Holley selection?
Thread Starter
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Holley selection?
Need a recommendation for a carb. Vacuum secondaries. 650-750 cfm. Let's not get into the Holley vs Qjet squabble - ok.
First off. Is it all that much of a difference (performance wise...) to use a square bore instead of a spread bore carb? For example there is a Holley 4175 that is a spreadbore replacement for a Qjet. For the cost is it any "better"?
I have been looking at a #80783 (650 cfm) and a #80670 Street Avenger (670 cfm). An engine builder shop near here in Cleveland recommends a 750 cfm and said "the vacuum secondaries will take care of any oversize cfm, and you can't go wrong with a 750 vac sec Holley!"
I looked at a Speed Demon but it is a bit pricey compared to a Holly.
I'm installing an XE262H or XE268H cam, Torquer heads (2.02/1.60) 67cc, and Performer intake this winter and exhaust is already true duals with no cat.
First off. Is it all that much of a difference (performance wise...) to use a square bore instead of a spread bore carb? For example there is a Holley 4175 that is a spreadbore replacement for a Qjet. For the cost is it any "better"?
I have been looking at a #80783 (650 cfm) and a #80670 Street Avenger (670 cfm). An engine builder shop near here in Cleveland recommends a 750 cfm and said "the vacuum secondaries will take care of any oversize cfm, and you can't go wrong with a 750 vac sec Holley!"
I looked at a Speed Demon but it is a bit pricey compared to a Holly.
I'm installing an XE262H or XE268H cam, Torquer heads (2.02/1.60) 67cc, and Performer intake this winter and exhaust is already true duals with no cat.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Holley selection? (KenSny)
I have never used the Speed Demon but believe it has adjustable air bleeds which can be a bonus when dealing with idle mixtures. Holleys do not have the adjustable air bleeds and when dealing with cams the mixture adjustment screws can cause problems, out of range for good idle mixture. Like I said I don't now Speed Demons but I have used alot of holleys and they can be hard to get right without alot of modifications.
Norval
Norval
Racer
Joined: Jan 2001
Posts: 455
Likes: 0
From: Virginia Beach VA
Re: Holley selection? (KenSny)
I just bought the #80670 Street Avenger (670 cfm) for my 71. I love it. Holley made this carb idiot proof for the consumer. It did require a spread to a square bore adapter ($15). Stock air cleaner will not fit. Don't know what kind of intake u have. Mine was stock. The carb and the adapter did fit under the hood but it was close. U can't go wrong with a lifetime warranty. If your vette is stock then the 750 is probably too big.
I looked at the 4175 also. Several forum members said the Holley spread bores are not very good. I don't personaly know that though.
If u get the avenger you will not be disappointed.
Randy
I looked at the 4175 also. Several forum members said the Holley spread bores are not very good. I don't personaly know that though.
If u get the avenger you will not be disappointed.
Randy
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: Holley selection? (KenSny)
I currently have a 6211 Holley spreadbore and 68 Vette Aluminum Q-Jet manifold on my 70 454. It runs excellent. No problems. It is a mechanical secondary double pumper. The vacuum secondaries should be a good choice and more tuneable via the secondary diaphragm. I do not have any first hand knowledge (i.e.- actual experience) with the adapters, but several performance books that I have say not to use them because you lose horespower.. Something about the transition of the airflow. That's what the books say.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: Holley selection? (KenSny)
Ken
A carb is a responsive device so if it is sized & adjusted correctly you can expect about the same hp +/- 5.
Have run Carters, Q-Js & Holleys. No problem making any so fast nobody wants to ride. :cool:
If you want a Holley would go squarebore.
A carb is a responsive device so if it is sized & adjusted correctly you can expect about the same hp +/- 5.
Have run Carters, Q-Js & Holleys. No problem making any so fast nobody wants to ride. :cool:
If you want a Holley would go squarebore.
Drifting
Joined: Nov 2000
Posts: 1,390
Likes: 39
From: North Brunswick NJ
Re: Holley selection? (Ganey)
Ken,
Holley 3310 is hard to beat for the price.[$220].
You can put all the trick parts the new Avenger sereies has and you can add them as you need them. In the long run I think you save money.
Ed
Holley 3310 is hard to beat for the price.[$220].
You can put all the trick parts the new Avenger sereies has and you can add them as you need them. In the long run I think you save money.
Ed
Senior Member since 1492
Joined: Aug 2000
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
Re: Holley selection? (ED DINAPOLI)
I just switched from an Edelbrock 1406 to a Holley 3310 750 dual feed. Worked great right outa the box. Just needed to set idle speed. It's been about 6 months and haven't had to touch it. Holds an idle better and has better throttle response than the Edelbrock. If it's a daily driver you might want to get the elec. choke. I didn't but don't mind the slow, high rpm warmups.
Len
Len
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