damn timing...

[reddog64]

ok it's a 400 small block 30 over... maybe 7500 miles.. the timing was set at 0 degrees.. it runs.. but pinged and dieseled.. so i advanced it.. it dieseld... it diesels to the point that i have to put it in reverse and hope it turns off... sometimes even that doesnt turn the truck off...

if i retard the timing it pings but where it's at now it diesels and if i go advanced more it just diesles or too far it wont start...

HELP!!!

 

[TopOff]

Vaccum leak.

 

[reddog64]

vaccum leak... where would it be to cause that???

 

[Highlander]

Well mine will Diesel if I run low octane gas. I run 91oct. and it's fine. I also run my timing at 10deg. I do run a Edlebrock carb. And was told by a Hotrod shop that if I were to put the fast idle silnoid (sp) on the carb it would stop the dieseling but I haven't done it yet maybe someday.

Eric

 

[70jimmy]

Don't the 400's have a harmonic balancer that can be put on in 3 different ways. Each one is a difference of like 8 degrees. In my 74 I put a 400 out of my chevelle in and had it built and wouldnt run worth a darn and took it to the shop that did the work and that is what they said the problem was. They fixed it so cant be any more help. Some of the better speed shops I hear can put it on a computer and time it using that instead of trusting the marks. My current 350 I am told the balancer is slipping and the marks are off. Good luck.

 

[TrcksR4ME]

What kind of gas are you running? I know my truck will ping and run like crap if I put any no name gas in or Arco. Texeco is what I consider to be the best. But my guess is you have tried different gas octanes and all that already.

 

[TopOff]

My frined rebuilt a 350 all the cool hop-ups. He couldn't get it to idle, and stay in gear (auto). It kept surging whenever he put it in gear. But when running/driving it ran great! He had a spacer on the carb, the spacer had the vacuum port on it for the brake assist. He didn't plug this.. he got dieseling too!

CHeck carb (TBI as it applies) gaskets and all vaccuum lines. If in doubt plug them for now, and see if it diesels.

It could also be an overheating condition. Do you have a mechanical temp gauge?

Timing:
The outside of the balancer could have moved too...
Get the motor to NEAR TDC.... check the woodruff key the woodruff key on the crank is pointing at #1 and should be pointing directly to head! Line that up with the timing mark on your balancer.. are they lined up?

If not, make a new mark (white-out, or some Tester's white enamel works well) on your balancer lined up with the woodruff key. Now check your timing.!

 

[Grim-Reaper]

There are several things that can cause that. Too much compression is a biggie. If it has been doing it since word go I would start wondering about that. Rich idle mixture with a vacume leak. Wrong heat range spark plugs. Carbon deposits could cause it. Crappy holly carbs are known for that also.