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Carb for Stan's Mutt...

7K views 75 replies 15 participants last post by  Tom Mobley 
#1 ·
The mutt...1970 Chevelle clone SS
454, .030 over, '70 model LS6 rec. port heads, big valves extensive porting. Guessing 10.1 compression maybe a tad less ...Comp cams N+LS6 solid lifter cam
part #11-671-4. Turbo 400, 2800 stall conv. , 3.31 gears, 245/60-14 BFGs,

Going with a vacuum secondarys for sure... need opinions for "specific carb." with cfm and part numbers if possible.

Thanks...Stan
 
#5 ·
I'd run a 780/750 Holley. Good enough in 1970, good now.
I agree with Tom of its only street driven.
Holley 750 3310 or a 770 Street Avenger.
I agree, shouldn’t be too hard to find an old 780 vacuum secondary. If you’re not patient, or can’t find one, pick up a used 3310...looks almost correct.
 
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#23 ·
Hard to beat a 780...it used to be the only Holley carb I would own...

I was and still am a big fan of Quadra-Jets too.
I built a bunch of them in the 23 years I was in the garage business.

Not nearly as many Holleys though...as I worked on mostly factory stuff. Of course when I did work on a stock Holley I just kitted it...no mods. Take it apart, carb cleaner over night, put it back together.
 
#8 ·
I have a 770 Ultra Street Avenger...for my wife's chromed out GTO custom 400 engine, runs great. But it's kinda gaudy for a stock looking engine bay.

I'll have a dropped base air cleaner..and the engine was dynoed with a RPM Air Gap and a 1/2 inch spacer. Not sure if the hood will close on the 70 cowl hood(no flapper)yet...engine isn't installed.

Looks like this: https://www.holley.com/products/fue.../avenger/ultra_street_avenger/parts/0-86770BK

My machinist likes 850's...I'm not so sure. But considered this: https://www.summitracing.com/parts/hly-0-80531?
seid=srese1&gclid=EAIaIQobChMIrZrlhLyd5QIVSr7ACh1V6AXyEAQYASABEgJPGfD_BwE

I dont see a 770 in the Dichromate finish which would probably look better on this stock engine well.

I don't think the Mutt cares if it has a shiny or a dichromate carb hidden under it breather...so long as it hauls A$$ and is well mannered.
 
#10 ·
For those that have late model Holleys, "and" the old carbs that we had back in the day...are the new ones as good as old carbs?
If it was me I would stay away from that 850. All that tries them including myself seems to have problems with them.
Just use a 3310 than.

I have used several 3310’s the last ten years on different BB’s and feel the quality is as good as in the older ones. I use to convert them to 4150 with holleys kit https://www.holley.com/products/fue...ts/metering_block_conversion_kits/parts/34-13

I like the hex bowl screws over the older ”screwdrive” version.
 
#14 ·
I have had several 454s recently that I've converted over to Edelbrock thunder avs2 in the 750cfm configuration with great success. I was a tried and true Holley guy for years, but just got tired of messing with them to really getting them dialed in.Annual boosters in these new Edelbrocks really improved throttle response 100% over any 780cfm holley I have ever tuned. Bolt on and go for the most part with some choke tuning for colder climates.
 
#15 ·
The new 770 street avenger is not calibrated the same as the old 780. The 780 had dog leg boosters, the 770 has straight leg boosters. I would go with a Quick Fuel HR780 or SS 780. But then relocate the IFR to the lower position on the metering blocks, change the emulsion to 2 open instead of 3 or 4 as they come, install transfer slot restrictors in the main body for primary and secondary side of .081". Then tune from there.
 
#18 ·
Thanks Pockets..
Exactly what I had in mind...or wait, I do have a good quadra-jet, it's simplier...lol.

Just kidding.... but I can see I need to bone up on Holley emulsion and IFRs...before I can tune a Holley.

I was just planning on buying a new carb., most Holleys I have bought used, have been screwed with so much they would take a month to tune them out.
 
#17 ·
Here is my take on VS Holley's. The 850's such as the 80531 and the 80870 are both good carbs it just takes time to tune them. The other is a the 3418 Vette 850, but like the other guy said if you are required to use a specific number Holley then I would look at the QF or one of the aftermarket VS carbs. One thing to make sure of is that the there is the little brass tubs sticking out of the RH side venturi if it's not there then the secondary side will not open right. There are places on line to fix that but if you get a new carb just make sure it's there before you run it as after that you will own it. That's the only problem I see and you could always get an old 3310-1 and reuse that as that is one of the best VS carbs out there.
 
#20 ·
The 3310-1 and the GM OEM version with the GM number ending in "EH" are th only 3310's with a secondary metering block with replaceable jets, the rest use a fixed orifice plate for the secondary, unless you buy the Holley conversion kit and install it. The 3310-2 or 3, etc. have fixed jet plates in the secondary. Choose carefully.
 
#21 ·
Funny, I just bolted on a prepped 850 DP and it ran mint. For me, its a track carb tho, not a street carb. I'd choose a new dichromate 3310, although I like the "carter thermoquad" design of the new Street Demon series.

PS I'll be running a Qjet for street use. Both the 3310 and Street Demon are modestly priced carbs.
 
#28 ·
Here on TC there are more than one Member who have the Street Demons

Read all the Threaqd and my # 14 Post
https://www.chevelles.com/forums/45...-holley-carb.html?highlight=Street+Demon+Carb

Also
Re: 396 carb recommendations
Russell
Replacement Carburetor Replacement Carburetor - Chevelle Tech
I will be buying one of these to replace my Holley 750 DP
Demon Carburetion Street Demon Carburetors Q jet type JEGs # 333-1904 $ 346.95
http://www.jegs.com/p/Demon-Carburet...75515/10002/-1
750 cfm 1-11/16" Primary Throttle Bores / Universal / Vacuum Secondary / Electric Choke / PolymerFinish
The DP Holleys give very poor mileage even cruzin on the hwy at 70 miles an hour and I have had it rebuilt many times,
plus the Demon Qjet has Dual mounting bolt pattern(square/spread bore) fits any street 4-barrel intake manifold
is reason I listed it as my # 1 choice along with the fact the car could/should run on the smaller front primaries when cruzin on hwy !
Look at the 2 videos on JEGs site plus this You Tube one http://youtu.be/HoR0uZLBJp0
RE: adjustment required before bolting onto Intake
and Here are some TC Threads on them Need New Carb - Chevelle Tech
https://www.chevelles.com/forums/13-p...ml#post5870665

https://www.chevelles.com/forums/13-performance/563850-need-new-carb-2.html
# 16 Re: Need New Carb MY Post on TC Need New Carb - Chevelle Tech
I really like my polymer Street Demon. It's been very easy to adjust and I plan to tune it more in the spring.
I have run double pumpers and they do seem to get very poor mileage. Big Al SleeperBBC
# 17 Re: Need New Carb So Big Al do you have the one I mentioned in my post # 1
1. Demon Carburetion Street Demon Carburetors Q jet type JEGs # 333-1904 $ 399.95
Demon Carburetion Street Demon Carburetors | JEGS
750 cfm 1-11/16" Primary Throttle Bores / Universal / Vacuum Secondary / Electric Choke / Polymer Finish
Yes the DP Holleys give very poor mileage even cruzin on the hwy at 70 miles an hour
and the Demon Qjet has Dual mounting bolt pattern(square/spread bore) fits any street 4-barrel intake manifold
is reason I listed it as my # 1 choice along with the fact the car could/should run
on the smaller front primaries when cruzin on hwy !
Greg.
 
#31 ·
But I wouldn't fear a 4779, 4780, 4781. My 4781 850DP is getting better fuel mileage on my 496 than the 3310 did on the 467 that it replaced. Hard to believe but I can't argue with the fuel gauge.

My results aren't typical and I've done a lot of fine-tuning to the new engine, though.
 
#32 ·
Same here my 1000hp gets better mileage than a new 3310 I tried just to see if it was better.
 
#36 ·
Ok ...well there's a lot of information here. Seems like a 780 cfm is a good all around choice. ...and /or up to 800 cfm.

Problem is there's a lot of carbs to choose from these days...I was thinking Holley to start with, but new 780 Holleys arn't available....while Quick Fuel and others? ........maybe are.

I guess ...my question at this point is "exactly" what NEW carburetor would YOU buy for the Mutt's engine??



To refresh what the engine is:
The Mutt...1970 Chevelle clone SS
454, .030 over, '70 model LS6 rec. port heads, big valves extensive porting. Guessing 10.1 compression maybe a tad less ...Comp cams N+LS6 solid lifter cam
part #11-671-4. Turbo 400, 2800 stall conv. , 3.31 gears, 245/60-14 BFGs,

Dyno specs.. 532hp@5900 rpm and 499 ft. lbs torque (forgot rpm for torque)...with a non tuned Holley 850 double pumper. (other than air mixture)

Going with a vacuum secondarys for sure... need opinions for a "specific carb."



This time around let's try NOT USED, but NEW off the shelf from Summit or Jegs.....I don't think I want to refurbish a used carb right now. Please list only ONE carb...

It would be interesting to know what the deciding factor/factors were for the ONE carburetor you narrowed your choice down to....

Thanks...Stan
 
#41 ·
This is my next Carb for my 468 ci 550 hpish which has a Weiand Stealth Hi Rise Dual Plane 4150 Carb Flange/Sq Bore/OvalPorts# 8019

https://www.jegs.com/i/Demon-Carburetion/333/1904/10002/-1
Vac Secondary / E Choke / Ploymer Middle Section / Dual Mount bolt pattern (square or spread bore) fits any street 4-barrel intake manifold
/ Integrated 700R4/200R4 transmission kickdown cable mounting location

You should not need any Spacer for Vapour Lock

Will provide Good Gas Mileage and Performance IMHO as it is like, but better than a old Quadra Jet

Check out the Videos
 
#44 ·
Depends on the purpose of the car

Street/Strip then the 750 CFM Street Demon should be fine

Strip Only then a Larger CFM Carb would fit better for yours

I have these Heads = Edelbrock Perf RPM Alum # 6045 / 60455 http://www.jegs.com/i/Edelbrock/350/60455/10002/-1
290cc Oval Port - Large / 110cc Combustion Chambers / Exhaust Port Shape Square
/ 2.190'' Int/1.880'' ExhaustValves / 1.550'' ValveSprings, .700'' Max Lift 7/16'' Rocker Studs Stroke = 4.000
CAM https://www.howardscams.com/hydraul...-502-mark-iv-2400-6000-howards-cams-120255-12
Specs rpm 2,400 to 6,000 / Valve Lift Intake .578 Exhaust .618
Duration 284° Intake 288° Exhaust
/ @ 050 Intake 231 Exhaust 235 / Lobe Sep 112 / Intake Centerline 108

I have run 750 Holley DP 4150 Carb no choke for the Street/Strip and got good Times but not great Gas Mileage
now have a 950 Holley Pro Systems 415Q no choke http://www.jegs.com/i/Holley/510/0-80805RDX/10002/-1

I drive my car on the Street & Hwy on 100+ Mile one way Trips to Relatives Etc....
on a Monthly if not Weekly Bases when Weather is Good
and then to the Track on the Weekends Sat or Sunday dependant on the Weather

Going out today for a End of Season Run for Fun before she gets put away for the Winter
 
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#45 ·
Hello again Chris and thanks...

I shifted gears on this a little...and I'm trying to decide what NEW carb I might get from Summit or Jegs. (see Post 36) that members like for these Chevelle bbc's.

There's so many carbs out there...and I've got a whole car to bring up to speed. I decided that I would like to "not" have to spend an extended period of time on "just" the carb.

I'm getting ready to rebuild the rear end and add a posi right now....then install the engine.

Thanks..Stan
 
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