Need fast help brand new 770 holley

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tekslk

tekslk

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Just installed brand new holley 770 seams to work real good, EXCEPT jump on throttle from dead stop and there is about a 1 second hesitation bog are my secondaries opening too quick or do I need more accelleration pump?
 
Well, gee could be a LOT of stuff. If you put that on say, a stock 318 with single exhaust, then, yeah, it'll bog.

More info--

car, weight, gears, engine specs, etc??

I have not kept up on Holley. Is this a vacuum sec, double pumper, what.

What you running for cam, exhaust, cid, compression, distributor, timing, advance curve........?
 
HERES THE DEAL

If it bogs upon xcerleration, it has too much pump shot/too big a shooter size.

if it cuts out for second then go's or even pops out of the carb...it's to small a pump shot 'lean', so increase the shooter...but try the the 2nd position on the pump cam 'located on the throttle lever'.

tell us what size 'number' shooter is on it now along with the pump cam color.

Then...we also need to address the power valve and when it opens by 1st taking a measurement of engine vacuum in gear @ idle 'brakes applied, then checking the factory spec installed pv rating in your carb, it should be rated at least 2'' below the vac reading you get when checking like mentioned above.

once you dial this, take it for a cruise and see if it surges a lil, if not...put 1 size smaller primary jets and test drive again and again untill it surges a lil at cruise 50mph...once it does surge...go back up 2 sizes primary jets and you've just dial the main jetting in on your new carb.
 
67Dart273 said:
Well, gee could be a LOT of stuff. If you put that on say, a stock 318 with single exhaust, then, yeah, it'll bog.

More info--

car, weight, gears, engine specs, etc??

I have not kept up on Holley. Is this a vacuum sec, double pumper, what.

What you running for cam, exhaust, cid, compression, distributor, timing, advance curve........?
Click to expand...
67 barracuda 2800lb 391 gears dual exshaust 360 30 over purple shaft cam vacume secondaries, great at idle, great response down the road, Just falls when you dead step it off idle.
 
What distributor? What is your idle speed?
I think if you bump up the initial and cut the centrifical by the same amount, I think you will find it is more responsive without affecting anything else. Always set timing before the carb because timing affects carb, carb does not affect timing. If it's lazy off idle, I would start with 18° initial, 20° centrifical, and bring it in by 2500 if it doesnt ping. If it does, slow it down to "all in" by 3K.
 
I wouldn't start changing things on the carb untill ALL other areas are in tune (especially the timing)

What purple shaft is it? knowing the dur. @50 makes it much easier to determine where the int. timing & curve should be.

Whats the manifold vacuum in gear?

Many people the 1st. thing they do is start jacking with the carb when the real problem is in the timing & curve along with lower manifold readings, I'd take mopers suggestions & get the timing & curve where it needs too be "first", run as much int. as possible, then play with the curve, I strongly suggest getting an MSD adj. dist. that is easy to dial in the curve, there set up like the old chevy point style (weights & rotor) with the springs on top, they are very simple, You'd be amazed how currecting the timing for your cam/intake & vacuum levels amazingly cure all your carb problems LOL.

The avenger carb is set up with a less aggressive metering then your adverage DPers but still gives you the holley perf., plus its a vacuum secondary, They like higher manifold vacuum signals on adverage then a true perf. holley. I still think a 670 would have run better all around, but the 770 should work fine.
 
Agreed on the timing, 14* likely isn't enough if it's got anything larger than a .474 hyd in it. The 484 and 509 need in the 20* initial area.

Once you get that dialed in, then get concerned with the squirter/pump cams. 1Wild has a good handle on that side of the post.
 
All I'm going to say is for your motor you would have been way better off with the 670 Avenger. Right now your over carbed.

After your lengthy post on carb selection, and all the advice you were given, you think you would have made a better decission CFM wise.

I hope you can make it work, but it looks like you will be buying unecessary parts where a 670 would have been a bolt on. Hopefully I'm wrong.
 
Johnny Dart said:
All I'm going to say is for your motor you would have been way better off with the 670 Avenger. Right now your over carbed.

After your lengthy post on carb selection, and all the advice you were given, you think you would have made a better decission CFM wise.

I hope you can make it work, but it looks like you will be buying unecessary parts where a 670 would have been a bolt on. Hopefully I'm wrong.
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(OUCH) nothing like getting spanked when your a grown man buy someone you dont know... youll get it worked out, i had an 850 dp on an stock 340 with a purple 509 and i work out hesitations and blubbers do your timing an listen to 1wild, youll get it. as far as im concerned you did take good advice
 
the wall said:
(OUCH) nothing like getting spanked when your a grown man buy someone you dont know... youll get it worked out, i had an 850 dp on an stock 340 with a purple 509 and i work out hesitations and blubbers do your timing an listen to 1wild, youll get it. as far as im concerned you did take good advice
Click to expand...

No disrespect or spanking was intended. Sorry if thats the way I came across. Just calling it as I see it. .02

Looking back at the post, it turned into a Holley vs Edelbrock wrestling match as usual (how rare):p

I dont think anyone concentrated on proper CFM for the application.
Do the math. As stated before, about 100cfm over the top.
I'm sure we can all agree when choosing a carb, bigger isnt always better.

Again....Hope it works out for you.
 
He needs to get other areas sorted out before worrying about the carb at this point.

It's a VACUUM secondary carb, sizing is not as important as with a DP carb. It's basically a 2bbl carb. Might the signal be stronger with a smaller carb, of course, will the guys carb work once tuned up, yes it will.

The math is good to determine a MINIMUM sized carb to perform well. If that MATH was so infallable, why does a nasty 360 with a 1050 dominator make more power and run harder than a "correctly" sized 600ish carb. Still going to follow the outdated pressure drop assumption and VE component they tell you to include?

All carbs have something redeeming about them. Everybody has an opinion and I enjoy reading the Holley bashing.

Like I say, pick you parts, pay your money.
 
crackedback said:
He needs to get other areas sorted out before worrying about the carb at this point.

It's a VACUUM secondary carb, sizing is not as important as with a DP carb. It's basically a 2bbl carb. Might the signal be stronger with a smaller carb, of course, will the guys carb work once tuned up, yes it will.


this is a very good point thanks crackedback for some good common sense very often over looked

think about it 340 6pk wow talk about over carbed oh ya its a vac secondary set up
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I don't know why everyone thinks you need to put such small carbs on, I call BS.

Now for the important stuff, Increase you pump discharge nozzle size to a .038-.040, if it still hesitates put a stiffer spring in the vacuum secondary pod. That should take care of it. I think your timing is ok but you may need lighter centrifigul advance springs. If it's a stock distrubutor try just removing the heavy spring and see how it does. If that works get some light advance springs. MP used to sell them, but they probably don't anymore.
 
Heck, if thats the case why stop at a 770 then ?

Why not put an 1150 Dominator on the dang thing ? :p
 
Johnny Dart said:
Heck, if thats the case why stop at a 770 then ?

Why not put an 1150 Dominator on the dang thing ? :p
Click to expand...

Well there does a reach a point... but look at it this way, a 1000 cfm throttle body with electronic injection would work fine on his engine. The engine will only take in as much air as it can use. Vacuum secondary carbs are very forgiving in that area. The 770 is just fine, remember the ThermoQuads? Those things were 700-850 and when properly adjusted ran great.

I personally think the generally accepted formula for carb sizing is bullcrap. It may be fine for a Chevy but Mopars make more torque thus they need more carb.
 
Vacuum secondaries cure a lot of evils, let's remember that the stock 340's came with thermoquads that were what, 850? And GM used Quadrajunks on some pretty small and mild engines.
 
Well the way the question is worded it seems to me the car ran fine with whatever was on there before, it seems to say he put on a brand new carb and now has this problem. Maybe I'm wrong, I don't know. He didn't give a lot of info.
 
crackedback said:
He needs to get other areas sorted out before worrying about the carb at this point.

It's a VACUUM secondary carb, sizing is not as important as with a DP carb. It's basically a 2bbl carb. Might the signal be stronger with a smaller carb, of course, will the guys carb work once tuned up, yes it will.

The math is good to determine a MINIMUM sized carb to perform well. If that MATH was so infallable, why does a nasty 360 with a 1050 dominator make more power and run harder than a "correctly" sized 600ish carb. Still going to follow the outdated pressure drop assumption and VE component they tell you to include?

All carbs have something redeeming about them. Everybody has an opinion and I enjoy reading the Holley bashing.

Like I say, pick you parts, pay your money.
Click to expand...

so true! why would my built slant with a 600DP??
 
I ended up putting light spring in secondariesand switching the squirter from a 25 to a 35 all is well now thanks every one. Car idles great very good response and no more bog Im a happy camper going to a cruise tomorrow.
 
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