what h/g should i buy
- Thread starter tyler
- Start date
- Status
As long as its metal, buy it. :evil2: If its not metal, you tell that dealer/mechanic.....sir, you have no idea what you are doing.
If you are only pulling the head off, and not completely removing the engine for machine work. I would suggest a cometic MHG, the 1.4mm. I think 935 Motorsports sells them as well as Paradise racing. But the easiest and quickest way to get one is to order a Titan Motorsports 1.4mm MHG. They have them in stock and they are extremely quick with shipping. They have a website, www.titanmotorsports.com or just give them a call. (407) 277-8423
Hope this helps
Denny
Hope this helps
Denny
Kind of off topic but what is the stock hg size (so I know how much to machine off of the head)?
Chris
Chris
For the 7M... Cometic. The others are good as well, but they really do require the smoothest of mating surfaces and the tolerances are very narrow.
Unless you can get a guaranteed/for-sure RA (?) smoothness necessary for the head and block surfaces, go with the Cometic.
If you are not having the head/block prepped for a metal headgasket, stick with the stock/dealer one. Don't plan to turn up the boost tho, because it will also eventually fail if you do.
Unless you can get a guaranteed/for-sure RA (?) smoothness necessary for the head and block surfaces, go with the Cometic.
If you are not having the head/block prepped for a metal headgasket, stick with the stock/dealer one. Don't plan to turn up the boost tho, because it will also eventually fail if you do.
JustAnotherVictim
Supramania Contributor
Good post Satan...I'm gonna elaborate 
Stock HG - composite material, very forgiving of block/head surface RA. Good for 14 psi (some have run more) with ARP hardware.
HKS Stopper type - best there is, also the most expensive. 30 RA spec. Crank the boost to your hearts content (you can still blow the motor though) <edit IJ 100% correct on this>
HKS, Titan, Greddy Bead type - Very good, also requires a 30 RA. 20+ psi easily
Cometic - Bead type, also very good. Big difference is the RA spec is 50. 20+ psi easily
More info on HKS metal head gaskets:
http://www.supramania.com/forums/showpost.php?p=216396&postcount=5
Ok...guess I gotta go into this again.
- You can't just take the head off and slap a MHG on. Both the block and head have to be decked to the RA spec required for the MHG you choose...that is if you want to do it right...and do it once.
- You can't just go out and buy a MHG...you have to determine how much material was removed during the decking process 1st! The thickness of the MHG affects compression. The stock HG is 1.37mm thick compressed. There is 0.040" in 1mm. If your machinist removes 0.005" from the block and 0.005" from the head (0.010" total), that is = 0.25mm. 1.37mm + 0.25mm = 1.62mm...use a 1.60mm thick MHG to retain the stock compression.
- Pay attention to the spec sheet that comes with the MHG. Some have rivets that have to be removed (Titan, Cometic).
- Do not use a spray sealer on a new MHG. It destroys the factory coating and can compromise the initial seal. Use of a spray sealer on a composite HG is fine.
- If you use the factory head bolts, torque to 75 ft/lbs. If you elect to use ARP hardware use the torque spec that comes with the package. Pay attention to this sheet! ARP Studs have a different spec from ARP bolts and the spec is different depending on the lube you use (oil vs. moly).
- Torque the head down according to the pattern in the TRSM using multiple passes.
- The front timing plate also has to be machined if the block is decked...the top edge of the plate will be higher if you don't, preventing the MHG from sealing. The TRSM also requires sealant along the top front of the timing plate where it meets the head...this has nothing to do with the MHG seal, everything to do with preventing an oil leak.
- The head will need to be re-torqued after 4-5 heat cycles. This includes new ARP hardware (studs or bolts). ARP studs that have already been heat cycled will not require a re-torque.
Stock HG - composite material, very forgiving of block/head surface RA. Good for 14 psi (some have run more) with ARP hardware.
HKS Stopper type - best there is, also the most expensive. 30 RA spec. Crank the boost to your hearts content (you can still blow the motor though) <edit IJ 100% correct on this
> HKS, Titan, Greddy Bead type - Very good, also requires a 30 RA. 20+ psi easily
Cometic - Bead type, also very good. Big difference is the RA spec is 50. 20+ psi easily
More info on HKS metal head gaskets:
http://www.supramania.com/forums/showpost.php?p=216396&postcount=5
Ok...guess I gotta go into this again.
- You can't just take the head off and slap a MHG on. Both the block and head have to be decked to the RA spec required for the MHG you choose...that is if you want to do it right...and do it once.
- You can't just go out and buy a MHG...you have to determine how much material was removed during the decking process 1st! The thickness of the MHG affects compression. The stock HG is 1.37mm thick compressed. There is 0.040" in 1mm. If your machinist removes 0.005" from the block and 0.005" from the head (0.010" total), that is = 0.25mm. 1.37mm + 0.25mm = 1.62mm...use a 1.60mm thick MHG to retain the stock compression.
- Pay attention to the spec sheet that comes with the MHG. Some have rivets that have to be removed (Titan, Cometic).
- Do not use a spray sealer on a new MHG. It destroys the factory coating and can compromise the initial seal. Use of a spray sealer on a composite HG is fine.
- If you use the factory head bolts, torque to 75 ft/lbs. If you elect to use ARP hardware use the torque spec that comes with the package. Pay attention to this sheet! ARP Studs have a different spec from ARP bolts and the spec is different depending on the lube you use (oil vs. moly).
- Torque the head down according to the pattern in the TRSM using multiple passes.
- The front timing plate also has to be machined if the block is decked...the top edge of the plate will be higher if you don't, preventing the MHG from sealing. The TRSM also requires sealant along the top front of the timing plate where it meets the head...this has nothing to do with the MHG seal, everything to do with preventing an oil leak.
- The head will need to be re-torqued after 4-5 heat cycles. This includes new ARP hardware (studs or bolts). ARP studs that have already been heat cycled will not require a re-torque.
^^ Listen to this guy!!! Everything in that post is crucial.
Before jdub responded, i was gonna lash some of you guys, How are you going to go and recommend a thickness for someone elses motor, when you have no idea if it needs a 3mm!!! I know it's good intentions answering this guys question, but seriously, if you know enough to answer that question, you should NOT be recommending a thickness!!!!!
Before jdub responded, i was gonna lash some of you guys, How are you going to go and recommend a thickness for someone elses motor, when you have no idea if it needs a 3mm!!! I know it's good intentions answering this guys question, but seriously, if you know enough to answer that question, you should NOT be recommending a thickness!!!!!
JustAnotherVictim
Supramania Contributor
Jaguar_5 said:
As I stated if the block is not being decked, then the 1.4 is what you need, and the Titan MHG is a Cometic copy. So if you get your head resurfaced, and just sand the block surface, a 1.4 Cometic or Titan gasket will work, done it twice no problems, running 17psi all day long. That is of course using ARP studs torqued to 90 ft/lbs.
drbowser3 said:
Gotta question for ya...how can you possibily keep the block surface straight if you sand it? In fact, that's the best possible way to FUBAR a block there is. If you want to getto your MHG install...have at it. This IS NOT the right way to surface a block!
Take a look at the ARP stud spec sheet below.
And where did you get 90 ft/lbs? Did you use oil or moly? My "buddy told me" is not the ARP spec sheet...it specifies 81 ft/lbs using moly and 105 ft/lbs using oil. I'll let you in on something...ARP fastener strength is based on 75% of the torque value specified. If you use 90 ft/lbs (assuming moly), you just went to 83% of fastener strength. I'm pretty sure the ARP engineers know what they are doing...using torque values based on hearsay is not the correct way to do this either.
Attachments
drbowser3 said:
But (apart from what Jdub said) you cannot prep for a MHG and not take any material off, even with your sanding method you still took material off! And then you took even more off with getting the head shaved. Sorry but just because you've gone through the process, doesn't mean you did it right!
Have you ever performed a leak down, or compression test on your car? I'm curious!
Btw, I think Titan = Cometic is just a rumor, i asked some guys at Titan and they had never heard of anything like that. Doesn't mean i asked the right people though, so i could be wrong.
JustAnotherVictim
Supramania Contributor
Jdub, are you sure about the stock gasket being 1.37mm? I remember micing it and getting more like 1.2mm, and I think IJ said it was 1mm compressed.
Anyway, I installed the thinnest Cometic MLS gasket (0.051"=1.30mm) and had .25mm total removed from the head and block. My measured compression was
#1 142psi
#2 145psi
#3 140psi
#4 144psi
#5 142psi
#6 145psi
which is pretty damn close to the stock 142psi. Based on that I think the stock thickness value of 1mm may be closest.
Anyway, I installed the thinnest Cometic MLS gasket (0.051"=1.30mm) and had .25mm total removed from the head and block. My measured compression was
#1 142psi
#2 145psi
#3 140psi
#4 144psi
#5 142psi
#6 145psi
which is pretty damn close to the stock 142psi. Based on that I think the stock thickness value of 1mm may be closest.
3p141592654 said:
Well...I thought it was 1.0mm myself. IJ corrected me in another thread...I'm very sure Ian knows what he's talking about :bowdown:
I did the same as you. Used a 1.30mm Cometic and had a total of 0.010" removed from the block and head. My compression runs 150 +/-2 psi across all cylinders. I'm using Ross pistons & rings.
Yeah, a quick search shows everything from 1.0 to 1.4 mm. I'm sticking with 1.0 mm since my numbers add up to that. I was pretty sure I saw a post where IJ said 1.0mm, but now I can't find it. Oh well!
What pistons you use makes a difference...here's a few compression ratios:
JE - 8.4:1
Ross - 8.5:1
Wisco - 9.0:1
Increasing the compression a bit is not necessarily a bad thing. The lower compression pistons allow you to add more boost, effectively increasing compression. If you use the pistons to increase compression, your bottom end power will actually improve...what you have to be careful about is increasing boost to the point where you may detonate. That may occur at a lower boost than a motor with lower compression pistons.
JE - 8.4:1
Ross - 8.5:1
Wisco - 9.0:1
Increasing the compression a bit is not necessarily a bad thing. The lower compression pistons allow you to add more boost, effectively increasing compression. If you use the pistons to increase compression, your bottom end power will actually improve...what you have to be careful about is increasing boost to the point where you may detonate. That may occur at a lower boost than a motor with lower compression pistons.
- Status