When doing a HG, should you machine both the head and block?

steveyblack

Member
Jun 21, 2007
529
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16
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Nj
or just the head??? is the block thick enough to withstand more then the head?

just wondering, might be buying a 7mgte and i want to do the HG and such before its in the car...i think he said its already going...
 

black89t

boost'en down 101
Oct 27, 2007
951
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humboldt, ca
you have to have or barrow a precision straight edge to check the surfaces for flatness. then go from there. for example when i change my hg i check the block and it was fine. then i checked the head and it was warped .004'' which isn't horrible, but would have needed machine work. then i grabed my extra head of my rodknock motor. i couldn't even fit a .001 in there. also when i held a light behind it i saw no light. which is good (no gap). also it looked like it had been to the machine shop before by the condion of the surface and it had helicoiled exhaust studs. i used it and its been working great since march. no more missing coolent. 11psi all day felpro head set. i dd and drag race my car btw.
 

7Mboost

7M Powered
Aug 15, 2006
2,201
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Gainesville, FL
Absolutley, a good FLAT surface is a must for 7m's, you don't have to look had to find the dreaded BHG stories, so do it right the first time, machine both.
 

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
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Valley of the Sun
If installing a MHG...do both. The surfaces must be flat and meet the RA spec for the MHG used.

If installing a stock composite HG, both surfaces must be flat. But, you do not have to worry about the RA spec...this type HG will seal with standard machine finish.

It is very important to torque either HG down correctly using the TSRM sequence. For stock head bolts, 70-75 ft/lbs will allow moderate levels of boost. If you choose ARP hardware, use the torque indicated on the spec sheet that comes with it.
 

black89t

boost'en down 101
Oct 27, 2007
951
0
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humboldt, ca
i read it wrong. sorry. i thought you had the motor in the car. if your going to run boost over the fuel cut you might as well go the full nine yards. machine both surfaces, mhg and arp stud/bolts. for some reason i thought the block was still in the car. i'm not postive, but i think i read by ij that when you lap the block you want it to be a bare block. being that all the lapping shit is going to get everywhere. i guess detemine how far you want to go with upgrades then go from there.
 

VooDoo

Draggin ass on his build
Mar 20, 2008
342
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Valdosta ,Ga
I Don't know why you would not. You already have it out of the car. You should go ahead and invest in a MHG w/arp head studs.now to save yourself the headache and flaming later when you post about you BLOWING IT. For the money you could not ask for a more stronger feeling of security. This is just my opinion however you will see it all day across every thread in this forum. Good luck