Hitting a flat spot

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Dalton697

Dalton697

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Okay totally frustrated at this point, I have .60 360 complete rebuild stock heads comp cam xe268 with stock distributor and weiand dual plane high rise manifold and edelbrock 650 avs run good temp but at times I go to accelarate and it sputters like a fuel lock issue...anyone have any idea, wires plug everything is new cap rotor everyone just can't get this figure out, and it not all the time
 
Only between 3 and 4 grand? If still a mechanical fuel pump,I would start here. Check the fuel filter& if the fuel lines are collapsing internally. 2 nd,I would pull the fuel line at the Carb,and insert it into a can or jar. Crank the engine over,for 15 seconds. You should get close to a pint of fuel. Before you attack Carb adjustment, make sure you have adequate fuel supply.
 
Take it to a dyno and get the bugs worked out. Cost as much as a wideband and ur car will run good or sort out all problems
 
Years ago I had a factory ignition box do this. Would run great until upper rpm 3 to 4 K and would just go flat and not run good at all. Swapped a known good box in and all was well.
 
Dalton697,, I have the same problem. I have changed everything electrical. I put the car together with used parts,So I changed 1 item at a time with new or known good parts. I did find some wiring issues but the problem was still there. Like you it's on to the fuel system. The car has a new fuel tank, pickup, mechanical pump, filters and Carb. IF I nail it around 3000 rpm it starts to break up about 4200. If I run up the rpm's to 4000 before tipping in the secondaries it will rev to about 52-5400 rpm and start to break up. so I'm thinking fuel "delivery" problem. Please keep us informed if you find the problem. I will post my findings here after going thru the fuel system. I will start with float level, pump volume and pressure this weekend.
Hope we both find our problem.
Also I'm running a Edelbrock 600 so our combo is very similar.
 
I got the impression it was a fuel issue when I read this, and Eddies have small float bowls so maybe that's another clue pointing to fuel starvation.
Darter6, are you also running and Edelbrock carb by chance?
 
I never had this exact problem Dalton, and even though you and Darter seem to have similar issues, I'm not sure if the problem is the same? You are both using a different style carb, and I just can't see where it's a secondary tip in or fuel volume problem for both of you.

I'm no ignition/dizzy system expert by any means, i always farmed my work out to the local guru, but this still seems like a electrical problem to me, as Dez spoke of. Are your ign boxes well grounded? Is the reluctor gap within spec....008"? Are you getting a full 12v thru the appropriate wiring?

I admit, i may be way off base here and I know both of you have changed a lot of parts, but i hope some other, more knowledgeable members of the electrical side will chime in.

Good Luck, both of you!
 
Trailbeast, Yes I have a Edelbrock AFB 600. HE is Running A Edelbrock 650 AVS. So they are similar carbs.
OldmanRick, Yes, Good grounds, reluctor gap correct, All wiring for ignition replaced,voltage drop check,Several different ohm coils, Ballast hooked with proper coil,Ballast bypassed with proper coil. Everything is the same as my drag car(Low horsepower about 230 at the wheels) "Except" that I run a electric fuel pump and regulator on the drag car and this is a street car with a mechanical pump.I think that the pump is not keeping up and the Idea of the"small" Edelbrock fuel bowls sounds like it could be the culperet.Because the fuel line from tank to carb is 5/16'' I think a electric booster pump from the tank to mechanical pump is in order.A switch will be installed and the electric pump will be turned on during speed trials. I have talked to several that say that's the way to go or a high volume mechanical pump. I have a basic parts store mechanical pump on it now. We will see.
 
Darter6 said:
Trailbeast, Yes I have a Edelbrock AFB 600. HE is Running A Edelbrock 650 AVS. So they are similar carbs.
I think that the pump is not keeping up and the Idea of the"small" Edelbrock fuel bowls sounds like it could be the culperet.Because the fuel line from tank to carb is 5/16'' I think a electric booster pump from the tank to mechanical pump is in order.QUOTE]

It was just a thought, in case you couldn't find any other reason for it.
Click to expand...
 
ok, here's what is happening. when the secondaries are opening there is not enough fuel being pulled into the boosters. which means there is not enough vacuum to pull the fuel up out of the bowels into the emulsion tubes and out of the boosters. the cure, slow the open rate down. when the throttle is on the floor or close to it there is zero vacuum signal so no fuel will flow which means the engine is too lean and will not fire or miss fire. so by slowing the opening rate you are giving time for the engine to produce more vacuum to start pulling fuel up and into the boosters. this is just what the one member said, he pulls the engine up slowly and it will pass through the mid rpms ok but will again miss fire at high rpms. he let the motor produce vacuum through the mid range by having the throttle plate partly closed. the high rpm miss fire he has is a lean condition also but is cause by too low fuel bowel level or not enough pump output.
 
bOb shingler said:
ok, here's what is happening. when the secondaries are opening there is not enough fuel being pulled into the boosters. which means there is not enough vacuum to pull the fuel up out of the bowels into the emulsion tubes and out of the boosters. the cure, slow the open rate down. when the throttle is on the floor or close to it there is zero vacuum signal so no fuel will flow which means the engine is too lean and will not fire or miss fire. so by slowing the opening rate you are giving time for the engine to produce more vacuum to start pulling fuel up and into the boosters. this is just what the one member said, he pulls the engine up slowly and it will pass through the mid rpms ok but will again miss fire at high rpms. he let the motor produce vacuum through the mid range by having the throttle plate partly closed. the high rpm miss fire he has is a lean condition also but is cause by too low fuel bowel level or not enough pump output.
Click to expand...

I considered that too Bob. More thinking about it and I came to the conclusion that these carbs came adjusted with a fairly slow opening rate from the factory. Now that you've chimed in, I'm rethinking my original idea.

I DO think you're onto something here.
 
Not to take this away from Dalton697,,what I did find(so far) on my car was the fuel line very corroded on the "inside". Looks like cholestrol needing stantin drugs. In the process of replacing line complete from tank to pump.That's what I get for thinking that the 50 year old line wasn't as bad as the rusted tank that I pulled out. :banghead:
 
Thanks for everyone's input, really appreciate it. I've tried two factory ignition boxes and had the same problem, so was really thinking fuel. Think I'm going with electric fuel pump and see what it does. The car does great running around town/highway or a quick pull off a light in drive, but under a load seem to flatten out, no back fire or miss just seems to drain bowls. Had it on the dyno and is pushing 200 rwhp. Car is pretty stock manifolds J heads, just really hate when it flatten out
 
Try running it without the air filter?
Restrictive exhaust system?

Could be fuel, test pressure and quantity.

Old or wrong valve springs can cause similar problems
 
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