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Vacuum advance is a GOOD thing at light throttle, but some of the "random" vac cans folks find themselves with can kill.

You want to limit it to ~10-15 degrees, depends a bit on your vac signal.

Ray had a neat trick for limiting it in a similar fashion to the stock adjustable ones, If I only had a brain I'd remember it...

BTW, I'll be getting a MegaSquirt setup real soon now, but it will be running the Megaspark SW... If I have an ignition issue, I can drop in a spare dizzy in 5 minutes or less.

I'll hopefully get the CIS going this weekend.

so is the 12/28 setting jake talks about a way to give you the centrifugal advance at idle without a vacuum assist?

is the goal to have a maximum total advance of 28 degrees even with the vacuum assist? is the vacuum assist only there to help off idle and then you want it to "go away" once you get higher up in the rpms?

No. 12/28 MECHANICAL, vac hose(s) disconnected.

Limit your vacuum advance to <15 degrees beyond that...
It has virtually NO effect at WOT and absolutely none at idle.

BTW, make sure you are connected to the RIGHT vac port, it should not suck at idle, but start when you open the throttle a little.

At light loads, the vacuum advance is very helpful, as the charge burns slower.

The vacuum advance "goes away" under LOAD...
(More load. reduced mainfold vacuum, less vac advance)

Mallory (or someone) used to make distributors (or magnetos???) with mechanical advance AND retard...
That's easy to make happen with a programmable EMS like Jake uses or Megaspark or MegaSquirtNspark (software variations of MS)

You can adjust the total vac advance of the mallory by putting a small allen key in the vacuum port and turning it down. Forget which size

Paul

well... i just drove about 800+ miles and my head temp gauge showed me at about 500 degrees the whole time. i pulled over and checked the plugs, timing and anything else i could think of but it doesn't appear to be messed up. i drove around with the vacuum line plugged for a few miles but it didn't seem to make things run any cooler.

i can only guess my gauge isn't accurate or gremlins have infected my bus. hopefully i'll have my oil temp sensor back in for the drive home so i have something to compare it to b/c at least i'm familiar with the readings i get from that gauge.

WOW! ID you bolt that sender to the exhaust manifold?


THings start *moving around* on an aircooled head at those temps!

What color are your plugs?

Don

the plugs were a light grey. i killed the engine while at high speed and coasted to a stop before i checked them so it should be accurate. my gauge doesn't sit at 0 degrees or all the way down, it's already at 150 before i even start my engine. is it possible the gauge needs to be calibrated? i'm pretty sure my engine isn't 150 degrees first thing in the morning.

Where is the sender located??

If your engine was running 500 degrees- You need a new engine!

[quote="ggggarret"]... i'm pretty sure my engine isn't 150 degrees first thing in the morning.[/quote]

Unless you live in Saudi...

Boil a pot of water and have the sender in your hand. ready to drop it in after you remove the pot from the heat source.

Remove the pot from the heat and drop the sender in the pot of still boiling water. Should be very close to 212F, or 100C when you notice the water barely stop *moving* or boiling.

That should give you an idea of how far off it is!

Don

the sender is under the spark plug on the #3 cylinder between the plug and the crush washer. the sender doesn't sit in there very well, it gets a little bent up when you tighten down the plug. is it possible that the plug is a bit loose and it's getting some extra heat from the cylinder? i'm really starting to think it's the gauge. stupid gauges...

Thats the correct place (only place) for the sender.. I have never seen a CHT gauge be that far off (not even remotely close to that)

Mechanical parts are not stupid......they just get out of adjustment,
or are used incorrectly for their designed purpose.


Yes, on a type 4 engine, those senders don't sit very well.

Search for earlier posts on this forum that have links to pictures
showing how to pre-bend the sender for use on a type 4 engine.

And YES, if 1300 degree combustion gases are leaking, it could raise
the temp, but that wouldn't be o fconcern to me if it were my engine.

Escaping combustion gases will burn the aluminium out, anywhere they
are leaking from, in short order.

Find out if it's leaking, and if it is, fix it!

Don

ggggarret wrote:the sender is under the spark plug on the #3 cylinder between the plug and the crush washer. ..

Next time better remove the crush washer from the spark plug you put the sender onto...With a crush washer and a sender unit under the plug, your nr. 3 spark plug is not sitting far enough into the combustion chamber...
That might affect things a little as well.

Regards,
Walter

Someone else recently had a VDO temp setup that (when checked against boiling water etc) was 100F off, reading high.
http://shoptalkforums.com/viewtopic.php ... hlight=vdo

Check the calibration and remove all doubt.