Holley spread bore carb.

[Jeff Lee]

I know the 1973 and newer Autolite is a spreadbore but I'm pretty sure the bolt pattern for the four studs is something weird. But there are adaptors available.

[Dwight Southerland]

Jeff is correct. The Autolite spread-bore pattern is different than Q-jet, Thermoquad, and Holley layout. There used to be adapters available, so maybe you can find one.

[Mike Taylor 3601]

Spread bores work good,sometimes they take more tuning than regular holley,secondary can be hard to get smooth,vac. secondaries are harder to tune than mechanical secondaries spread bores came both ways
Mike Taylor 3601

[Carguy49]

I have used several of these carbs in the past (20 years ago). They are very tunable and when setup properly can give reasonable fuel mileage on the street. Since they use small primaries and larger secondaries tuning can be somewhat tricky. Shouldn't be a problem for anyone who has spent time tuning a carb for a certain combination. Good luck and should be a very doable project. I have a question, does Holley still build spreadbore carbs??

[astikhossw]

Thanks guys i just had a performance carb. guy with his own shop tell me that the spread bore holley was junk.And with the rarity of the cleveland aluminum intake not available to often and with the old spread bore iron intakes cheap and plentiful its good to have another choice in a stocker build.

[Mike Taylor 3601]

You just said stocker build?
Unless I have missed something a spread bore holley would'nt be legal on a stocker,you would have to use the autolite on the spread bore ford intake.BTW if need to know mech secondary spread bore is easier to tune,is very hard to get smooth secondary opening on vac secondary,due to large butterflies and no accelerator pump

Carguy49
Spread bores are still in catalog and in price list from performance warehouse I use
Mike Taylor 3601

[peteprostock]

only # I know that Holley still offers is a 650 model 0-80555C vacuum secondaries with electric choke