Smooshy
12-09-2003, 05:07 AM
Its annoying because I consider myself to be an ok mechanic and pretty good engine builder...
Just for Reference: AMC 360, comp 268H cam, high compression forged piston, Edelbrock intake, mallory ignition, various new carburators.
This problem as come and gone a couple times over the past few weeks but now seems to be here to stay, what is weird is the problem happens almost instantly. When it has cleared up the motor runs excelent.
The problem is the motor acts and sounds like it has waaaay retarded ign timing and is not very drivable due to surgin and backfiring. I also here some valve noise. The richer it runs the better but still not drivable. Above 2000 RPMs it mostly clears up. The vac is VERY low (about 8, 18.5 is normal for that motor)
Here is what I have so far
1. Absolutely no vacuum leaks, just trust me on that one.
2. Vac is 8
3. Compression is 145 cept on # 6 is a little under 140
4. #6 and #8 plugs look VERY lean while other plugs look rich
5. Timing is at 13 deg. and VERY consistant
6. When it ran right it had a valve tap in mornings but went away pretty fast and very slightly knock a couple times (sounds like main, not rods)
Things that are making this hard to diagnose are
1. Comes and goes quickly and motor runs excelent when it runs good
2. Very consistant timing
I have also swaped 3 news carbs I have had laying around and the conditions are the same. Comes and goes...
What you think smile.gif
Just for Reference: AMC 360, comp 268H cam, high compression forged piston, Edelbrock intake, mallory ignition, various new carburators.
This problem as come and gone a couple times over the past few weeks but now seems to be here to stay, what is weird is the problem happens almost instantly. When it has cleared up the motor runs excelent.
The problem is the motor acts and sounds like it has waaaay retarded ign timing and is not very drivable due to surgin and backfiring. I also here some valve noise. The richer it runs the better but still not drivable. Above 2000 RPMs it mostly clears up. The vac is VERY low (about 8, 18.5 is normal for that motor)
Here is what I have so far
1. Absolutely no vacuum leaks, just trust me on that one.
2. Vac is 8
3. Compression is 145 cept on # 6 is a little under 140
4. #6 and #8 plugs look VERY lean while other plugs look rich
5. Timing is at 13 deg. and VERY consistant
6. When it ran right it had a valve tap in mornings but went away pretty fast and very slightly knock a couple times (sounds like main, not rods)
Things that are making this hard to diagnose are
1. Comes and goes quickly and motor runs excelent when it runs good
2. Very consistant timing
I have also swaped 3 news carbs I have had laying around and the conditions are the same. Comes and goes...
What you think smile.gif