I'm running two 97's on an adapter to a 4 barrel intake on my 302. The carbs have been completely rebuilt and run great, but suddenly I have to pour gas down them to start the car if it sits for any length of time. I wouldn't think it's a leakdown issue, because I can still see gas in the lines leading up to the carbs. Any suggestions?
I'd pull a top-cover off after it has set -- to see where the fuel level is at. Before you do that, take the air-cleaner off and move the throttle by hand - to see if the accelerator pumps are spraying. If they're not, then you're losing the fuel in the float bowl and accel pump area (probably a leaking gasket that is letting them go dry).
OK Bored&Stroked, so far your right on. Accelerator pumps aren't squirting and upon poping the top, the fuel bowl area only had a bit of fuel in the bottom. I poured some gas into the bowl and reinstalled the top and presto.......I've got gas! So now before I tear the carbs completely apart, is there a specific gasket that would be the culprit. And, judging by the fact that I haven't seen any gas on the intake, I'm guessing that it's leaking down into the motor and I should probably change the oil too huh?
Hi: I don't have a 97 in front of me . . . will check in the shop later on. I don't have a fuel diagram of a 97 in front of me, but the thing to think about is WHERE could the gas possibly leak to . . . and how? In most downdraft carbs, the fuel is ****ed up to the venturis via va***e, which pulls through the main jets and UP to the discharge nozzles. There are not that many places where gas can leak DOWN through the carb. On a 97, I believe there are probably only two areas to leak gas (guys help me on this one?): 1) The br*** caps that you take off to get to the jets (you may see gas stains on the manifold). After you've ran the car, just put your hand down there and see if there is any wet gas around these areas. 2) Maybe the br*** check-valve in the bottom of the accel-pump area? I'm not sure (sitting here in the kitchen), whether or not there is a potential leak point here? Seems the only place it could go is back UP through the accel pump squirters. I'll check a carb body out in the shop and let you know. Question: When you say the car sits for awhile and then doesn't start -- how long are we talking about? If the garage warm . . . heated? Some gas will naturally "cooK' out of the carbs - due to the hot engine and/or sitting for awhile. That is one of the reasons I always like electric fuel pumps -- I turn them on, make sure I have gas to the carbs, hit the throttle a couple times and then start the car. Note: Hopefully you have a fuel pressure regulator inline to the carbs -- as Strombergs can only take about 2 lbs of fuel pressure before you risk sticking a float and flooding the carb (can you say fire potential ). Don't hookup an electric pump without one! . . . or even run a manual pump for that matter . . . you absolutely should have a quality pressure reg. Will drop you a line later on today . . .
If they're leaking,before you go tearing things apart and replacing things, Check the fuel pressure. Stromberg's will rarely function well with over 2lb. of fuel pressure. That's why they have the bad rap for leaking. Regulator will probably fix your problem.
The car only has to sit for a few hours before I have the problem. The garage is heated, but temp doesn't seem to make any difference. When we first got the car together, I had one of those dial type regulators and a cool "looking" el cheapo gauge. They were both garbage. I now run a Holley regulator and a Barry Grant gauge. Oh, and it's a mechanical fuel pump. I've been running the pressure at 3 1/2psi, although before I switched out the cheap pump and regulator, there's no telling what kind of pressure was pushing in to the carbs. Maybe the extra pressure blew out a gasket? I'm pretty sure it's leaking down internally, cause I haven't noticed any gas outside the carbs or on the intake.
My guess it isn't a pressure issue. Usually the excess pressure over comes the needle and seat therefore flooding the carb. Gas spills over the top into and onto the intake. The carb is over full not empty. Your carbs are leaking from the bottom of the bowl. It was empty right? I'd replace the richening valve gasket in the bottom of the accellerator pump well. The valve is supposed to remain shut until the accelerator pump pushes the little pin down opening the valve when it's floored. If the spring is weak in the valve it could drain the bowl there also. I'd get new richening valves and their gaskets. Mine leak down over a couple of weeks. One thing I like about an electric fuel pump. It will fill the empty carbs with out grinding the starter motor. Over night is excessive IMHO
I don't know that it's the richening valve gasket in the bottom of the accellerator pump well. Even though the bowl was nearly empty, the acc. pump well was still full to the bottom of the vertical slot in the front.
Do it! I don't have a carb or manual handy here at work, but I can't think of any path for a Stromberg to leak into the manifold--I think it's gotta be an external leak.
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