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  Topic Review (Newest First)
03-17-2011 09:41 AM
Hotrod Sometimes a worn cam lobe can give you a popping noise thru the carb. Do you hear that? But I am not sure which lobe (intake or exhaust) will make the popping noise (thru the carb) when worn. I think it's specific only to exhaust.

Have you considered the accelerator pump (carb), if it's bad or misadjusted, it will give you a flat spot during accel and will backfire thru carb. Could be you have multiple problems here. But check it out and let us know. Good Luck!!!
02-27-2011 01:29 PM glad to help, let us know what you find.
02-27-2011 09:49 AM
clydecrashcup63 I still need to check the cap and rotor. I put them on not to long ago, but you know how that goes. Wiring looks fine and can't see any burned wires. Could start the car up in the dark and see if there is any cross firing happening. I do need to do the compression check again and possibly a leak down for a bent valve, etc. I hadn't thought about checking the normal lift of the rockers. I am going to check the plugs for fouling carbon. I have wondered about the possiblity of the worn cam lobe. The engine/cam doesn't have many miles, but that doesn't necessarily mean that the cam lobe is worn.

I'll keep checking, thanks again for your thoughts. I initially needed to get the car idling correct and go from there.
02-26-2011 03:27 PM when a engine backfires, it could have several causes...check your cap and rotor first for damage, and that the advance mechanism is working..any chance you have a plug wire burnt or two wires crossed on the wrong plugs? If not, I would do a compression check on all could have a burnt or bent intake valve, or a worn exhaust cam lobe . If you get a low compression reading on one cylinder, pull the valve cover and verify the rockers for that cylinder are moving in proportion to the other cylinders on that side.
02-26-2011 02:49 PM
clydecrashcup63 Got the engine to idle. No vacuum leaks. Looks like timing is 10 degrees. Took car out for a test drive and seems like no power. Step on the gas and engine noses over, has a tendency to back fire. Turned around, went back home and shut the garage door.

Any thoughts?
02-17-2011 04:22 PM thats a healthy cam, with not a lot of idle vacuum..if you are using full vac instead of ported, that will certainly cause what you describe.. also, when you had the cap off, did you make sure the vac adv moves?
02-17-2011 03:01 PM
clydecrashcup63 1) fishslayer - I forgot to answer about the cam ? earlier. The cam @50 intake is 240 and exhaust is 246 with lobe separation of 110.

I checked the distr. springs and arms and didn't appear to be any problem. No drag on the arms while sliding. I plan on Sat. checking the vacuum and putting a T in the line for the gauge while it is running to see what is happening then.

2) hot rod - I have considered the manifold leak, I plan this weekend to spray some carb cleaner around the manifold to see what happens. Thanks for your help in brainstorming my problem.
02-17-2011 07:45 AM
Hotrod Ported vacuum which is what you want for the dist Vac adv. is obtained from a vacuum port located above the throttle blades, whereas manifold vac on the carb is located on the base plate of the carb. Like Fish says also a vac gauge will confirm this. As a side note have you considered an intake manifold leak?
02-17-2011 05:58 AM weak cent. adv. springs could cause the same effect, by allowing adv at idle... you won t be sorry if you upgrade ignition to MSD box.. good luck..
02-16-2011 05:59 PM
clydecrashcup63 thanks for the reply. Yes, I have the vaccum to the correct side. I don't have a vacuum gauge. A friend is bringing one up this weekend. I am going to check the springs, etc. in the distributor to see if one is broken and if the arms are moving freely. It is the original distributor my have updated it to electronics and MSD box for good spark.
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