Overheating

[Chryco Psycho]

Should respond better Mike

[miketyler]

....and sure enough, it does seem a bit more responsive. With idle set around 725RPM, Va disconnected and vacuum plugged, I dialed in the timing to 15^o BTDC. Temp gauge needle stayed mostly horizontal or just above during a 20min test drive. I didnt try any real load testing or freeway runs yet but this is looking promising. Maybe I can keep my electric fans after all? So best to leave the VA disconnected or? What affect will this have on gas mileage? 

[Mopar73340]

my engine is a stock 340 w/stock cam. I just wonder if my 340 will choke on the 12-16^oBTDC? I'll try it and see what happens.     

My 340 is basically stock and I have the init timing set at 18* with total mechanical advance of 15* which = 33* total. There is another 15* in the vacuum advance unit and it runs great. You will have to limit the total mechanical advance in your dist to run the init vacuum highter than the factory settings because your total advance will be to high and cause the engine to knock. Mine dosen't like more than about 33-35* total mechanical. It runs way better with the vacuum advance HOOKED up to ported vacuum. I drove back from Carlisle Sunday with the A/C on, the outside temp was 90+*. Car never got over 195*. Stock cooling system.

[miketyler]

any how-to's on modifying the mechanical advance mech?

[MEK-Dangerfield]

any how-to's on modifying the mechanical advance mech?

I'm sorry I can't help you there. You can drive without the vacuum advance connected(plug the hole in the carb). The vacuum advance is all about fuel economy while the engine isn't under load, in other words, at cruising speed. For my case, it boils down to probably about 1 mile per gallon or less.  I would suggest going with whatever gives you the best performance without heating problems. I'm still surprised your temp gauge goes up half-way though. I don't think mine has ever been close to that.   


  Mike

[matt63]

any how-to's on modifying the mechanical advance mech?

It depends on what distributor you have.  The older distributors were not adjustable without disassembling them, welding-up the slots and it is a big guessing game.  If you have a newer MP distributor there is 2 set screws that can be loosened to adjust the plates that slide.  Again, it is trial and error.  I found I had to take the distributor out to do this.  If you have an MSD distributor they use offset bushings and it is easier.  The other option is to take it to a shop that has a distributor machine and they can set it up for you with the right springs too.

[Mopar73340]

It depends on what distributor you have.  The older distributors were not adjustable without disassembling them, welding-up the slots and it is a big guessing game.  If you have a newer MP distributor there is 2 set screws that can be loosened to adjust the plates that slide.  Again, it is trial and error.  I found I had to take the distributor out to do this.  If you have an MSD distributor they use offset bushings and it is easier.  The other option is to take it to a shop that has a distributor machine and they can set it up for you with the right springs too.

   Except that your low speed and part throttle responce will suffer without the vacuum advance hooked up to ported vacuum. While you may not loose much fuel mileage, you will feel a big difference in part throttle responce.  I used the new MP dist and took half of the slots away and had 15* of mechanical advance.

[Bullitt-]

A local Mopar club guru posted this document  on the subject of timing...breaks down step by step how to get the initial & total timing #s & make adjustments
 http://www.tvmoparclub.com/files/tech/Mopar%20Timing.pdf

[miketyler]

wow - that is pretty slick. Seems well thought out. I will ck that out. On one other note, I am running the March Performance pulleys. Is there a possiblity that my pump is under driven? Here's what I measured yesterday:

               Old              New      
Crank           7.25"            6.25"

WP              6.0"              6.5"

Am running the 8 blade impeller WP. Also, noticed PCV valve seems a little sloppy in the grommet in the drivers side valve cover. Could a leak there be contributing to my higher operating temps?   

[Bullitt-]

MATH!?!?!    found this on-line calculator....whew.  http://www.metricshop.com/tech/beltpulleycalc.htm

tells me that with OE pulleys your ratio is 1.25  with March pulleys .923  so your loosing ~25%

Doubt if the PCV grommet could be a problem.

[miketyler]

Would it make any difference that the WP belt circuit includes the alternator and AC?

[Bullitt-]

Would it make any difference that the WP belt circuit includes the alternator and AC?

Mathematically no, of course your alt. & A/C will be turning slower due to the smaller drive pulley and the 25% loss probably only effects these things noticeably at idle/low RPM.

[miketyler]

ok. Reconnecting the VA as-is will give me more advance timing than is optimal. To reconnect it would most assuredly add to my overheat condition, right? Can you link me to the new style mopar distributors with the adjustable advance?

I have been dancing around the carb issue and although it works ok and my plugs indicate a decent fuel mixture, I would like to replace it with a new one as the old one looks pretty ratty. I was always interested in TBI fuel injection. Is there any benefit that would reduce my overheating condition if I go that route or does that introduce more problems? Ideally I would like to get this over-heat condition under control before I upgraade to the fuel injected method.

 

[Bullitt-]

I think in some fashion all vacuum advances can be adjusted....here are some at Mancini Racing
http://chucker54.stores.yahoo.net/vacadeldis.html
From what I have read EFI reduces fuel consumption & should run cooler  Don't know about TBI but it should be more efficient as well. Check w/Shelbydog.