trouble tuning mild 351c with holley 3310

I finally have my car on the road and need some help tuning. here is my setup all parts new/ rebuilt

71 351c 4v heads

comp cams flat tappet cam  duration 270/270 lift 519 519

rebult stock distrubtor with single vacuum advance and pertronix ignitor 3 and matching coil

autolite 25

edelbrock intake

holley 3310-c

4 speed trans

3:50 gears

vaccum about 15 at idle

Issues:

1.) bog with giving it slight gas while driving stutters, shutters, wants to die out, occasionally gives a small pop out of carb, I'm guessing this has to do with size of accelerator pump nozzle? right now has .31 in it not sure if I need to go smaller or bigger

Make sure the accelerator pump check valve is in place and functioning, check to see the over travelspring is properly adjusted, make sure the check needle is in place under the nozzle, and nothing is obstructing discharge nozzle itself. If everything is working properly the .031 nozzle should work. You could try a .028 to see where the edge is on size.

2.) spark knock at higher rpm maybe 2800-3500 while under load acceleration,   my timing is as follows without vac advance its at 12 btdc.  with vacuum hooked up 26 @ 2000rpm.   ive tried multiple combos with not much improvement.

Disconnect and plug the advance vacuum hose. With a timing light slowly bring the RPM up until you stop seeing an increase in advance. Note the amount of advance and the RPM at which the advance stopped advancing. Now repeat with the vacuum advance connected. This will tell you how much mechanical and vacuum advance you have as well as telling you a lot about the curve in the distributor. I don't know the details of the engine but, with 4V heads and the cam you have, 14-16 degrees initial, 20 degrees mechanical, and 6-8 degrees vacuum advance. If you don't want to do all of that, just drive the car with the vacuum advance hose disconnected and plugged. If the pinging stops you know the problem is in the calibration of the distributor/advance unit.

Me and my neighbor have been trying our best to get it right but he is an amc guy so he is not familiar with Cleveland.  driving it after pulling out and rpms get a bit higher it goes better but to much acceleration it pings/ rattles

plugs have a slight carbon build up. a little rich?  witish electrode tips,       idle mixture screws have been adjusted

The Autolite 25 plugs are probably one heat range too hot, try a 24. If the 25s are showing rich it sounds like the carb is rich. The porcelain ring at the center conductor shows AFR at idle. The middle part of the porcelain shows AFR at cruise. The very bottom of the porcelain (very hard to see) shows AFR at WOT. The point, on the ground strap, that you see a color change tells you something about timing. You want to see the color change at the middle of the curve in the ground strap.

appreciate any leads   hoping someone has used this carb and can get me close thanks!

Please let us know what you find out, it will help others in the future.  Chuck

 


EDIT: I looked up the 3310C, 72 primary jets and 6.5 in/hg power valve. You might try 70 jets and since you have 15 in/hg vacuum at idle you might try a 8.5 power valve (it will richen the mixture sooner). Just some thoughts. Chuck

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