When you say that whilst cruising if you accelerate it dies then drives normally, how hard are you pushing the pedal. If the spring is too light in the vacuum dash pot which controls the secondary barrels it will bog down like this. That's what it sounds like to me.

Lock the secondary barrels off and see if it still does it. If not the problem is the secondary barrels opening too soon.

Normally a weak secondary sping will make the car pretty awful to drive anytime you open the throttle.

It doesn't sound like the accelerator pump is the problem.

A low float level might give something like the same, though it would be a tad gutless throughout the whole range and would probably misfire or surge when you open the throttle.

You also need to make sure that the secondaries are setup correctly. There was an earlier post about setting the throttle blades with relation to the idle transfer slot. Check that out as well.

As others have said the Holleys are a great carb and will rub sweet when set up correctly.

Regards

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

Back to the jets.Have you changed the jets at all because I believe they come stock with an odball "512" jet which is too small for the bigger engines like the 292 272.These carbs are used on everything from 4 cyl pintos right up to 312 V-8.They purposely come with small main jets.Is your vacuum reading in neutral or park if an auto like mine which has about 14-15 in drive.19-20 in neutral.

  

Seeing as how you’ve tried a larger sized shooter, then try the ‘red’ cam for the accelerator pump actuation.  Before doing this though, I’d go ahead and try the #35 shooter first.  And I’m assuming the accelerator linkage is properly adjusted?  This means absolutely no freeplay in the accelerator linkage at idle and at full throttle there should only be 0.015” travel remaining before the diaphragm is bottomed out.  Fuel float levels are also players.  If they are on the low side, then the fuel pickup for the main system is delayed and the secondary float level is just as important as the primary float level in this regard.  There is a fixed idle circuit on the secondary side that requires the proper fuel level for it to work and this circuit helps in keeping the fuel from stagnating by using it as an idle circuit in those instances where the secondaries do not get used very often.

Lorena, Texas (South of Waco)

We've been through this a few times on here - the basics have to be right too. Big flat spot is always available if the Holley primary blade isn't at the right spot on the idle transfer slot. There is a thread with photos etc. and its easy to get it right. The idle speed then gets set with the secondary blade. I looked at the Holley directions for the 390 and it plainly shows how to do this. 

If you don't set it up, the old answer was always "flood it with fuel".

Make sure you distributor is set-up right. Needs to have plenty of low rev advance - which then requires a top end limit of 36°-38°(thats mechanical - vacuum blocked). Basic tuning rule is set up distributor, tune carb to suit.

If you use ported vacuum source for distributor - design the curve to start at 14° and end as above. If you use live manifold vacuum - use 10°, top end as above - and then limit the vacuum travel to about 7° max. Both set-ups will run well with stock engines.

 
 Steve Metzger       Tucson, Arizona

Man, this is a lot to digest & I'll bet the answer is here somewhere. Ted, I already tried 37 squirters & I think it may have been a little worse, maybe not, but didn't fix it. (I can look down in there and pull the throttle back & things look normal (engine off). If I am cruising & stab it to the floor it goes through that flat spot almost un-noticed. It's when you're cruisin' along, say 50 or 60 & just accelerate a little bit (normal, like you was going to pass someone) is where it's the worst. If accelerated very slow it will go through OK. Again, thanks a ton guys.

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

Good site AAR, thanks..... !!

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

This has been my experience too (albeit with a mildly cammed 312), that the culprit was ignition more than carb. Over time I tried several dizzy combinations...including a '57 setup with both vacuum and mechanical advance...and ended up with the Mallory which has been rock solid. Used one very light spring + one normal under the distributor plate. Result: 39 degrees overall (15 initial timing + 24 advance), but plenty of advance early in the curve. Eliminated my low-end flat spot.

EJ, up the jet sive in the primaries and see if that fixes your problem, we had to do the same with the 570 avengers as well. It seems holley simply jets the 390's and 570's just too small on the primary side for 292 and 312 y-blocks which gives us those dreaded flat spots upon taking off and during cruising. Charlie had the same issues with his 570 and many other y-blockers had the same problems as well.

-Gary Burnette-

That will be my next move. Going to Atlanta the day after Christmas so will stop at Summit & get some. Somebody on here said 56's so I'll try that. Thanks guys...


Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

How long will you be in Atlanta?


Lawrenceville, GA