So, I just put a new used engine in my teener and the troubles don't seem to end! I finally got the thing timed and I've adjusted the valves. Now I'm getting a very hollow sound in one of my carbs. It's like a "bop-bop-bop" every time the cylinder fires. I synced the carburetors and am in the process of adjusting the mixture. Today I removed my spark plugs to find out what the mixture is, and sure enough three of them were black. When I was putting them back in, I think I cross-threaded one of the plugs. I got it so the plug seals, but I'm guessing that it won't last too long. Is there any way to fix this without removing the heads or engine?

Will I ever get my car drivable again?

work like spark plug threads and such are much easier with the engine out. with practice, you can remove it in < 1 hr and it's worth the effort for the convenience of accessibility to repair areas.

Even if it is really messed up, it can be fixed. I had a blown out plug fixed using a threaded "case-saver" sleeve with the motor in the car. It was on #1 in my situation. An old school VW place can do it. It isn't elegant, and you need a new sleeve for every plug change ( I have some extra if you can't find one), but it works and its cheap too. Sure, probably got metal shreds in there, but when I replaced those heads later the cylinder was fine inside.

Cool, thanks guys, that makes me feel a lot better, knowing that I won't need the heads machined r something wacky like that.

Any insights on the carb sound? The carbs are balanced, I'm just trying to set the mixture correctly. The carbs are DellOrto. 36's I think. I've thoroughly cleaned both carburetors.

Besides carb operation, the only thing I can think of is valve adjustment. I know you just did it but might be worth a second look at the offending cylinder.

About the plug threads, my dad always put a little oil on the threads of plugs just to help ease the plugs into their threads to avoid crossthreading. Plugs should be hand tightened until seated then use the ratchet to tighten. I do the same thing with wheel lug bolts/nuts.

is the engine unresponsive (no effect) when you are trying to adjust the idle air mixture screw on the cyl making the strange noise? with the i/a mixture screw run fully in (lightly seated), the engine should stumble if not slightly backfire. the stumble/bf denotes a lean condition.

k

Umm, before I cleaned the carbs the engine was unresponsive when turning the screw all the way in. I haven't tried it since, though.

Ok, update. I did a compression check and all the cylinders seemed fine. The two cylinders that aren't having problems (3 and 4) are at 140. The noisy cylinder is at 150, and the cylinder with the stripped plug socket is at 135-140 (I checked it twice). However, the mixture control screw on cylinder 3 is unresponsive when turned all the way in. Valves are all adjusted correctly.

If it's not a vacuum leak where the intake meets the head, I'll eat my hat. (I don't wear hats)

You mean the noisy cylinder? Could be, and that's what I'll check next, thanks.

As for the unresponsive mixture screw on cylinder #3, I found the source of the problem. I backed out the screw and found that it was bent. I hadn't noticed it before, but it definitely is bent beyond repair. Anyone know if/where I can order just that part?

Rich Bomprezi(sp?) could help with the part I bet. I believe he has a store front in vendor area? He had an idle adjust screw for my 1.8.

Good Luck
JKP

Aircooled.net is where I get my weber parts.

Are you sure the noisy cylinder isn't due to exhaust leak?

Rich Bontempi? Yup, he's the guy that regularly services my car. He has parts for Webers, but not DellOrto's


They're DellOrto carbs, though.

As or an exhaust leak, I just got my exhaust worked on because I had an exhaust leak, so I haven't checked that. It does sound like an exhaust leak, but it sounds like it's coming from the top of the engine instead of underneath. However, I have been wrong before, and I'll go and listen to the exhaust to see if I can figure anything out.

Carb popping is caused by a lean condition. I always wondered why, and one day I finally found out, after a couple hours of googling. At excessively lean mixtures, gasoline burns too slowly. So slowly in fact that the flame is still burning when the intake valve opens again, after the exhaust stroke. The fire then goes foomp, up into the carb, making that popping sound. I've always found the cause of carb backfiring to be either a clogged carb (pops all the time) or a vacuum leak (pops at low throttle settings only). That's the reasoning behind my hat eating statement earlier.

Oh, also... I think empi sells dellorto carbs, maybe they sell parts for them?

Ahh! awesome, so it's just running too lean then? And as far as backfiring, that went mostly away when I adjusted the timing again, but it's still backfiring a bit. And I just cleaned it completely so it can't be clogged. I guess it must be a vacuum leak then?


No worries, I found the part. CB performance had it, so I'm golden.

Well I certainly think so. Rule of thumb is lean pops out the carbs, and rich pops out the tailpipe. Of course that only applies if the popping is because of a mixture issue, many other things can cause it.