how much abuse, and boost would my stock 7mgte, including stock head gasket stand up to with a sp61gt? lets say i have a full 3" turbo back system including elbow and an k&n fipk. and 50,000 on my motor.what do you think?
how high can i go
- Thread starter 89turboguy
- Start date
i say hg is gone at a few good 10psi pulls. that turbo flows alot better then the ct-26, and i lost my hg w/ arp's at 14psi.. w/ct26
I think you shouldn't even be asking that question until you get a MHG put on the engine correctly. I say correctly because the mechanic my cousin hired to do the job didn't tighten the ARP studs enough or didn't do it in the right sequence.
If your going to spend the money on the SP, id fork up the little bit extra and save your motor and a lot of down time.
If you do it now, and the blocks still good, you dont have to resurface and you can put a cometic on there!
If you do it now, and the blocks still good, you dont have to resurface and you can put a cometic on there!
s383mmber1 said:
:umno:
The Cometic MHG requires a RA spec of 50 or less. If you use one on a block/head that has not been decked to this spec, you are very likely not to get a good seal. That means a re-do when the MHG blows.
IMO, a composite HG is good to about 12 psi...and no more. A SP61 (I've got one) is good to 20 psi all day...that will blow a composite HG in a heartbeat.
jdub said:
Hmm, i thought this was possible! I know people that have done this and get great results......
:dunno:
s383mmber1 said:
Read this...page 3 on installing a Cometic:
http://www.cometic.com/catalogs/AutoCat04.pdf
I use the manufacture's spec when I build a motor...not what "my buddy told me". No offense, but hearsay has killed more motors than I can count.
aye mate said:
That is true...a composite HG is designed to make up for the machining imperfections on a stock block/head surface. The downside is a composite HG is only good for about 12 psi with the head bolts at 75 ft/lbs...if your HP goals requires less that that amount of boost, you will be fine
wow, this thread took off. well i am just going to keep the boost low until i sell my truck, because i am going to get pistons, rods and all once i sell my truck. nobody ever commented on what the motor would be good for, boost wise with this turbo. with stock internals.
yeah i saw that, but im saying if i did the headgasket, and it was just the internals i was worried about now, pistons and rods. how much boost would they take stock?
Well...now you're talking HP. Boost has a lot to do with that on a 7M, but so does mods to the fuel and air intake system to support the higher boost.
Stock rods and pistons are good to around 500 HP safely. That assumes a re-build to put all bearing clearances into spec, decking the block & head for a MHG, balancing the crank/rods/pistons. Fuel upgrades to an adjustable FPR, walbro pump, 550 cc injectors, and removing the "J" tube. Intake upgrade to a Lex AFM....that will allow you to get to 18 psi of boost before you hit fuel cut.
If you are planning to bolt on a new turbo on a 100,000 mile motor and turn the boost up...you are asking for a BHG, rod knock, or throwing a rod out the side of the motor. Been done many times.
If you are going to put on a MHG, you have to pull the motor to get the block decked to the RA spec for the MHG you use.
Stock rods and pistons are good to around 500 HP safely. That assumes a re-build to put all bearing clearances into spec, decking the block & head for a MHG, balancing the crank/rods/pistons. Fuel upgrades to an adjustable FPR, walbro pump, 550 cc injectors, and removing the "J" tube. Intake upgrade to a Lex AFM....that will allow you to get to 18 psi of boost before you hit fuel cut.
If you are planning to bolt on a new turbo on a 100,000 mile motor and turn the boost up...you are asking for a BHG, rod knock, or throwing a rod out the side of the motor. Been done many times.
If you are going to put on a MHG, you have to pull the motor to get the block decked to the RA spec for the MHG you use.
Not so fast...I'm running a stock HG at 15psi on the ct-26 and its doing fine. I think it has been decided (at least in my mind) that the weak link is low head bolt torque. Toyota spec head bolt torque is only 56ft.lbs. Grim Jack ran a composite HG to about 20psi on a 57trim CT-26 (about 400+hp) before it blew. The key was he had the head torqued to around 90ft.lbs.jdub said:
aye mate said:
Over 14 psi, you are running a composite HG at it's limit...I'm not saying you can't do it, but running anything at max is going to cause a failure. It's just a matter of time.
And exceeding torque spec for ARP harware is not a good idea. For the stock head bolts, 75 ft/lbs is safe...more than that and you approach the design strength limit of the bolt.Can you do it...sure you can...might get away with it too (for a while). I'm talking safe limits...not pushing the envelope.
