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2,368 Posts
At least it's puzzling the heck out of me. Motor is a 468 cu in BBF basically stock. Hydraulic flat tappet cam, roller rockers, Comp pushrods with guideplates, stock crank and rods, edelbrock Performer RPM heads with small chambers (75cc) and about 10.5:1 compression, tunnelram with two holley 750 dps.
Problem new fuel pump carbs and 4 port regulator. Fuel pressure is at 6.5 psi, idle mixture screws are 1.5 turns out and floats adjusted.
One pump on the throttle when cold and she lights right up. Idle sounds real good and no indication of any problem. When running there's a bit of a hesitation off idle then she gets up and runs pretty good (thinking this is unrelated to the problem but something else to work on).
While under way sounds like it's hitting on all 8 cylinders and I'm pulling my normal rpm at WOT and various ranges of throttle. Ran it about 4 miles just taking it easy most the way and romping on it a few times. Got to the cove and let her settle into an idle and it sounds like it's running on 7. Kinda popping and coughing. Got into the cove and let it sit for a bit. After about 10 minutes I disconnected my driveline via the jetaway and it fired right up and sounded normal again.
Later left the cove and did the same routine on the way back. Started up with a bump of the key and sounded fine at idle, cruise and everything in between, but when I got back to the ramp and let it idle it started crapping out again. After it's on the trailer for ten minutes or so, fire it back up and everything is back to normal again.
I'm thinking I've got a hydraulic lifter taking a shit one me. Can't figure out what could be changing from cruise to idle and why after sitting everythings o.k. again. Keep in mind if you just start it and let it idle without running it around, it'll idle fine as long as you care to run it. It's not until you take it out and cruise around a little that the problem arises.
Any ideas?
Problem new fuel pump carbs and 4 port regulator. Fuel pressure is at 6.5 psi, idle mixture screws are 1.5 turns out and floats adjusted.
One pump on the throttle when cold and she lights right up. Idle sounds real good and no indication of any problem. When running there's a bit of a hesitation off idle then she gets up and runs pretty good (thinking this is unrelated to the problem but something else to work on).
While under way sounds like it's hitting on all 8 cylinders and I'm pulling my normal rpm at WOT and various ranges of throttle. Ran it about 4 miles just taking it easy most the way and romping on it a few times. Got to the cove and let her settle into an idle and it sounds like it's running on 7. Kinda popping and coughing. Got into the cove and let it sit for a bit. After about 10 minutes I disconnected my driveline via the jetaway and it fired right up and sounded normal again.
Later left the cove and did the same routine on the way back. Started up with a bump of the key and sounded fine at idle, cruise and everything in between, but when I got back to the ramp and let it idle it started crapping out again. After it's on the trailer for ten minutes or so, fire it back up and everything is back to normal again.
I'm thinking I've got a hydraulic lifter taking a shit one me. Can't figure out what could be changing from cruise to idle and why after sitting everythings o.k. again. Keep in mind if you just start it and let it idle without running it around, it'll idle fine as long as you care to run it. It's not until you take it out and cruise around a little that the problem arises.
Any ideas?
