[Trent7276]

Well here goes, I need help.

My 1968 Pontiac Firebird 400 just got a new Performer RPM intake manifold and Edelbrock 1411 750 CFM carb with Electric Choke. I hooked it all up along with a new inline filter and steel braided fuel hose, everything nice.

Started it up and she idled at around 2500 RPM. I let her run for about 30 sec. I turned her off.

Adjusted the fast idle cam out a few turns and started her up. Perfect idle speed of 1500 RPMÂ…4 sec later she died. I cranked again, 4 sec later diedÂ….I cranked one more time. She fire up and BOOOOM, a large fireball above the carburetor about 2 feet!!! (Air Cleaner was not on) and then I TURNED HER OFF!!!

Suspecting flooding, I pinched the fuel line and cranked, it started and died, I cranked more and she never started from then on. I released the fuel line and cranked, she started and died 4 sec later. Again I cranked, started and died 4 sec laterÂ…What could the problem be and how do I fix it???

[Trent7276]

Well here goes, I need help.

My 1968 Pontiac Firebird 400 just got a new Performer RPM intake manifold and Edelbrock 1411 750 CFM carb with Electric Choke. I hooked it all up along with a new inline filter and steel braided fuel hose, everything nice.

Started it up and she idled at around 2500 RPM. I let her run for about 30 sec. I turned her off.

Adjusted the fast idle cam out a few turns and started her up. Perfect idle speed of 1500 RPMÂ…4 sec later she died. I cranked again, 4 sec later diedÂ….I cranked one more time. She fire up and BOOOOM, a large fireball above the carburetor about 2 feet!!! (Air Cleaner was not on) and then I TURNED HER OFF!!!

Suspecting flooding, I pinched the fuel line and cranked, it started and died, I cranked more and she never started from then on. I released the fuel line and cranked, she started and died 4 sec later. Again I cranked, started and died 4 sec laterÂ…What could the problem be and how do I fix it???

[78 GHOST]

What is your initial timing set at?

-Matt

[BAB]

Speaking of fires...try this one on for size. Shorlty after I had my engine compartment restored I was taking my quadrajet on and off for tuning. I would always start the metal fuel line into the front of the carb and then go around and finish the four bolts to ensure I had a good straight bite on the brass fitting. Well, I did everything as normal except go back and tighten my fuel line! As I backed out of the garage I immediatley smelled gas and went to shut the car off. Just as I turned the key back "KABOOM"! Flames were coming out the side of the hood. I had a fire extinguisher in the car because the week before I had a second temperory line running to my windshield when I was checking fuel pressure so I just "happen" to have it still in the car. I popped the hood and gave it some good shots. I got it out but it had melted my new plug wires and wiring harness in several spots besides making a big mess. This wasn't your "typical" carb fire. This fuel line pumped gas everywhere before it started and if anyone would have been watching I'm sure it would have been very funny as I looked like Barney Phife reacting to it. I imagine the fuel hit my already hot manifolds or my carb back fired, but either way it was a little scary? I'm the first to take risk, however this situation made me MUCH more cautious in what I do! (Sorry to take away from your original question but I seen your topic and it got me "fired" up...beside would you really want advice from me after that story )

[johnta1]

Check that all vacuum lines are connected.
Do you have an electric pump?

Sounds like a vacuum leak and/or the fuel bowl is not filling up.

[Trent7276]

My engine is a 1971 400 so I set the timing at 12 deg, same as it was before the swap when I had the Rochester. Today I fired it up some more but only one backfire out the carb all day...the rest of the time I'm just trying to keep it from dying at 1000 RPM idle. At 1000 this engine and car feel like they are shaking violently! I must have too hot a cam in it? I must have a problem since it gets a really loud "sucking through a small hose high pitch" sound when I try to get it down to a 1000 RPM idle. Also, initial testing shows vaccum pressure at 15 when 1500 RPM, then I let off the gas and let it drop to 1000 RPM, vaccum goes to 6 or 7, sometimes stumbles to 5,4,3 and dies. I'm not even running my Power brakes but the hole in the Carb backside is plugged as they suggest if no Power Brakes. I've tried the tuning procedure to no avail from Edelbrock. Some help on how to tune this thing?? Why is vaccum so low now and not before. Is it the new RPM Manifold? With the stock manifold and Rochester, I would get a good 15-16 Hg at 1000 RPM idle. Initial thoughts are my cam is too hot, my #47 heads are sufforcating my engine, and I might have a vaccum leak...anyone else?

[A455GTO]

Sounds like you have a nasty vacuum leak somewhere. I've had a few in my time also, similar symptoms. Check the carb base to intake mounting area - maybe the gasket isn't sealing properly. Also make sure that there aren't any vacuum ports open on the carb - sometimes they are a lot, and easy to miss. Good luck, keep us posted!

[Trent7276]

YOU GUYS ARE GREAT!!!

Everyone always says "Check all vaccum connections and open ports". It seems so routine! How effective was this...tuning a new intake and carb with a 3/8 inch hole in the top of your manifold left unplugged! Thats right, right behind the carb toward the distributor, Edelbrock stuck another threaded hole for a vaccum tube attachment that my original manifold did not have. There was my sucking noise! No wonder it couldn't hold a vaccum. That is probably where the fireball came from too. Well, I plugged it! No more sucking noise, I've got my 16 Hg back at idle, the carb tuned in an instant, and much quieter sounding car, no more violent shakes, in fact doesn't shake at all! I even got her tuned to 800 RPM with no problem! Wow, just goes to show, look at the simple things first. I was only 1 step from pulling the whole intake and ordering new gaskets. I'm new at this but this will be a great learning experience! Thanks again everyone...now I wait for my fenders, front bumper, front valance, and hood to come in and take her for a spin!

Trent

[78 GHOST]

Trent, I'm very happy to hear your simple solution, It's good to hear your solution as many fix their problem without updating the solution.

The next time I do a manifold, I'll think of you and double check the obvious sources of leakage.

Take care and don't waste too much rubber on the test drive [img]smile.gif[/img]

-Matt

[Garry Sr]

Trent, stop drinking while working on the car!