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I lost .5 in the quarter and don't know why!

736 views 4 replies 4 participants last post by  DOUG G 
#1 ·
My 1969 Camaro (383 w/ Edelbrock RPM Package-including heads-, 350 turbo, and 3.42 gears, MSD Box, Electronic Ignition, Electrict Holley Blue Fuel Pump) has slowed down.

It normally runs very consistent 12.8 to 12.9, depending on the weather.

Last week it ran 12.96, 12.96, 12.94, and then ran a 13.15 for no apparent reason. No spin, no missed shift, and the weather got better. I figured I must have missed a shift and blew it off.

Took it back to the track today and it went 13.25 and 13.35. All the times (60ft , 330ft , etc) are slow. I have lost 4 mph at the quarter mile.

The problem is I don't know why. No ticking, no pinging, timing is at the same spot (35). Secondaries are still opening on the carb. I changed the plugs before I went racing last week with the same brand and type.

What do you guys think? Fuel filters maybe? Bad Plug?

Thanks for the help. I'll keep everyone informed of the progress.



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Mike Steinkamp
69 Camaro w/ 383 Edelbrock RPM System (including heads),
Nitrous, 350 Turbo, 3:42 gears
12.83 on motor, 11.91 with 125 hp shot of nitrous
 
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#2 ·
How does your tranny feel? We had a problem with a TH350 with similar symptoms. The car would just drop off 3 or 4 tenths and was very inconsistent.

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1967 Nova coupe daily driver
406, 10:1, 224° cam, Q-jet, 700R4, 3465# w/driver
11.75 @ 117 thru the mufflers
18 mpg on the road
 
#3 ·
I don't think it is the tranny. It has had a lot of work done to it by a very good shop in town. The car has been extremely consistent all summer (at least until last week).

I pulled the plugs I installed last week and they looked blacker than the old ones I took out. I also did a compression check on the cylinders I could reach without removing the headers. All cylinders tested at 130.

I am wondering about those plugs though. I did a little reading of some old posts and think I am going to try NGKs. I was using Motorcrafts on the recommendations of a friend/shop owner.



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Mike Steinkamp
69 Camaro w/ 383 Edelbrock RPM System (including heads),
Nitrous, 350 Turbo, 3:42 gears
12.83 on motor, 11.91 with 125 hp shot of nitrous
 
#4 ·
Mike,
If the plugs are black, it sounds like it has gone rich for some reason. Might be time to pull the carb apart for a quick cleanup / re-gasket. I consider that normal maintainance on a race motor.

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Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner
 
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