Edelbrock 500cfm carb issue

wayne petty · September 07, 2014, 10:22:41 AM

Quote from: "Mac"Correction:
My intake is an Edel. Performer egr version (blocked off), probably model 3701. According to the Edel site it works for square and spreadbore and no mention of an adapter.

is there an egr gasket under the egr block off plate to seal it properly...

or are yours sealed with cup plugs.

?

since you have sprayed liquids around the base of the carb.. and not gotten any leak..

do you have one of those neat engine lifting plates that bolts to the carb mounting flange... or can you create a block off plate. using a carb base gasket.. so you can drill the mounting holes needed and then tap a 1/4 pipe thread so you can hook up a hose barb.. allow you do do either a hand vacuum pump test. to verify the intake gasket is not leaking where it bolts to the heads.. you will get leakage thru open intake ports and from the valve guides..

you have a leak someplace.. that is allowing air to get into the intake... blown power brake booster..
leaking intake manifold gaskets
leaking egr gasket..
leaking carb mounting gasket and i have had to install the adapter plate on some intakes.. remove carb.. read the gasket imprints made by the carb base and the intake mounting face.
leaking carb throttle blades. almost always the source of the issue and really easy to happen. another friend got a great deal on a returned carb to his speed shop.. the throttle blades were actually loose.. the guy who had returned it had loosened them.. he reset them and it worked perfectly..

the last and this is a weird reverse issue is the LACK OF A PCV VALVE allowing air leaks into the system. without a pcv valve.. the primary throttle has to be opened too far and exposes too much of the idle transition slots.. this causes an uncontrollable idle air fuel mixture..

Mac · September 07, 2014, 01:12:15 PM

The egr block off has a gasket, it's never been disturbed thru use on 2 engines.

It looks like we're focused on a vacuum leak. I reported earlier my reading was 18-19. It must have been with a high idle speed (900 or so). Now I'm reading 15-16 @ 700.
I sprayed carb cleaner all around the intake to heads mating surfaces, the back side as best I could as well as the throttle shafts with no reaction.
I did your PCV test for proper valve and it responded correctly.

I guess if i have a vacuum leak it's to the inside, valley area or coolant passage?

Mikej · September 10, 2014, 09:03:48 AM

Do you have an extra carb you can try? ( A Holley perhaps)

Mac · September 10, 2014, 05:57:33 PM

Quote from: "Mikej"Do you have an extra carb you can try? ( A Holley perhaps)

Well Mike I have a 750 DP that was on the 283 when I bought the truck

I have a 2300 2bbl 350cfm also, with a homemade adapter for the Edel 4bbl manifold. I see what you're saying; swapping one on might be useful to prove a vacuum leak in the manifold.... or you're just an Edelbrock carb hater?

Both Holleys have been on the shelf for a while and I could chase a bunch of different problems.

Mikej · September 11, 2014, 10:01:52 AM

I do prefer Holleys. I could tune it and get good mileage but not the performance I thought it should have. It would heat sink and drain the fuel bowls. Wouldn't stay in adjustment. The guy I gave it to , said it worked great on his 289. But it didn't on my BBC.

wayne petty · September 11, 2014, 10:40:56 AM

Quote from: "Mikej"I do prefer Holleys. I could tune it and get good mileage but not the performance I thought it should have. It would heat sink and drain the fuel bowls. Wouldn't stay in adjustment. The guy I gave it to , said it worked great on his 289. But it didn't on my BBC.

mike.. FYI..

holleys have idle feed restrictions just like every other carb.. and on bigger motors if you have a flat spot off idle.. you will need to increase the idle feed restriction diameter.. either by changing it out as some have changeable versions most others are pressed in and have to be drilled one size at a time. some are hidden under the cup plugs in the top of the metering block. the outer two well plugs..

and empty float bowls and vapor lock issues are almost always sediment in the mechanical fuel pump check valves. what.. if the fuel pump check valves are contaminated by the sediment that comes from our own fuel systems or even the gas stations.. it will reduce pumping abilities..

the clean seats of the fuel pump check valves allow the upwards movement of the diaphragm to pull fuel up from the tank. then the downward spring pressure allows the fuel pressure to be pushed into the tube to the carb.. the second check valve holds the pressure in that line so the carb sees a constant pressure..

when the check valves hang open with sediment. the line to the carb does not get a steady fuel pressure.. it gets pulsing or reduced fuel pressure.. the heat from the engine can boil the fuel in the line to the carb.. turning it into vapor. this expanding vapor pushes fuel backwards thru the check valves and the pump cannot handle vapors. so the carb leans out and the engine vapor locks.. this lean out also overheats the pistons and expands them making the engine really hard to start. .

i have solved fuel contamination issues with super magnets dropped into the fuel tank.. 10 micron element fuel filters.. usually for fuel injection applications directly before the fuel pumps so the pump only gets clean filtered fuel.

i have had cars and trucks that start cold and die. then need to be cranked for 20 to 45 seconds before they restart.. i used some clear hose on the fuel line disconnected from the carb.. i cranked the engine.. the hose filled.. i stopped cranking and the fuel drained out of the hose.. backwards thru both check valves.. yes..i blew into the hose at the carb and made bubble noises in the tank..

this was not even ask for.. but i thought i would explain the failure as a LOT of people experience this failure.. and hopefully it will turn on a light bulb when a forum member reads this.. going AHHAAA..

and the last thing.. those clear tube fuel filters do not have a small enough media filtration to catch the super fine sediment.

Mikej · September 11, 2014, 04:40:53 PM

I figured Edelbrocks needed a heat sink to prevent them from boiling the gas after you shut down. I thought it was pushing thru the main circuit. Just my thoughts. The Edelbrock I had blew black smoke on acceleration and was rich at idle. Talked to the Edelbrock rep and he had me richen up the main circuit. Richening up didn't make sense but it worked.
It took care of most of the problems but it pinged and was never quite good enough. I am happy with the Holley. I should have bought the 850 HP instead of the 750. My point was that if he put on a carb that works and his problems went away he would know the carb was bad.

Mac · September 11, 2014, 11:56:34 PM

Edelbroke vs Hauley polarizes people almost like Ford and Chevy or Yankees and Red Sox.

It seems that if you favor strip performance you like Holleys and if you like cruising and MPGs you lean (pun intended) toward Eddys.

They both teach you lessons and I'm starting to think about going EFI, maybe getting my feet wet with TBI. :?