40 psi on stock internal bottom end. So I think everything will be fine depending on tune.

Click to expand...

Believe me unless you want your feelings hurt Don't go off what Ostar did .p Regular Arp's have been proven over 40+psi and over 900+ whp. I ran regular arp's to 38 psi with no issues. The L19 etc are better but not necessary.

spoolin ddub said:

Believe me unless you want your feelings hurt Don't go off what Ostar did .p Regular Arp's have been proven over 40+psi and over 900+ whp. I ran regular arp's to 38 psi with no issues. The L19 etc are better but not necessary.

Click to expand...

I'm not gonna disagree But merely say... . The majority of the people reading what your saying are not on their own going to be able to keep their tune in check anywhere close enough to do anything close to that.

It's not a bad Idea to Keep in mind your posting in the newb forum and a lot of people will read that and think that because someone can do something they can... .

MY1GDSM said:

I'm not gonna disagree But merely say... . The majority of the people reading what your saying are not on their own going to be able to keep their tune in check anywhere close enough to do anything close to that.

It's not a bad Idea to Keep in mind your posting in the newb forum and a lot of people will read that and think that because someone can do something they can... .

Click to expand...

thats why i posted what i did. because by reading the response of what people hear they usually think it is possible

spoolin ddub said:

Believe me unless you want your feelings hurt Don't go off what Ostar did .p Regular Arp's have been proven over 40+psi and over 900+ whp. I ran regular arp's to 38 psi with no issues. The L19 etc are better but not necessary.

Click to expand...

Not saying that cannot be done but, I had a stud go bad on me at 25psi with normal arp studs. The front left stud bound up with the threads of the nut and lifted. Only that one did. I put the stud on a vise and could not get the nut off. It may have been a dud. I got L19s and had the head done and used a MLS gasket and running 20 but have been up to 30 and no issues as of now. I believe tha everyone has a story about a good and bad....by the way, the head lifted as I was blowing bubbles but, the head gasket was still just fine but, did not reuse it though.

spoolin ddub said:

Regular Arp's have been proven over 40+psi and over 900+ whp. I ran regular arp's to 38 psi with no issues. The L19 etc are better but not necessary.

Click to expand...

This is WAY out of the ordinary. I bet 99 out of 100 people would not be able to get anywhere near that much power out of regular ARPs.

FWIW - My standard ARP's stretched and I lifted the head at 33-35psi, flowing something like 58lbs/min on E85.

spoolin ddub said:

Believe me unless you want your feelings hurt Don't go off what Ostar did .p Regular Arp's have been proven over 40+psi and over 900+ whp. I ran regular arp's to 38 psi with no issues. The L19 etc are better but not necessary.

Click to expand...

That's bogus... Running regular ARPS at 900hp....