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New carb, idle surge. Need to adjust timing?

cameronsaddress

cameronsaddress

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Hey guys,
I just removed my 450 holly and installed a 650 edlebrock on my chevy 350. I have a mild cam. The idle was stable with the 450 carb but now surges with the 650. I have checked for vacuum leaks and found none. I have set idle mixture screws to factory recommended 1.5 turns. I have the dizzy timing advance connected to timed vacuum port on carb.

Also noticed that idle stays high when coming to a stop sometimes, requiring me to blip the throttle to settle it back down.

Is it necessary to adjust timing after installing a carb that intakes more cfm?

Thanks!
 
Tried moving the vacuum advance to full vacuum port and also capped it off. Neither changed anything. It still surges.

Any ideas?
 
I've checked and double checked. I've used carb cleaner trick all around engine and can't find a leak.

Any other suggestions?
 
did you use a new carb gasket? which e-brock?
 
Yea brand new gaskets. I used a square bore adapter for spread bore manifold. New Gaskets above and below adapter plate.

Manifold edl performer 2101 I think
Carb edl thunder avs 650

Thanks ryoken
 
Check the choke, make sure it is open all the way when warmed up, that will cause the high idle. Could be the problem with surging as well
 
Electric. I haven't messed with it yet. Instructions say its configured to run right out of the box... :(

What do I need to check on it?
 
warm up the motor, pull the air cleaner and there is a little metal flap that closs of the front half of the carb, make sure that it is straight up and down. If not loosen the screws holding the round black plastic housing and rotate until open. Do you have 12v to it and a good ground?
 
Yes. Grounded to the choke housing screw and hot lead connected to accessory on fuse box.
 
I checked the choke this morning. It seemed to accelerate instead of lower rpm over time. I actually had to blip the pedal after 10 or so minutes to get it to settle at an idle.

At idle, the choke blades are completely open though. They are not choking the card like when the choke was activated.

I have sprayed carb cleaner around the base of the carb, the hoses and connections and it doesnt find a leak (rpm surge).

Please confirm that I am using the correct carb adapter plate:

http://www.summitracing.com/parts/SUM-G1420/
sum-g1420_sn_m.jpg


http://www.jegs.com/i/Edelbrock/350/2101/10002/-1
350-2101.jpg


http://www.summitracing.com/parts/EDL-1826/
edl-1826_w_m.jpg



I am freakin stumped... and bummed. My truck idles like crap now.

Im gonna try to call edelbrock this afternoon.


thanks,
cam
 
not to bum you out any more, but, that's ridiculous to me.... ya have a spreadbore dual plane intake, perfect for street driving with smaller primaries and now it's adapted to run a square bore... big hp, sure, run a squarebore, anything that sees street time, spreadbore and a quadrabog imo...

personally, I'd sell the adapter and edelpuke and just slap a stage 2 Jet quad on that intake..


anyway... is it just surging at idle, and ok thru the rest of the range?

personally I like ether for vac leaks, the clear increase in rpm's is much easier to notice imo... care should be taken tho...
 
is it a new intake, or just the adapter and carb?

I have to agree, it really sounds like a vac leak, that's a notorious condition.. the only other thing i can think of off the top of the head is that the idle circuits have some sh*t in em from the factory... ya may wanna try totally taking the idle mixture screws out and carb cleaner em in the passages, maybe put a bit of air to em... reinstall... in case you didn't know, when seating them, just barely get em to stop, then adjust out... more people screw em up by going to tight when closing em off.. real easy to damage them that way...
 
it shouldn't need it if it was correct prior... and that's generally not an issue you would have from being out of time.. 99% of the time surging is a fuel delivery prob.. whether it's clogged something, or a vac reference prob due to a leak...
 
Ryoken, the air through the idle circuit fixed the issue! Must have been crap stick in there from the factory?

It is running much better now. I just need to figure out the friggin electric choke. There is a vacuum port at the very bottom of the choke housing that is leaking quite a bit of vacuum... Is that normal? It is actually loud enough of a leak to hear from outside the engine compartment. It came that way from edlebrock so I'm not sure if they missed a plug or cap?

Thanks,
Cm
 
yeah, probably a chunk of casting flash or something.. good...

now.. I'm not overly familiar with E-brocks version on that Carter design, but afaik, it's should be a standard electric choke with no interaction with vacuum for the choke itself... iirc, they did have a vac port that runs thru the choke housing tho... so there is a seal between the choke and housing and a small barb at the base of the choke that is vac.. iirc, it is a non-ported source, but either way make sure it is plugged... if it's plugged and you still hear it, check the seal area over at the lower choke mount....

if ya need help setting the choke holla...
 
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