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#21
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Locate the secondary stamp on the heads to see what size chamber you have. Wallace Racing on this board has a handy guide here: http://www.wallaceracing.com/head1.htm
If your car has a combination of low compression heads and an aggressive camshaft, you can wind up with a lazy engine that doesn't build cylinder pressure early enough to have a strong low-end performance. In other makes, you might compensate with higher stall and lower gearing to keep the engine the "fun zone" but Pontiacs don't respond well to those methods. If vacuum advance, carburetion and compression (static) are where they should be, then the camshaft is the culprit. A cranking compression check should confirm this.
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Triple Black 1971 GTO |
#22
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#23
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Yeah, I blew right by that with my tires spinning. lol
A really quick check is to throw on a vacuum gauge. If you're down in the 10" Hg area, you have a bit more cam than the compression may be able to handle.
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Triple Black 1971 GTO |
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#24
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Last time I checked idle vaccum was around 12° at 900rpm on a warm engine
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#25
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As mentioned, get a cranking PSI, go from there.
Those tires are way tall...car needs 3.73's to compensate for that... Advance the timing a couple of degrees, see if you can get it to ping, if not try a couple more degrees, being careful..
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... |
#26
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Car has 3.73 its been stated 4 times already lol
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#27
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Your hugely tall tires could probably do well with a 4 series gear, like a 4.10, and not have a lot og highway RPM. Looking forward to more of your posts concerning your awesome car!!!
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... |
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#28
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I was under the impression that going to a 4 something gear would make my highway rpms even worse Sent from my SM-G996U using Tapatalk |
#29
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You`ve got plenty of gear. So, it`s either a basic tune or a hardware tune. Did you find the version of the head casting you have?
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#30
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#31
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Back to the original question. For the money, 72cc aluminum heads will wake that thing up, even if the cam, converter, carb is not optimized. If you get a good combo together after the heads, that car will rip. You will have to get your driving skills together. |
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#32
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#33
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Ain`t been shopping lately. The bigger boys will prolly get heads faster. Summit, Butler, SD Perf, etc for edel heads. Don`t forget KRE.
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#34
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Fully agree. Aluminum heads will reduce low RPM torque, and the more money spent on porting will make the problem worse. Hate to see people talk the OP into spending money on aluminum heads only to have less low RPM torque.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon in progress. |
#35
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Gimme a break. How much port volume and cfm does my daily driver 5.3 have? I know it`s OBD2. But, it doesn`t have VVT.
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#36
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KRE told me 12 weeks … that was 2 weeks back. No heads in stock.
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Triple Black 1971 GTO |
#37
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#38
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Worth the wait for Made in the USA. |
#39
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Orders filled on FIFO basis once heads are cast is what I was told. While they didn't mention it, I assume they need sufficient paid-in-advance orders to proceed with a run of head castings. The 12 weeks is part estimate for minimum casting run orders to accumulate plus actual casting and machining time.
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Triple Black 1971 GTO |
#40
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unless the plans are making a lot more HP that alum heads can support, the price doesnt really justify the performance gain, especially with an unknown cam, vs the cost of upgrading the 5c or 6x & picking a good HR or FT cam to match the rest of the combo. again just a suggestion of a different way to increase power/tq based on the parts he has & spending less money than alum heads. |
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