Piston Ring Gap Dilemma....

[Sside]

I am having a Local Machine Shop do my 7mgte rebuild and the guy in charge of my build was concerned about me boosting 13 pounds on a stock ring size gap. He recommended and said he wanted to go a little bigger on the Gap so that I would not run into problems later on. With that being said, I would love to have a spec sheet for the pistons I bought from Driftmotion but they dont come with one due to the fact that they are basically the same thing as oem factory pistons just 20 over... I ordered the machine shop to do oem specs on everything like recommended by Andy at driftmotion prior to the ring gap issue. My gut feeling says stick with oem specs on the ring size gap but the guy from the shop wants to go a little bit over. This is a well known shop, if not the best or one of the best in Houston. They have done tons of 7mgte's but they are also not a performance shop. When he asked how much I would be boosting his jaw dropped a bit as if it were a great number. So my question to yall who know more about this then I do is Do I stick to the oem gap? or Do I let the guy go a little over?. I do plan on going with a 57 trim and fuel upgrades in the future, My goal is a humble 350 hp to max 400 hp but I doubt any more then that since I want to keep my car reliable as possible for it will be my DD.

Thanks a million to all you guys who have read this.. Would really appriciate yalls opinions.

-Salvy

 

[suprafanatic]

i wouldn't mess with it, keep it oem. 13psi isn't much anyway. just make sure you got a good head gasket and arp's! As far as HP numbers and daily driving, im making right at about 500hp and i daily drive my supra, its been extremely reliable "knock on wood"

 

[Sside]

i wouldn't mess with it, keep it oem. 13psi isn't much anyway. just make sure you got a good head gasket and arp's! As far as HP numbers and daily driving, im making right at about 500hp and i daily drive my supra, its been extremely reliable "knock on wood"

Ok +1 for oem.... And yeah, I never believed 13 psi would be a great amount. I am going with a Hks metal head gasket and with ARP everything but the rod bolts... I might still go with the ARP rod bolts just to feel better about this build. I am waiting for the Arp Main studs to come this friday and taking the last two oil squirters and the studs to the shop monday. So I have a few days to get opinions before this block comes toghether. And about your dd supra, hope it stays reliable for many more years to come ... Thanks..

 

[Jeff Lange]

OE specs allow for quite a large ring gap. I wouldn't think you'd have any problems running a larger gap. Smaller gap is a much bigger problem than too big of a gap.

That being said, 13psi is not much, so I wouldn't think it would be needed.

OE Specs:

No. 1: 0.29mm - 0.44mm (Max Allowable: 0.74mm) -- NOTE: 0.06mm larger than 7M-GE
No. 2: 0.25mm - 0.53mm (Max Allowable: 1.13mm) -- NOTE: Same as 7M-GE
Oil: 0.10 - 0.44mm (Max Allowable: 1.04mm) -- NOTE: 0.04mm larger than 7M-GE

Jeff

 

[Sside]

OE specs allow for quite a large ring gap. I wouldn't think you'd have any problems running a larger gap. Smaller gap is a much bigger problem than too big of a gap.
That being said, 13psi is not much, so I wouldn't think it would be needed.

OE Specs:

No. 1: 0.29mm - 0.44mm (Max Allowable: 0.74mm) -- NOTE: 0.06mm larger than 7M-GE
No. 2: 0.25mm - 0.53mm (Max Allowable: 1.13mm) -- NOTE: Same as 7M-GE
Oil: 0.10 - 0.44mm (Max Allowable: 1.04mm) -- NOTE: 0.04mm larger than 7M-GE

Jeff

Ok 1+/- for a larger gap... But 13 psi is right after I break engine in, after that maybe come december I will be wanting to go with a 57 trim, 550 cc injectors and a fuel upgrade. So maybe a gap a bit bigger is not such a bad idea at 16-18 psi... Thanks alot Jeff, Really appriciate it and the OE specs..

 

[NewWestSupras]

If you are going to all the trouble of building your engine with quality parts and service, I'd strongly recommend Arp fasteners to replace stock rod bolts. If you ever decide to up the boost sometime down the road, it's nice to have the extra tensile strength they offer, imho. I'm happy I used them in mine, one less thing to worry about, sorta. gl.

 

[Sside]

If you are going to all the trouble of building your engine with quality parts and service, I'd strongly recommend Arp fasteners to replace stock rod bolts. If you ever decide to up the boost sometime down the road, it's nice to have the extra tensile strength they offer, imho. I'm happy I used them in mine, one less thing to worry about, sorta. gl.

Thanks for the heads up, Will look into it. And yes, alot of trouble, money, wait, patience and work for this build. Only thing I would worry about is those stock Rod Bolts. Truth be told, I am reaching the end of my budget and yet need to purchase the HKs metal head gasket and a few more parts like a water pump and small things like that for this car to run. I do need the car asap for school. And yeah I know intial reaction will be Why cheap out now? right. Right, I agree... I will look into the fastners or atleast get Arp rod bolts if $$ allows.

 

[JDMMA70]

Thanks for the heads up, Will look into it. And yes, alot of trouble, money, wait, patience and work for this build. Only thing I would worry about is those stock Rod Bolts. Truth be told, I am reaching the end of my budget and yet need to purchase the HKs metal head gasket and a few more parts like a water pump and small things like that for this car to run. I do need the car asap for school. And yeah I know intial reaction will be Why cheap out now? right. Right, I agree... I will look into the fastners or atleast get Arp rod bolts if $$ allows.

Fastners = ARP Rod Bolts, headbolts, studs, etc

 

[Sside]

Fastners = ARP Rod Bolts, headbolts, studs, etc

Thank You Derek, for showing me I failed greatly in understanding something so simple... The noob in me came out... :biglaugh:

 

[suprafanatic]

i would go with the arp studs over the bolts any day, thats what i used with a cometic MHG

 

[Sside]

i would go with the arp studs over the bolts any day, thats what i used with a cometic MHG

Ah, I have arp Main studs but Arp head bolts.... :3d_frown:

 

[suprafanatic]

you'll be alright with them, your not planning on boosting much anyway

 

[Sside]

you'll be alright with them, your not planning on boosting much anyway

I doubt I will ever go over 20... How much are you boosting? with that 500 hp beast you have there...