Holley spread bore carb.

astikhossw · 04-03-2013, 10:47 AM

Are these carb.'s any good for a performance motor a friend has about 7 of them and i was thinking about buying them.I have a cleveland iron intake i wanted to put one on.

Jeff Lee · 04-03-2013, 01:18 PM

Why wouldn't they be? It's a Holley so all Holley tuning tricks & parts apply. The rear metering plate can be replaced with a metering block, the vacuum secondary springs can be changed, jets can be changed, cams, etc., all in the name of tuning for performance or mileage.

jims5600 · 04-03-2013, 06:15 PM

Jeff is spot on,take his advise

Jeff Lee · 04-03-2013, 07:11 PM

I'm not sure the Holley spread bore is a direct bolt-on for a 351C factory Autolite 4bbl intake. I think it needs an adapter. Been a while since I've messed with 351's....

bad440 · 04-04-2013, 03:13 AM

thinking 73s were spreadbore intakes...

Jeff Lee · 04-04-2013, 03:30 AM

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 · 04-04-2013, 06:20 AM

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 · 04-04-2013, 08:33 AM

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 · 04-04-2013, 01:34 PM

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 · 04-04-2013, 10:06 PM

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.

04-03-2013, 10:47 AM	#1
astikhossw Member Join Date: Jul 2008 Location: moreno valley Ca Posts: 266 Likes: 2 Liked 20 Times in 9 Posts	Holley spread bore carb. Are these carb.'s any good for a performance motor a friend has about 7 of them and i was thinking about buying them.I have a cleveland iron intake i wanted to put one on.

04-03-2013, 01:18 PM	#2
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: Holley spread bore carb. Why wouldn't they be? It's a Holley so all Holley tuning tricks & parts apply. The rear metering plate can be replaced with a metering block, the vacuum secondary springs can be changed, jets can be changed, cams, etc., all in the name of tuning for performance or mileage. __________________ Jeff Lee 7494 D/S '70 AMX

04-03-2013, 06:15 PM	#3
jims5600 Member Join Date: Oct 2011 Posts: 125 Likes: 47 Liked 21 Times in 9 Posts	Re: Holley spread bore carb. Jeff is spot on,take his advise

04-03-2013, 07:11 PM	#4
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: Holley spread bore carb. I'm not sure the Holley spread bore is a direct bolt-on for a 351C factory Autolite 4bbl intake. I think it needs an adapter. Been a while since I've messed with 351's.... __________________ Jeff Lee 7494 D/S '70 AMX

04-04-2013, 03:13 AM	#5
bad440 Junior Member Join Date: Apr 2010 Location: livermore ca. Posts: 19 Likes: 0 Liked 0 Times in 0 Posts	Re: Holley spread bore carb. thinking 73s were spreadbore intakes...

04-04-2013, 03:30 AM	#6
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: Holley spread bore carb. 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. __________________ Jeff Lee 7494 D/S '70 AMX

04-04-2013, 06:20 AM	#7
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 2,000 Likes: 64 Liked 777 Times in 193 Posts	Re: Holley spread bore carb. 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.

04-04-2013, 08:33 AM	#8
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,371 Likes: 352 Liked 304 Times in 102 Posts	Re: Holley spread bore carb. 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

04-04-2013, 01:34 PM	#9
Carguy49 VIP Member Join Date: Aug 2011 Location: Fife, Washington Posts: 1,977 Likes: 2,466 Liked 2,939 Times in 707 Posts	Re: Holley spread bore carb. 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?? __________________ Ron McDowell - Did Race Every day is a Gift - Enjoy with family and friends.

04-04-2013, 10:06 PM	#10
astikhossw Member Join Date: Jul 2008 Location: moreno valley Ca Posts: 266 Likes: 2 Liked 20 Times in 9 Posts	Re: Holley spread bore carb. 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.