Here's the story: Did an intake swap, 4 core radiator, and tranny lines all at the same time. I also added triple guages and a tach in the last week. I have since then developed a pretty apparent miss - and I can't find the culprit. Checked: Points, plugs, wires (new today - MSD 8.5 super conductors), cap and rotor.... I have a hunch that it is the carburetor. It is running a bit rich all of the sudden, and I can't tune it out. The top gasket is starting to leak fuel...mostly around the accelerator pump. Do I need to rebuild? Seems as though it is the only option left for me at this point. Could it be a bad coil?
I was under the impression that was the case for that problem, but does anyone have an idea as to why have a miss?o No: I've also checked for vacuum leaks. On the same note, when I cover my hand over the choke plate, the idle goes up. This is only if I lightly cover it...and allow air to pass through my hand. I thought I remember reading about this...is it a problem?:gt:
Adam Putting your hand over the carb while it's running restricts the air flow changing the air fuel ratio. If you do this and the idle speeds up then its probably a vaccum leak and you are improving the air fuel ratio. Dave Berry
I gotta make a run to the parts store anyway. I was just talking to a friend and he mentioned bad gas... Anyone ever experience this? I mean fuel, not bean gasp :gt: Arrrgh
Adam, I am assumming the firing order is correct. Don't laugh it happens a lot. When does the miss occur? If it is just at idle and not under load, it could be from an impropperly set float.
WIll do Jeff! I just need to keep this thing on the road for now. I'll send it to him over the winter, along with my distributor to Dave. I'll just throw a rebuild kit in this thing to keep it running for now. cheap cheap!
oy..... I rebuilt the carb today and slapped it back on. It was kind of a mess inside there....plus the float hook for the needle was non-existant!uzzled: So I got it back together with new everything.... Still misses. I tuned it the best I could. It seems to be running a bit rich. I have adjusted the idle mixture screws as good as they get. Why would it run rich? Is it because I am misfiring that the gas does not get burned and exits the exhaust as a rich mixture? It was doing it before I rebuilt the carb. One more question.... Regardless if the age of my points, could they be fried? This is my next target of suspicion.o No: :gt: :af:
Adam, Can you do a compression check? I would take off both valvecovers, and do a quick check to see if all your pushrods and rocker arms are intact and doing their job. You can also do a cylinder balance test to find a dead cylinder. Run the engine at 2000 RPM, and use an insulated pair of pliers to pull off the plug wires one at a time. Hook up a tachometer. You should see a consistant drop in RPM as you disable each cylinder. When you find a cylinder that doesn't drop RPM, you've found a dead cylinder. Could be a broken rocker or bent pushrod.
Compression test results....coming soon. I'll check for broken pushrods and/or rockers tomorrow. I think I can get the compression test done tonight.
1 - 145 2 - 150 3 - 140 4 - 145 5 - 138 6 - 158 7 - 142 8 - 142 Anything out of the ordinary? Would a bent pushrod or rocker result in low compression for cylinder #5? All spark plugs look decent...nothing stands out as too rich or lean really. Most of them are on the lean side (whiter than black) I'm pulling the left valve cover to inspect rockers and rods. Anything in particular to look for with these?
Compression looks good Adam, you're missing something. Take a good look at the inside of the distibutor cap and coil tower. Look for carbon tracks. I don't think you'll find anything wrong with the valvetrain. It has to be something simple. Don't assume new parts are good parts.
I have a lifter ticking now. Did I reinstall a pushrod wrong? Or does it take a while for the oil to fill the pushrods again? I'll buy a new set of points tomorrow to see if that is it. Definitely getting tired of chasing dead ends. All pushrods and rockers look good. None bent or broken.
In a case like this, one of the best things you can do is get a flashlight and crawl (very carefully) on top of the running engine and look down the primary barrels. If some fuel is intermittently dribbling down the barrels, this will cause a rich misfire. If this is the case I would look at float level or needle valve problems. Sounds like a vacuum leak though.
Adam, you said that you didi an intake swap. You could have a vacuum leak or maybe even a leak between the intake ports becuase of a gasket problem. Was that intake new or has the deck or heads been cut? If so there is probably a leak at the intake gasket. If it is a used intake, it may have been cut at some time also. Good luck! Brian
Vacuum leak... Adam, if you suspect a vacuum leak, get a can of starting fluid and spray small amounts near the intake gaskets while it's idling. If the rpm's rise, there is a leak at the gasket where you sprayed it. Although I would still check the carb for leak by. You never know. Good luck.:TU:
grrrrrrrrrrrrrrrrrrrr I have 19-20 inches of vacuum at low idle. I also checked for leaks around the intake gasket. I have some suspicions that this may be aiding in the problem, but not the whole thing. It ran fine for a couple weeks after I put the intake on. Why would it develop a vacuum leak after then? I don't want to pull it and reseal, but if I have to I will. Tomorrow (if time allows) I will buy a new rotor and points, since I highly suspect this is the problem. It's an erratic miss... I have replaced the dist cap and wires, checked the plugs, and all those check out. Something's not right with the ignition...I suspect. But that still doesn't account for a rich mixture.....does it???:blast:
