706, 243, or 799 heads on LM7
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Teching In
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From: Chicago burbs
706, 243, or 799 heads on LM7 In my attempt to P&P 706 heads on my LM7, I cut though to the water channel. Now I have to buy new heads. This is my first rebuild and I should have asked before I started but- will I have to increase octane above 87 after the P&P if I stay with the 706s?
Also if I go with the 243s or 799s will I have to mill the heads to maintain the same CR?
Will 87 octane be okay with the 243s or 799s? How about after a P&P?
Also if I go with the 243s or 799s will I have to mill the heads to maintain the same CR?
Will 87 octane be okay with the 243s or 799s? How about after a P&P?
Thread Starter
Teching In
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From: Chicago burbs
After a little research it seems I would have to mill the 243/799s in order to maintain the 706 compression ratio. Will clearance become an issue here?
Will I need to increase octane above 87 after swap to 243/799 with no porting?
If no, would I need to increase octane if I did port them?
Will I need to increase octane above 87 after swap to 243/799 with no porting?
If no, would I need to increase octane if I did port them?
Thread Starter
Teching In
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From: Chicago burbs
Is there a possible clearance issue after milling 243/799 heads for an LM7?
Will I need to increase from 87 octane after switch to 243 or 799 heads?
How about if I mill the new heads- 87 octane okay?
What about after porting the heads- 87 octane okay?
If the answers to above questions are all no, would 87 octane be okay for 243/709 heads that have been both milled, and ported & polished?
Will I need to increase from 87 octane after switch to 243 or 799 heads?
How about if I mill the new heads- 87 octane okay?
What about after porting the heads- 87 octane okay?
If the answers to above questions are all no, would 87 octane be okay for 243/709 heads that have been both milled, and ported & polished?
untouched 243/799 will be a good flow upgrade over 706s but 243/799 would need milling to keep the same compression or to get a small bumb. Increased octane is not needed for more flow but needed for more compression. If you want to stay 87 octane Id stick with stock compression and put a good custom spec camshaft. Basically its all whatever is in your budget if its in your budget get a set of shaved ported 243s and a good cam.
Thread Starter
Teching In
Joined: Dec 2013
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From: Chicago burbs
Thank you 726.0chevelle! I'm guessing the machine shop will know how much to shave to keep the same CR - if not I'll research more and get it right. I am also now leaning to a new camshaft too. Arrrrrrg budget!!!!
