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Discussion Starter · #1 ·
i got a 66 gt with a 289 .030 over, 10.5 to 1 compression, .472 lift cam, performer rpm intake, demon 625 carb, 69 351windsor heads with 1.94 intake and 1.60 exhaust valves. trans is a stock c-4 with a shift kit and a 2500 rpm stall. 389 gears in an eight inch rear.
now the question....with this setup, what horsepower should i be running and what 1/4 mile numbers. the builder told me that I should have around 350-375 hp but it sure don't run like it. Feels real weak. Are the heads too big for the car?? Anything i should check?? What size intake runner cc do these haeds have stock?? Any help???
 

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By no means are those heads too big for your motor. GOing by your lift numbers your cam sounds a little small but we need to know your duration at .050 inches fo lift to tell you anything about that. With those heads Id say you are probibly more in the 250 to 275 horse range.
 

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That's a small cam. Don't think you have a chance to make the numbers you were told with that combo.

Also are you sure about that compression ratio? What pistons?
 

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Yeah that cam is pretty small.I'd run something more in the 230 degree @.050..Sounds like a good combo though.What kind of headers are you running?
 

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Discussion Starter · #8 ·
i was thinking about changin cams to a lunati voodoo cam with 284 adv. duration and .560 lift. and maybe afr 165cc or 185cc heads. I know the combo i have now sux and i need to do something.
 

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The combo you have now does not suck..Other than the cam it looks very well matched..That camshaft is just a mild step up from stock so that would be my first upgrade...Advertised cam specs don't mean much its the [email protected] and lift that we need to try and help.
 

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Discussion Starter · #12 ·
i have an old school performer intake sittin on the shelf...my dad said he had one on his car back in the 70's...saw it at CARLISLE...thought it might be better than the performer rpm
 

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The combo you describe can be fairly quick. I ran a similar combo to what you describe in the early 80's. It had a bigger cam, and a single plane intake. Car went [email protected]

With the C9/D0 heads you need 12: 1 domed (289) pistons to get the compression your stating. If you have flat tops your compression might be lower than you think???

Don't be afraid to rev it up, those little 289s like to be buzzed.
 

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Discussion Starter · #14 ·
the cam i have is the same specs as the performer cam from edelbrock
204/214 duration at .050 and .448/.472 lift. part # EDL-2122 in summit
 

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Discussion Starter · #15 ·
so should i change cam and heads...or tear it down and put in domes and then cams....the 69 351's have a 62 cc combustion chamber so i think the compression is close.
 

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351's(60cc) with a 12.5cr will yield 11.7-11.8 actual cr. Leave the RPM manifold on,more cam,more gear(4.10,s)and if the bottom end is in good shape,don't be afraid of RPM! (7000-7200) Small block 289's are like 2-STROKES,they NEED rpm to work! MARK
 

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Ask your builder what he actually did and what he replaced. IF you have an actual 66GT motor , you may have 10-10.5cr cause I think that cr was with stock 58cc 289 heads..........don't give up yet!
 

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My C5 289 heads had 54cc chambers.
My C9/D0 351 heads had 61cc chambers

I think the 68 289's had big combustion chambers 63cc
 
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