Carb suggestions, looking at going Holley

I'm looking to go from an Edelbrock 800 to a 4150 type Holley.

The rundown on the car and combo is a 67 Belvedere, 727, 451 with Edelbrock heads ootb, RPM intake, 10.5 comp, .520-254 solid cam, 9.5 converter, 4:10. This is street car but not interested in an electric choke as I have never used one being in Phoenix. If I decide to go that route it seems this time of year is as about as cheap as I am going find prices.

What carb would you guys recommend here?

You might want to think EFI

On your deal a 850 to 1050 CFM double pumper 4150 HP carb. is what I would buy, maybe a similar Quick Fuel or one of your other favorite brand carbs.
EFI with a single 1000 to 1250 CFM 4150 throttle body is as good or a tiny bit better (and not compatable (SP?) with the dual plane intake you have) but a lot more money to start with

I'm sticking with a carb on this. The basic 850 4781 model is what I was thinking. Thanks Cab.

A 4781 would be a good choice to put on an affordable carb that shouldn't need too much tuning to drive well on the street. If you are concerned about on-track performance as well, there are other carbs that will be quicker at the track, but may not be as happy cruising around town.

The Holley 850DP is calibrated as a track carb. It will be very fat for a street car OOTB.

If you are comfortable with tuning the cruise and transitions, it would work for your application.

i think you'd be better off buying one of the quick fuel carbs.
maybe an HR or a SS carb, being able to tune the idle feed restricter is pretty nice on a street car.

I agree. Something like a Sniper or the MSD Atomic for a car like that.

If you insist on a carb then I'd highly recommend something with billet metering blocks so you have a fighting chance at tuning it. The problem there is the better carbs with the latest features (idle air adjust, billet metering blocks, clear sight glass, etc.) are expensive. The really good carbs are close to $1000 and you still have to spend a few weekends with a screwdriver and a wide band to tune them.......

Andy, are you referring to an HP type 4150? From what I understand the HP line doesn't flow what they are rated by Holley to flow. The throttle bores are smaller. The 950 HP is the same bore size as an 850 4781.

I know this isn't a street carb but I'm going to buy a 750 for my little Ford, I've had great success with the 950 e-85 version on my Mopar. The shop that does my dyno work has been selling quite a few of them after working on mine.
https://www.summitracing.com/parts/hly-0-80804hbx
And yes the gass carbs are usually set up fat.

Any of the billet block/base-plate carbs can be dialed in easy enuff especially if you have a wide-band afr gauge...........I`d stay clear of Holley personally and go QF, Pro-form etc. but I prefer and build from BLP parts and at a minimum a cast alum. main body OR step up to a full boogie billet...........

EFI.........

I have a Demon 850 and absolutely love it!

Lots of track days and street miles.

What is your goal, what is your budget?

I've run a 4781 on mine and was surprised how well it ran from the minute I put it on. Bought it used for like $160 and rebuilt it.

I've run a small venturi 950 hp that probably flows about the same as a 4781 or a little less. It actually ran fatter than the 4781 and required more tuning. It did make a bit more power than the 4781.

I've run a lot of carbs over the years, and I really like my 950 hp style carb. Kinda drives like a 4779, but better power than a 4781.

You will have to lean down the transition fuel feed to get it happy at light part throttle cruise Try around .055 restrictors in each side on the primary transition circuits to start with You will have to drill and tap them to do that with brass set screws
If you don't have the tools, skill or desire to do that your self maybe you should contact Thumper about one of his carbs or have him mod yours for good results
I have four 4781 carbs. starting from a old non dash original to my latest one which is a 4781-7, they work good with jetting and modifying the transition circuits to lean them down

OP combo is almost identical to mine. I ran an 830 DP for years with pretty good success. Last year I switched to a Holley 1000 HP Annular Booster carb. Every aspect of the way the car ran improved, both street and strip, with the exception of gas mileage. I don't really keep track of mileage, but I feel as though it was a notable difference in the "less MPG” direction. No question however that the cars throttle response improved. I attributed this primarily to the Annular boosters. At the track, which I'm primarily concerned with, I gained 2 tenths

I felt pretty good about my choice and results.

I'll say the budget is around $500ish. I'm also not opposed to going with a good used carb. I can tune the Holley up to a point but when/if it comes to drilling and tapping and such I would farm that out to one of the carb gurus. (i.e. Thumper).

I'm just looking for carb that idles better than the 800 Eddy I have now mainly. The Eddy performs extremely well in all areas except the idle. I'm pretty much done with trying to tune it. I'm getting 10" of vacuum at idle and the metering rods are just bouncing up and down. Its like it cant figure which circuit its on - the idle or the main. I'm not looking for all out strip performance but something that works well on the street which is less than 500 miles a year with very short local trips here and there and then very very rare strip occasion. I figure if the thing runs a mid to high 11 then I'm happy with it.

Either replace those springs with thinner ones or trim one or two coils off of them now and see if they will stay seated then
Don't we love working on race cars

I've ran every spring in the strip kit and ended up with the orange 5mmHg spring. Yeah this stuff can be aggravating at times.

Myself I run your basic Holley 850 DP thats been on my 63 since 2006. Only after I had to jet up a good bit when I built my 493 did I notice it a tad fat at cruise but I just lean down IFR a bit. And I have been very happy with the driveability and performance of the carb. Its still very basic as all I have done is some jetting and P/V changes and some squirter work along with leaning the IFR a tad. Ron

If you don't use a choke, check out the Holley Days sale on the Quick Fuel "Brawler" 950. Don't freak about them calling it a 950 because the venturi size is only 1.45" vs 1.56" for a 4781. IIRC, the sale price is about $520 right now. It's Quick Fuel's version of the Proform 950, FWIW.

That sounds like the hot ticket for ya Belvedere1.

I would suggest a 950 4150 carb for your combo. If you have the extra money a 950 from Thumper would be the best way to go. If you don't want to go that route you can buy a carb custom built to your combo. The last time I bought a custom Quickfuel from Summit Racing I don't even think there was any extra charge for it money wise. You just fill out a form and they order it, this was several years ago though.

The custom carbs I've used have been spot on, just bolt them on and enjoy your car. The 950 ProSystems carb on my current Duster, I bought it used on Racingjunk. Turns out the thing was only 2 weeks old because his customer wanted efi, and the guy selling it used to work for Prosytems, so he even set it up for my combo, and it runs like perfection. So you can find good deals out there, you just have to hope they haven't messed with the carb much.

I'll check that Quick Fuel out. They have some great deals going right now through that sale which is what boosted my motivation to look at making a change. I would like to get Thumper's input on either putting one together or tweaking one that I buy.

This add in race parts for sale


Dbl"00"Joe Offline
mopar

Registered: 07/28/06
Posts: 484
Loc: N.W. Indiana
Like new 80496-1 Holley 950HP

Has been Tuned by Thumper Carbs
Nice consistent carb only selling to go bigger.

$750
PM me here Thanks


Attachments
950hp.jpg

I saw that one but a little over my budget.

I will be researching the SQ 950 Quick Fuel, the Brawler that Brad mentioned although I am not a fan of the purple throttle plate and metering blocks, and the 0-82591 4150 HP 950.

Every carb sent to me even new in the box need work and some more than others. $500 doesn't get ya much imo but try one of those mentioned and see how it works out for ya but I'd at least take it apart and make sure the tech carb matches the carb cos you'd be surprised how many don't...........

I picked up a refurbished 950xp straight from Holley and saved $200 over Summit, FWIW.

Do jets, floats, gaskets, power valves, air bleeds, etc interchange between the Holley and Quick Fuel carbs?

Yes.

Give me your thoughts on this QFT based SQ-950. I can get this built to my specs but this a starting point.


      It has been assembled with high-flow .110" needle & seat assemblies, 30cc pumps, #33 squirters with pink #330 racing pump cams, non-stick bowl and block gaskets, nylon bowl screw gaskets, and vent baffle. The jetting is 78 up front with a 6.5" Hg high-flow power valve, and 86 in the rear with the power valve circuit blocked. The mounting gaskets are included as shown.  
   Here's a list of features;
   QFT polished lightweight aluminum main body with screw-in air bleeds. .073" idle and .030" high speed bleeds installed.
    Red anodized billet aluminum metering blocks that are custom calibrated for maximum performance.
   4 corner idle for fine tuning your idle circuit.
   
    Teflon coated throttle shafts, stainless steel throttle blades, and loctited button-head screws for increased flow due to decreased turbulence.

Have them put in .120 cos .110 are not "high flowing" and need more pressure to be stable like 7 psi instead of 6 or less w/the .120`s...........

I'd want to know what QF uses as an out-of-the-box tune in order to see how much "custom calibration" is really done to a carb built to "your" specs.

Wouldn't be the first time I've heard about "custom calibrated" carbs being about 95% out-of-the-box, and part of the 5% difference includes the decals for the shop that sells it.

Yeah, I'm pretty jaded these days.

my dad has a couple of new carbs in the box..quickfuel P950 and P1050.he's in the hospital right now and should be home this weekend.maybe drop him a line i know he wants to get them sold
aj
link to pictures
https://imgur.com/a/VcnLb

YEP..............

holley list 3916 .

1ts what i use and no issues !

It shouldn't be that difficult to compare what is in a box stock SQ-950 to the changes that would be made. I'm still in research mode on the whole thing. I hope to have something figured out in the next couple of days.

I was very happy with my QTF carb they set up for me..
it was a E-85 carb and they did a fine job.. they asked
a bunch of questions and when I put it on the car it was
on the money even with the AF meter on it.. even the idle

Was that buying direct from them?

yep.. built for me

Well I ended up going with a Quick Fuel Street Q 950. I'll report back once I get it on the car and get it dialed in. Thanks to you all and a big thanks to Thumperdart for his guidance.

What venturi size is it............When you get it on and running call me if you need some help tuning it in...........

1.45 venturi and 1.75 throttle blades. Its supposedly flows 950 cfm but I'm not convinced.

Not quite but should work..........

I agree, as long as its not less than 800 I don't really care.

Update:

I got the carb on and the car running again. It runs great right out of the box, the one and only adjustment was the idle speed. The float levels were spot on too. It was tweaked slightly from the box stock settings by the guy I bought it from. It seems that he nailed the settings. Jet 78/86, 4.5 power valve, rear blocked, idle restrictor .037, idle bleeds .030, high speed .073, 35 squirters front and rear, 30cc cam in front and 50 in rear. The only issue that is still there that I had with the Edelbrock 800 is at a warm idle when the engine starts to shudder like it drops a cylinder then picks back up again. The idle is better with this carb but the shuddering is still there. I'm at a loss from where to go from here on that.

BTT

Holley 3310 heavier vehicle street driven that's what I would buy get secondary spring set and forget it and run it

That would be a major step down from what I just bought, IMO.

Look for a vacuum leak or a bad spark plug wire or spark plug

Fresh plugs, have inspected every inch of each wire and boot and no sign of anything that looks suspect on those. Ive done all the vacuum leak checks known to man and cannot find one. I may try and crank the timing to 24 intial and see if that changes anything???

You might need to get the car on a scope to trace down a problem like that. My guess is that it is electrical and probably something thermal related. Most likely a bad coil or a bad part in the ignition box. When it gets hot you have a solder joint opening up or something like that. Very hard to find without a scope or other test equipment. If you have a buddy who has the same ignition system as you maybe you can swap coils and boxes and stuff like that until you run it down. I doubt it is carb related.

That's hard to say unless you make back to back passes bench racing YES

The baffling part is that its just the idle only but anything is possible with electrical issues in my experience. I started down that road a few months back with swapping to an old known good orange box and a stock coil with no change. I'm using a chrome box and an MSD Blaster coil. I'll see if a buddy of mine still has his scope at his shop.

Can you add some more description around this? Not real clear what happens and when.

These Thumper carbs are very nice

At anything from just a couple minutes after start up to just about 180 on the water temp gauge the idle is smooth or as smooth as it can be given the cam with a very consistent idle. When the temp gets to normal operating the idle rpm in gear will get a little erratic almost to the point of it feeling like it drops a cylinder and picks back up and then feels like a miss again, and on and on. In gear idle is around 800 and in park it will smooth out slightly at around 1000 to 1100. The best vacuum reading I get is 10 with an initial timing setting of 20. I thought the problem with the old Edelbrock carb was it not getting a decent vacuum signal causing the metering rods to bounce up and down and the carb to hunt between the idle and main circuit. This new carb made things overall slightly better.

That looks too nice to get dirty! He is great and helped me a ton in choosing the carb I bought.

Fat it up a taste and see what happens. The low vac. signal probably isn't allowing the manifold to get "wet". I have a 400 with a big cam and I had to make it idle a little fat but it's happy.

Do your self(and us)a favor and install a wide band and venture into the REAL tuning zone but be prepared to learn more about carbs than you imagined and have a damn near EFI running machine..........

I tried another stock parts store replacement ECU I find that I didnt realize I had with no change on the idle. I'll throw another coil on there the next time I get the car out. I tried an extremely rich jet and rod combo on the old carb and that didnt help the situation either. I totally agree on fine tuning with a wideband but how useful would it be just to establish a base idle and is there a such a thing as a no weld O2 bung kit?

You can buy the clamp to the exhaust deal or just chassis dyno it then tune to suit your needs but even dynos run WB's it's the BEST and you're guessing otherwise............

Okay. Thanks

I still would not rule out a vacuum leak, but I'm thinking you simply need to get into the weed on your idle tune-up. That size cam at 800 rpm in gear needs to be right, IMO. Without an A/F meter, I would maybe start with a bit more initial timing (make sure that it is not moving between 800 and 1100 rpm too) and try a bit fatter.

The only vacuum leak method that always works for me is the simple hand over the carb test.

I'm assuming the effect of a hand over the carb neck "should" kill the motor correct? If I'm off base here how do you do that test? I'll try and bump the timing to 24 but anymore than that I would be nervous.

Cup your hand to choke it out. It usually takes a me a couple of hand position adjustments. It will choke out and die with or without a vacuum leak. The difference is if there is a leak, there will be an very brief increase in rpm before it dies. It is subtle and pretty quick and you'll need to be listening closely.

Engine has to be fully warmed up. If it dies instantly. No leak and you can move on to the next thing.

I've always been able to identify if there is a leak this way, but not necessarily able to find it with soapy water, or spraying stuff around.

I don't know if this is your problem. As I said, I don't think so, but I'm still not quite following your description. If your idle is what I call "wondering" at idle, I have found that it is either a vacuum leak, or the mechanical advance weights are too week and the timing moves around at idle, especially when you put it in gear.

Good luck.

The distributor is new Firecore unit. I left the stock silver springs in on the advice of Rich and a couple others on here. Should I try playing with springs and or weights? I don't think there any options on weights for those though.

"wondering" would be an accurate description as well.

I just looked at the timing curve chart from Firecore and I have the blue springs in there as shipped from them, not the silver.

agreed, first thing i would do is go over the idle tune once it gets completely warm.
the motor should be gradually idling smoother and stronger as it warms up until it's finally completely warm.

I agree completely but it does the opposite at operating temp. The cold idle just after it runs for a couple minutes before hitting 180 and all other throttle positions are just fine. My next move is to set the timing at 24 initial, see how that goes. Then, try a different combination of advance springs and see how that works or not. I'll put the chrome box back on too as I have ruled that out as the culprit.

After that I'll wave the white flag and deal with it as is.

If the electrical stuff doesn't fix it, let me know cos there's a couple things you can do to hopefully make it better..............

Will do, thanks for the offer!

Well, it doesn't like the timing at 24, I got it to detonate on moderate acceleration. I changed the advance springs to the lightest silver springs in the kit without much of a difference there. I was home alone so wasn't able to check the in gear timing. I'll play around with it again next week.

The timing at 24 was only to see if it had an impact on your idle problem. Any change there?

That did actually help having it at 24 but when I heard it start to rattle I put it back at 20. I repeated the hands over the carb throat and it killed the motor with no brief increase of RPM.

If it's really pinging at light load like that, you need to step up fuel grade or mix imo...........

I think 24 initial would be too much timing. I would take one thing at a time here. If the RPM is wandering or hunting at idle, I would think that is a lean condition. A fat condition would load up and die at some point.

The idle screws are 1.5 out, it doesn't smell lean at all. I think the carb is pretty well dialed in overall.

I also didn't reduce the mechanical advance to it was still advancing higher than it should have with 4 more deg of initial. 91 is the best pump gas you can get at 99.99% of stations.

95 is about 5.40/gal and 100 is 7.40/gal

Generally what I've seen is as much initial as needed(or locked out)then limit the total to where it's happy octane wise...........

I’ve been lurking here listening to all the advice. I’m not a professional tuner but I know enough to keep me out of trouble. With the exception of the heads your engine is about equal to the 451 I had in my Charger. Not really a Holley guy but know enough to be dangerous.

From the latest postings it’s sounding more and more to be ignition. Having not seen your car in over a year it would be hard for me to comment. Let’s say we get together and solve this problem. Just set aside a day to give us time. Between the two of us we should be able to solve the problem. Send me a PM or text me. I know you have a busy work schedule but being retired I’m flexible.

I really appreciate the offer and short of me making a couple of distributor adjustments I will take you up on it. I feel like I am closer than I have ever been on this. I agree the that remedy lies in the ignition and all signs point to the distributor. If I don't see any improvement I'm ready to for a fresh set of eyes and ideas. I think sometimes you get so wrapped up in something you lose that perspective of being able to step back and have a different approach.

Have you verified the TDC mark on the dampener and timing tab are accurate? If not, please do so now
Some things can drive you nuts until you find them, do the basics checks now instead of later

Yep, did that when I changed timing covers as the new one had a slightly different tab.

Sometimes it takes the blinding flash of the obvious to see the problem.