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357 c.i.,750DP
bought motor from another car and ran fine.

Problem is if I open the secondary's quickly it dies or stumbles bad.Otherwise it starts right up great throttle response unless I hit the secondary's quickly.

I did replace the accelerator pump on the secondary's because it was leaking.Original was black,new one is green.Are they different and if so what pump do I need?
Don't say the black one please.
Thanks Mike

 

When you say black/green, exactly what part are you talking about?

 

The diaphram in the accelerator pump.

 

Make sure you didnt replace a 30cc with a 50cc.

What size shooters and jets are you running?

 

OK, sounds like you still aren't getting a secondary pump shot. Do you see the streams in the secondaries with the engine off?

 

bluegrazz I'm not sure about the jets,but it ran fine before I installed it in my car.It is running a little rich cause the plugs are black.The original diaphram is gone so I don't know what size it was.Got new one from A.Z.so who knows,it was in a kit that only had one where as my carb obviously has 2.So that may be it.
fleet,I do see the stream with the engine off.

thanks guys keep the info coming

trying to make the Sep.7 t&t at M.I.R

 

You might have to play with the accelerator pump cams, pump stroke length, squirter sizes etc. to get this one put to bed. you might also have to go a 50cc pump on the secondary.

 

Going to the speed shop today to get an assortment of parts.
Anymore suggestions welcome.

The more I think about it I may have the wrong diaphram in there because it was fine till I replaced that.Will have to get both and try them.

thanks again,the suggestions coming

 

So was the carb on 357 you bought, or did you have the carb already?

Check the jet size and the squirters. Then adjust the accelerator pump so it dosent have any slack, but is not compressing the diaphram. Check your float levels also.

 

The carb came on the motor.
Checked diaphram today and it had a 30cc and I installed a 30.
Gonna check squirter size tomorrow.But motor ran fine in other car.

 

What about your fuel system. What psi are you running?

You did check and re-adjust the floats right!

 

I have the stock electric pump from a Buick G.N.,3/8 supply and return.
7p.s.i.at the carb.
The motor had a Holley manual pump when I got it,so maybe that change could be affecting it.
Will check floats today, but my sights are hard to see through.

 

Check the rear float levels. Might have a stuck float from the sec bowl.

 

So you do have a fpr on it?

See through sight plugs are ok, but they fog up over time. Get the car level and just pull them out. What few seconds it takes to remove the stock style isnt a big deal. I had the clear on my old carb, but left the original on my new 750 Street Hp.

The rear float might have stuck while doing the swap. You would be fine at idle and crusing, soon as the back opens then you would go rich.

 

I have the Mallory return style FPR.
rear squirter is a 28.
Did not get a chance to check float level,but I am leaning toward that since the motor sat for about a year waiting to be installed.
And I will be installing original plugs on carb,the faded clears look bad and have to be removed anyway.
I will post results of float check as soon as I finish installing the wife's washer and dryer.

Thanks again
Mike

 

You might want to check the needle and seat for dirt while your at it.

 

Ok.I checked float levels and the back was a little low so I raised it to the bottom of sight(bought new ones).This got rid of the dying out but it still has a stumble for about a second.
It has a red pump cam on the rear and 28 squirters,which are very touchy.Should I go with a bigger squirter since it seems better since I added fuel?
I am going to play with the pump lever adjustments also and see if this helps.
I know this is trial and error but it is so much easier with someone pointing in the right direction and the help is much appreciated.

Thanks again Mike

 

OK
Just checked jets.
70+71 pri
77+78sec ????
Changed to 69+69pri.
73+73sec

Just the slightest hesitation now,almost non-existent.
Gonna try a bigger squirter and lower the float a little bit.
Squirters are now 25 primary and 28 sec.
Guy at speed shop told me pri. should be larger,he had a similar combo and ran a 35pri. and 31 sec.
Sound right?

update:adjusted timing from approx. 30 initial,40 total to 25 initial ,35total
Idles better,feels stronger,almost there,still gonna play with the squirters

 

Go to a 31 squirter in front and make sure there is no slack in the accelerator pump arm. You should be good to go.


(OK
Just checked jets.
70+71 pri
77+78sec ????
Changed to 69+69pri.
73+73sec)


So were the jets mis-matched from side to side?

 

Got a set of 31 and 35's I'm gonna try .
There is no slack in pump arm.
Yea they were mismatched from side to side and was burn your eyes rich .Smells better now runs better now just need to play with squirters and hook up the wideband.

 

Sounds like someone tried to cheap out on jets. You never stagger from side to side.

Let us know how it works out for you.

 

35 squirter up front 31 in rear
69 jets up front 73 in rear
timing 25int-app 38 all in

no hesitation,but doesnt leave very hard.
t+t'd yesterday and best 60' was a 1.83,footbraking at 1,500 anythig higher 60' went up.
Did get a best of 13.23 @ 103.19

Thanks for the help

 

You shouldn't need a 35 squirter up front. Assuming this is a 4779, stock was .028/.031 (http://www.holley.com/data/TechServi...%20Listing.pdf - if it doesn't take you directly to the numerical listing, click on "Tech Services", "Technical Library", and "Carb Numerical Listing").

38 degrees total is usually too much for a SBC (I assume you had the vacuum advance disconnected when checking timing). Back it off to 34-36. This is assuming that your timing mark is accurate - only way to know is to use a piston stop and verify it. Or, if you compare runs with known timing variation and your current timing setting is verified to be the one that makes the most power (as measured by MPH, not ET, on the track; or on a dyno).

The floats should be set so gas just barely dribbles out of the sight plug (or barely visible with clear sight plugs). If changing the float level from there makes it run better, you've got something else wrong (like jetting). By the way, those clear sight plugs are for tuning only, not for running. If you're leaving them in there, they are going to deteriorate and fail on you.

The power valve restrictors are equivalent to ~8 jet sizes. So, if 69's are the right size in the front, you should have at least 77's in back. Stock jetting for a 4779 was 70-71 in the primaries and 80 in the secondaries.

Of course, if you're traction limited, you might be better off the way it is.

 

Yeah I had a 31 up front and changed to a 35 trying to get it to leave harder,but change.
Timing marker is probably off,I gained almost 4MPH going from 20int to 25int by the marker.It has about 12-15 degrees of advance,which I will lock once I get it dialed in.
Had 70&71 up front and was burn your eye's rich.The 69's helped.
I agree the secondary jets may be small because it just feels sluggish and it did have 77&78 to begin with.
This carb was on the motor when I bought it and I'm trying to dial it in.
Traction is not an issue,I'm trying to leave as hard as I can.

Thanks,Five7 and keep the info coming.

The floats are set as you describe.

 

Going from 71 to 69 primary jets shouldn't take it from "burn your eyes rich" to okay. Under what conditions was it "burn your eyes rich"?

What PV does it have? I assume it has a primary PV only (should have verified that before making jetting recommendations).

 

It was real bad at idle.I know 2 sizes isn't much but it did make a noticeable difference,at idle anyway.

P.V. only in primary and not sure what size,almost gaurantee has not been change from original.

I have read the sticky but car is not tagged so I don't have the luxury of street tuning.

I bought a wideband but it does not work properly so I'm in the process of returning that now.

I know the heads are killing me from making max power but I am so close to 12.99 .
The intake manifold is a "Professional Products" copy of the Edelbrock air-gap.

Thanks again

 

Did you try flashing the converter? Did you adjust the air screws with a vaccum gauge?

You need to know what size PV you are running. It should be a 6.5 stock.

 

How do I flash the converter?I was footbraking at 1500rpm then flooring it.Going to do a search now.


Just got a vacuum gauge and will be working with that soon.

I will also pull front off and check P.V. size.

Next time out I will also try 70's up front and 78's out back.

I now recall reading that the main jets do not come in at idle so maybe the float level change helped the smell at idle?

Thanks

 

The main jets don't affect the idle mixture unless the throttle blades are open too far at idle and fuel is being drawn through the booster venturi. The Holley tuning sticky details how to set the throttle blades for proper idle (have to have the carb off to do this). Having the float level too high can enrichen the idle.

Do you mean "Professional Products" intake? Edelbrock makes more than one style of air gap manifold, having both the stock replacement type Performer and the higher powerband Performer RPM in the air gap style. Is yours the Crosswind or Cyclone model? I'm guessing Crosswind.

If you are footbraking to 1500 RPMs and have a 3000 stall converter, you are "flashing" it. When you foot brake to full stall RPMs, the car can be a little sluggish off the line. Braking well below the stall RPMs tends to allow the converter to "flash" to a slightly higher RPMs when you let go of the brake and mash the throttle.

 

Five7 you are correct it is a "Professional Products" manifold.

Not sure which one,as with the rest of my set up,it was here when I bought it.

The primary float was a little high at first,which I set at same time as changing the jets,so that is where I probably threw off my train of thought on that.

I will still check the throttle blades per the sticky to be sure.

And yes the higher rpm I left at the higher my 60' was.

 

I was thinking that the brakes would only hold on the line at 1500. Anything more was pushing through.

I was suggesting going from about 100 above idle then flooring it. I wasnt sure if you had tried that.

 

Yes I launched anywhere between 1000-1500 with similar 60'.

And yes looking back at my slips the 3rd pass,which I left at about 1000-1100 was .01 faster than the next 2 where I launched at or close to 1500.

Standing on the brakes I was able to get it to hold about 1700 for the last 2 yellows but that was my worst 60' a 1.89.

This was my 1st time at the track in 3 years so my mind was going 100mph.

There was no hesitation from carb at all,thanks Bluegrassz, I just need to fine tune it now.

Thanks to all
Mike T

 

Is your car lowered? Are you running LCARB's? What kind of tires are you running?

 

Car is stock height,Lcarb's yes,M.T. drag radials