c3-4me

I installed the Performer EPS and BG 625 Road Demon on my L48. I have adjusted timing and mixture screws to what I think it should be. It seemed to run good, but after idling awhile, it started to run rough. I pulled it back into the garage just in case it would stall, then popped the hood. I rev'd the engine a little, then POW. It backfired through the carb and I have flamage inside my air cleaner!!!!

This is the 2nd time I have gone through these steps, but this is the only time it started a fire. The first time, it finally wouldn't run anymore, so I pulled the plugs and they were extremely fouled. I put new plugs in tonight, and now this happens.

What could be wrong!!!!!!

Xx Grave

Did you take the distributor out? Maybe its 180 out or the firing order is wrong?

c3-4me

Yeah it came out to put the manifold on. The thing I can't figure out is how well it will run for awhile, ( 20 minute drive), the after idling for 5 minutes, turn so rough and backfire so bad. I could see you point if the car didn't run right when I first started it.

OH, by the way, this is really weird. After pulling the a/c off, I heard hissing coming from the carb. I looked at the sight glasses on the carb and the friggin gas is BOILING!!!

helix60

I'd recommend checking your fuel pressure. A lot of the new performance carbs require no more than 6 lbs of pressure. Any more will at the least cause fooding at an idle.

If your distributor was installed 180 out it would not run. If you are one tooth out it will run but will be corrected when you timed it with a light.

Hope this helps

Regards,
Heli

ddecart

How rich is your idle mixture? It it eye-burning? If you;re supplying too much fuel at idle, raw fuel may well be building up in the intake manifold and then ignites at an opportune moment, backfiring.

Just one theory.

c3-4me

I have leaned it out. The mixture screws are not quite 1 full turn out.
What is eye burning???

ddecart

Get it rich enough and you'll know. Standing behind the car, the fumes will be so bad that they burn your eyes.

do your idle screws make a difference? Do you hear a difference when you screw them in & out?

With some engines (due to the cam) they actually can't get enough air in them with the throttle plate & mixture screws in a normal zone. What happens then is that the throttle plate needs to be opened a bit (and the idle screws can be screwed further in). If the throttle plate is opened too far, the airflow will draw fuel from the main circuit and not just the idle circuit. So it may, from the idle screws, look like you have it lean, when in reality it's overly rich.

What cam are you running?

Xx Grave

Now that i think back, i had the same problem..... Carb backfires and such after i changed my intake. Turned out my harmonic balancer spun on the outside and was impossible to time until i brought it to TDC and made a new mark. Do you still have the original harmonic on it?

c3-4me

Everything is original. (the cam and H/B) One thing I noticed may be a problem. The fuel hose that leads to the hard plumbing that came with demon is running under the SS heater hose and is in direct contact with it. Is it possible that this is heating up the gas so much to cause it to boil in the carb and make all these things happen after the gasoline gets so hot?????

Older Than Dirt

Sounds like manifold heat under the fuel bowls. Maybe you need a heat shield and spacer to isolate the carb from the intake.

c3-4me

Would a plate be enough?? Would the gas being so hot couse the problems I have??

Older Than Dirt

From your description of what is happening after idling for a time it has to be manifold heat. After the engine cools down it runs fine, right? A plate alone might work but a spacer too would work better. That's something you would just have to try. Boiling fuel is not a good thing and with you eyewitnessing that happening I would say that is your problem.

c3-4me

Thanks OTD! Looks like I will have to order that L88 hood sooner than expected. I only have 1/8 - 1/4" clearance with this setup now.

I am going to try it this morning to see if it is back to normal, I just hope the flames didn't cause any damage in the carb!

Thanks again!

R1234

Just a thought and it might not be your problem but, I had similar thing happen to me. It turned out that I wasn't tightening down the distributor clamp adequately and the timing got off due to the distributor turning with the engine running. I reset the timing, tightened down the distributor clamp good and tight. Its been running great.