sudden timing issue..
#11
Thanks for asking. I bolted a 90 GT mustang roller motor into my 66. It has headman shorty headers, RPM Air Gap intake, mallory unilite distributor with old style coil and a holley mechanical secondary carb. I replaced the timing chain with a new one.
The carb was heavily modified. The air horn was machined off and I suspect the jetting has been altered as well. The carb appears to be a 650 or 600.
Timing is set at 34 degrees max with an idle timing of 9 degrees or so.
The problem is an intermittent explosion in the headers at higher rpm under load. I am assuming that there is unburnt gas exiting the cylinder or a valve timing problem. I would suspect a valve timing problem to be consistent.
Today, I plan on replacing the old spark plugs and checking for compression.
I was hoping someone can give me some guideline jetting specs. Maybe from a stock holley carb. Main jet, accelerator pump cam, etc.
Thanks for the help.
The carb was heavily modified. The air horn was machined off and I suspect the jetting has been altered as well. The carb appears to be a 650 or 600.
Timing is set at 34 degrees max with an idle timing of 9 degrees or so.
The problem is an intermittent explosion in the headers at higher rpm under load. I am assuming that there is unburnt gas exiting the cylinder or a valve timing problem. I would suspect a valve timing problem to be consistent.
Today, I plan on replacing the old spark plugs and checking for compression.
I was hoping someone can give me some guideline jetting specs. Maybe from a stock holley carb. Main jet, accelerator pump cam, etc.
Thanks for the help.
#12
Thanks for asking. I bolted a 90 GT mustang roller motor into my 66. It has headman shorty headers, RPM Air Gap intake, mallory unilite distributor with old style coil and a holley mechanical secondary carb. I replaced the timing chain with a new one.
The carb was heavily modified. The air horn was machined off and I suspect the jetting has been altered as well. The carb appears to be a 650 or 600.
Timing is set at 34 degrees max with an idle timing of 9 degrees or so.
The problem is an intermittent explosion in the headers at higher rpm under load. I am assuming that there is unburnt gas exiting the cylinder or a valve timing problem. I would suspect a valve timing problem to be consistent.
Today, I plan on replacing the old spark plugs and checking for compression.
I was hoping someone can give me some guideline jetting specs. Maybe from a stock holley carb. Main jet, accelerator pump cam, etc.
Thanks for the help.
The carb was heavily modified. The air horn was machined off and I suspect the jetting has been altered as well. The carb appears to be a 650 or 600.
Timing is set at 34 degrees max with an idle timing of 9 degrees or so.
The problem is an intermittent explosion in the headers at higher rpm under load. I am assuming that there is unburnt gas exiting the cylinder or a valve timing problem. I would suspect a valve timing problem to be consistent.
Today, I plan on replacing the old spark plugs and checking for compression.
I was hoping someone can give me some guideline jetting specs. Maybe from a stock holley carb. Main jet, accelerator pump cam, etc.
Thanks for the help.
#14
I pulled the plugs. 5 and 6 were black, the rest were the correct brown/tan color. I have 180 compression in 1, 175 in 3 and 170 psi in the other 4 cylinders.
I replaced the plugs and gapped them to .050. I have the same miss. I'll post this to its' own thread.
I replaced the plugs and gapped them to .050. I have the same miss. I'll post this to its' own thread.
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