Holley 950 3 Barrel & a Felony 427 (571 HP @5800)

[4twennyAint]

We had a laugh at Barry's yesterday, finishing my dad's 427.  The undisputed king on the dyno was a 40 year old Holley 950 vac secondary 3 barrel, besting a Holley HP 950, Holley 850 and a customized carb from a certain Engine Masters Challenge effort.  The engine specs are from memory here: '64 center oiler, 4.25 crank, 10.6:1 compression, Felony heads w/1.71 exh valves, as-cast ports, 250/.660 custom flat tappet solid, RPM intake.
The carb was last used in 1982 on a 427 low riser, and was shelved.  We made some repairs to gaskets and replaced an entire misbehaving float bowl.  It made 10 HP more than the other carbs, and we forgot to even use the velocity stack on it.  Call the engine 575 HP since the stack would for sure have added at 4 HP.  Torque was over 550

[jayb]

A lot of people swear by those three barrels.  They flow a lot of air; they are an honest 950 cfm, compared to a new 950 Holley, which flows somewhere between 750 and 850.   

[thatdarncat]

And don't forget, there's a 1050 cfm 3 bbl also - in case you want to step up. It's been a few years since I checked, but Holley did have the rebuild kits still available. Biggest issue is the rubber secondary diaphram hasn't been available for decades. For anyone rebuilding one be careful not to tear the diaphram with the housing screws.

[Rory428]

Over the years, I have owned both versions of the Holley 3 barrels, and ran them on my Fairmont. They ran great performancewise, but lacked some of  the part throttle drivability of later Holleys. They were basically a 3310 780 Holley with the material between the 2 secondary butterfies of the baseplate and main body cut away, and a single, large oval secondary plate installed. They used a large angled vacuum secondary housing, similar to a Chevy or Mopar 3x2 barrel unit, although the length of the vac diagphram rod is different. As mentioned, the sec. diagphram is onbsolete, not sure about carb kit availability either now. They used a funky cable operated manual choke flap, with no choke tower. To tella 950 vs 1050 cfm 3 barrel, check the secondary venturi area. A 950 has 2 booster, like most other Holley 4 barrels, but a 1050 has 2 simple brass tubes, with no booster bell to get in the way. Kinda crude, but it did work well at WOT.

[machoneman]

2X to what Rory said. Haven't seen a 3-bbl in years. But, way back then a pal had one that we swapped onto 3 or 4 different engines to try it out. In all cases, low speed operation was poor but once  engine rpms rose to a high enough level, the carb was a real screamer.

Btw, I did not realize that modern 4-bbl 950's (see Jay's words) do not flow at least that amount but substantially less cfm. What dummy decided to change that relationship (advertised size not equal to actual flow) and for what reason? 

[jayb]

2X to what Rory said. Haven't seen a 3-bbl in years. But, way back then a pal had one that we swapped onto 3 or 4 different engines to try it out. In all cases, low speed operation was poor but once  engine rpms rose to a high enough level, the carb was a real screamer.

Btw, I did not realize that modern 4-bbl 950's (see Jay's words) do not flow at least that amount but substantially less cfm. What dummy decided to change that relationship (advertised size not equal to actual flow) and for what reason?

As I understand it, a new 950 Holley is comprised of the same throttle body casting as a 750, and a base plate and throttle butterflies from an 850.  Why they decided to call it the 950, and totally screw up their otherwise reliable cfm ratings, is beyond me.  They  pull the same kind of trick with their 1000 carbs, which are basically just 850s with the choke horn removed.  They do probably flow more than an 850, but I doubt its close to 1000.

Barry R knows a lot about this having been involved with Holley earlier in his career; maybe he'll chime in and comment.

[RJP]

I ran a 950 3bbl on a 427 powered Hondo Vdrive flat. One of the best carbs I've ever run. Pulled hard to 7K, no flat spots, no blubbers, no issues what so ever and started as easily as a stock Motorcraft carb.

[blykins]

The new Holley Ultra HP 950's are true 950's, but the venturis are much, much larger than a comparable Q-950 Quick Fuel, which can cause issues with smaller engines and street driving.  I did a back to back test with a 445ci Windsor and the Q-950 QFT was good for 11 more horsepower.

[RJP]

2X to what Rory said. Haven't seen a 3-bbl in years. But, way back then a pal had one that we swapped onto 3 or 4 different engines to try it out. In all cases, low speed operation was poor but once  engine rpms rose to a high enough level, the carb was a real screamer.

Btw, I did not realize that modern 4-bbl 950's (see Jay's words) do not flow at least that amount but substantially less cfm. What dummy decided to change that relationship (advertised size not equal to actual flow) and for what reason?

I
As I understand it, a new 950 Holley is comprised of the same throttle body casting as a 750, and a base plate and throttle butterflies from an 850.  Why they decided to call it the 950, and totally screw up their otherwise reliable cfm ratings, is beyond me.  They  pull the same kind of trick with their 1000 carbs, which are basically just 850s with the choke horn removed.  They do probably flow more than an 850, but I doubt its close to 1000.

Barry R knows a lot about this having been involved with Holley earlier in his career; maybe he'll chime in and comment.

Did Holley play with the pressure drop values to get a 950 cfm rating? Old Holley 4bbls are rated at 1.5" of p/d... could they have mearly changed that to say 2" of p/d? This wouldn't be the 1st time Holley catered to their lowest common denominator in order to sell their product. Afterall CFM sells.

[jayb]

The new Holley Ultra HP 950's are true 950's, but the venturis are much, much larger than a comparable Q-950 Quick Fuel, which can cause issues with smaller engines and street driving.  I did a back to back test with a 445ci Windsor and the Q-950 QFT was good for 11 more horsepower.

Back to back between what, Brent?  A Holley 950 and the Quick Fuel unit, or the Ultra HP 950 and the Quick Fuel?  Thanks for the info about the Ultra HP 950, by the way, I didn't know Holley had a real 950 cfm carb available...

[blykins]

Sorry, the QFT 950 and the Holley HP Ultra 950. 

[Barry_R]

I am currently buried in this year's Engine Masters Challenge effort - along with no less than four customer engines that are ready for dyno - well one less since we got this one wrapped up....  I will do a full write up on this one as soon as I get the chance - really cool engine with a dual plane and a flat tappet cam.

We ran four different carbs on this engine - the 3 barrel, a vintage 850 vacuum Corvette carb, a 950HP, and a custom Randy Malik built piece borrowed from Adney Brown - one of the EMC entrants.  Adney and Randy Malik are local EMC competitors and friends, and he had this one as a spare for me to try out.  Randy worked at Holley for longer than I did and since he was in engineering there he knows more about carbs than many trick builders do.

The three barrel required some handiwork to get it ready - turns out that they have a unique rear metering plate and gasket arrangement.  I did know realize it, but the boosters are in a slightly different location than on a normal 4160.  Three barrels are actually pretty tricked out for the time - they were the NASCAR carb before the Dominator came out.  As noted, the old 3 bbl finished in first place by a clear margin in this comparison....pretty cool to see.  Some of us old guys are smiling right now...

The SAE wet flow carb ratings have been largely abandoned - but Holley was really the last to do that - not the first.  All the carb modification folks started advertising with dry flow numbers, saying that "their" custom 750 would flow 800, 900, or more cfm.  Eventually something had to give, and rather than call out many of their customers Holley just went with the "flow".  The 950HP is as Jay said - a 750 with an 850 base - a really, really good combination that many racers used for many years, probably flows in the low 800s.  The original HP had design input from Braswell among others, and the main body shows significant improvements compared to the common 4150 design.  Its a really nice carb, but in this case airflow won the contest.

[FErocious]

The 950HP is as Jay said - a 750 with an 850 base - a really, really good combination that many racers used for many years, probably flows in the low 800s.  The original HP had design input from Braswell among others, and the main body shows significant improvements compared to the common 4150 design.  Its a really nice carb, but in this case airflow won the contest.


The previous 950 ultra HP Holley was indeed as you have stated above, BUT the newest true cfm ultra HP 950 is much larger. The early 950 with a venturi of 1.375", contrasted with the 850 at 1.560" and finally the true 950 ultra at 1.590" venturi , all utilizing a 1.750" throttle body.

[babybolt]

On some of those old three barrels, the rear boosters were re-spaced.  Some are moved outboard.  It seems kind of incongruous on why a metering plate was used instead of a block, unless it has to do with some kind of racing class rule about the legality of a 4160 vs a 4150. 

Also, I think you guys are comparing double pumpers vs a vacuum secondary carb (the three barrel).  I have an old three barrel but have not been able to find the secondary diaphragm so as a back burner project have been figuring out how to convert it to a double pumper.

[TimeWarpF100]

I had a brand new 3v carb a few years back bolted it on my 427 Comet worked wonderful.

I think I may have a boat load of those diaphrams new in holley package if you need one.  A few minutes ago was digging thru my holley stash and saw them sitting there. Much larger than typical Holley?