Holley HP Series Carbs

[Sieg]

I'm in the market for a new carb for my 355 Gen 1 motor after the engine fire. There are a number of configurations of the HP, I like the features of this new HP Ultra: http://www.speedwaymotors.com/Holley-Ultra-HP-Gas-Carburetor-750-CFM,55779.html Sight glass, larger bowls w/ drain plugs, billet baseplate, etc.

The question is 650 or 750? I'm leaning 750 since the motor didn't feel over-carbed with the previous 650 Speed Demon and my goal is a larger displacement 370-380 Gen 1 motor.

The hydraulic cam is unkown but rather aggressive 10.5-11" at 950-1K idle, estimate the compression at 10-10.5, will have AFR 190 heads with Edelbrock Performer RPM Air Gap manifold, I also need to replace the ignition - I'm leaning toward this MSD kit:http://www.summitracing.com/parts/MSD-84741/

Your question and input are greatly appreciated. :thumbsup:

[GregWeld]

Simple math....


683 CFM --- using 355 ci -- 7000 rpms -- mildly built motor.


Here's my real world take on it.... for the street -- the 650 is PLENTY.... if you're going to race and want WOT HP go with the 750

I prefer the throttle response of the smaller carb for 99% of most driving needs.

[GregWeld]

Shoulda put a caveat in there -- the CAM only makes a difference when it comes to IDLE QUALITY... some carbs are built for big azz cams and some are built for stockers. If you have a "duntov 30/30" kind of cam like the old 327/350hp --- I wouldn't factor that in to your choice. It's just not enough cam to mess with a big cam carb.

[intocarss]

650 Cfm

[GregWeld]

.... and one more caveat.

Whatever you do -- stay clear of their "Avenger" POS useless crap of a carb.


Trust me on this one. :D

[Sieg]

Thanks guys! The Air Gap RPM and 650 HP with mechanical secondaries, no choke, contoured venturi's, notched floats with jet extentions, and float bowls with additional baffling should be an improvement in tunability and a decent gain in mid to upper rpm over the Torker II and 650 VS Demon ..........I hope.

I doubt I'll regrete having a choke, they've been more of a pain than benefit on the last two carbs.

[GregWeld]

No need for a choke on a car like this... IMHO

[Flash68]

The new Ultra HP is the best carb Holley has ever made. Even my engine builder who only likes the $1000-1500 carbs from Braswell or Bob Book said it's pretty dang good out of the box and wouldn't throw it in the garbage if I brought him one.

[Sieg]

No need for a choke on a car like this... IMHO
Thanks - I typically warm the old skool think up to at least 130* before it moves so I should be able to get the tune close enough that it won't require a lot of babysitting until 130*

The new Ultra HP is the best carb Holley has ever made. Even my engine builder who only likes the $1000-1500 carbs from Braswell or Bob Book said it's pretty dang good out of the box and wouldn't throw it in the garbage if I brought him one.

Thanks Dave, that's great information. :thumbsup:

.........I didn't know you actually had an engine builder. I thought you only had a parts advisor and machining specifications specialist on retainer. :D

[sik68]

I'm running a 780cfm chokeless carb on my 355 (236/242 SR) and on the street it is definitely soft below 2500 rpm, and doesn't really come into its own until 4k. I think if it were more of a driver, I would really appreciate the 650 carb on it.

I dont miss the choke one bit though like the other guys are saying. 2 pumps, fire it up, idles on its own from dead cold.

[Sieg]

I'm running a 780cfm chokeless carb on my 355 (236/242 SR) and on the street it is definitely soft below 2500 rpm, and doesn't really come into its own until 4k. I think if it were more of a driver, I would really appreciate the 650 carb on it.

I dont miss the choke one bit though like the other guys are saying. 2 pumps, fire it up, idles on its own from dead cold.

Thanks Steven, great confirmations!

[Sieg]

This Holley technical document pretty much closed the sale for me: http://www.holley.com/data/Products/Technical/199R10565rev1.pdf

That and the functional improvements made to the new Ultra HP over the HP: http://www.holley.com/0-80802HB.asp

Poor man's fuel injection!

[Vegas69]

I wouldn't go that far. It's a cool carb but modern fuels aren't meant for carburetors and I don't see anyway it will prevent heat soak or flooding under heavy braking. Then throw in worse gas mileage and cold performance. :lol: Back off the cam a touch and throw EZ EFI on it and be done.

[Sieg]

I wouldn't go that far. It's a cool carb but modern fuels aren't meant for carburetors and I don't see anyway it will prevent heat soak or flooding under heavy braking. Then throw in worse gas mileage and cold performance. :lol: Back off the cam a touch and throw EZ EFI on it and be done.
Todd I know where you're coming from......the EZ EFI would be great but the budget isn't there right now ($2180 less $457 insurance credit). :(

I typically run clear (non ethanol base) premium in the car. My card lock account has it at a couple local stations, road trips would most likely force the use of E10.

The baffling in the new Ultra float bowl "may" actually help the braking issues: http://www.holley.com/data/products/pictures/largeFuelBowl.jpg

[-Freak-]

Have you looked at any of the Quick Fuel carbs?
Ive heard a lot of good things about them.
http://www.quickfueltechnology.com/

[Sieg]

Have you looked at any of the Quick Fuel carbs?
Ive heard a lot of good things about them.
http://www.quickfueltechnology.com/I have and they are very nice.......I just don't like the blingy color combo on my car with the orange and blackout theme. The stealth Holley has the function and fits the theme. :thumbsup:

[sevillaz28]

Just a quick reply to this. I have a 500hp 383 in my 69 and I went from a Quick Fuel Q-750 to the new Holley Ultra HP 750 and its a world of differance. Better responding carb by far out of the box and after changing jets for my engine and tuning it in I'm going to change out the carb on my 67 to an Ultra HP also.

Holley did an excelent job with this carb and to go from sea level to 9000 feet with no issues for 4 days bouncing around Reno and Tahoe, says a lot for the carb.

[Sieg]

Thank you, that input is very helpful! :thumbsup:

[alvin3a]

.... and one more caveat.

Whatever you do -- stay clear of their "Avenger" POS useless crap of a carb.


Trust me on this one. :D

Just curious why you say this... please tell us more

Thanks
Alan

[GregWeld]

Just curious why you say this... please tell us more

Thanks
Alan

No point messing up this good thread with useless info -- but those carbs are just nothing more than a OEM replacement carb and not for replacements on a HP motor.

[alvin3a]

No point messing up this good thread with useless info -- but those carbs are just nothing more than a OEM replacement carb and not for replacements on a HP motor.

whew I'm fine then since I have a pretty stock motor :)

Thanks
Alan