Timing issue

[1969CoronetR/T]

I had my 1969 Coronet R/T at a shop to see if they can help with a run on issue (dieseling). They rebuilt my carburetor and used engine cleaner to get what they believed was a carbon build up. Lastly, they adjusted my timing. I picked the car up and it ran fine although it seemed sluggish. The next morning, it was back firing like crazy and finally stopped after warning up. The timing must be off and is stills diesels after a hard run. What should the timing be set?
499 cid engine. The cam is 545 lift with a 235/241 duration and 110 lobe separator / 106 centerline. The compression is 9.6 to 1.
Thanks
Mark

 

[hunt2elk]

I bet it will want more initial timing than what it has now....

 

[BLK 68 R/T]

Gonna guess around 18-20 degrees BTDC and 36-38 total. What’s your idle rpm?

 

[1969CoronetR/T]

how would I know the idle rpm? It is also very hard to start and I noticed my rpm gauge isn’t responding like it did before it went in the shop.

 

[BLK 68 R/T]

Have to hook up a timing light that shows rpm or have a tachometer.

Could also be an electrical problem in the ignition system or fuel related problem as well.

 

[davek]

A good read on timing,I do 2000 rpm at 34 degrees on my 440. Ignition Timing questions

 

[davek]

also Lucas octane boost gas is junk now a days.

 

[DanielSlocum]

is the heat cross-over passage in the intake blocked? if not.....you may have enough heat in the engine to cause run-on/dieseling; especially with cast iron heads.
is there an insulated spacer between the carb and intake? having one there helps in more ways than one.
i agree that your initial timing should be about 18 degrees and about 36 total. fuel octane is another big factor; i think you need at least 91 octane. good luck.

 

[Kern Dog]

No mention of the carburetor, the ignition, the timing settings you currently have or anything that would help.
You have a car built like this and have others work on it ?
The further you deviate from stock, the higher your skill level needs to be. Do you have a timing light?
Dieseling is usually a result of the primary throttle blades being partially open even at idle but there are other contributing factors.
Spark plugs for a heat range higher than optimal.
Incorrect ignition timing.
Overheating.
That cam and engine will need at least 16 degrees in initial, maybe more. Total depends on the type and efficiency of the heads which you didn't mention either. A more efficient aluminum head can make the most power at 35 degrees or less. A less efficient cylinder head will need more timing.

 

[1969CoronetR/T]

Kern dog,
The engine builder died about two years ago and he initially built the engine back in 2010. He was the best and I miss his expertise and now have to find another shop.
The shop did mention that the throttle blades would not close and that the idle was too high. I’ll have to bring it back down to then to see if they can fix it since again. I need my old engine builder back from the grave

 

[1969CoronetR/T]

Ok, now the shop wants to block off my vacuum advance and add a MSD distributor. Would this be hurtful to the engine?

 

[Kern Dog]

The guys there sound like parts swappers and not genuine mechanics.
Running without vacuum advance on the street will not immediately hurt anything but fuel economy. Over the long run, the lack of it leads to carbon buildup and faster piston ring wear from unburned fuel washing the oil from the cylinder walls.
See, the vacuum advance helps during part throttle operation, a place where our street cars spend most of their time. During part throttle, the fuel molecules are not tightly packed together so they don't burn as fast. To aid in a more complete burn, the timing needs to be advanced a bit to start the fire a bit earlier. By eliminating the advance that the vacuum can adds, the engine now has more unburned fuel going through on every cycle. Some of the unburned fuel just goes out the exhaust, some eats away at the oil on the cylinder walls shortening the life of the engine.

 

[BLK 68 R/T]

Ok, now the shop wants to block off my vacuum advance and add a MSD distributor. Would this be hurtful to the engine?

Why do they want to do that?

 

[66 Sat]

Don't take it back to this shop.
When did the original dieseling issue arise? You said the engine was built in 2010 - was it a recent issue? What carburetor do you have?
There are plenty of knowledgeable guys on here and who probably live local to you that can help.
The "shop" sound useless. Engine cleaner to fix the issue. Mechanic-in-a-can.

 

[hunt2elk]

Ok, now the shop wants to block off my vacuum advance and add a MSD distributor. Would this be hurtful to the engine?

You need to find a different shop, or learn how to do some of this easier stuff on your own. Believe me, we have all been in your shoes.

 

[1969CoronetR/T]

Thanks Kern Dog. I had a great mechanic (ASA Performance) that unfortunately smoked two packs a day and died.
The engine was rebuilt back in 2015 by Ed at ASA and it stated dieseling a few years ago. It seemed to do it after a long ride when the engine was nice and hot. Not too often though.
Anyone in the McCandless (north hills of Pittsburgh) area that is a competent mechanic? I screw up pealing an orange

 

[Geetex]

I screw up pealing an orange

I don't mean to laugh, but that's funny, even though you did misspell peeling.

 

[Roscoethug]

Stupid question.....how old is the gas? Old gas will cause backfire, trouble holding an idle etc. Don't ask how I know. Drove me nuts until I figured it was just bad gas.

 

[T Brashears]

Call Ron Tonetti North Hills Cycle 412 931 6205 leave a message Tell him Tim recommended him.

 

[toolmanmike]

how would I know the idle rpm? It is also very hard to start and I noticed my rpm gauge isn’t responding like it did before it went in the shop.

You may be in trouble. Not to be disrespectful but you have a 69 RT with a 500 cube wedge and you don't know about Idle RPM? I'm out.