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#1
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ok..i give up....and im goin nuts here
my motor has ran great the last two years...even after the winter, fire it up an runs great.
then i was messing around and went to go from 1st to 2nd and had a brain fart and went into neutral. after that i was popping and by the next day it was popping loudly at idle. changed plugs...(autolites) and it seems that it ran great for a day and then started popping again, though not as bad. also noticed that my insulator on #1 plug was offset a bit so i ordered another box of ngks and put them in...was less noticable but still there...since i have not been able to get rid of the popping. at idle and up to maybe 1800 rpm all is well then it starts missing...popping out exhaust and around 2500 it allmost feels like something is dragging on the car due to the surge then after 3200 or so it seems to lessen up some. (all at very light or no throttle) now if i give it a lil gas it smooths out and with the foot in it it will pull to redline with out missing a beat. ive bypassed my ignition box, hooked up diff coil, swapped out my 850 with my 750...(better throttle response) also hooked up a hp150 pump with 100 micron filter in front and 1/2 line and better regulator... i figured for sure this had to be fuel related since as soon as u give it some fuel it seems to go away but the 750 seems to act the same way. ive jetted up and its not lean. so....any ideas before a light a match?
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#2
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Timing chain might have jumped a tooth.
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Why is he not suspended? |
#3
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Over-revved it?
Could be broken valve spring, collapsed or pumped up lifter, bent valve, rocker arm out of adjustment. |
#4
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Put a timing light on it.
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1970 Burgundy GTO hardtop. CVMS built 455 4sp. May the Torque be with you! John. |
#5
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Check for bent pushrods also.
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#6
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Compression test all 8 CYLS to find that bent pushrod. OR pop the valvecovers and feel each rocker combo OR just start-it-up and see which rocker does not rock like the others. HIS
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#7
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no bent pushrods...running smith brothers 5/16x .116 push rods along with
a stud girdle. compression was all 148-152. my compressor is dead so no way to do a leak down test. also no broken springs. also did i mention car has no lack of power and throttle response is good, as long as you are stepping into the throttle.
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#8
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i'll double check the timing but last i checked it was sitting at about 14 initial which has been checked since it started doing this.
doubt timing chain...no popping through carb and motor is probably under 5000 miles (billet chain)
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#9
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i don't think we understand exactly what 'popping' is. out of the exhust? carb? is it constant or rhythmic? how loud? sound muffled? increase with rpm? sorry, but we don't have alot to go on here.
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John J. |
#10
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Quote:
my pipes are 3 in with dynomax race bullets and no tail pipes so its far from quiet but the sound does seem to be coming from the rear part of it. as the rpms get higher i think maybe the cycle of the missing becomes faster...making it less noticeable. i can drive up a road with a slight incline and its pretty un noticable.
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#11
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sounds wise especially just revving in neutral it almost sounds like the exhaust is under water
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#12
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wow i had that kind of a prob when a power valve stuck open ran great with my foot in it
but when i let up on the throttel it would start surging and poping it almost sounds like the exhaust is under water but with two dif carbs wow?? could it be the first carb the power valve stuck and the second carb is just way rich?
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1980 TA 455 th400 2.56 posi 12.27@111.48 http://www.dragtimes.com/Pontiac-Tra...lip-29967.html http://www.youtube.com/watch?v=6X5XJ9PR1Qw https://www.youtube.com/user/hal101/videos |
#13
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how old is the gas in the tank? anything over a week old is suspect
now that I think about it gas fresh from the pump is not necessarily any good either. I bought a full tank of crap a few years ago and spent weeks trying to find the problem. new gas solved the problem I had to dispose of about 8 gallons as the lawnmower wouldnt even run on that crap. Your symptoms also sound like my ford holley with a blown power valve if its a qjet check the power piston is stuck open or closed, you can do that with a soda straw dropped in the bowl vent, see if it goes up and down with change in vacuum |
#14
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do we all agree that the sound is 'afterburn' in the exhaut pipe?
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John J. |
#15
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as far as the power valve.... i would suspect...because its the same power valve. had to take the one out and put it in the other carb due to only 3.5 i have. however........it idles fine...does not seem to be loading up. i'll find out soon enough though because i have a 2.5 pv that should be here in the am. (had already ordered it)..
gas....ive pretty much ran out twice and put more in since. id suspect the station but i run the same stuff in my jeep with no problem.
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#16
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Quote:
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#17
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Check all of your wires and the carbon button inside the distributor cap.
Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#18
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checked the button and wiped the inside down earlier (msd)....the wires msd also are not that old but one did get a lil burnt from a header once..course that was quite a while ago, over a year..at the time i just have it isolated where it cant jump to anything and never caused an issue before. all the plugs are burnt very clean (white) so i figure they must be firing..all look the same also
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
#19
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ok if jeting is good then i think it's the power valve
yea mine idles fine to with the bad power valve
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1980 TA 455 th400 2.56 posi 12.27@111.48 http://www.dragtimes.com/Pontiac-Tra...lip-29967.html http://www.youtube.com/watch?v=6X5XJ9PR1Qw https://www.youtube.com/user/hal101/videos |
#20
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i'll find out tomorrow i think...hopefully your right...
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69 bird, 428 custom solid roller, rpm intake, #62 heads sd ported 260 cfm, 850 holley dp. arias pistons.scat rods redneck tranny, continental 3200 stall |
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