CAM SURGE

[Walden02]

I have 350, not sure of the cam size, just installed a Edelbrock AVS2, she runs great, clean, but I have cam surge now. I did not have this before when I had old carb that was running super rich.
Any ideas on what to do to reduce the cam surge? I checked timing and vacuum all good. Could it be torque converter issue? I do not know a ton, newbie trying to learn. thanks

 

[Bextreme04]

I have 350, not sure of the cam size, just installed a Edelbrock AVS2, she runs great, clean, but I have cam surge now. I did not have this before when I had old carb that was running super rich.
Any ideas on what to do to reduce the cam surge? I checked timing and vacuum all good. Could it be torque converter issue? I do not know a ton, newbie trying to learn. thanks

Have you already adjusted the idle mixture? You should get a tach and adjust using the idle drop method.

Set the idle mixture screws lightly bottomed out(all the way in clockwise) then back them each out 1 turn.

Start the truck and let it fully warm up.

Make sure the choke is off.

Set idle to ~750RPM.

Adjust the idle mixture screws out(counter-clockwise) 1/4 turn at a time until the idle tops out and starts dropping again.

Adjust the idle set screw as you go to make sure that it stays within ~100rpm of the 750rpm you are looking for.

Once you have found the amount of idle mixture adjustment that yields maximum RPM, set the idle RPM to exactly 750RPM, then you want to screw the idle mixture screws in(clockwise) until the idle RPM drops to 650-700RPM.

I actually do this final adjustment with it in gear, parking brake set, wheels chocked with BIG blocks. Make all adjustments small and carefully.

Once the final idle drop is set to 650-700RPM in-gear, I put it back in park and adjust the out of gear idle back to around 750RPM, then make sure everything feels right when driving it around. Once that is done, you can set the high idle and choke setting the next morning after it has fully cooled down.

 

[Walden02]

thanks I will give that a try

 

[xm20k]

As the engine idles up and down from the chop of the cam, is it trying to pull/lunge forward at a stop thru the breaks? If so, that's the torque converter needing to have more stall.

 

[Ricko1966]

I have 350, not sure of the cam size, just installed a Edelbrock AVS2, she runs great, clean, but I have cam surge now. I did not have this before when I had old carb that was running super rich.
Any ideas on what to do to reduce the cam surge? I checked timing and vacuum all good. Could it be torque converter issue? I do not know a ton, newbie trying to learn. thanks

What's your idle rpm. And check to see that your vacuum advance cannister is staying fully deployed,if it's moving in and out you need a can with a lower vacuum rating.

 

[Walden02]

As the engine idles up and down from the chop of the cam, is it trying to pull/lunge forward at a stop thru the breaks? If so, that's the torque converter needing to have more stall.

Is there a way to determine torque converter size without pulling tran?

 

[Sad Sack]

Edit

 

[xm20k]

Is there a way to determine torque converter size without pulling tran?

Not by looking at it as most of the lower stall speed converters will look very similar to stock.
If it does need a converter because the cam is just a bit rowdier than stock, you may only need something in the 2500-2800 range which should be on the cheaper end when it comes to converters. If it needed anything bigger you would have the same issue lunging forward while sitting at a stop in gear as well as very little to no vacuum assist on your brakes.

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[xm20k]

Just to be sure we are talking about this, correct?

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[Ricko1966]

Is there a way to determine torque converter size without pulling tran?

You can check and see if the vacuum advance is advancing and retarding at idle real easy. Why don't you give that a check.

 

[Zelph]

Why not throw on the old carb and see if the issue goes away?

just installed a Edelbrock AVS2, I did not have this before when I had old carb that was running super rich.

 

[Ricko1966]

Why not throw on the old carb and see if the issue goes away?

I think it's just an adjustment issue personally. Changes carbureator and suddenly has a cam and converter issue.Throttle plate open too far,mixture too lean,I also have a feeling the vacuum advance is dithering. But let's let him pursue the converter for a while,then we can get back to easy stuff like tuning.

 

[xm20k]

Well, he never answered the question as to whether it was while cruising (tuning) or sitting still (TC) and no cam specs, and others seemed to have the tuning part covered so I figured I'd cover the issue if tuning wasn't the issue. I may be wrong, but I've seen a lot of cams installed with no consideration for stall.