Carb tuning

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JimmyV

JimmyV

MOPAR!!
Joined
Mar 28, 2006
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Hey guys as some of you may have helped me a while back i got the car running and driving have a holley carb on it thing runs out great but if i am cruising as well as sitting at a stop and mash it to the floor it cuts out for a second then kicks in and takes off i checked the vacumm and put a smaller power valve in it and it helped alot then put a bigger squirter in it and adjusted the secondaries and again helped out alot but it is still doing it ever so slightly..any ideas. Tricks. Tips?? Anything helps

its a holley double pumper 650 cfm
 
It might be a bit of a small car for my setup but just trying to get it as good as i can little tight on fundage right now! And also has anybody ever installed one of those proform 750 main bodies..are they worth it or just buy a hole new carb?
 
Sometimes if you give the front accelerator pump arm more clearance it can help.
It gives the butter flys a chance to open up a little more before giving the shot of fuel.
Try to tighten the lock nut on the accelerator arm.
It makes the bolt that hits the pump arm a little shorter giving you more space between the arm and the bolt.
If this doesn't work i would try different pump cams.
Keep trying.
Once it's right, it will be worth it.
 
Sometimes if you give the front accelerator pump arm more clearance it can help.
It give the butter flys a chance to open up a little more before giving the shot of fuel.
 
You could try this. It worked for my set up the blue one in the number 2 position
http://www.holley.com/20-12.asp
I did this and also put a lighter spring for the vac secondaries. When i had my engine dynoed Brian at IMM and Rob (crackedback) had me do this.
 
What jets are you running, i have found my 650dp on my mild 360 magnum likes a 70/76 split from the 67/73 factory, you may want to jet it up & see, if its an abrumpt stumble then its most likely a "lean" transition, you have already mentioned that you installed a "larger" squirter, PV with a weaker spring & they helped, both of these changes "fattened" things up a bit, so your going in the right direction, thats why i say jet it at least 69/75 or 70/76 & try it, your stumble may magically disapear. As for the 750 PF MB, i'd say "yes" on your combo, but you'll be mighty surprized how well those 650dpers run once dialed in.
 
If I remember correctly Holley recommends .0015 clearance on the accelerator pump arm for initial clearance as a starting point. T67 is correct sometimes you need to get the butterflies cracked slightly before you have the squirter kick in. Also you might also eventually consider a 50cc accelerator pump if you don't already have one on it.
 
JoeDust451 said:
What jets are you running, i have found my 650dp on my mild 360 magnum likes a 70/76 split from the 67/73 factory, you may want to jet it up & see, if its an abrumpt stumble then its most likely a "lean" transition, you have already mentioned that you installed a "larger" squirter, PV with a weaker spring & they helped, both of these changes "fattened" things up a bit, so your going in the right direction, thats why i say jet it at least 69/75 or 70/76 & try it, your stumble may magically disapear. As for the 750 PF MB, i'd say "yes" on your combo, but you'll be mighty surprized how well those 650dpers run once dialed in.
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ok i am ordering cams a bigger pump and a jet kit..where should i start first just want to have it all ready to go incase i need them i dotn have to wait around i am running the 67/73 right now i am assuming i change both jets seeing as how there are 2 in each metoring block..
 
Jimmy, What is your vacuum reading like "in gear", my set-up is alot milder then yours, i'm getting 17 inches. of vacuum so i'm pulling a stronger signal, In your cases, you may also need a larger pump shot too like .031" squirters F&R.

You want to change all 4 jets, 2 fronts/2 rears, just try 70s in front & 76s in the rear. I would leave the pink cams in it for now. You really don't want any slack between the arms, you just don't want them to bottom out at WOT, its ok to have some preload on the arms, your looking to have about .015" clearance at WOT, in all my years of messing with these holleys, the pump arm adj. is not as tricky as alot my think, they don't have to be "perfect" on the adj., just alittle preload (so theres no slack) & not bottom out the diaphram at WOT & make sure they flow a steady steam of fuel, that simple, at this point if your still having stumble, then its in the transition over.
 
JimmyV said:
ok i am ordering cams a bigger pump and a jet kit..where should i start first just want to have it all ready to go incase i need them i dotn have to wait around i am running the 67/73 right now i am assuming i change both jets seeing as how there are 2 in each metoring block..
Click to expand...

start with 35 shooters front and rear w/orange cams no.1 position.

automatics usually take a couple/few sizes 'larger' shooters, add a high stall and the need for cover during transition increases.

the last 440 I did with a turbo action 3200 stall required [trying to remember] 37 or 42's, but it had some cam..
 
i have a 31 squirter in the front left the rear alone..i dunn kind having fun messing with the carb and trying stuff out so i will just wait for the parts to get here and probably start with the jets..has anybody ever had to change the secondary accelerator pump to a 50cc or should the secondary one stay at 30cc
 
Keep the 30cc pumps on both ends, that carb is relatively small & won't require all that hit, the only reason i see you needing a 50cc on any end would be if you were running a 5500 stall & shifting at 8000 rpm, running a huge cam & foot braking it, but at that level you'll have at least a 750dp or bigger, i don't really see you needing any larger then 31 squirters F&R, so stay with the 30cc pumps, I think you'll like the orange/red or even the clear cams, the only problem is you only get 1 of each unless you buy 2 sets.
 
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