Carb Tuneing Question

Posted By: CUDAJAS

Carb Tuneing Question - 09/13/10 04:14 AM

I am working out a bog/hesitation in my carb...

Running a cuda with a 360,
Eddy torker II intake,
Eddy torker Plus cam,
The specs are as follows:
@050 Int dur. 222 , Ex dur. 234
Lift Int .447 Ex .450
Intake Centre line 107 Ex centerline 116.
About 9:1 compression.
Holley 750 vac secondary carb.
Dizzy has been recurved, running 17 initial, 38 total all in before 3000.

727 with stock converter (i know -its on the list!)
8-3/4 with 3.22s

I was running the blue accel pump cam in the number 2 hole.
The car had a slight hesitation at WOT from idle. At part throttle no hesitation.

I recently switched to the number 1 hole, from WOT that car just died. Part throtle was not much better, very sensitive.

I went to the red cam, at WOT the engine sort of coughed two or three times and took off, not bad from part throtle.

Tried the orange cam..numb one hole made it worse
Number two hole, seemed to be better, but still coughed twice at WOT.

I think I am getting too much fuel at intial tip in at WOT and I am thinking of going to the white cam (little less fuel over all).

This seems to be counter intuitive to normal carb tuning loging, but the smaller cam seems to make it better, am I on the right track???

Jason

Posted By: StealthWedge67

Re: Carb Tuneing Question - 09/13/10 04:24 AM

If it doesn't bog at part throttle, but does when you stab it WOT, then the issue is probobly with the secondary's. I'd start by trying a slower spring in the secondary vacuum canister.

Posted By: B5 Bee

Re: Carb Tuneing Question - 09/13/10 04:54 AM

Go up one size on the squirter (acc pump discharge nozzle). Most 750 vac sec come with .028, try .031.
Tip, don't overtighten the screw when changing the squirter.

Posted By: RapidRobert

Re: Carb Tuneing Question - 09/13/10 04:56 AM

too lean. exp w jets/pv also

Posted By: Magnum

Re: Carb Tuneing Question - 09/13/10 07:03 AM

Have you read this thread?

My new Holley.

Posted By: YO7_A66

Re: Carb Tuneing Question - 09/13/10 11:52 AM

""This seems to be counter intuitive to normal carb tuning loging, but the smaller cam seems to make it better""

With a street car, you want to use the smallest pump cam and squirter that does not make a bog or a hesitation. If you drive away "slowly" from a stop light with no hesitation or surge forward (too fast fuel delivery) in speed, then you are getting close on the primary side accel pump setup. Once you have this with a vacuum secondary carb, then it is time to tune the secondary spring.

That blue cam is HUGE on the primary side. It sounds like you have too small of a squirter and your using too large of a pump cam. Try testing with the white or the red cam again with a 031-035 squirter, assuming that you are using the .028. Outside weather will affect this setup, so if you are testing, then try to do it when the temps are about the same. Your setup may be different at 50 degrees than at 80 degrees.

What secondary spring are you using?

Posted By: CUDAJAS

Re: Carb Tuneing Question - 09/13/10 04:55 PM

Quote:

""This seems to be counter intuitive to normal carb tuning loging, but the smaller cam seems to make it better""

With a street car, you want to use the smallest pump cam and squirter that does not make a bog or a hesitation. If you drive away "slowly" from a stop light with no hesitation or surge forward (too fast fuel delivery) in speed, then you are getting close on the primary side accel pump setup. Once you have this with a vacuum secondary carb, then it is time to tune the secondary spring.

That blue cam is HUGE on the primary side. It sounds like you have too small of a squirter and your using too large of a pump cam. Try testing with the white or the red cam again with a 031-035 squirter, assuming that you are using the .028. Outside weather will affect this setup, so if you are testing, then try to do it when the temps are about the same. Your setup may be different at 50 degrees than at 80 degrees.

What secondary spring are you using?

Thansk for all the feed back guys.

I am currently running the purple spring... and a 31 squiter (factory setting o the 3310).

I have a 40 squirter that I could try, but that may be too big of a jump.

I have a quick change secondary spring kit, and the assortment of springs, so changing that out is not a problem.

I will also try the trick with the washers. I did notice that I am not getting the full arm movement (lots of play at WOT). When I tighten the adjustment to remove slack and set as per the factory recomendations, the arm does not ride on the cam at idle (does not shoot gas at tip in).

hope to get back at it this week! and then

Posted By: Magnum

Re: Carb Tuneing Question - 09/13/10 05:59 PM

To verify if this is a pri or sec bog. Just throw in the heavy spring to hold the secondaries closed for now or disconnect it.

As for the primary. A 40 shooter needs a hollow screw.

The washers trick is not to change any play or slack. Washers or no washers. You need no play at tip in and clearance at WOT. The washers is only effectively making the spring stronger. This will only help if the bog is from a super quick application of throttle.

Posted By: CUDAJAS

Re: Carb Tuneing Question - 09/13/10 06:45 PM

Quote:

To verify if this is a pri or sec bog. Just throw in the heavy spring to hold the secondaries closed for now or disconnect it.

As for the primary. A 40 shooter needs a hollow screw.

The washers trick is not to change any play or slack. Washers or no washers. You need no play at tip in and clearance at WOT. The washers is only effectively making the spring stronger. This will only help if the bog is from a super quick application of throttle.

Yep..have the hollow screw.

Will try with the heavier spring.

understood about the washers... I currently have good tip in and tons of play at WOT! The bog only happens when I go from idle (standing start) imediately to WOT.

Jason