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Sitting Bull

169 Posts

Posted - 15 May 2017 :  11:02:59 PM  Show Profile  Reply with Quote
I'm going to be installing a completely rebuilt set of 6x4 heads w/new guides/pos.seals on all guides/new 2.11/1.66 SI. SS valves/new springs/ to match cam specs,w/new roller tips 1.5 comp.rockers, w/RARE ex. manifolds w/2 1/2" mandrel bent pipes on my 76 F/bird . These are to replace the 6x4's w/standard stock valves o ring seals/stock rocker arms w/log type manifolds,reg bent exhaust pipes. The biggest diff is the mandrel bent pipes and RARE exhaust manifolds but I'm wondering if anyone has any idea weather I'll be able to actually tell any difference in performance when all is done ? Mostly just a better/beefier and more reliable engine is the main goal . Thanks for any input !!! 76 F/Bird 455/30 over /308 pos./350 trans !!

Edited by - bober on 15 May 2017 11:05:45 PM

Bill Boyle
Horse Feathers (Charter Member)

5092 Posts

Posted - 16 May 2017 :  05:40:02 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Performance "is in the details." One of the classic improvements to build more power is better breathing. Moving away from the stock log exhaust manifold to the RARE and mandrel bent pipes will increase torque and that means more hp. Is it detectable on the street? I say yes.

If you have old time slips you could make some new runs and compare the numbers. I'd bet the time slips would show an improvement in trap speed and if traction was not a problem, better ET.

"Dedicated to keeping the classic Pontiac engine alive."

400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.

Edited by - Bill Boyle on 16 May 2017 05:40:46 AM
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5438 Posts

Posted - 16 May 2017 :  09:39:19 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Also, just having fresh heads can feel better.

More importantly, while you're in there, might as well rebuild...while rebuilding, might as well stroke it...since you're stroking it, might as well go aluminum heads. Also check the grounds. I think that covers everything ;)
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Blued and Painted

3505 Posts

Posted - 16 May 2017 :  09:47:03 AM  Show Profile  Reply with Quote
A valve job with new springs will make it more snappy/crisp. The exhaust parts will improve mid range and top end for sure.
Also the exhaust note will change making it sound more impressive while cruising thru the DQ.

Are these the heads with the port an runner clean-up?

Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Sitting Bull

169 Posts

Posted - 16 May 2017 :  9:07:25 PM  Show Profile  Reply with Quote
This 455 was all rebuilt about 5,000 mi. ago . trw forged pistons/CAT H-beam forged rods/balanced/ mild cam ,all other components are new along w/fresh Q/jet . Part of the reason for the newly redone heads are the pos./valve seals and better valves. I've had some what I call Xtra oil usage since the rebuild . I figure it's pretty much the V/seals . I didn't have the $'s for all the xtra valves and such at the time so now I have a complete set of FRESH 6x4's to R+R along w/the manifolds. It's been pretty consistent on the amount of oil it uses. It would probably use less if I didn't enjoy the smoke from the tires so much. It runs very nice and I wouldn't touch it if it weren't for the oil use but I'll feel better about the new SS valves and the rest of it . Thanks ALL for the info
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