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shaving the head
Topic Started: Jul 28 2014, 07:28 PM (1,627 Views)
3tech
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I actually received this question as a PM, and suggested that he ask on the forum.

I get a lot of tech questions via PM and email, and unless its a customer with a specific question, I will not answer them. Instead, I prefer to see them asked on the forum, where everybody can benefit from the answers, right, or wrong. Some people get mad when i do that, but some people ask on the forum and get their answer.

Interesting who's not answering.

Anyway, this is what you need to know: You cannot make the 89-94 G10 motor interference by removing material from the head. We have removed greater than .100", almost getting into the manifold studs in the process. With a flat top piston, it was still not interference, and (if I recall from memory) the compression ratio was approaching 14-1. we built a few of those motors for a fuel economy competition in the US about 6 or 7 years ago. At .080" and a stock (.040") head gasket, I would expect in the mid 11 to 1 compression ratio.

From our experience, and we've built a lot of them, the sweet spot for a street driven G10 (89-94) seems to be in the .040" range. Once you start to get higher in the compression, you're limiting your timing advance because of available fuel, and that starts to degrade power. If this were a full on econo, or race build, and you had access to high octane fuels, then go ahead. If you're driving on the street, stick in the .040" range, and run as much timing as is possible. The combustion chamber design is lousy, and it wants lot's of timing. Don't forget to allow for the alteration of your cam timing.
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Beer4Blood
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3tech
Aug 1 2014, 09:45 AM
I actually received this question as a PM, and suggested that he ask on the forum.

I get a lot of tech questions via PM and email, and unless its a customer with a specific question, I will not answer them. Instead, I prefer to see them asked on the forum, where everybody can benefit from the answers, right, or wrong. Some people get mad when i do that, but some people ask on the forum and get their answer.

Interesting who's not answering.

Anyway, this is what you need to know: You cannot make the 89-94 G10 motor interference by removing material from the head. We have removed greater than .100", almost getting into the manifold studs in the process. With a flat top piston, it was still not interference, and (if I recall from memory) the compression ratio was approaching 14-1. we built a few of those motors for a fuel economy competition in the US about 6 or 7 years ago. At .080" and a stock (.040") head gasket, I would expect in the mid 11 to 1 compression ratio.

From our experience, and we've built a lot of them, the sweet spot for a street driven G10 (89-94) seems to be in the .040" range. Once you start to get higher in the compression, you're limiting your timing advance because of available fuel, and that starts to degrade power. If this were a full on econo, or race build, and you had access to high octane fuels, then go ahead. If you're driving on the street, stick in the .040" range, and run as much timing as is possible. The combustion chamber design is lousy, and it wants lot's of timing. Don't forget to allow for the alteration of your cam timing.
The god of all things 3 has spoken!!! :rocker so what of the timing issue?? does it require the aforementioned larger tensioner pulley?? any other timing adjustments that made need to be made??? I'm already running a +8 pulley that I purchased from you and plan on chunking the old tbi for a set of old ninja carbs I have collecting dust
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nemoskull
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eh, what octane on the '040 shave?
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Beer4Blood
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93
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Joe Dirt
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i had a metro head cut in the early 2000's so much it had to have 1/2" of hardened washers. under the head boltsto torque down because they bottomed out in the block.. running lil mother would spin in 3rd gear
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Beer4Blood
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That's my end goal Joe.... ridiculous output from the unexpected. I know silly pointless blah blah blah! But to those that judge well it's mine so I don't care
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