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Old 03-18-2014, 05:21 PM
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Jet or squirter adjustment?

Hello. New motor, working out the bugs. Its 355, 10.1 comp, rhs aluminum heads with 180 runners, still just edelbrock performer, Harland sharp 1.5 roller rockers, xe284 cam, and the carb is 3160 750vs. I'm running a little lean after reading plugs, wondering which would help more and how to start. The idle is 1200 or so in park, 750-850 in gear. But to achieve this I have to have the mixture screws 4 turns out. From idle, when revving in gear if not careful it has the slightest bit of hesitation. Then revs extremely fast. (what we designed te motor for Mostly, what I asked for). I believe last I checked te timing was 28 Or so initial, 35 by 2500. Pretty much locked out. And it'll pull really strong but feels it is holding back a little. It'll keep going well past 6k if I allowed. The plugs read just literally a hair lean. It still has 72 stock jets, and all rest stock. Other then cam gear I went to second slot which did help a good bit.

Rest is 2800 stall, 400 trans and 4.11 rear.

Which sounds like it needs messed with? My friend has some 75 jets that he is gonna let me try this weekend.. think that could help? Or squirter size first? Or both? It is a 70 c10 that shouldn't weigh more then 3300-3400. No vacuum advance, plugged off. It's a weekend toy, not a dd. thanks!

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Old 03-18-2014, 05:39 PM
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*4160 Sorry guys.
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Old 03-18-2014, 05:54 PM
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if its when you first hit it its NOT the main jets so the squirters are the more likely culprit. does it have a real strong idle? if its weak as in surgy the idle circuit could also be really too lean. if your at 1200 and it drops to 800 in gear that raises lean idle questions. it sounds like your timing is ballpark total may be able to be closer to 38 but thats neither here nor there.
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Old 03-18-2014, 06:29 PM
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Idle is pretty strong, but should I go further then 4 turn just to try? How far out does The screw adjust? cam does have 110 lobe Sep, 285 29? Duration and I think like 508 and 510 lift. My machine shop, guy who designed it with rhs and comp, thought thats about how the idle was gonna work. But try going more out? Was concerned I was going to unscrew completely. the squirter is indeed the stock squirter. And as I said, I went to the second hole on the cam gear and it seemed to help a bit.

Last edited by KyleG; 03-18-2014 at 06:41 PM.
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Old 03-18-2014, 07:29 PM
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Sounds like two issues to me.

Needs a larger squirter to eliminate the hesitation when revved.

You may need to slightly open the rear throttle blades just a bit and close down the front blades. Screw for the rear blades is accessed from the bottom of the carb near where the vacuum pod rod connects to the rear throttle shaft - - you can see the end of the screw against the throttle stop for the rear blades from the top but you can't adjust it from the top, it is screwed in from the bottom.

If this doesn't get you closer to 2 turns out on the mixture screws to get a good idle then see the next paragraph

Needs to have the idle feed restrictors in the metering block enlarged slightly (just a few thousandths) to feed more fuel to the idle mixture screws. The idle mixture screws just feed more or less amounts of a pre-mixed ratio of fuel -- the mix is decided by the idle feed restrictors and the idle air bleed sizes. You'll need a pin vise and drill sizes #61 thru #80 numbered drills. These usually come as a 61-80 set, easily found at a good hobby shop.

Stock feed restrictor is around .032" if I remember correctly, you will want to go to .034" or .035" and retest the carb. Check the original size first, using the drill set, before you drill....make changes of just a couple thousandths of an inch (.002") at a time.
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Old 03-18-2014, 08:10 PM
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Alright, thanks! I'll see what happens.
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Old 03-18-2014, 08:20 PM
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Now, how many turns for that screw. Or how do i set it?
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Old 03-18-2014, 08:35 PM
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Quote:
Originally Posted by KyleG View Post
Now, how many turns for that screw. Or how do i set it?
Just open the rear blades a bit, maybe 1/4-1/2 turn on the rear screw, then close the front some when it is back on the manifold to get your idle speed correct again. This balances the airflow and mixture distribution a bit.

If you go too much on the rear you won't be able to close the front down enough to get your idle speed back down.
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Old 03-18-2014, 08:39 PM
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Did you set up the transition slots ? And adjust idle using the rear barrels ? The A/F screws should have alot more effect before 4 full turns.. And that slight hesitation may be part of that.
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Old 03-19-2014, 10:19 AM
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Could also be a small vacuum leak
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