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Old 02-11-2003, 08:24 PM
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Post stuttering 455

Today, i was driving around playin Bandit in my (new to me)77t/a. Some guy driving a sorrority girl special (97 or so trasam) pulls up next to and revs it a little bit. i gave him a "you dont want none of this" look. i just thought he'd not want to embarrass himself, but he punched it off the line. So i gave it all it had and caught back up to him in first. NOw to get to the point: at this point it was doing 5700 rpm and it was starting to stuttrer like it was running out of gas. When i hit second i started passing him but then my car stared the same thing, it kept surging like it was out of gas to . finally i part throttled and it smoothed out and i beat him, but it was still embarrassing as hell. not aacceptable at allat open throttle it feels like the fuel pump cant keep up with the demand for more than a couple of seconds. from a dead stop there is a noticable bog by 5000 rpms. Engine is 455 .030 over, edelbrock performer, street cam (dont know figures , just bought car) idles fine at 750, quadrajet carb,electric fuek pump in trunk, didnt see regulator- thinking maybe this is a stock pump? runs great at part throttle . 3-spd manual, 373 gears. Any help will be appreciated

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Old 02-11-2003, 09:50 PM
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well, i am pretty sure that 5700 is over the redline for that engine first of all. I am pretty sure that engine redlines at like 5100 or 5200, 5500 tops(what year is the engine?). Second, those huge pontiac engines don't gain much past 4500 anyway, accually you start losing it. You are better off just shifting before you get above 5000. Keep driving it like that and you will start tearing it to pieces in no time.

[ February 11, 2003: Message edited by: Croz ]</p>
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Old 02-11-2003, 10:11 PM
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Cool

Smile fella. You just dodged a big one. Go give the guy that built your engine another $500 or so, he saved you thousands by doing an exemplary assembly job.

Your 455 isn't going to live long if you turn it much past 5,000, and as Croz mentioned a stocker is all done by 4500 or so.

Good Luck
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Old 02-11-2003, 10:18 PM
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i would say you are already lucky if your rods are still in good shape.
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Old 02-12-2003, 08:12 AM
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Thanks for the posts "fellas". The engine is out of a 74. It has the 6x heads on it. As for the cam, it has a very pronounced lope but idles fine. i drove my car again this morning. I looked at the tach more closely and realized that the yellow started at 4500 and the red started at 5500. I ve had numerous sbc cars with tachs and I believe the yellow on them started at 5k and red at 5500. So i was probably shifting around 5200 and it was still pulling really hard. Besides something letting go, this still doesnt answer the question of the engine dying down in second as well. Im still thinking it is dropping fuel pressure. Thanks again,
joe
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Old 02-12-2003, 08:22 AM
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Also on www.pontiacwarriors.com they have dyno sheets for different head combos, and they show many combos that have peak torque down low but just a few of the just the basic with more duration - not even a huge lift make peak torque at 4500 and peak hp at 5500. of course some of them had peak torque at 3500 as well.
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Old 02-12-2003, 12:00 PM
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sounds like you are on the right track with the fuel pump.
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Old 02-12-2003, 01:11 PM
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QJ is probley empting the float bowl if the carb hasnt been driled, need a holley or drill the QJ, 455 WORKS WELL WITH 850 HOLLEY. good luck.
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Old 02-12-2003, 01:23 PM
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It could be either fuel or just running out of air. Pontiacs, especially 455s don't like to turn over 5000 rpms. If it is running out of breath on the top end your could be floating valves, the heads aren't flowing enough, the carb is too small, or your have a fuel delivery problem. Convert to an electric pump and see if it improves. Either way you don't want to spin a 455 over 5000rpms with factory internals, unless you like to replace broken parts. You can safely tunr about 5500 rpms with ARP rod bolts.
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Old 02-12-2003, 02:18 PM
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There is an electric fuel pump. How do you drill the qj carb? are you talking about the throttle plates? I've heard that the qj's that came on the 455's flowed 800cfm-- thats a whole lot of air. there is pretty healthy cam, 6x heads are supposed to be the large valve high compression pontiac heads and it has headers to 3" pipes to 2- chamber flows it should be breathing to 5200 i would think. I have heard about pontiacs being prone to float the valves - could you explain what happens and what i could look for? Could this be elminated by stiffer springs? Is there any way i could get the cam measurements with it in the car? is there a way to check running fuel pressure besides having the car on a dyno?
joe b. reynolds
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Old 02-12-2003, 02:33 PM
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to drill a QJ you remove the top of the carb all the little pockets inside have a hole already drilled but to small for the fuel to drain out to be useful, make the hole larger I drill them with a 1/8 in drill bit (very carefuly)really not that hard to do if you can take the carb apart and put it back togheter, besure to remove all the drill mess, raced a 455 for years but never went over 5000, out of power band any way all that happens is more rpm not more power. good luck.
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