Ever since I put a new Holly 390 carb on my 272 it has had a flat spot when accelerated. (I never liked Holly carburetors to begin with but my son talked me into it). Cruising at a constant position on the pedal when I accelerate it will fall on it's face for a second then accelerate normally. I went through my Holly CD & tried everything it said. I changed the cam position & made it worse. According to the CD it should be the squirter but after setting the accelerator pump as per Holly instructions, I changed the accelerator pump nozzle (squirter) from a 25 to a 31. That made it a little better but did not eliminate it. I changed that one to a 37 & no change, maybe worse. I put a vacuum gauge on it & it is rock solid at about 14" at idle so I don't think there's a vacuum leak. I looked down the carb & actuated the throttle & gas squirts out of both squirters from any throttle position. I checked my timing & set it @ 10 degrees. I'm at my wits end. I'm about ready to get an Edelbrock carburetor & start all over.

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

Try stepping up the jet size a little.

Butchering up everything I can get my hands on in Dayton Ohio

Is your 272 stock? I think the vacuum should be higher if it is stock. 14 is about what I'd expect for a mild performance motor.


Lawrenceville, GA

Step the jet size up like Jeff said to about 4 numbers from stock. I believe you'll see an improvement like so many of us have. Holleys are known for easy tuning and in the end work great and usually better than the others and I've tried most of the them.

-Gary Burnette-

Thanks guys..... Yep Charlie, stock as a rock 'cept for electronic ignition.

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

So if your 272 is a '56 and "stock as a stone", does it still have the original '56 all vacuum distributer? If so the Holley will not provide the proper vacuum signal for it to function. Replace the Dist with a '57 dual advance dist and a lot of problems will go away.

Doug T

The Highlands, Louisville, Ky.

could be fixed by working with accelerator pump

Holley has a 'how to' on their website

guy said something about vacuum and distributor

yep you better eliminate everything else before

looking at accelerator pump

make sure it's working like it should

could be something obscure like

low float level etc. etc.

Ford 292 & Fordomatic

removed from '64 F100

I have the 390 Holley on mine and works great.I did go to 56 jets.I would do that and check the distributor.The vacuum reading at idle is low I think.Should be closer to 18-19 at idle in neutral.

  

Doug I said stock "except for electronic ignition"... Has a 59 distributor with a Mallory electronic kit. I'll try the jet thing & check Holly's website although I've got their CD for tuning & troubleshooting. Thanks again... Oh, I'll recheck that vacuum.. I may have misspoke on that.


Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

here's link

http://www.holley.com/TechService/FAQ.asp

it's just a paragraph in FAQ's

think it's question #3 there

Ford 292 & Fordomatic

removed from '64 F100