secondary bog

[cobragus]

Gentlemen, I have a 302 with a ford e 303 cam, alloy heads, dual plane manifold and a quick fuel 600 cfm double pumper, with a 276 rear end in my FFR roadster. here's my question, when I accelerate hard in first, second and third gear the engine bogs, breaks up about 4500 rpm on. the linkage to acuate the secondaries is set for the primaries to open after 60% primary. If I disconnect the secondaries no more bog just sluggish. Do I need to change the secondary pump cam for a longer shot, which color ?, larger or smaller squirter. The carb works very well with good street manners untill I put my foot in it real hard.
Thanks in advance. gus cobragus

[Gordon Levy]

First question is what distributor are you using?
You may have carb issues but if your car is breaking up at 4500 revs I would look first to ignition system.

[cobragus]

I am using a Ford distributor from an 80's 302. with a blue ford box. gus

[Gordon Levy]

OK, I bet you have the vacuum advance hooked up.
First thing I want you to do is disconnect the vacuum advance and plug the carb or intake port it's plugged into.
Then reset your time to 33 degrees at 3000 rpm's.
Take it out and see how it runs then we will tackle the carb.

[cobragus]

Mr Levy, I have done as you suggested and set the timing to 33 degs at 3000 rpm with no vacum advance.
It does not break up above 4000 rpm now.
It does run rougher between 1500 and 2200 rpm though.
I use a performance meter with my runs and see no appreciable differences in my 0 to 60 times or eighth mile times. with this change.
Question did you mean for me to leave the vacum advance pluged after resetting the timing ?

[Gordon Levy]

Yes I do want you to leave it disconnected. The reason it was breaking up at higher revs is the distributor was over advancing. I have seen it many times with the duraspark distributor. Disconnecting the vacuum in most cases with cure that. You may want to consider changing to a MSD ignition system at some point.
The roughness at low rpm's should be able to be cured with some carb adjustments.

[cobragus]

Mr levy, This duraspary distributor has been cured... What I did was weld a tab on the mechanical advance plate, then file and shape it so that as the centrifical force would only allow 20 degrees mechanical advance. selected springs for a smooth advance. I ended up with 32 degrees total advance with 12 deg inital. The engine has no more hesitation, flat spots and clean spark thru 5000 rpm. On regular gas.
Thank you so much for your advice. Gus Williams ( cobragus)

[Gordon Levy]

Glad I could help.

[cobragus]

Mr Levy, since I now have the vacum advance disconnected, the engine is considerably louder. is this correct for no vac/advance? I have to tell you i am pretty deaf and it gets my attention!
Thanks gus

[Gordon Levy]

The car is now firing at the correct times and making all the power it should. That could contribute to it being louder.

[ehodger]

I have a very similar problem. I am running a Mallory distributor, magnetic breakerless electronic ignition. It also has a vacuum advance. It almost seems like there is a rev limiter built into it. As soon as it hits 5k it starts missing. I was running 6 lbs of fuel pressure, I turned it up to 7.5 but I have not had a chance to drive it because it's raining (finally). I really don't think it is a fuel problem though. Do you think I should try the same thing?

[Gordon Levy]

Put a timing light on it and see where the timing goes as you bring the revs up past 3K. You should have around 34 degrees of advance total at higher revs. If you have more than that disconnect the vacuum advance and try it again and see how far advanced the timing goes.

[ehodger]

Base timing was at 20 degrees with the vacuum advance disconnected, I must have used the wrong line on the damper. I reset it to 10 degrees and the total advance with vacuum advance hooked up is 44 degrees. disconnected vacuum advance and total advance is 28 degrees. I removed the cap thinking there would be some type of adjustment for the advance but I did no see anything?

[Gordon Levy]

If you want to advance the timing you need to loosen the dizzy and turn it clowise to advance and counter-clockwise to retard. Get some help. bring the revs up to 3K and adjust the timing untill you have 33 degrees. Then tighten the dizzy. Leave the vacuum disconnected.

[ehodger]

It is at 33-35 with no vacuum to it. I will take it for a ride later and let you know how it does.

Thanks, Ed

[Gordon Levy]

Yes, 33-25 with no vacuum hooked up. Lever the vacuum disconnected and plug the ports.

[ehodger]

It ran right up to 6k with no miss.

Thanks again, Ed

[ehodger]

I noticed today that the miss was still there and it only happens at W.O.T. I changed the timing back to 10 degrees base timing and hooked the vacuum advance back up and drove it again. Same problem, 80% throttle it will run right up to 6k but with the throttle wide open I am lucky to get 4k. My tank is from a 92 donor and sat for 4 years. do you think it could be as simple as a fuel filter even though it is practically new with just over 2000 miles on it?

[Gordon Levy]

Check your fuel pressure. What pump and pick up are you using?

[ehodger]

I am running the stock Mustang pump with an Aeromotive return style regulator. I am running about 7 1/2 lbs of pressure but that is at the regulator port, there is an inline filter between the regulator and the carb.

[Gordon Levy]

You are regulating the EFI pump down to 7.5#?

[ehodger]

Yes I am using the EFI pump and returning the majority to the tank through the regulator.

[ehodger]

I did it this way so when I eventually build the stroker of my dreams I can add VCP's cool stack injection system.

[Gordon Levy]

Replace the pre-filter thats on the in tank pump

[ehodger]

I knew I should have put an access panel in the trunk.

[Gordon Levy]

Drop the tank, it's easy and take about 15 minutes.

[ehodger]

I dropped the tank tonight after work. The sock filter looked fine but I thought while the tank is out I might as well go ahead and put a new pump and filter in the tank just for piece of mind. So I replaced them and went for a drive, same problem as before. Removed the inline filter between the regulator and carb and "tried" to blow through it, I don't think Goliath could blow through that filter. I can't believe the car ran at all. Hopefully I will get off in time tomorrow to pick up a new one.

[ehodger]

Replaced the filter, same problem. It only happens at W.O.T.as soon as I back out of it to 70-80% throttle it revs right up without ant hesitation. It still seems to me that it must be fuel related. How would the distributor know where the throttle is.

[Gordon Levy]

Have you checked your floats?

[ehodger]

The float levels were low, so I adjusted them. But that did not seem to have any effect. Still misses at W.O.T. 70-80% throttle it runs great?