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88 MA70 Supra
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1 Posts
Discussion Starter #1
So I just bought my first mk3 with bhg. The engine was rebuilt 80,000kms ago with the block o’ringed and machined with the head, arp head studs and the oem gasket. Just wondering if anyone else has an o’ringed block and could give me some advice on what head gasket they used? I’ve read that MHG’s do not seal well with o’ringed blocks? I haven’t been able to find much info on the topic and would appreciate if someone could point me in the right direction.
Thanks.
 

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Moderator, l337 M0d3r4t0r
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12,199 Posts
Don't know of anyone who's oringed a 7m. People usually toss the block if they machine that much off it.
 

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ƒ=1/2π(√k/m)
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10,047 Posts
Don't think I've ever seen a 7M with o-rings.

Post a pic? That'll be neat to see.
 

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10,075 Posts
O rings were the rage when composite gaskets couldn't hold the HP in things like V8 builds and before metal headgaskets (aka MHG's or MLS gaskets) came around.
I've seen three copper O-ringed 7M-GTE blocks done, back in the late 90's early 2000's dark ages when the HKS Catalog was god and none of us really knew what we were doing. All three of those builds failed at thresholds easily survived with ARP studs and a common 1.2mm bead, and cost a shitload more.

The key to MHG survival is block and cyl head prep. 30 RA or better and you're good to go. Skip the O-rings or any of that crap. If your machine shop doesn't understand what Roughness Average is, find an actual machine shop. You can remove an incredible amount of material from a block and head and compensate for it with a 2.0mm MHG. Just make sure you degree your cams on adjustable cam gears to compensate for the deck height difference.
 
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ƒ=1/2π(√k/m)
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10,047 Posts
It’s a very common approach in the Honda world. I’ve seen many o-ring K20 setups. They’re well into the 1000hp area. It’s amazing how technology and manufacturing has advanced. I agree with you about the “dark ages” lol.
I still can’t believe the levels we reached with alphabet soup setups. 😂
 

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I used a metal shim gasket (Silver Seal) to replace the material removed to get it back into spec (not more than 0.010" total from stock) and a standard head gasket on top of that. Spraying the bottom of the shim gasket that contacts the block with Permatex copper is the way to go. 6 years and 35,000 miles later no problems. I have ARP studs torqued to 90 foot-pounds.
 
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