Ok so I have a blow thru holley with a proform main body(hanger 18 mods). The carb and the car has run flawless for about 3 years. All of a sudden while on a long pull its starts leaning on in 3rd gear and breaking up. I have went thru and blew out all the holes and cleaned the metering blocks. I thought I would check the float levels. As soon as I get the front float level screw out the engine shuts off........it does it everytime. Even holding it at 3000rpm. It doesnt do this with the rear float level screw. Any ideas what can be causing this...? I have check for vacuum leaks eveywhere and cant find a thing.

 

Are you talking about the sight plug or the float level adjuster?

What was your fuel pressure doing?

Have you checked the fuel filter?

 

Fuel pressure is constant 7 psi. Yes I'm talking about the sight glass.

 

Fuel pressure should fluctuate with boost pressure.

That is really weird that the engine dies when you remove that plug.

Maybe check to see if the primary fuel bowl vent is open and flowing air.

 

Yes it is boost referenced I was saying its constant 7psi at idle. The first thing I did was blow out the vent tubes. It's very strange. Was hoping to run across someone that has had the same problem.

 

Got ya. I was thinking that if your fp dropped when you said it leaned out, the filter could be plugged up.

Does it seem like the engine floods when you remove that plug?

 

Not really because it fires right back up easily. It's actually leaned out a whole point at cruise as well.

 

I am drawing a blank on what to check for next.

 

Guess ill have to take it apart and re check everything again.

 

I don't have an answer but mine used to do the same. Killed the engine as quick as turning the key off when the sight plug came out.

 

I wish you could remember what was causing it.

 

Never found a definitive reason why. The carb had erratic tune and just seemed all over the place. Had Kevin at CSU check it out but he found nothing wrong, but it worked well after he went through it. Must have been a spec of dirt or something.

 

ok thanks

 

Did you change metering gaskets right before it started doing this? Maybe something didnt line up?

 

we had a 600dp that did this also , never figured it out,, cleaned and put some different gaskets in and it seemed to fix the problem

 

Does it die with the hat off? Have you replaced the gasket between the metering plate and the main body? They shrink over time. Also swap the front metering plate with the rear see if problem moves. I just believe it's a gasket problem, when plug is removed vacuume from vent to idle and hsab is plulling air now instead of fuel. Try covering idle air bleeds when taking plug out see if it makes any difference.

 

It does not die with the carb hat off....I haven't changed anything on the carb it just sit for about 2 months.

 

While it is idling slowly put your finger over bowl vent as you take plug out and see if it continues to idle. Get someone to watch wideband while it is idling and put your finger over vent tube, does it get richer if so it is sucking air somewhere replace the metering plate gasket please.

 

I replaced the metering gaskets yesterday with no change. i will check the vents soon. i have a lot of play in my throttle shaft. can it leak around there?

 

It can leak around shaft but shouldn't just show up all of a sudden. Watch your wideband while moving shaft around if you think that is a problem. Did you try moving front metering plate to rear to see if problem moves? Any pics?