Thread: Recent FE 390 Rebuild. Engine Bogging when 4 Barrel kicking in. New Carb installed

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Hello friends. First of all I'm sorry for showing my lack of discipline when breaking in my recent rebuild but I'm only human. I recently have been in the process of breaking in my 68 Ford Fairlane 500 Fastback. It has an FE 390 with a C6 transmission in it. It has a high performance cam, solid lifters and has been bored .060 over. I called Edelbrock before purchasing a carb for it and they suggested a 650 cfm Performer carb for it. I thought a 750 would be more appropriate but they thought the 650 was plenty. My problem is that the motor keeps spitting and sputtering most of the time whenever I put my foot down on the gas pedal. Appears as though when the 4 barrel is opening the car wants to bog in a most depressing manner. It idles fine and if I just give it some gentle pedal it's fine. Coming home just now it seemed to get a little better but then when I floored it bogging occurred til I let off of the gas some. I've never been thrilled with the amount of gas I'm seeing coming out of the jets when you look in the carb and pump the gas. I've adjusted the timing in several positions and it seems to not change anything. Just wondered what you good folks thought about this. Is this carb too wimpy for this motor? Seems to get a little better at times but never like it should be. Thanks in advance for any help. I did have an earlier post where I was complaining of it smoking some and the motor still only has about 125 miles on the new rebuild. The fuel filter is new as is the fuel pump. I was getting about 6 psi on the fuel line at the carb without even starting it up. I'm not smelling any fuel being wasted. I just think I'm not getting enough

borrow a 750 holley from someone for a test blast .. edelbrock carbs are for your wifes car ..

What is your initial timing set at?

Be sure you are checking timing with vacuum advance plugged and idle speed below 800rpm. Big cams need more initial timing to get them to idle, if your idle speed is above 800rpm your mechanical advance could be starting and messing with your initial setting. Edelbrock carbs run just fine on the street, they just tune a little differently than Holleys. But regardless of the carb type you have, you will need to tune your ignition and carb to work with your motor.

Intermediate hesitations are often caused by carb idle incorrectly set and not enough initial timing. Bogs (sometimes with pops) are usually caused by accelerator pump adjustment too lean. The performer carbs use a weighted secondary valve and seldom is this the cause of any bogs as it opens with venturi vacuum.

Depending on the cam you have, your motor may need more initial timing, which will increase idle speed allowing you to set the carbs idle speed adjustment lower, which in turn sets the transition slots in the carb’s primary throttle body better. Once the initial timing is set to the liking of your motor to get it to idle correctly, you will need to check and adjust total timing to prevent detonation. Once the total timing is set, it is time to set the mechanical advance curve to match your motors needs. Now you can start adjusting the carb’s other circuits, such as accelerator pump, primary and secondary jets and metering rod circuits. Fortunately, Edelbrock provides excellent instructions on how to do all the adjustments.

Everyone thinks you can just throw a cam in it and go, but it's the tuning that makes it go.

Originally Posted by stotzbotz

I've never been thrilled with the amount of gas I'm seeing coming out of the jets when you look in the carb and pump the gas.

One thing that jumped out at me was your statement regarding the shot of fuel "...coming out of the jets". The fuel that you're seeing shooting into the venturi as you pump the throttle is your accelerator pump shot, which is there to enrich the air/fuel charge as you increase your throttle opening, easing the transition of increased throttle position by providing an extra shot of raw fuel to offset the fact that your air flow has not yet increased to match your throttle demand. The volume of that "shot" has nothing to do with jets, but rather is controlled by the position of the linkage in the accelerator pump arm. Have you gone through ALL of the tuning instructions that Edlebrock provides with their carbs? Like 35 sedan says, tuning is the key.

BTW, did you get the blowby problem resolved?

Do you still have the point type dist' if so check the dwell if you don't have a dwell meter use a feeler gage if you put new points in did you lube the cam and get the screws tight too small of a gap gives too long of coil saturation and not enough discharge time and will cause the problem you describe

I guess what doesn't make sense to me is that just last week me and my brother were testing the power of this motor at my expense of course and it was just blasting through all gears and not bogging at all although I never floored it at a dead stop. A few days later I get in it and it started the bogging thing and I never made any new adjustments prior to taking off. Fuel tank is new. I guess I'm a little spoiled with the last carb I got from Edelbrock. It was the same performer carb but a 750cfm. My Nova has a 454 4 speed with a performance cam and I installed it and proceeded to do burnouts and enjoy the heck out of my car with no problems whatsoever. Maybe I got lucky with that one. I don't have any specks on the cam I have in this engine so I'm not sure how to go about tuning this set up. The engine is equipped with a high performance HEI distributor by the way. By Blowby problem seems to be slowly getting better and the smoking coming out of the exhaust seems to be sporadic. Hoping the break in will solve those problems but I'm still nervous about everything. If anyone could explain the best way to fine tune this puppy I would love to apply to this beast. I know that I shouldn't be gunning it too much this early in the break in period so I will try to restrain myself. Yah right.

According to Edelbrock's web page (link - Performance Carburetors and Accessories Introduction - Edelbrock, LLC. ) every new Performer carb comes with an installation and tuning DVD. Also, in their Owner's Manual (link - http://www.edelbrock.com/automotive/...ers_manual.pdf ) the tuning process is spelled out. It's a matter of running it through a strong pass with an immediate shut down (ideally ignition off at speed, coast to a stop) and reading a plug or two, then adjusting jets accordingly. Just my $0.02 on the process.

Most Edelbrocks and AFB's prefer 5- 5 1/2 psi over that they can bog. Have you tried changing the pump shot ? Sometimes that will cure it. Since the Performer is based on the Carter AFB and even use the same rebuild kits check this out as it has a very detailed troubleshooting section: http://www.mymopar.com/downloads/carterafbtuning.pdf

Originally Posted by stotzbotz

I don't have any specks on the cam I have in this engine so I'm not sure how to go about tuning this set up.

Originally Posted by stotzbotz

It has a high performance cam, solid lifters

How did you set your valves? What are the valve clearances set at?

The person who had the car before me was a little strange but he did give me some info about the car's engine. He told me to adjust the valves at 18 on the intake and 20 on the exhaust. It hasn't been adjusted since we first did it after the rebuild initial set up so maybe it's a good idea to go back and re adjust the valves even though there hasn't been more than roughly 150 miles put on the car.

What does "high performance cam" mean exactly. Can you give us the part number? Knowing the specs on the cam will tell you how much ignition timing to put in the motor.

Also, I like 4 1/2 to 5 psi on an Edelbrock/Carter with 1/2" delivery lines.

MORE FUEL PRESSURE WILL NOT MAKE MORE POWER ON A CARBURETED MOTOR. ALL IT WILL DO IS TO OVERPOWER THE NEEDLE AND SEAT SPRING AND ALLOW THE PUMP TO BLOW RAW FUEL INTO THE INTAKE MANIFOLD, CREATING A TUNING NIGHTMARE FOR YOU. USE 4 1/2 TO 5 MAX ON AN EDELBROCK WITH BIG LINES FOR HIGH VOLUME, NOT HIGH PRESSURE.





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Sorry but I unfortunately don't have any specs or numbers for the cam. Going to have to be some trial and error here to properly tune it I guess.
Should I be installing a fuel pressure regulator on the line then to limit the pressure? If I'm getting 6 psi with just cranking the engine over then the pressure must be insane once the car is running.
I don't know if it has anything to do with what's going on but when this car is hot and I go to restart it I usually have to pump the gas peddle about 6 times in order to get it to start. Maybe this is normal for a big block Ford but my Nova engine is bigger and just 1 pump after it's hot fires it right up.

Most of the moderate ford style cams back in the FE days took .025-.027 valve lash-------set before engine start up and again after warm up and head re torqueing.

Set initial timing to around 12*btdc and total at 36-38 depending on the gas octane-I liked to lock out the advance curve, find where it would start and idle nice-then advance it to point where it performed max-then build curve to accommodate those numbers with the fastest curve with springs that would drag it back on shutdown which then will not buck the starter. Also-on Ford stuff--its venture vacume that the ignition system uses--------