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Old 06-03-2013, 05:35 AM
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670 heads

hi after help with my 1968 firebird 455 I live in Australia and have a chance to buy some 670 heads they are 72 cc I realise that CR would be high but could you used dish pistons larger head gaskets or are they no good on a 455 .its hard to find heads in Aus . my heads are 4X with 113 so CR is to low and everyone seems to say throw them away.also could you increase combustion chambers on the 670 heads .
thanks blake

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Old 06-03-2013, 06:52 AM
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according to stan weis,those heads flow 205 CFM,no horse power there.
we have pontiac guys here that will answer when online
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Old 06-03-2013, 07:55 AM
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The standard procedure to lower the compression on Pontiac engines is to use dished pistons or use 1971 or later heads. With 72 CC heads on a 462 CI engine, forged pistons need to be dished for an additional 20 cc combustion chamber volume in order to reduce the compression ratio from 12:1 to 10.4:1. The 670 heads will be difficult to use on a 455 engine unless you want to pour in at least 5 gallons of VP C-12, 108 octane, racing fuel for every 15 gallons of 93 octane pump gas.

You need at least 92 CC combustion chamber volume on a 462 CI engine to use 93 octane pump gas. I am not sure a piston can be dished enough to obtain 20 CC without making the engine run too hot. Dishing a piston and practically eliminating the piston quench area will increase engine running temperature.
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Old 06-03-2013, 06:51 PM
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X2 with Mousefink. Get a good set of heads that are 96-98 CCs.
Install screw in rocker studs if the dont allready have them.
Lots of horsepower can be had from poncho heads. High flow numbers at low lifts give gobbs of torque where other engine are typically anemic.
5250 rpms is the redline on a stock 455 bottom end, so high lift flow doesnt come into play as a major factor in most street build on a poncho.
flow rates on most poncho heads is max at about .470 -.480
# 46 heads from a 73 350 are 96 CC s . I am sure because I own a virgin unmolested set.
Also 1973 4X heads have 98 CC chambers. I have a non molested set of those I CC ed so I am certain.
Not tryin to sell these heads, just sayin. Most of the charts I have checked are WRONG on the chamber size for these heads. THAT is why I mentioned it. Now you wont end up with 3 sets of heads you dont need ( Like me) because a chart was mis informed.
Happy head hunting. LA
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