So,,,,,,,,,,,,,,,,I have a question concerning the distributor on my '70 340 Dart. It has an MSD Digital ignition,,,,, but,,, on the distributor,,, there is a vacuum advance dash-pot on it. Mine is not hooked up to engine vacuum,it was not hooked up when I got the car,,, I have seen guys go either way with the vac. advance,,,,,, for a Dodge 340,,,,, should it be hooked up for better all-a-round performance
Vacuum Advance
- Thread starter PtownDart
- Start date
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MOPAROFFICIAL
Oogliboogli
It's for gas mileage .. and itll keep the chamber cleaner.
Is it a necessity...no, technically not.
Yes . But you will need to verify how much advance it provides and when it starts ( inches of vacuum ) it comes in at . The MSD digital ignition allows you to program mechanical advance but you willneed to lock outthe distributor.
Ironracer
Gearhead
If you can lay hands on a timing light, you can "Map" the advance curve, with, and without, the VA connected. There are also 2 manners of hooking it up. Ported vac and non ported... get a note book. Or you could just go by seat o' the pants, sound, but not always the most accurate. The thing is you want to run proper initial advance for your motor but you don't want the vacuum advance to kick in too much, and end up with engine damage from detonation
The more the engine is modified, the greater the benefit gained from using manifold connected VA.
Scroll down to post #6. The last few lines are veeeeeery important:
www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
Scroll down to post #6. The last few lines are veeeeeery important:
www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
In modern day you take the amount of vacuum advance and add it to your initial advance and block the vacuum. For example now your initial advance will be 15* and all the rest mechanical. Same total.
It's long been my opinion that if the car sees street time, the vacuum advance is a benefit. Now, whether ported or manifold vacuum, yall can argue that out.
Kendog 170
Let the boy go !
We've been talking about this a lot this week. You should read it.
360 Tune Up | Page 5 | For A Bodies Only Mopar Forum
360 Tune Up | Page 5 | For A Bodies Only Mopar Forum
dashpot or solenoid?
Deceleration timing was the issue
The solenoid was a more sophisticated way to get the timing reduced at idle and deceleration.
For solenoid see here
Let's Keep It Clean (Session 270) from the Master Technician's Service Conference
As far as what you should do for your particular combination, first figure out what distributor you have and measure the advance. If its a quick and long advance afrom idle to 1500 rpm, then to use a non-emissions initial timing you will have to make changes to shorten that long advance.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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For best performance in any mode, all engines require the peak cylinder pressure to occur at a specific place in the rotation of the crank. All your ignition timing systems are designed to hit that target as often as possible.The more time the engine spends at that specific point, the more average torque it will produce, and at Part Throttle, the less fuel it will take to do whatever work you are asking it to do.
So yes, this opens the door to steady-state fuel-economy. But there is so much more to it.
Does your street engine need it?
IMO, absolutely yes.
Here is just one example;
Start your engine and warm it up. Then without regard to reading the timing, just advance it until the rpm no longer rises. This is near to the perfect amount of idle-timing the engine wants. Now read it. Don't be surprised to see 25/30 to even 35 degrees.
Not many engines with distributors can be tuned for whatever you read there. Nor would you want to, especially with a manual trans nor with a lo-stall TC, because the power pulses are just too strong, and the rest of the timing curve is just too hard to achieve. With a manual trans, it becomes very hard to drive the car at low rpm as the pulses hammer the gear-train. With a hi-stall, you can sorta get away with it.
If your T-slot synchronization is pretty accurate, you can retard the timing at idle to as little as 5*, even with the 292/292/108 cam. Well OK, I have done it and with good results.
Put your timing back, lol.
So yes, this opens the door to steady-state fuel-economy. But there is so much more to it.
Does your street engine need it?
IMO, absolutely yes.
Here is just one example;
Start your engine and warm it up. Then without regard to reading the timing, just advance it until the rpm no longer rises. This is near to the perfect amount of idle-timing the engine wants. Now read it. Don't be surprised to see 25/30 to even 35 degrees.
Not many engines with distributors can be tuned for whatever you read there. Nor would you want to, especially with a manual trans nor with a lo-stall TC, because the power pulses are just too strong, and the rest of the timing curve is just too hard to achieve. With a manual trans, it becomes very hard to drive the car at low rpm as the pulses hammer the gear-train. With a hi-stall, you can sorta get away with it.
If your T-slot synchronization is pretty accurate, you can retard the timing at idle to as little as 5*, even with the 292/292/108 cam. Well OK, I have done it and with good results.
Put your timing back, lol.
Rat Bastid
Dunamis Metron
Yes use the VA. Save the grief and find someone with a distributor machine and get it set up correctly.
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