New Carb

[agro1]

When I had my motor rear wheel dyno tuned it was aparent that my hp/trq figures were nosing over at about 5500 rpms. I was told that if I changed the carb (I have a Holley 750) to a Holley 850 with annular boosters it would help the motor breathe better and the hp would continue to climb up to 6000, giving me a bit more revs that I would like to have. I usually don't rev the thing past 6500 (at the MOST) cause I don't think my bottom end could handle it on a regular basis. Any thoughts ? Thanks in advance.

[Mr.Fixit]

I always put 850 DP holley's on stroked small blocks that make 500hp. Under carbing makes for better low rpm throttle response, but limits top end HP. Overcarbing causes a loss of some low rpm throttle response, but lets the motor make peak power at rpm. So would you rather have 1800 rpm throttle sensativity, or more power at 6000 rpm?

[agro1]

I think I have PLENTY at 1800, actually more than enough and who really drives around at 2000 rpms anyway ??? I am always above 3 grand if not more. Sounds like I gotta get me a new carb for X-Mas....

I was told to get the Holley 850cfm with annular boosters, and that does NOT have a 1:1 linkage, will this one work ?

http://www.holley.com/HiOctn/ProdLin...SC/0-9380.html

Thanks as always...

[scottj]

My 434's make 20hp more with the Holley 850HP than with the Holley 750HP and one engine turns 6900rpm, the other 8200rpm. I run which ever carb has better off-corner response for that track on that day. In the last 30 races I've run the 750 twenty-eight times and the 850 twice.

[scottj]

agro1,

I would get the Holley HP series and you won't find an 850HP with better off corner response than a Braswell.

[Roscoe]

You may want to check out the AED carb at

http://www.aedperformance.com/Frame2.html

Roscoe

[Mr.Fixit]

Originally posted by agro1


I was told to get the Holley 850cfm with annular boosters, and that does NOT have a 1:1 linkage

First off, you may make more power with the 850, but you may not notice it. Get the HP series holley, it is better. AS for the 1:1 linkage, this is very easy to change from a progressive to a 1:1, or vice versa, it's just a little 1" long linkage rod that you bend or replace. You may want to get your secondaries on the 750 to open a we bit sooner by changing that on your current carb. It's the little linkage rod on the driver's side that connects the front thottle blade shaft to the rear shaft, look at the one you have right now, is it straight or bent?

[agro1]

Mr. Woodruff already bent that little guy last time we were at the track...I need to be able to rev the thing up to 6000 though - that is the only reason I want to change the carb. Dean said it is not getting enough air. At 5500 it falls on it's face and Dean said when he did the same thing to another cutomers motor (same as mine from CHP) it really "woke the motor up"...Any thoughts Fixit ?

[Mr.Fixit]

Originally posted by agro1
Mr. Woodruff already bent that little guy last time we were at the track... At 5500 it falls on it's face and Dean said when he did the same thing to another cutomers motor (same as mine from CHP) it really "woke the motor up"...Any thoughts Fixit ?

Did the same thing: you are referring to the bending of the linkage, right?

That will get the secondaries open sooner, and can help. But it will not increase the total airflow capabilities of the carb. Are you running an aircleaner? Your carb is a 750 with annular boosters. Annular boosters are larger than the regular or downleg boosters and thus reduce the CFM of the carb a little bit. Most guys run the straight boosters which are considerably smaller. The annulars are nicer, but you need a carb with slightly more CFM to start with, the annulars have better throttle response so that makes up the difference of lower air velocity through the carb at low rpm's.

[agro1]

Yeah - he bent the linkage...I guess I need to go to a bigger cfm carb, that seems to be what I am hearing...And I do not think my 750 has annular boosters...but then again, I could be wrong...

[Mr.Fixit]

They look quite differemt, the boosters that is. There are 3 major types: straight, down-leg, and annular (and truck boosters, not popular). I like the downleg boosters most of the time. The straight and the downleg boosters are small in diameter, about 1/2". The annular boosters are much larger, closer to 1" in diameter. The only difference between the straight and the downlegs is how deep they sit into the carb. Look at some pictures in a catalog, you will notice the three different types.

[agro1]

Thanks Fixit....

[TC Cobra]

Roscoe,

Do you run the AED?

If so, how do you like it?
Any comments re: comparison w/what you ran before?

Thanks for your insight!
Dwain

[decooney]

Hey Argo,
I went with the Holley HP 830 series with annular discharge (no horn/choke, etc). Previously I ran a regular 750, and there is a noticeable difference throughout the power band, but not at first. I had to rejet the HP down a little and go up on the discharge nozzles a bit to get it spot on for good throttle response. For some reason, my 830 carb came with larger jets than my friends 1000 HP carb stock from Holley. Depending on how well your motor flows air - you may need to do some carb tuning on the HP. If you are not sure what to do with tuning, find a great carb tuner (with your new carb on your car) to assist you to bypass having to purchase extra/multiple discharge nozzles, jets, pump cams, carb gaskets...and it saves time. Good Luck.

[Roscoe]

TC Cobra,
I have a Speed Demon but a friend put one on a 460 in a Superformance and loved it.
Good carb,
Roscoe

[Tinker51]

This may not apply because this was on a small block (HIPO 289 block) but a friend had a motor built that was running on the dyno with a 650 and making a little more than 370 Hp. Just for kicks we changed to a 750 to see what would happen, Power dropped by about 25 Hp no matter what jets we ran in the 750 carb. Just food for thought.