Stumble

[BSB67]

372 horsepower 450 ft lbs of torque

When was that dyno testing done? What carb then? Did it stumble then? What’s changed?

 

[Aron Gleason]

When was that dyno testing done? What carb then? Did it stumble then? What’s changed?

The dyno was done last year and the guy said there's no way he could get rid of the stumble. Dyno testing was done with the current 950 double pump. Not much has changed since then.

 

[QuickBpBp]

Good luck finding the stumble... But I have to say. Sounds like a weird combo 284 484 Cam with a 950DP 28 inch tire w/4.57 gears

 

[Aron Gleason]

Good luck finding the stumble... But I have to say. Sounds like a weird combo 284 484 Cam with a 950DP 28 inch tire w/4.57 gears

Um ok. I've been told it can be tuned out. And it's not a weird combo. But thanks for the insight.

 

[QuickBpBp]

Um ok. I've been told it can be tuned out. And it's not a weird combo. But thanks for the insight.

I am not here to argue with you. I hope you get your car fixed as it appears it's been like this for over a year. What Convertor is in it?

 

[Aron Gleason]

I am not here to argue with you. I hope you get your car fixed as it appears it's been like this for over a year. What Convertor is in it?

J converter

 

[Aron Gleason]

I've gone as far as buying a pro billet msd Distributor, new wires and a better coil. And still nothing. I did get the Distributor recurved with the black bushing and 1 light silver spring and light blue spring. Initial is 20...total is 38. Wondering if I should go with a different bushing to get more Initial?

 

[Aron Gleason]

I've tried different pump cams and squirter combos with no real change

 

[1STMP]

My apologies for buttin' in.
On a smaller scale AMC 360/401
heads, Holley 750 DP.
Chased the same problem you
describe.
Tried pretty much all remedies you
mention. I found that by changing
to the yellow secondary vacuum
diaphram spring, the bog pretty
much disappeared.
Also changed to a 6.5 PV, 65 pri/
72 sec jets, pink pump cam. I left
the aquirters stock, but can't
remember the numbers.
Following this post with interest.

 

[hunt2elk]

I thought the power valve was supposed to be half of idle vacuum as a rule of thumb. I believe yours maybe open at idle and your jetting is compensating for it. You may need to go down on your pri and secondary a few sizes then stick something in there around 5 and see what that does.

Although that rule of thumb will work, it usually doesn't give the optimum results. It is not possible for the power valve to open at idle, so the valve # can be higher than your idle vac, and is on a couple of my cars. Cruise vac is what you need to concentrate on when choosing a power valve. I drive around with a vac gauge in the car to determine when I want the power valve to open. Then you can also change the power valve feed restrictors to customize how much fuel comes in when the valve opens.

 

[Aron Gleason]

My apologies for buttin' in.
On a smaller scale AMC 360/401
heads, Holley 750 DP.
Chased the same problem you
describe.
Tried pretty much all remedies you
mention. I found that by changing
to the yellow secondary vacuum
diaphram spring, the bog pretty
much disappeared.
Also changed to a 6.5 PV, 65 pri/
72 sec jets, pink pump cam. I left
the aquirters stock, but can't
remember the numbers.
Following this post with

My apologies for buttin' in.
On a smaller scale AMC 360/401
heads, Holley 750 DP.
Chased the same problem you
describe.
Tried pretty much all remedies you
mention. I found that by changing
to the yellow secondary vacuum
diaphram spring, the bog pretty
much disappeared.
Also changed to a 6.5 PV, 65 pri/
72 sec jets, pink pump cam. I left
the aquirters stock, but can't
remember the numbers.
Following this post with interest.

A vacuum secondary on a double pump carburetor?

 

[68-500]

Im sure Holley doesn’t know how t tune the carbs it designed.
I think I’d try a vacuum secondary carb. I hope you get it worked out. I was very frustrated with an afb a one time. Found it had the wrong top gasket.

 

[1STMP]

A vacuum secondary on a double pump carburetor?

My apologies. Not a DP. I stand
corrected. Thanks.

 

[Aron Gleason]

My apologies. Not a DP. I stand
corrected. Thanks.

No problem

 

[Aron Gleason]

Im sure Holley doesn’t know how t tune the carbs it designed.
I think I’d try a vacuum secondary carb. I hope you get it worked out. I was very frustrated with an afb a one time. Found it had the wrong top gasket.

I had a vacuum secondary carb years ago. Did the same thing. I was ready to throw that pos in the garbage.

 

[4speed68rt]

Too big of a carburetor for mild engine. A good 650 even a 750cfm would be much more responsive. The 950 is probably very sensitive on the secondary spring rate with that huge secondary venturi. jetting right for altitude and power valve right as per Holley recommendation would be a good place to start.

 

[Aron Gleason]

Too big of a carburetor for mild engine. A good 650 even a 750cfm would be much more responsive. The 950 is probably very sensitive on the secondary spring rate with that huge secondary venturi. jetting right for altitude and power valve right as per Holley recommendation would be a good place to start.

Thanks for the info. That carburetor is what my carburetor guy said would be good for the combination. And a 750 vs and double pump carburetor did the same thing.

 

[Geoff 2]

Beanhead,
post #21.

I have tuned more Holleys than you have had hot dinners.

That is when/how I found out that there are better carbs out there.....& they are NOT Holleys.
My current car has four downdraft Weber carbs on it, street driven, the only one in the world that I am aware of. The only one because there was never a dedicated Weber intake made for this engine. Do you think getting those tuned is done with zero carb tuning knowledge?
As for credibility/advice, I have people thanking me publicly & via PMs for my advice.
I say it how it is [ others do not like to ] because I really do not care what people think, so get used to it.

 

[Geoff 2]

Of interest...

 

[Geoff 2]

And this....