Holley Main Body Upgrade.

[BattlestarGalactic]

 

In the way back, had a friend running a Firebird drag car with a 454 and 8.5:1 compression.  He was using a 850 DP and kept having to screw with it.  AT one of the Friday TnTs, I lent him a 750 vacuum "3310" that had a updated ProForm main body for a comparison test.  The car picked up like 5 MPH and over 1 full second in the 1/8 mile.  Had to ask a few time later to get the carb back LOL.

But it's a "race car" and it HAS to have a BIG DOUBLE PUMPER on it to go fast....LOL!!   

Buddy was wanting to get a new carb for his 302 in his foxbody.  He was set on a 650-700DP.  It's a mild pump gas street car.  Never much to ever see WOT again in his current physical condition.  I told him to put a 1850 on it and just drive it.  He gave in, finally.   He's just amazed how well it runs, crisp throttle response, etc.  He was not believing a vacuum carb would work well.   Jeez, I run two of them on my wagon for decades with no issue.  Some times it's hard to break old school habits.

[Falcon67]

Venturi design has not really changed in over 100 years.  An optimal tube is still an optimal tube.

I will say, that booster design and science has improved a considerable amount.
Maybe not on shelf carbs or parts, but many booster designs will simply work better, seeing more signal while taking up less room, thus the carb flows more.

Have to send you a pic of the alcohol carb I borrowed for a test.  The main body looks "ProForm" but the boosters are big annulars with the step at the bottom.  Unusual.  Was on a small block car, supposedly ran really good.  .059 shooters in it is all the detail I know LOL.  The base plate sorta says "850" but haven't measured the bores yet. 

[plovett]

 

In the way back, had a friend running a Firebird drag car with a 454 and 8.5:1 compression.  He was using a 850 DP and kept having to screw with it.  AT one of the Friday TnTs, I lent him a 750 vacuum "3310" that had a updated ProForm main body for a comparison test.  The car picked up like 5 MPH and over 1 full second in the 1/8 mile.  Had to ask a few time later to get the carb back LOL.

But it's a "race car" and it HAS to have a BIG DOUBLE PUMPER on it to go fast....LOL!!   

Buddy was wanting to get a new carb for his 302 in his foxbody.  He was set on a 650-700DP.  It's a mild pump gas street car.  Never much to ever see WOT again in his current physical condition.  I told him to put a 1850 on it and just drive it.  He gave in, finally.   He's just amazed how well it runs, crisp throttle response, etc.  He was not believing a vacuum carb would work well.   Jeez, I run two of them on my wagon for decades with no issue.  Some times it's hard to break old school habits.

The counter-argument is that a double pumper (mechanical secondary) Holley will often produce more low end power.   I know the magazines have been preaching the opposite for decades......  Often times, but not always, a vacuum secondary carb will not open the secondaries fast enough and far enough at low rpm and power is lost.  It of course depends on the tuning and parts used, but a properly sized mechanical secondary will always provide what is asked of it.   It is not always about ego and the racing image.

paul

[BattlestarGalactic]

No doubting it, a DP carb will work great.  Yes, magazine preach VS carbs, but most times they are talking run of the mill street cars and not "full blown" race cars.   The magazines know that most will try to bolt a big DP on the family truckster and wonder why it just bogs and runs like crap on the street.

[Falcon67]

The best carb I have in house is a 650DP.  Paid $40 for it at a swap about 20 years ago, replaced the base plate, jetted it and it just works.  It's been on everything from a mild 302 shifted at 5500 to the 393C on the dragster shifted at 7000.  No jetting changes between those extremes.  Drives nice even with a tighter converter.  I've also run a 600DP on the 302, that one ran very well also.

[cjshaker]

Often times, but not always, a vacuum secondary carb will not open the secondaries fast enough and far enough at low rpm and power is lost.

paul

The reason for dual carb intakes, which Ford made plenty of for the FE.

[Rory428]

I see no reason why a properly set up Holley with vacuum secondaries should provide any less performance that an equivalently sized double pumper. My FE Fairmont ran its quickest and fastest numbers with a crusty looking old 310-1 780 vacuum secondary carb, than it did with 750,800, or 850 DPs.

[plovett]

I like vacuum secondary carbs and they can run fast.   In fact, I've said before that I think the Holley 3310-1 is probably the best all around street and strip carb ever made.   It is so versatile.  It can work well on a mild 302 and also on a 10 second street/strip car.   

If I have a beef it is with the car magazines that, for decades, tried to scare everybody into being overly conservative, using small vacuum secondary carbs, small cams, no more than 9.5:1 compression, etc.   They made it sound like a double pumper would always kill low end power and response compared to a vacuum secondary carb.   Not true, and sometimes it is the other way around.  I remember seeing dyno tests where the same size double pumper makes more low end power.  Granted, that could likely be fixed with the proper secondary springs.

I have several vacuum secondary carbs in my garage including a 3310-1.   I just don't have the right application to use them right now. 

paul

[427John]

I like vacuum secondary carbs and they can run fast.   In fact, I've said before that I think the Holley 3310-1 is probably the best all around street and strip carb ever made.   It is so versatile.  It can work well on a mild 302 and also on a 10 second street/strip car.   

If I have a beef it is with the car magazines that, for decades, tried to scare everybody into being overly conservative, using small vacuum secondary carbs, small cams, no more than 9.5:1 compression, etc.   They made it sound like a double pumper would always kill low end power and response compared to a vacuum secondary carb.   Not true, and sometimes it is the other way around.  I remember seeing dyno tests where the same size double pumper makes more low end power.  Granted, that could likely be fixed with the proper secondary springs.

I have several vacuum secondary carbs in my garage including a 3310-1.   I just don't have the right application to use them right now. 

paul

I agree with this and your previous post,the key is to choose the right DP for your application and get it calibrated correctly.The problem with that is it can expensive in a hurry if you don't choose wisely,its not like you can take it back and swap it for the right one if you miss on the first try.The advantage of the vac sec. carbs is that if you overshoot on the size you can still tune it to work well.That is probably the single biggest reason the 3310 stayed in production for as long as it did,it could be calibrated to work well on engines from 283 cubic inches to 460+ cubic inches in differing states of tune by a guy that knew his way around a Holley.