Tuning Question on Nozzle Size, Stall etc

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J

jlhunsinger

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Hey guys,

A couple of years back bought an already built 440 Dart. I don't think it has been lightened up much so I estimate 3300 - 3500 lb range.

Parts that I know of:
Indy EZ-1 Aluminum Heads
Indy Dual Plane Intake
727 Trans with 3.55 Rear
10.5:1 Compression
Holley 850 DP, electric fuel pump @ 6.5PSI
Hooker Fenderwell Headers 2.75"
MSD 6AL and Blaster Coil

.509 Purple Cam but do not have any of the cam specs beyond that unfortunately.
I'm told it has a 1900 Stall in it but can not verify for certain.


Overall the car runs great, pulls real hard at WOT but stumbles off the line a quite a bit unless you slowly feed the throttle to it. I'd describe the best results I achieve as going from 0 throttle to 25% to build some momentum (10-15 mph) then feed the remaining 75% to get to WOT. Suggestions have been all over the board on how to fix it so I'm curious what some of you more educated/experienced guys can tell me.

This past weekend I pulled the plugs and noticed they were dark...not oily though. I assumed it was a rich idle condition since I mostly idled or part throttle around the neighborhood the run before to set the pads on the disk brake conversion.

The Holley has a 5.5 Power valve so I hooked up the vacuum gauge to see approx where I'm at. Had all four corner idle screws at 1.5 turns. With the vacuum gauge and making 1/8 turn adjustments to maximize vacuum at idle I ended up around 1 and 1/8th turn which got the idle vacuum hovering around 11-12. Before adjusting it was down around 8-9 so I'm hoping that rich idle adjustment and maybe the PV caused the plugs to be so dark..?

The float levels are set correctly. The jets are 80 in primary and 81 in secondary. I have the 35cc accelerator pump setup with 31 nozzles in both primary and secondary. I was hoping to avoid buying an entire tuning kit to dial it in. I don't have to 100% perfect high performance, I just want more crisp throttle response off the line. Any suggestions on most cost effective way to dial this carb in based on what I'm working with?
 
are you stumbling off the line in the primaries? Pump shot comes to mind, thats the EZ one. Adjust the pump arm so its just touching, then abck of 1/8 turn. you want like a .005 feeler gauge in there when its sitting there. Remember the shooter dictates how long (duration) the shot is, not the volume (thats the cam). You may also want to check your check valve under the front shooter. If that leaks, youll get a late shot as it has to fill the passage again. There are 3 screws on the pump cam itself. You can adjust the cam to get you an earlier shot somehow, but I think its volume related. Also check advanve plate in distributor for snappy action, not a gummed up crawler.
 
I'm running a Proform 900 with a 50 cc front pump and 37 nozzle with a home made cam and 30 cc rear with 32 nozzle on a 452. It's just about right with the engine up to temp but I'd like to use a hollow screw on the front nozzle but all the ones I find are oversize. That no stall converter is going to be your big choke point. Run as much initial as you can and as big a shot as it will take. A vacuum secondary would also be a good way to get out of the hole..... You can compensate a little on the bottom by under carbing it and slowing the secondary opening. I think you would be surprised by a good 3310 on that thing.
 
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Have you checked your transfer slots yet?
AJ should be chiming in shortly
 
What's your initial and advance timing? I've seen the same problem with not enough initial timing or the wrong curve
 
I hate to admit this, but I've got no idea what the timing is right now. I'll do some research on that, figure it and then bump this thread when I know more. Thank you all for the input thus far!
 
Yea, that could very well be the problem, but get your timing sorted then try it, if it persists then it has to be fuel related,
Also I'm pretty sure the 509 cam would like more gear and converter, but if that's what you have I'm sure it will be fine! Good luck!
 
ok get the timing correct first like was already said. adjust pump arm with the carb fully open and get .015" clearance on both front and back. with the motor running at idle open the carb up as fast as you can and leave it go straight back to idle right away. if it stumbles install larger nozzles. do it again. if it still stumbles install larger nozzles. now keep doing this until the stumble is gone. you can go up in size several each time. now head out to the road and nail it off an idle. if it stumbles up the nozzles size until it's gone. after a nozzle of .045" you need to install hollow nozzle screws.
 
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