Avs2 650 tuning on a 340
- Thread starter fez440
- Start date
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If hooking up VA made zero difference, then the VA is not working. Ruptured diaphragm or insufficient vacuum to pull in the VA.
Here is the good news. You can have your cake & eat it too!
Please read the link below FIRST, & then come back to here.
You need an adjustable VA unit, connected to a manifold vacuum source. Adjust the Allen Key fully CW. Trying to do this with a factory VA unit & 10" of vac will not work.
You use the VA unit to provide the extra timing that you found [ earlier ] that the engine likes. You can use any combo of VA + initial to give you the desired idle timing, while keeping the starter happy. Example, if the idle sweet spot was 34*, then you could use 14* initial + 20* VA. You will probably have to fabricate a movement limiter for the VA actuator.
Contrary to an earlier post in this thread, adding VA in the above manner can cure an off idle flat spot. I have done it many times. What happens is the engine is making more HP with the extra timing & the extra HP allows the engine to carry the load, so no stumble.
Yes, there is a bit of messing around to get this right but that is what hot rodding is about....
www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
Scroll down to post #6.
Here is the good news. You can have your cake & eat it too!
Please read the link below FIRST, & then come back to here.
You need an adjustable VA unit, connected to a manifold vacuum source. Adjust the Allen Key fully CW. Trying to do this with a factory VA unit & 10" of vac will not work.
You use the VA unit to provide the extra timing that you found [ earlier ] that the engine likes. You can use any combo of VA + initial to give you the desired idle timing, while keeping the starter happy. Example, if the idle sweet spot was 34*, then you could use 14* initial + 20* VA. You will probably have to fabricate a movement limiter for the VA actuator.
Contrary to an earlier post in this thread, adding VA in the above manner can cure an off idle flat spot. I have done it many times. What happens is the engine is making more HP with the extra timing & the extra HP allows the engine to carry the load, so no stumble.
Yes, there is a bit of messing around to get this right but that is what hot rodding is about....
www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
Scroll down to post #6.
I agree. No way should your engine be wanting that much timing with that much cylinder pressure. Are you SURE you're attached to #1 plug wire? Stupid question, I know. First one in the front on the driver's side. If so, I'm almost inclined to think the balancer may have slipped.
Without checking with a piston stop, you know absolutely nothing. The purpose of that is to check that the balancer is in phase with "everything else". If you're not willing to do something as simple as that, we may as well end these shenanigans right now, because if you won't listen and do that, then everything else might be wrong.
Whether the vacuum advance is hooked to ported or manifold vacuum has ZERO to do with your problem. If you go running down that rabbit hole before you actually find out what's going on, you're going to lose yourself even further. I don't know about the rest of these guys, but you're getting closer and closer to this being a waste of time if you won't listen. We're trying to tell you how to diagnose this as hard as possible. It seems you're trying your best to do the exact opposite.
@Bewy is correct in a sense . Certain engines could benefit from using ported vacuum exactly as he says but like RRR stated your cam is too mild to fall into that category .
It took me a long time to get mine running correct but I did it . For a while I was sure either the carb was defective or the cam was ground wrong ...
You will get it.
It took me a long time to get mine running correct but I did it . For a while I was sure either the carb was defective or the cam was ground wrong ...
You will get it.
I'm not sure what you mean here. I'm trying to do everything I can that is being recommended to me. I'm still learning. I never said I won't use a piston stop. Just dont have 1 at the moment.
I'll be looking into checking over the timing this week hopfully and will report back. Had to order it so it will take a few days
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Ok. New here.
Did you run the carb straight out of the box?
I would check the float level.
I’m sure UPS/FedEx bounced it around a bit.
Sounds like timing is about right, BUT,
I think high float level would make it run richer.
Did you run the carb straight out of the box?
I would check the float level.
I’m sure UPS/FedEx bounced it around a bit.
Sounds like timing is about right, BUT,
I think high float level would make it run richer.
Thanks for the reply. Yes I checked float height . It is set to factory specs. I did run it out of the box. Stock calibration was very rich
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I did the piston stop procedure today. Started at number 1 and tdc at 10 degree after then rotated around and it stopped at 10 degrees before. So I say 0 is correct. 1st time doing that. Good procedure to known. Thanks for sharing
The Mark's on the left were from this procedure
Also went through the distributor. All looked good
Gap of about .008 . Rotor pointing at number 1 plug. Set timing to 15 and 35. Maybe I'll try running manifold vacuum. Never tried that only ported once. It's just cuz the ignition company says not run vacuum advance that I have not ran it.
The Mark's on the left were from this procedure
Also went through the distributor. All looked good
Gap of about .008 . Rotor pointing at number 1 plug. Set timing to 15 and 35. Maybe I'll try running manifold vacuum. Never tried that only ported once. It's just cuz the ignition company says not run vacuum advance that I have not ran it.
I mean it's that important to use a piston stop. Anything else is just a guess. I thought that was the clear message. Does that clear it up further?
Good job!
Yes it does. I understand it much better now. Thanks
Slantsix64
Well-Known Member
.098 with a 73 rod will give a bog from idle to cruise in the low rpms, that combo is not on the chart. I think .101 and that 73x52 will be your sweet spot youll get rid of that off idle transition bog with the 2 sizes up jet and have a lean cruise with that rod combo.
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