some more rebuild questions

[doom26464]

havn't been on here for awhile supra done nothing but sit for the last few months. So I figure I would get off my ass and do something about it since no one going to come and take it off my hands.

-Ok my first question I am looking at buying a mhg for it. Was looking on ebay and came across basiclly either the greddy metal headgasket or the hks stopper. Now I noticed they come in different sizes such as 1.0mm or 2.0mm and 3mm. Now I have no clue as to what the difference in size does?? plus I have heard of cosmetic being the most forgiving as well but dunno what that means. Plus the block has to be decked to a certain smoothness as well doesn't it or something(i realize this doesn't make alot of sense but plz some one try and explain the whole mhg situation too me as best they can lol)

-next question since the turbo on there right now was leaking oil+buring it (the main cause of the rod knock) I figured it be a good idea to get rid of the problem and buy another turbo. Was figuring migth as well go with a .57 trim or .59 but with thoses turbo would i have a problem hitting fuel cut, I would still be running the stock afm and fuel system. ( I would have a mbc to control it though)


hope some one can answer these questions for me and help me figure this out before I dive into this rebuild.

 

[steven89]

This i found and saved the link as im planning on getting a supra http://www.supramania.com/forums/showpost.php?p=216396&postcount=5

Then there is VVV this copied from somewhere on here.. forgot though, whoever wrote this needs to claim it! lol

_____________________________________________________________________________________________________________

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


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.

______________________________________________________________________________________________________________

Hope this helps...it helped me understand the HGs


And heres another link of what to change while under there http://www.supramania.com/forums/showthread.php?t=1103

 

[doom26464]

This i found and saved the link as im planning on getting a supra http://www.supramania.com/forums/showpost.php?p=216396&postcount=5

Then there is VVV this copied from somewhere on here.. forgot though, whoever wrote this needs to claim it! lol

_____________________________________________________________________________________________________________

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


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.

______________________________________________________________________________________________________________

Hope this helps...it helped me understand the HGs


And heres another link of what to change while under there http://www.supramania.com/forums/showthread.php?t=1103

Damn that shit sounds like alot of work. plus I wouldn't be doing it myself probaly paying a shop to do it so they probaly wouldn't know all this stuff and might slip up somewhere. Guess I'll probaly just stick with a good ole oem hg with arp hardware once again....


Also this is a bottom end rebuild this time around. I had the hg blow on me last year had it replaced with a new one with arp headbolts, along with all new gaskets and seals, new head and cams, thermostat and did the timing belt. Then got a rod knock like 8 months later lol

 

[doom26464]

bump

 

[doom26464]

no one has any other info on the turbo??? bump:1zhelp:

 

[jdub]

Then there is VVV this copied from somewhere on here.. forgot though, whoever wrote this needs to claim it! lol

That was me
Glad it helped you.

 

[doom26464]

bump again....No one has an answer to these question?? wow guess Supramania has no traffic on it??? I'll try my luck on supraforums.:3d_frown: :1zhelp:

 

[Halsupramk3]

for your turbo question.

if you plan on using stock fuel management i would go with a 57 trim ct rebuild. if you go bigger some piggyback fuel management may be necessary but it is no problem with a 57. Also i and others believe the longevity of the 57 trim is much better than larger ct26 rebuilds. the 57 will be a bigger seat of the pants feeling turbo over oem size. be careful with manual boost controllers. they will produce different max boost amounts in different gears. It may boost 7psi in first and 8.5 in 2nd and 10psi in 4th or some sequentially higher boost pattern for each gear and particular load on the engine at the time.

As posted by others select your head gasket size after you know how much metal is removed from the head and block. if the head and block has been decked sometime before in the past you would have to add in that number to calculate the total metal removed to know how thick the head gasket needs to be to get back close to the original size combustion chamber to obtain close to a stock compression ratio. I had to mill off alot of metal off my engine so to replace the metal removed i used a 2mm. that still gets me a 9:1 compression ratio. I would have to use a 3mm to get the CR back down to 8.5:1 which i dont like the idea of a HG that thick.