Holley HP Series Carbs
 

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...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:

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.

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.

650 Cfm

.... and one more caveat.

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


Trust me on this one. :D

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.

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

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 - 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*

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

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.