I'm getting a new carb and trying to decide between them for the 454. It's going to be a mostly street driven motor but maybe some track time in the future. I like the already milled choke horn of the hp but just wanted to see if it was still a good carb for the street.
Thanks

Steven

 

should be okay and if tuned right wont be too much of a bear on cold days.

 

Yah i think it will be fine

 

They work fine on the street.....what size are you going to get? Don't be afraid of the larger ones....the HP 950 works well on 454's.

JIM

 

I was going to go 750 only thing the engine has is a mild cam the PO put on it and hooker super comps. Probably going this next weekend to get new 2.5 mandrel bent and super 40s. I was thinking the 750 is where I need to be for now should I got bigger?

 

850 at the very least.

 

Holley's rating system is wet flow and they don't compare dead on with BG's etc. The bores aren't that big. I know several folks with the 950's that do well on 454's. For that much money I would get the 950 and have the ability to grow into it.

My oval port 427 ran much better with a 1050 than it did with a 750!!

Big carbs are not bad for the street....a 750 is perfect on a nice little street modified 350. Maybe a real mild 427..but it's getting edgy there.

A 454 needs more air. You have headers and I'm sure you will fix that cam issue later on right?

2.5" pipes are OK up to the 500 hp or so range....but if I was going to spend the $$ for a mandrell system, I'd have 3" put in there. They will fit through stock frame holes...many of us have done it. Again you will never have to mess with it again and you will love the sound. You can use large case 3" mufflers to keep noise down and keep performance up.

I'd also look into installing an X-pipe in the system and NOT using the Flowmasters. I'd look at some UltraFlows from Dynomax. I ran the Flows on mine and they were Ok with the 427..but again...later on with even the milder version of the 540 they KILLED it!!


I hate it when I have to re-do stuff later on because I didn't think out far enough. Some of the magazine tests showed great results with 3" pipes even on low 400 hp 454 crate motors.

Think ahead and remember..big blocks need to breathe!!

JIM

 

I use the 80514 HP series 1000 cfm on my 406 small block.. Great carb. I'd day that even a 1000 cfm carb will work fine on a milder engine if properly tuned..and if you decide to upgrade performance, you'll only need to re-jet and not get a new carb..

 

I have a 4150HP 750cfm on my 383 and it is just right. I agree with the other guys that an 850 would be the smallest I would go. With our low hood clearence issues, I don't see how we can leave the choke horn in place, it barely clears the air cleaner lid. A couple of squirts from the accelerator pumps and she should fire right up . You do have to stay on the gas till she warms up, but it's a minor inconvienece.

 

Another deal is that with a dual plane intake..you want to use a larger carb. Check Edelbrock's Tech section for a good write up. I wouldn't be scared of the 1000 HP either. We used one on a relatively mild 540 and it got 18.9 mpg with 3.08's and a Tremec.

But at least the 950 HP for sure.

JIM

 

How about an 850 Annular speed demon part #1563020 double pump
or a 850 annular speed demon Part # 1563020VE vacuum sec.
From what I have been able to read on carbs Annular seems to be
the way to go for street engines and 850 cfm would feed a 454
thats not going to be at higher rpms. the catalog says for these carbs
468 to 510 mild big blocks. Barry grants CFM ratings are considered to
be conservative by 10 percent.

 

Definately plan to change out the cam later on...but by the time I get to that point and pull the entire engine out I'll want to do an entire rebuild anyways. You've sold me on the 950, but regarding the exhaust I'm nowhere near 500 hp maybe someday, but certainly not now. I've heard that the 3" won't fit without major modification but I would love to be wrong about that. Know of any shops in GA/SC closer to augusta or columbia that could do the work?

 

If you're a do-it-yourselfer, you could pick up a used 750 cheap give it an overhaul, do this to it, and save a bunch of bucks. Note how the venturies have been "shaped in" (like the HP models) rather than just a straight mill of the choke horn as is typically done.

Actually, you can still often save some bucks by buying a used double pumper and a new HP center piece and you still end up with an HP.

 

I believe an engine can only move so much cfm. And when you add the cam all it is doing is making your engine more efficient. I mean only so much air can go into a 427 cubic inch space. But there are alot of varibles that can change this.

 

The 3" isn't that big of a deal. If they have mandrel bent pipes it's even easier. The hardest part is the bend from the right header into the hole in crossmember. But it's not a big deal. The pipes go through and don't rattle as long as you support them right there at crossmember somehow just like the factory did. From there back it's wide open..you can stick an X pipe right there in front of the rear crossmember. You can even get oval pipe and adapters to give more ground clearance...but if done right, the regular stuff will clear. Mufflers are all the same size..just put in what you can fit. Are you keeping the spare tire carrier? The pipes really look cool from the rear if a good guy does them as they come up from under diff.

I would hate to spend all the money on a mandrel 2.5 and then later have to do it again for a 3". Just do it now and be done with it.


'Cause when you pull it out you know we're going to be talking a 496...a 540..a 598....or a 632!!!


JIM

 

Even though it's not listed on-line, you can get an annular double pumper through Holley, just give them a call.

 

You are correct about the different way of measuring CFM According to Barry Grant, my 825 Race Demon actually flows 982 CFM:

"We rate our carburetors differently than Holley does. The "CFM" number on our carburetors is a median or average flow number that you would see if the carburetor was installed on an application that we’d recommend. For example our 825 Series carburetors are actually larger than a Holley® 950HP.

Here’s where it gets really fun. A 950 HP is actually smaller than an 850 Holley®. A 950 HP uses 1.375” Venturi, and an 1-3/4” Butterfly, an 825 Demon™ uses a 1.425” Venturi and an 1-3/4” Butterfly. An 825 Demon™ will flow 982 CFM @ 1.5” Hg @ 12.5:1 A/F. The reason we do not rate them in this manor is that most engines will not see 1.5” Hg at WOT in the real world. "