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#1
07-13-2005, 08:12 AM
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i have a set of '67 6x and 670 heads. what are the compression ratios of these? i think pretty high. can they be made to run on pump gas? thanks in advance for your help.
paul |
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#2
07-13-2005, 03:39 PM
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The 670s are considered a little small for todays pump gas, for the most part. You'd have to be a heck of a tuner and have exactly the right cam to make them work without fear of detonation. Or you could have your pistons dished to get to a more pump gas freindly compression ratio. Mid-70s 6Xs should be fine for a 400, or a 455 for that matter.
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67 LeMans vert w/462 68 GTO bone stock |
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#3
07-13-2005, 06:09 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brew:
The 670s are considered a little small for todays pump gas, for the most part. You'd have to be a heck of a tuner and have exactly the right cam to make them work without fear of detonation. Or you could have your pistons dished to get to a more pump gas freindly compression ratio. Mid-70s 6Xs should be fine for a 400, or a 455 for that matter. </div></BLOCKQUOTE> What? Can you explain the 670 a little further?
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Take a ride in my Twin Turbo 63 Lemans.......  http://www.youtube.com/watch?v=Ad8g9IfWxKI Hot Rod Cover Car -April '07 PHR Magazine Sept.'08 1244HP Pump Gas Dyno @ 11psi (32PSI MAX) http://s297.photobucket.com/albums/m...ipumpgas-2.flv |
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#4
07-13-2005, 07:56 PM
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the 670's would come about 10.75 : 1 CR on a 400 with std pistons. believe they CC in the high 70's.
the 6X's come in at least 2 chamber sizes - 91 and 101 CC. with the 6X '8's (101 cc) I'm running about 9.2 : 1 CR on a 455. |
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#5
07-14-2005, 05:43 AM
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670s had a factory listed cc of 72, but that was probably optimistic. My wife's uncle used to race Ponitac stockers all through the 60s-70s, and said they never got set of Pontiac heads (not even RA IVs) that delived the advertised ratio. They always had to mill them.
I run 670s on my 67 428. I have a small dish in the piston with a 744 cam. Car doesn't ping on 94 octane, but I do mix toluene with my fuel. Whe I rebuild the orignal 400 HO for my '67 (with 670s), I plan on dishing the piston enough so I don't have to mix fuel anymore.
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Three times the sound peaks, falls back, peaks again. A throttling back to cruising speed, a dwindling grumble of thunder and...gone. The frogs take up where they left off. |
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#6
07-18-2005, 08:35 AM
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racerboy... how much Toluene do you mix into a tank of gas with your '67 ?
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#7
07-18-2005, 09:06 AM
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Scott,
I have the formula at home (I took it out of a Buick GS Facts and Fugures book). I will post it later this evening.
__________________
Three times the sound peaks, falls back, peaks again. A throttling back to cruising speed, a dwindling grumble of thunder and...gone. The frogs take up where they left off. |
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#8
07-18-2005, 05:48 PM
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I would appreciate that formula because my 400 sure doesn't like the 93 octane we have here. Are you guys also using a lead additive?
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#9
07-19-2005, 03:38 PM
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__________________
Three times the sound peaks, falls back, peaks again. A throttling back to cruising speed, a dwindling grumble of thunder and...gone. The frogs take up where they left off. |
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