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#1
06-15-2023, 06:13 PM
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Tuning
OK, so we got the newer engine in our '67. It's '77 T/A motor. I got it fired up, it starts easy and is definitely much better than the motor that t replaced.
But I still have a problem getting it to idle properly and it runs with a bit of a roughness. It doesn't seem to want to settle down and the only way it sounds good is to have the timing way advanced, like off the charts. The vacuum drops off dramatically if I back off the timing, and the needle bounces slightly no matter what. I've adjusted the rebuilt Quadrajet carb a couple of times. The vacuum sits at around 15in with the timing way advanced, but goes down to 12 or less when I set the timing to even 10 or 12 degrees BTDC. Any suggestions? I've checked every port and I don't believe that there were any vacuum leaks. |
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#2
06-15-2023, 06:34 PM
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How much advance is a lot? Is the distributor adding advance through a vacuum can? It’s not unheard of to run 10-12 degrees of mechanical advance at idle plus around 10 degrees from the vacuum advance.
If you’re concerned about how much timing you are feeding the engine, have you verified that the balancer’s timing mark is accurate to TDC? It’s possible you aren’t feeding the engine as much timing as you think.
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-Jason 1969 Pontiac Firebird |
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#3
06-15-2023, 06:47 PM
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On those engines, the lower compression engine with 6X-8 heads, the factory spec in 18 degrees initial, and 16 degrees for the "high" compression 6X-4 heads......I am pretty sure.
The lower compression usually has the "hub only" balancer.
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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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#4
06-16-2023, 02:04 AM
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Quote:
2. Timing chain/sprockets not installed properly--cam timing not correct. Perhaps due to a multi-keyway sprocket not indexed properly. What are the cranking compression pressures of each cylinder? |
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#5
06-16-2023, 06:02 AM
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X2, what if the hot cranking compression with the plugs out ?
Be sure to unpower the HEI with the plugs disconnected.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#6
06-16-2023, 10:48 AM
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Thanks, guys. I'll be checking these things out this weekend.
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#7
06-18-2023, 08:40 AM
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Stock engine?
Rebuilt Quadrajet or from a parts store (remanufactured)? In any case I'd start buy checking the distributor to make sure it doesn't have on of those POS recurve kits in it. They make idle tuning difficult if not near impossible if you don't have any other issues.....
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#8
06-18-2023, 09:27 AM
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X2 on the cranking compression
What ci? Do you know what cam is in this engine? Do you know what CR this engine has? Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
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