catthefish

-so im going with cosworth for the head gasket but no clue what thickness I was thinking 1.8 but I have no clue.
-Any uses etc.?

S13 curtis

that will probly put you to 8:0:1 compression ratio

the thicker the head gasket the lower the compression you will have.

catthefish

Cool thanx

MadScientist

Headgasket will effect your compression ratio and your throtle response.

Run what you want but know that most people are running a 1.2 - 1.3.
If you had the head or block resurfaced (decked) then you should run a 1.8.

If your blowing headgaskets then you need to resurface.

-Drew

jr_ss

Stock is 1.1mm for reference. I have a milled head and decked block, but I chose to run a 1.5mm to up compression for better off boost response and higher power levels.

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s14unimog

^ that doesn't make any sense. Installing a thicker head gasket will not raise compression. I currently run a Cosworth 1.5mm head gasket on my SR to lower compression a little.

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Propaganda

Maybe that's because he removed a good amount off of the head and block........................

godsmack

ya when you have a milled head and decked block and use the oem gasket you will raise the compression so that's why some ppl will go with the 1.8 gasket. IMO 1.2 FTW without milled head.

Teambadrun

Dude, I have a 1.5mm gasket on my 2.2L but i wouldnt go 1.5 MM ona stock engine because the compression would be too low.. around 8.0 or so.. not good for low boost applications

just run 1.2MM cosworth 87mm gasket, you can get it off FRSport.com - Aftermarket Performance Parts
you should deck your head while your there around 10thou and you should see 8.6:1 compression which is what you would want for 200-400rwhp

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venom

my head gasket is leaking oil. so im getting a new one. dont know which one. whats better for my stock T25. thank u.

alesserfate

go with a 1.1

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j87w

One other thing people need to realize when changing headgasket thickness/decking head or block is that it changes camshaft timing. You will need camgears to correct your camshaft timing.

Skreech_Powerz

Since when does head gasket height have anything what so ever to do with cam shaft timing? It only changes if you don't corectly re-imstall your cams... then it changes your timing

Skreech_Powerz

And your headgasket effects your C/R, and also how much boost you CAN run, For instance I Run 13psi on my stock Headgasket, and stock ones have been known to hold up to 17Psi befpre blowing, so if your looking to run Low PSI for Example 7/10 Psi a 1.8mm is too thick and you'll loose most of your HP&TQ, the gasket your lookinh into can take 20-25psi and stilk ask for more... so.it depends. And if you plan on runninh high boost 12+PSI highly recomend a 255 Hi-output walbro, or a 320 Hi-output Aem fuel pump , and a fuel pressure regulator

Mikester

Funny. I run OEM HG on a resurfaced block/head. For some weird reason, I didn't have to get cam gears. Oh wait- that's because it's not necessary



As stated above, I run OEM HG with ARP studs at 24psi (making 400+hp); and the only thing that's blown so far is the transmission... So why did the thick-ass steel tail shaft go before the 1.1mm thick head gasket? Simple- The key is proper installation and tuning- NOT reinforcing it with MLS so that other, more expensive internals will fail first. There are 700+hp SR's out there with OEM head gaskets that will take it all day long just like MLS!

This is right up there with the rocker stopper conversation- there are different camps out there; and plenty of threads for y'all to add your misconceptions into.

Since this conversation went on a tangent based on Jr_ss' post, stop by the builds section and see what he's talking about.

OP: A Cosworth headgasket is a good choice- just make sure you take all the proper precautions when installing (i.e. machining the front cover even with the deck, proper resurfacing etc); and most of all- GET A GOOD TUNE! There is no 'magic psi' number you need to worry about for the average 300-500hp SR... What you need to worry about is the impact on the internals in the event something goes wrong in the combustion chambers because all of that force has to go somewhere. If the HG is reinforced, it will go out the next path of least resistance- The only way to protect your motor against that is proper setup & tuning.

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Skreech_Powerz

Last I checked I didn't say u can't use a stock hG, I said a 1.8mm for stock use and stock boost is too big, and idk where u live but where I live in the carribean they blow at 20psi cause of the head here....

cotbu

Wrong again! stop just listen!

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jr_ss

Boy did this topic go on a tangent... That was for my OLD build, the one I did in 09', when this topic was relevant.

Either way, you can correct for material milled off the head by running a thicker head gasket to get back to "stock" specs. Do you need to time your cams if you don't? Probably, is it going to hurt you if you don't? Probably not. If you want every last horsepower out of your car, you're going to be degreeing cams as it is, so what does it matter?

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Danger_Dorn

A few things here...

1. Changing compression/ hg thickness has NOTHING to do with cam timing.

2. I have a stock rebuilt SR with a cosworth 1.8mm hg. I did have the head and block decked like you should anyway so if you do all that you may come out even or you might BARELY lower compression.

3. The best thing you can do is get your head and block milled and then as the machine shop how much they took off. From there take the difference and get the proper sized HG.

jr_ss

Increasing or decreasing the distance from the deck does change cam timing and compression. It is a minute change, but it does happen.

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pacotaco345

I was told I have to deck my head and block to run a metal gasket... I decked my head only, scraped the block clean with a razor blade & brake cleaner, then installed my 1.2mm tomei head gasket with arp headstuds and no copper spray.

I have no idea how much the head was milled nor what the current compression ratio is. I run California's shitty 91 instead of the 93 that the oem tune is for, stock timing & 11 psi of boost on the t25 with no problems. Plan on running 15 on a s15 t28 in the near future. Hate me.

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fliprayzin240sx

^^^Did you deck mill the oil pump cover to match the block? The oil pump cover is usually taller than the block and thats what usually get people in trouble with MHG. Stock paper gasket can correct for the difference.

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pacotaco345

No, from my understanding the front cover is actually lower than the front of the block, so when you install those front bolts to the head they stretch the cover to the level of the block. I also put RTV around that area. AND I have an update. With what my friend told me are gtir pistons and my previously setup I got 130 psi compression across the board even with the car cold. So I'm assuming its fine when warm especially since its all even.

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fliprayzin240sx

No, its usually taller. Its not often that they're matched up even from the factory. They're higher up to seal better with the head without needing to use RTV or anything.

As far as the compression, 125 is the minimum. Drop a capful of oil on each cylinder and see if the compression jumps. If it does, then rings are going bubye.

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pacotaco345

My test was cold lol, I'm not really concerned with my compression numbers because of that. I'm sure if it was warm it'd be up to 150 no problem.

EDIT, lol to clarify I have no compression with my setup, I was just posting my experience with a tomei metal hg and some headwork that I had done.

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codyace

Not to be a nerd, but the FSM says to use silicone across the front cover/oil pump to head seal.

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mewantkouki

^ +9000, I can attest to this. I used an apexi 1.1mm on my stock motor cleaned and checked both surfaces with a straight edge. Perfect 150psi compression after installing the HG but the bitch weeps oil from the front cover ever so slightly... Now I get to do it again. Yay