liltoothpick

I have a 91 z28 camaro that i bought, was converted from tpi to carburetor. About a year ago, when i got the car they had kept the stock fuel pump in and the carburetor was flooding like crazy so i dropped the tank and replaced the in tank one with an electric pump, also i modified the sending unit. The car has a 305 motor with a 700r4 transmission. The carburetor is a 600 cfm elderbrock carburetor, it is the 1406 model. The reason i am making this thread is i cant figure out how to fix this problem im having, I can drive the car without any problems, but when i turn the car off let it sit for 30 minutes and try to start it again the car will have a really hard time starting, if i look in the glass filter located by the carburetor, it will be not even close to full and i can see a bunch of bubbles coming up it. Now if i can get the motor to start without flooding, i can turn the pump off (with a switch i wired in) let it run until it dies, and then turn the pump on and most of the time that fills the filter back up and the car will run good again. I should also note that with the way i have it right now i do not have a return to the gas tank, the electric pump only pushes around 6 psi so i didnt believe i had to. Because of this problem i have not drove it on any hot days, anything above 80 degrees for fear of breaking down due to what i believe is vapor lock, i have looked into this quite a bit and it seems if i have vapor lock i need a carb spacer which is not going to fit since i already have zero room under the hood. i did cut out the holes in my hood scoops so they actually function, which seems to help with keeping the engine bay cooler. i also thought maybe if i run the gas line from behind the distributor, down the transmission and over to the frame might help with the fuel issue but i dont know if that is a good idea, i would like to know what you guys think, I have included pictures below to show you my setup.

Damon

In a running condition, the filter will not fill up all the way. So that's fairly normal.

GLASS fuel filter? If it's the one I think it is, that's both restrictive and more importantly DANGEROUS. NEVER use a glass-case fuel filter on.... well, really anything.

Might try a simple phenolic gasket/heat shield under the carb instead of the thin paper gasket. They can drop carb temps pretty dramatically and they're only a fraction of an inch thicker than what you're probably already using.

When an engine is running the latent heat of vaporization from the fuel atomizing out of the carb's venturis helps keep their operating temps down. But when you shut it off, that goes away and the heat from the engine quickly wicks up into the carb's aluminum body and, well, it can cause issues like this sometimes. I bet once you get it started it runs just fine, right?

That would be where I'd start, anyway.

liltoothpick

Yeah I runs fine after I get it started I'm about to go to autozone and see if I can pick one up there, two things though. Do I have to get new studs for the gasket, also do I have to tighten them down to a certain amount, or can I just wrench them as tight as they go? My only concern is hood clearence I really have no room. My air filter hits my hood when I close it.

Damon

For right now, just to test the theory, leave the air cleaner assy. off.

You tighten carbs down on the manifold gasket basically "screwdriver tight". Put the socket on the end of a driver handle and tighten down that way. Too easy to snap a mounting ear off the corner of the carb. Eveything you're tightening down/into is aluminum which has little strength.

If your studs/bolts are too short with the thicker gasket, get slightly longer ones. With an aluminum manifold I usually use studs since it's SO easy to rip the threads out of them, and then you've got an even bigger job to tackle.

liltoothpick

Alright I installed the carburetor spacer, I also found an air filter that that will fit but I have to take off the electric choke for it to fit, would that hurt anything? I made a video so you can hear the car run, with the new spacer installed does everything sound alright? Here's the link ----> https://youtu.be/c1j0H6UzZgw

Damon

Sounds OK to me. Motor seems to be running smooth. No visible shake on the underhood shot.

Electric choke removal won't hurt a thing in the warm months. When it gets cold... you'll probably wish you had it back on.

liltoothpick

My only concern was when I let off the gas, the sound of the motor revving down but then again I have sidepipes so that could effect it, thanks for the advice, I'm gonna run it tomorrow and post back what happened

danryanm

Any updates? I have a hard time believing a spacer could ever fix a hard-start condition, but accidents do happen. Before spending a single red cent or taking things apart, the are some often-overlooked diagnostic steps when dealing with carburetors.

1) NEVER ASSUME! Obviously something is wrong that wasn't before, so it is unwise to assume a part isn't the problem just because "it worked before" or "its rated at...". Every part of the affected system is suspect until AFTER it has been checked/tested. [My "factory" rated pump puts out 14lbs instead of 6.]

2) Is there fuel in the bowl? This is easily checked if your bowl has sight windows or bowl plugs; you can also move the throttle and look for the accelerator pump to squirt.

2a) Is there still fuel in the bowl? Let the car sit a while to try and duplicate the conditions when you noticed it was hard to start. If there isn't, then you may have a leak, be it internal or external. Before anyone even suggests it, fuel does NOT evaporate enough to leave a bowl dry in one day.

3) What is your fuel pressure (as measured on the car, not on paper)? This is almost always overlooked, yet it is possibly the most common problem when using aftermarket carbs. Even so much as half a pound over-pressure can upset needle-and-seat valves - sometimes (but not always) the effect of which is fuel visibly bubbling out. This is almost always misinterpreted as "fuel boiling", when in fact it is not.

There are further steps that can be taken to complete the diagnosis, but these are what should be done first, and usually the problem will present itself during these first steps. Spacers and "magic clothespins" are accidental "fixes" that are potentially little more than wastes of time and money (compounded by more time and money if you have to buy other parts to make them work). All that being said, ditch the glass filter. That is a horrible, crispy death waiting to happen.