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Discussion Starter #1
I have a 69 Camaro with a 385 stroker motor,single plane hurricane intake,crower cam near equal to the 305h cam alot of overlap with this cam, 10.5-1 comp. , stepped dyatech headers1 5/8-1 3/4. I have a 750 qft quick fuel carb with 74 primary jets,84 secondary jets,I put a 50cc acc. Pump on primary side, it has stock pink acc. Cams. Also has #45 power valve. Not sure on squirters? The car idles fine and drives good after the initial pull out. It's when I go to pull out or just barley get on the gas it will studder and sometimes backfire out the carb. I can't seem to get this stubble gone. Also it only pulls 5" of vacuum at idle. I've read power valve should be half of the idle vacuum. So should I get a 2" powervalve? Also when I put throttle to wot without car running I can push the acc. Pump lever down over half way( like an inch of travel) but the lever is pushing the acc pump right away. Anyone please help getting frustrated? Thanks
 

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Initial timing is at ____? If more is needed and added, it might increase vacuum and PV may be okay. If it stills stumbles, might decrease squirter and/or pump back to 30cc.
 

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Discussion Starter #3
ill double check initial timing but i think it is 15 or so. it is 35 total at full advance 4000rpm. it seems like a lean stumble only because when i hit the acc. pump by hand and rev it up it seems like no stumble. and it only when i just roll the throttle easy. when i stab it it hesitates a hair but barely noticable and revs good.?????
 

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You might have to lean out the PV to a lesser value.
Might try a larger squirter by a couple sizes and compare the results, if worst, lessen up on the squirter size. Do this before changing PV because of easier access than PV.
 

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Travis, when you say it has the stock pink pump cam, do you mean the one that came on the carb with the 30cc pump?
 

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Discussion Starter #6
Yes stock 30cc pump cam had 3 holes of adjustment. The kit I got has a yellow one and a dark maroon 1 both have 1 hole in each. How do you know which way to put it on ?
 

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Which cam on you using with the 50cc pump? Did you try tuning the 30cc pump before you went with the 50cc? Most apps. work best with the small pump.
 

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Discussion Starter #8
I didn't try the 30cc pump with this motor but it worked on my last motor. Just figured a 50cc would be better. I'll try the 30cc and see what I come up with ? Any info on power valve recommendations?
 

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Discussion Starter #9
put yellow 50cc cam back in and adjusted the idle air bleeds out 1 full turn and stumble and backfire seem to be gone for the most part . timing is 15 at idle and 36 at full advance. also have 31 squirters . will the idle air bleeds cause it to run a little lean under full throttle or is that just main jet changes? also it pulls 5" of vacuum at idle so do i still need the 2.5" powervalve or should i just block it off because the vacuum is so low?it has 4.5" power valve now. thanks
 

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Adjust mixture screws for best vacuum reading at idle. Use a vacuum gauge.
If no more than 5 inches of vacuum, then try a 2.5 or 3.0 PV.
 

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Discussion Starter #11
yeah i tried that but i have a real lopey cam and the needle jumps all over right now i think i have it near its best a whole 5" of vacuum. 104 lsa on cam
 

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I would imagine a lumpy cam would require an idle of around 1300-1500 rpm and a really loose convertor?
 

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Discussion Starter #13 (Edited)
It will sit and idle at 850-950 all day right now and that's in gear. It's around 1000to 1100 in neutral. I also have a 3600 stall converter.It has a real dark brown tint to plug at idle but when I rev it threw the gears and quick shut it off it looks like a new plug white. Is this main and secondary jetting that needs to be upped? Car pulls good and doesn't ping or anything plugs just look lean to me but rich at idle
 

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I have a 69 Camaro with a 385 stroker motor,single plane hurricane intake,crower cam near equal to the 305h cam alot of overlap with this cam, 10.5-1 comp. , stepped dyatech headers1 5/8-1 3/4. I have a 750 qft quick fuel carb with 74 primary jets,84 secondary jets,I put a 50cc acc. Pump on primary side, it has stock pink acc. Cams. Also has #45 power valve. Not sure on squirters? The car idles fine and drives good after the initial pull out. It's when I go to pull out or just barley get on the gas it will studder and sometimes backfire out the carb. I can't seem to get this stubble gone. Also it only pulls 5" of vacuum at idle. I've read power valve should be half of the idle vacuum. So should I get a 2" powervalve? Also when I put throttle to wot without car running I can push the acc. Pump lever down over half way( like an inch of travel) but the lever is pushing the acc pump right away. Anyone please help getting frustrated? Thanks

With a 50cc pump you need to use the BROWN 50cc cam, not a 30 cc pink one.

You should have more than 5" vacuum, so look in to where it is mistuned. Get accurate A/F mixture readings and tune the mixture screws and idle air bleeds accordingly.
Proper useof the vacuum gauge can do it too.
The hurricane itake, ditch that and get a RPM airgap.
 

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Discussion Starter #16
With a 50cc pump you need to use the BROWN 50cc cam, not a 30 cc pink one.

You should have more than 5" vacuum, so look in to where it is mistuned. Get accurate A/F mixture readings and tune the mixture screws and idle air bleeds accordingly.
Proper useof the vacuum gauge can do it too.
The hurricane itake, ditch that and get a RPM airgap.
Using 2 vacuum gauges 1 at front of carb a d 1 on my vacuum canister both read the same. So air/fuel reading is the only way to properly tune it? I have a 3600 stall converter so I'm in the rpm range for the single plane intake so rpm air gap wouldn't help to much because I am not using much low end
 

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Discussion Starter #17
so i have the car running pretty good now and got about 7-8" of vacuum now. i am pretty sure the car is still lean though the plugs all look white barely any color to them. i broke one off by slipping with the socket so i installed a new one and took it for 10-15 minutes and it has no color to it. i already jumped the primary jets from 74 to 76 and seems to be a little better the secondary jets are 84 still. do you think i should 78-80 on primary and 88-90 on seconds?
 

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You have a heap of overlap right....at low rpms the engie will be ineffient. hence rich at ildle
Dont be fooled by the plugs lean driving around...with the over lap a lot of gas will be sucked straight across the chamber and out the exhaust, but if stomped on at the rpms its designed to work at, lean out then is bad news big time.
you really need , as suggested above to data logg the O2 against, rpms
And also as suggested above...have the sec butterflys been set ? Can be done on the car while running or off.
Anless the timing and the curve is, in the ball park secondaries adjusted so idle speed and mixture screws are in the middle of factory spec, and accel pump gap and float levels are correct, nothing else should be changed.
 

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Discussion Starter #19
Ok I'll check our secondary butterflies. I was just out driving it and when I shut it off the engine backpeddled for a second not long at all but it did it. I'm sure this is timing. Is it retarded to much or advanced to much? My timing light says 15 at idle and 35-36 total advance
 

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My timing light says 15 at idle and 35-36 total advance
What is idle with VA attached?
VA not attached?
36 deg? At what RPM
What is it with VA attached And not attached
At what vac does the VA start to move ans stop moving?
use a hand vac pump, with the cap off and finger on the VA lever at the back to feel it move.
 
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