I have a 1987 IROC 305 with a newly installed 600 CFM Edelbrock Carb. The Quadrajet gave out on me. I had been wanting to put a new Carb on the car for a long time so this was the chance. I pulled all of the emissions stuff off of the engine and plugged all of the vacuum lines with caps. Before the Quadrajet gave out on me, the car ran fine and shut off fine. Since I put the new carb on, the car will diesal every time I shut it off. I have to put it in gear to actually get it to shut off. It will diesal forever. How do I stop this diesaling from happening ?
A friend stated that I need to change my timing chain. Car has about 186,000 original miles on it, no real work ever done on the engine, car stays in storage a lot.

The following is what I have already done.
Checked timing, seems to jump around a little, but stays pretty much in the area.
Checked fuel pressure seems a little high but not unnormal, about 8psi
Checked for vacuum leaks, none found.
Changed plugs and wires..
Iroc 305 LG4, M5, 4BBL (Everything else is standard for the year)

Thanks
Loo

 

It could be that the Edelbrock dosen't like 8psi. Fuel pressure higher than the carb was designed for will accually push its way past the needle and seat and cause fuel to leak by into the jets. The mechanical pump will keep going at long as its dieseling and keep feeding the engine fuel. The Edelbrock catalog I got says 6psi for a 'Performer' series carb. It could also be a float level set too high, causing the same problem of fuel leaking by the needle and seat.
I'd say a fuel pressure regulator may be needed.

Also I recomend an in-line fuel filter just before the carb if you haven't installed one yet.

Hope this helps

 

I installed a glass fuel filter on the fuel line before the Carb. I tried using a fuel pressure regulator but the one I purchased only went up to 5 psi. The car did not work well off of 5 psi, as long as it was already warmed up it would run ok, but trying to crank it in the morning was a bear, so I pulled it off. Do you have a suggestion on the type or make of pressure regulator that I should purchase ?

Thanks

 

Did the fuel pressure regulator fix the dieseling problem?
If so...
summitracing.com has their own brand regulator that goes from 4&1/2 to 9 psi for about 25 bucks. That would work. Part # SUM-G3131B.

Mike

 

I did not have it on long enough to figure it out, I put it on one night, it started raining on me, the car seemed to be acting ok, but due to the rain I figured I would try it the next morning and then I could not get the car started, so I pulled it off. It was a specter product anyway..

I had people tell me that it was to much fuel, to much carbon in my engine and that my timing was off due to my timing chain being worn...


I will try the one from summitracing.. I will post again as soon as I get the new regulator on there. Thanks for the tip on the regulator.

Loo

 

This is where most people's problems w/ these cars begins. Please tell me you did not just leave the stock distributor on the car. You need an HEI setup or the timing is going to be all screwed up w/ the CCC carb removed. If you have a stock distributor on there, you are going to have major problems.

Don't waste your money on a regulator. I am not quite sure why everyone is telling you that you need one. It's not like you are putting a carb on a fuel injected car w/ high pressure pump. A carbureted car is going to have close enough fuel pressure for another carb!! That is not it.

 

Your right... I have not pulled the stock distributor off the car it is still on there. So in concerning the HEI setup.. Where should I go and what should I purchase ?

Since I started having the diesaling problem after I put the knew carb on, will this stop the problem and fix the timing issue ?

I really like this car. I have had it all my life and I have put a lot into it over the years keeping it in great shape.. I would really love to have it run correctly again..

 

I can't even tell you where to begin troubleshooting your dieseling if the basics of the engine's controls are all screwed up. You can't run an engine w/ computer controlled distributor, without the CCC carb. The dist. controls timing, period. You need an old style mechanical HEI w/ vacuum advance from a junkyard, and to splice it into your current wiring. Then you need to set your initial timing (vac advance disconnected to check timing) to somewhere around 8-10 BDTC initial. Check the total timing and reset initial if necessary to achieve 36 total.

Regardless of the dieseling, you need to get the dist swapped over. Then see if it still diesels. I have a spare HEI dist but I'm semi hoarding it "just in case" . But you can get them in U pull it junkyards, or on ebay, for $10-20.

 

My advice is pretty much the same. Go to a Pull your own yard and pay 10-20 bucks for an HEI. While you are there acquire some various stock style weights from different vehicles. I have found that when you try to curve a distributor just the way you want it, the weights in a curve kit suck. The springs are good, the weights arent.

 

327tpi hit it right on the head. Mallory and Accell both offer brand new hei units at very reasonable prices. Dieseling will most always be from timing issues. When you go to change it, take off your dist. cap and mark where the tip of your rotor is pointing with a marker, then mark your new distributer in the same spot. This will help you to get the timing close enough to where the car will crank and you can get your timing set where you need it to be with a timing light.