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Old 07-31-2011, 08:10 AM
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bbc questions

hey guys new to the whole forum world hope im doing this rite. i have a 72 blazer with a 454 out of a 74 motorhome. i did a simple rebuild on it with a .030 overbore flattop pistons and it has the stock peanut port heads that the machine shop told me would liven up with the larger 2.19/1.88 valves and they surfaced them i think .030 to bring the comp. up some. it has a holley 670 truck avenger weiand aluminum dual plane intake and 4x4 comp cam with gross lift of .505 intake and .515 exhaust and a set of hedman headers. the truck has 33 inch tires and 3.73 gears with a posi. it ahs alot more power than the 327 that was in it before it doesnt seem to have the bag i thought it would with a big block is there something more i could do that would really waken it up? i was told ditch the peanut ports and find a good set of heads. is my comp. to low maybe?

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Old 07-31-2011, 09:21 AM
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Could probably use a bigger carb(750-770)
What is the actual compression?
Where do you have your timing set?(initial and full advance)

With a heavy truck, 4x4, big tires, you really want to improve on low and midrange torque, your heads should be fine for this. Its probably a matter of fine tuning the engine, and possibly changing the axle ratio's to 4.11's
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Old 07-31-2011, 10:07 AM
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i dont know what the acctual compression is i was wondering if someone might have an idea. as for the timing it is set to what a chiltons book wanted it at i cant remember rat this time what it was. i was thinking that gears would help but didnt want to just jump into that without asking around first. any clue as to what hp/torque would be? thanks for the advice.
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Old 08-10-2011, 11:26 AM
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i would say maybe the low 400 range. maybe high 300's. but you deffinatly need to get some shorter gears. i would say with your 33" tires i would go no lower than 4.11's. thats a tall tire to have higher gears with.
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Old 08-10-2011, 01:38 PM
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Well a couple of things you need to straighten out, BEFORE you spend big money on this engine. Peanut port heads have some positives you might want to keep. First they have the "good" combustion chamber! Most 70's BBC heads you normally find (oval port) have a "smog" chamber. Next up is the peanut port ...if your interested in a "quick" engine (across the intersection) they are really good ...flowing faster then oval or square port. BUT if you interested in more power ...oval or square is the way to go.
The other issue you need to check out is the crank, being from and RV I'll bet it's a cast iron crank ...it does "ok" but if you want to be in the high power/RPM range, then you need to look at getting a steel crank. ...Just my $0.02!
PS - Make SURE you put hardened seats under the exhaust valves in any GM head!!!
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Old 08-10-2011, 06:46 PM
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Advance your timing, add 4-6* initial and see how it runs. Check you centrifugal with vacuum disconnect and plugged.
Re-tune carb after you get the timing where it runs good without pinging
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Old 08-10-2011, 06:54 PM
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Did they put your cam in straight up or did they advance it? If the motor is a motor home block I would think it would have the harder valve seats from the factory. I think the bigger valves may hurt the bottom end more than help it. but to late now. I always advance a cam in a truck or pulling motor just help's the bottom end 9 out of 10. As said lower gears will help just don't go to low if this is something you drive on the street.
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Old 08-11-2011, 08:21 AM
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swvalcon ...If the motor is a motor home block I would think it would have the harder valve seats from the factory.
Your right they probably did, BUT if he's putting in larger valves that hardened area will be compromised, and why I advocate the hardened seat addition.
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