Minimum electric fuel pump pressure

[plumkrazee70]

Hey, hi there. Yeah that sync looks pretty close. And yes the low idle is odd.
1)Are you running a PCV system? The 218 cam will want it.
2)Have you verified the damper TDC mark?
3)Are the metering rods stuck down at idle, and are they staying down.
4)Is that spacer a 4-hole, or at least devided?
5)What are your day-time temps there?
The AVS carbs usually like a bit more idle mixture, try turning them out more, perhaps as much as 2.5 turns out. Set them for best quality of idle.
-If TDC is true, and the PCV is functioning, and there are NO vacuum leaks,then we need the engine to tell us if its rich or lean. The way to do that is to pass a shop-rag over the primaries, without choking it to a stall. But first, stuff the rag in the secondary side; it should make little-to-no difference in idle speed.Yank it back out! Back to the primaries;If the rpm goes up, its getting too much air. If the rpm goes down, it wants more air.
If it wants more air, you crack the secondary open a bit and retest.
If it wants less air, that really means;Why? Go back and make absolutely sure its not drawing air from somewhere it shouldnt be.When thats done and no source is found, then you will have to prove that the fuel level is on spec.
-The electric pump may be too much.With the engine warmed up and running, shut the pump off. Wait a minute or three. If the idle speed rises before it falls,then the fuel level is too high. If the idle speed drops continuously to a stall, the fuel level is too low.If the idle remains the same for about a half a minute before dropping, then its pretty close.This assumes the mixture screws are optimized between 1.5 and 2.5 or so.
-Oh yeah, I'm assuming that when you are setting the timing that the vacuum advance system is defeated, and that later, you are connecting it to the spark-port.
-Do all the above tests with a stable idle speed of 650 to 700, using timing to get it, not primary cracking.
Ok so, have at her.

Thanks for the wake-up call.

Thanks for the reply and Good Morning!

I'll answer a few of your questions:

1. Yes I run a PCV
2. It is a new damper, but I will verify TDC. (I made a piston stop from a spark plug)
3. I'm not sure how to verify if the metering rods are stuck down at idle.
4. Spacer is "divided"
5. Daily temps are 90+ lately

I will also double check there are no vacuum leaks. I don't have an electric fuel pump and am convinced that I don't need one. I believe my problems actually are lying within the tune. I also don't have a vacuum advance in my distributor. I have an MSD billet with 6A box.

I will report back this week.

Thanks!

 

[AJ/FormS]

Very good,then.
I thought I read that you had an E-pump.
Hey, I just had a thought. Next time the engine is warmed up, try this; Grab a long-nosed plier and pinch off the PCV line. The engine rpm should fall. Then with the line pinched off, remove the valve. Then slowly let the engine pull air into the hose by adjusting the amount of plier-pinch.The rpm should rise quite a bit past that which it was with the valve installed.Finally will come a point when the rpm peaks, and any more air introduced will slow the engine, and it will begin to run oddly.This is how it normally responds.
If yours behaves this way, but revs up quite a bit,its a good indication that; A) it wants more idle air, or B) its over-advanced, or C) the fuel level is too high.The easiest fix,if the fuel level is known to be good, is to crack the secondaries.If the rpm goes up, then back the timing down to 12* to 14*, and set the idle speed with the secondary cracking adjustment.
All of this depends on the metering rods staying down at idle. You cant tune that carb if the Mrods are dancing, or heaven-forbid;bent and/or, out of their jets.

And you're right,in that you probably dont need an E-pump.I say probably, because at less than about 300hp,on a streeter even the teener pump will do.For more spirited driving or occasional track runs, the 340 pump will do. For 400hp+, its probably a good idea to move up to an HP mechanical pump(your combo wont make 400 so the 340 pump would be enough) . However,if you are having trouble keeping fuel in the bowl due to evaporation, then an electric draw-through pump can be a help. This type of pump is only turned on to prime the carb and then turned off. The M-pump then draws through it.
The way to do the fuel level test then, with an M-pump is to pinch a rubber line somewhere,completely shutting the flow off.
If you discover that the fuel level needs to be changed, do not stray too far from spec; the other circuits still need to function even though they are not as sensitive to fuel level. If you discover that the idle circuit wants quite a different level, then we will have to look elsewhere to fine tune the idle circuit. A change of up to 5/64 from spec should be ok. More than that, and we will need to look at the airbleeds. But first;
Do you have a vacuum gauge? If yes, then hook it up to read manifold vacuum and lets see whats in there.If the vacuum is goofy, I have another idea.Vacuum with the 218@050 cam,@700ish rpm,warmed up, and 14* advance should be up around 14plus inches. Maybe as high as 15/16".

BTW, A well-tuned vacuum advance system,makes the car a pleasure to drive at small throttle openings, and a boon to better fuel mileage. I wouldnt run a streeter without it. I have tuned my 360 with a 223@050cam and 10.7 Scr, and a crappy Holley 1850 to get 32 mpgUS. The Vcan helped make it possible and kept it driveable.

 

[plumkrazee70]

Very good,then.
I thought I read that you had an E-pump.
Hey, I just had a thought. Next time the engine is warmed up, try this; Grab a long-nosed plier and pinch off the PCV line. The engine rpm should fall. Then with the line pinched off, remove the valve. Then slowly let the engine pull air into the hose by adjusting the amount of plier-pinch.The rpm should rise quite a bit past that which it was with the valve installed.Finally will come a point when the rpm peaks, and any more air introduced will slow the engine, and it will begin to run oddly.This is how it normally responds.
If yours behaves this way, but revs up quite a bit,its a good indication that; A) it wants more idle air, or B) its over-advanced, or C) the fuel level is too high.The easiest fix,if the fuel level is known to be good, is to crack the secondaries.If the rpm goes up, then back the timing down to 12* to 14*, and set the idle speed with the secondary cracking adjustment.
All of this depends on the metering rods staying down at idle. You cant tune that carb if the Mrods are dancing, or heaven-forbid;bent and/or, out of their jets.

And you're right,in that you probably dont need an E-pump.I say probably, because at less than about 300hp,on a streeter even the teener pump will do.For more spirited driving or occasional track runs, the 340 pump will do. For 400hp+, its probably a good idea to move up to an HP mechanical pump(your combo wont make 400 so the 340 pump would be enough) . However,if you are having trouble keeping fuel in the bowl due to evaporation, then an electric draw-through pump can be a help. This type of pump is only turned on to prime the carb and then turned off. The M-pump then draws through it.
The way to do the fuel level test then, with an M-pump is to pinch a rubber line somewhere,completely shutting the flow off.
If you discover that the fuel level needs to be changed, do not stray too far from spec; the other circuits still need to function even though they are not as sensitive to fuel level. If you discover that the idle circuit wants quite a different level, then we will have to look elsewhere to fine tune the idle circuit. A change of up to 5/64 from spec should be ok. More than that, and we will need to look at the airbleeds. But first;
Do you have a vacuum gauge? If yes, then hook it up to read manifold vacuum and lets see whats in there.If the vacuum is goofy, I have another idea.Vacuum with the 218@050 cam,@700ish rpm,warmed up, and 14* advance should be up around 14plus inches. Maybe as high as 15/16".

BTW, A well-tuned vacuum advance system,makes the car a pleasure to drive at small throttle openings, and a boon to better fuel mileage. I wouldnt run a streeter without it. I have tuned my 360 with a 223@050cam and 10.7 Scr, and a crappy Holley 1850 to get 32 mpgUS. The Vcan helped make it possible and kept it driveable.

Much appreciated. I will try to get some of these checks done this weekend and report back.