MakoShark72

Awhile ago, Lars (remember him??) recommended to me that I go with the Ultra 770 for my 383 build, due to the 4 corner metering, and that Holley had worked out the hesitation and flat spots problems of the original Street Avenger carbs.

Anyone had any experience with this "relatively new" Holley carb? I'm about to pull the trigger.

I am finishing up a 383-500 http://www.sallee-chevrolet.com/Chev...8s/383-500.cfm

Since these motors were never available for purchase, before Sallee Chev closed its doors, I elected to build my own with a few modifications. Hopefully, I will match or maybe even exceed, their HP/TQ (500/500) results...

Mine is slightly different than the original 383-500, in that it includes a...

Brand new GMPP ZZ383 bottom
Chris Straub custom cam http://www.straubtechnologies.com/
AFR 195's (64cc) milled to 58cc
Scorpion 1.6 rockers
Morel lifters
Smith Bros pushrods www.pushrods.net
Edelbrock RPM Air Gap
10:1+ CR
etc, etc, etc...

Since I have a 2004R, I wanted to go with vacuum secondaries and electric choke, thus considering the 770 Ultra...

Daily driver (sort of)... no racing or track.

Thanks!

dboz

I think it will be a good choice. It will give you more torque and good street manners.

I am running the 750 ultra since I wanted a double pumper because I was concerned with hesitation also but it is not on the street yet so I am not sure, but it is sounding very healthy in the garage LOL.

http://www.amazon.com/Holley-0-76750.../dp/B002TZQBFM

MotorHead

The carb you want to buy that will give you know problems and will work on a 300HP 355ci to 550HP 406ci and beyond is the Classic 750 Holley DP. I wonder sometimes why I even bother to post but all my posts are from personal experience, the 4779 (Holley mentioned above) is a great carb and not expensive, as you can see it is a very versatile carb

355ci with Holley 750 4779 made just under 300RWHP crank up the volume, that was only 5500 RPM



Same carb on my 406ci made 550HP crank up the volume this time the carb pulls to 6500 RPM

MakoShark72

MH,

Have long read about your satisfaction with the 750DP, but was thinking with a 2004R that vacuum secondaries would be preferable. Also electric choke, not a big deal of course.

billla

I've installed a number of the Street Avengers/Ultra Street Avengers and few of the new HPs. The Ultra's really aren't that different than the standard Street Avengers but have a few nice features including the 4-corner you noted. It's perfect for your application, and the sizing is in the ballpark - difficult to over-carb with a vacuum-secondary carb as long as you don't go nuts

The HPs are incredible if you want a very, VERY tuneable street carb and don't need a choke.

You'll want vacuum-secondaries on an auto trans unless perfect zero-to-WOT is your primary goal.

In the end, ANY carb will "work" - i.e. run and make power - but optmizing the size and configuration provides the best results

MakoShark72

Thanks Billa, thats what I was thinking.. Are you thinking the 770 is TOO MUCH carb, maybe going to the 670?

billla

Given the CID and AFR 195s, no. You'd maybe get a touch sharper low-and mid-range throttle response with a smaller carb, but the risk is being a even a bit into the secondaries in high cruise which kills fuel economy. You've got the right choice there.

MakoShark72

Thanks!

I am pretty excited with this motor. Cant wait to get it in. Havent decided whether to dyno it prior to install....

silver79

how about my Edelbrock RPM heads with 70cc chambers? i also have a speed demond 625 cfm would this set up be good for 450hp in my future 383

billla

Not sure how to approach this, as I don't see that power level from those heads...closer to 1 HP/CID, I would expect. At that level, your 625 CFM is in the ballpark.

ZZ71S

I really dig that engine you should dyno it before dropping it in

MakoShark72

Thinking about it...though I would hate to be disappointed!!!

billla

You picked all the right stuff - you won't be disappointed

Break-in and initial tune on the dyno is worth the $$$ if you can swing it.

MakoShark72

Billa,

Bud's Machine Shop in Lakewood has the motor right now. Although I have done it in the past, I wanted Bud to install the AFR's, align the valve train, etc... especially since I went with 1.6 rockers and I wanted to make sure the pushrods were correctly aligned, and no conflict with the AFR guide plates, installing the Straub cam, etc, etc!!!

Cheap insurance to make sure its "done right", and I really enjoy working with Bud...

He mentioned about $400 to put it on the dyno. I have never done that, so I assume that's a reasonable price. I'm leaning towards doing it. Will be in a couple of weeks minimum. He will be done with the motor on Friday, but we are headed down to central Oregon for a few days.

I will probably start a new thread just on the motor.

billla

Yeah, that's a great price for sure - especially if they've got all the stuff there to do some initial tuning, which I'm sure they do.

Love to see a thread on the beast It's nice to see a well-planned engine come together.

Solid LT1

Have you ever had a set on a flow bench? I have done early Edelbrocks, they went about mid 220's @0.500 lift. The later heads are in the mid 240-250CFM range. Rough calculation for HP is flowX2 so early heads will do low 420-440HP and later heads around 460-475 on similarly canned 383 motor. AFR 195's run 275CFM for early versions and right below 300CFM for the Eliminators so they would make around 25HP more the Edelbrocks. This assumes you have decent exhaust and carburation and many "built" Vettes seem to suffer in the exhaust department. From personal expirience, I have made 445HP with a set of re-worked Edelbrocks but, they had a lot of effort put into them on a 355 motor with a Victor Jr.

Solid LT1

My phone helped me with "cammed" it prefers canned. One last thought, if your going big on a cam with 0.600 lift, lose the Edelbrocks! They go turbulent at 0.550 lift. Even Brodix IK heads will outflow them at bigger lifts.

billla

A more realistic formula is the Superflow one - .257 x (Intake CFM * (1-Induction Loss %)) x Cylinders. Induction loss for a low-rise dual-plane is around 25+%.

Edelbrock claims 240 CFM @ .500, so working the numbers gives around 375 - 380 HP, which is consistent with what I've seen from these heads. Heavily ported heads with a single plane intake is not what the poster asked about

I'm simply going to chuckle and move on at a set of AFR 195's making only 25HP more than a set of Edelbrock RPMs, with 50-60 CFM more flow

I'll own being conservative on my estimates...but then again, I don't end up with any disappointed customers with my builds

CheezMoe

I just installed a 750 Ultra DP on my 383 with T400 and 2200 Converter. The carb works great and the electric choke is nice to have on chilly days. The 4 corner idle is nice, but time consuming to get the idle really smooth and low. The out of the box tuning was awful! Floats set too high, lean pump shot, super lean idle mixture. The car would not even run with the carb right out of the box. After a few hours of tuning she runs really nice! ...In fact went for a little tea cup ride the other day ...Im glad nobody was watching...