Author Topic: Help make my 340 run great  (Read 7100 times)

Offline YO7_A66

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Re: Help make my 340 run great
« Reply #30 on: November 05, 2015 - 11:19:46 AM »
 ""My cam is orange and in the 1 hole.""

 The orange cam is the second most aggressive cam for a 30cc pump. "If" the problem gets worse after testing a larger squirter, I would go down a couple of sizes on the cam (red or white). If the problem gets better after a larger squirter, then keep going up on the squirter size until it goes away.

 Note: Make sure that you have the pump cam linkage setup so that you get fuel as soon as the pedal moves.
 Note 2: They make a .021" and a .019" squirter. I have them both in my arsenal of carb parts.
« Last Edit: November 05, 2015 - 11:31:25 AM by YO7_A66 »




Offline moper

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Re: Help make my 340 run great
« Reply #31 on: November 06, 2015 - 12:24:07 PM »
My initial timing is 15* and the total is 37*. It is all in at 25 or 26 RPM. I'm having trouble with my idle circuit. The idle screws have no effect on the vacuum at all. The throttle plates are closed enough so that the slots are barely visible. I'm wondering if the fuel pressure is too high would that cause the problem? My pressure is about 9 lbs. I have a regulator and gauge on the way.

Idle screws having no affect tell me it's getting fuel from somewhere else. Are/were you viewing the slots fromt he top or bottom of the carb. The majority of the transfer slot should be visible from the top. A very small amount should be visible at the edges of the blades from the bottom. If it popped through the carb - is the power valve definately good? Popping used to be fatal for a power valve. Even only once. Pull the valve out and either get the tester or simply clean it off and suck on the non-threaded side where the diaphram is visible. If it holds vacuum it's good. If not - it's bad.
The vacuum level has to be taken in gear if it's an auto trans. I forgot if it was or not but if you're showing 14 it doesn't sound like it's in gear. You want a few numbers lower than your vaccum in gear for starters.
The squirter seems small. I would up that too. Leave the cams alone for now.

Offline Lbs

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Re: Help make my 340 run great
« Reply #32 on: November 06, 2015 - 01:00:40 PM »
Thanks moper.........a few updates, I am viewing the slots from the bottom side. I will be checking the power valve in the next hour and my car is a 4 speed so does that effect what I'm looking for in the vacuum? My squirt nozzle is now at 35 and that has helped the situation a lot. Going out to check that power valve now as their have been 3 or 4 backfires during this education I'm getting. Grrrrr

Offline jhaag

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Re: Help make my 340 run great
« Reply #33 on: November 06, 2015 - 01:55:50 PM »
You are getting too much fuel at idle. (after making sure PV is good) Most common issue is primary throttle blades open too much exposing too much transfer slot. This will cause a rich smelly idle, idle mixture screws having no affect, and hesitation on acceleration. Should only be able to see about .020" of the slot below the blade. It should look square (ie only expose as much vertically as it is wide) Are you aware that the secondary plates can be adjusted as well? They should be open just like the primary. Adjustment screw only accessible from the bottom, on passenger side. adjust the secondaries just like the primary. put carb on and start the car. If it idles too high, you may have to take the carb off and adjust again, by closing the primary and secondary curb idle screws an equal amount. You may end up with no transfer slot visible. Once you have this adjusted correctly, your mixture screw should work. You definitely don't want too much transfer slot exposed. If that is the only way it will run, you will have to introduce more air at idle. Only way to do this is by drilling holes in the throttle blades. You should not have to do this though. You also should not need a squirter bigger than a 31. I would recommend you disable the secondary vacuum can on the secondaries until you have all your issues worked out, as that could be skewing your results. Once you get a good idle and smooth acceleration on the primaries alone. Then you can test different springs in the secondary vacuum can.
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Offline Chryco Psycho

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Re: Help make my 340 run great
« Reply #34 on: November 06, 2015 - 08:55:55 PM »
4 spd cars will have more vacuum at idle as there is no load on the engine with the converter so idle vacuum is what it is make sure the PV is a couple of inches below that & you are good

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Offline Glow Worm

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Re: Help make my 340 run great
« Reply #35 on: November 08, 2015 - 10:52:54 AM »
Wasn't the factory Thermoquad 800 CFM on the 340? (1973)
"If I had all the money I've spent on cars . . . I'd spend it on cars."