Ugly misfire

[ChrisZ]

Good to here, did you ever get closer to the actual problem?

Chris

[Matches]

I am very certain it was the vacuum advance. Just sticking. The dirty old thing was due for a replacement anyway

[ktm]

Backfire is not the same as a misfire. Leaning out can cause a backfire through the intake. Misfire, or miss, is the spark being "blown" out (the plug can not create the spark). This is a result of increased air/fuel density in the cylinder. L28ET cars experience this issue quite frequently above 15 psi and the plugs must be gapped correctly to help mitigate the problem. Too much fuel can cause misfiring as well.

On your carb'ed engine it is most likely due to "retarded" timing at the higher RPMs. As others have noted, check that your distributor is advancing timing.

Edit: I did not read all through way through and see that you solved the problem with a new distributor.

[zcarmann]

Don't know if anyone else wrote this but anyway, Check out the Cam as I

bought one where the lobs were worn badly and it also had a bad miss at

certain RPM, put a new cam in her and still on the road today.

Also had a bad Distrib. in my white one and had similar problem.

Edited January 13, 2009 by zcarmann

[doradox]

I have done a lot of searching on this forum and found a lot of helpful stuff. Here is a quick list of what I have done so far:

New vacuum advance

New points

New coil

New condenser

New plug wires

New ignition rotor

New ignition cap

New spark plugs

New battery

New starter

Ignition timing at 7*

Removed and cleaned engine grounds

Tested for battery voltage at coil, good

Tested ground resistance at distributor breaker plate, good.

I had a Pertronix unit in, and I had the exact same issue. So I swapped back to points just to be sure. Problem still exists.

The distributor is old, but I don't know what to look for once it is too old. Should I be suspecting this?

Running out of ideas, help!

So first on the list you replaced the vacuum advance......

I am very certain it was the vacuum advance. Just sticking. The dirty old thing was due for a replacement anyway

....Or not?

Steve

[sblake01]

Yeah, I saw that too but wasn't going to comment. I guess if you throw enough parts at it........

[zcarmann]

So ya got it fixed ????????? or what Like I said I replaced the Cam with a semi-race Cam by Crane, had an Inske in it but it was worn badly, guy before me must of kept tighting the rockers, he said they made too much noise, guess he didn't know much about Zs and or over head cams. It was worn a good 1/8 inch but still ran. Can even give you the shop who done the work for me in Naples Florida.

Edited January 14, 2009 by zcarmann

[Matches]

To clear up my earlier post;

I did replace the vacuum advance on the old distributor, and that did not solve the issue.

In the next post after I had installed a rebuilt distributor, what I meant to say was that whatever the gizmo inside the dizzy that the vacuum advance moves was sticking. So problem is fixed.

Zcarman: I did a valve job after replacing the distributor and looked at the cams. They are worn, but I don't think all that badly. Valve job went well and yielded good results.

I won't bother with this engine much more now that it is running ok. It is a tired old non-stock L24/E88 combo that in my opinion, isn't worth modifying. Perhaps if I keep this car a high compression L28 will be in the future.