Distributor

[andrewbridges1]

Hey guys, looking at putting a new dizzy into my 1969 fj40. Right now it’s the original one but it’s been upgraded to electric points. It’s still vacuum driven. I’m also having a stutter that I believe is dizzy related because I pull the vacuum line and the stutter gets less. Would y’all just go ahead and put a hei dizzy in it?

 

[charliemeyer007]

Well is it vacuum advance or retard? Is the module working correctly and not leaking? There are test you can do. What is your vacuum reading at idle? How much slop is in the distributor shaft side to side?

Myself I prefer a straight mechanical advance - engine rpm's determines the advance. I like breaker points as I can fix/adjust them easily enough to get home/store. Only once has a set of breaker points left me stranded, black box ignition too many times to count.

 

[Grayscale]

GM HEI is not a good fit for an F in a Land Cruiser. Like Weber carburetors, or throttle barrel injection systems, they were never designed for those engines.

It is like, 50-years of heritage is all in the way of these performance upgrades, right? It started in the scrap yards before plastic money could be spent on the internet. But now, it seems either outdated, or you'll need a dyno to see any kind of results.

On the flip-side, maybe. When the intake charge is pressurized less, like when the throttle is barely above idle, there will be less compression pressure performed by the piston. So, the vacuum advance gives it a bit more time to burn when connected to a 'ported' vacuum type carburetor. I get it, in theory. And with more pressure, you have greater temps and combustion opportunity, according to the ideal gas law. Get your timing too advanced, and the cylinder will create pressurize on the compression stroke instead of the power stroke, and you'll introduce parasitic loss (the piston was still traveling up when the cylinder pressurized from the ignition). What the stock distributor, or swapped-in HEI, has as far as an centrifugal advance spark-curve remains elusive, depite the wealth of internet knowledge. The only factor that seems to improve performance on these engines is a warm carburetor, in my experience.

Straight vacuum advance was ditched by the 1980's because OEMs figured out how to deal with fuel better. Or, like my Datsun Z24, they simply used two spark plugs per cylinder (two flame-fronts set on a collision course), two coils, and fired in the combustion chamber in sync. One of the coils could be electronically controlled (on or off) to control the rate of combustion without pressurizing the cylinder on the intake stroke using vacuum spark advance, like at idle. The engine could be static timed at 3 deg. btdc because they were no longer using just a simple vac advance system that was common in the 1960's.

I'm happy with my new Nippon Denso F-distributor with vac advance, and semi-electronic (igniter) circuitry.

 

[65swb45]

I would baseline the motor before I started throwing parts at it. If you don’t know what the static timing is with the vacuum line connected and disconnected, you’re just shooting in the dark.

 

[Pighead]

Absolute newbie here. I have a stutter as soon as I hit the throttle. I did a vacuum test from the little hose in the carb. These are my readings. It actually seems like it runs better without it connected to the vacuum advance. Less of a stutter but still not gone. What would y’all do next?

View attachment 3805549

View attachment 3805550

Have you changed the source of the vacuum yet?

 

[cstav86]

Reach out to @4Cruisers for dizzy work. I’d stick with stock and if it’s retard change to advance. You’ll notice approximately zero power gain from any fancy electronic ignition so stick with what has worked for the last 50 years.

 

[andrewbridges1]

Have you changed the source of the vacuum yet?

what do you mean changed the source? All i had done was checked the vacuum on that one line. I believe that was the only vacuum line on it. Are you saying theres another spot i can put the vacuum line to get more or less vacuum? Could it maybe be a air leak at the carb spacer? When I rebuilt the carb i put it back together with the original gasket instead of waiting on a new one. Doesnt seem to leak becauase i can spray water/ brake clean around it and not get any difference in the truck running.

 

[Pighead]

Are you saying theres another spot i can put the vacuum line to get more or less vacuum?

Yes. I posted a pic of it in your last thread about this.
A '69 distributor with a Pertronix ignitor is one of my favorites. People keep asking you if it is a vacuum retard or a vacuum advance distributor...

 

[andrewbridges1]

Yes. I posted a pic of it in your last thread about this.
A '69 distributor with a Pertronix ignitor is one of my favorites. People keep asking you if it is a vacuum retard or a vacuum advance distributor...

How can I tell.

 

[Grayscale]

Is the vac barb fitting on the inside of the diaphragm (towards the distributor) or the outside, or both?

 

[Pighead]

How can I tell.

I use the position of the vacuum diaphragm to tell me. One of these LandCruiser distributors is a vacuum advance, the other is vacuum retard...

 

[73FJ40]

How can I tell.

If vacuum applied to the diaphragm rotates the points plate counterclockwise, it's vacuum advance. If vacuum rotates the plate clockwise, it's vacuum retard.

 

[Grayscale]

Clockwise breaker plate movement - vac retard '75

This one just needs a different diaphragm to make it a vac advance. It needs to pull not push.

 

[andrewbridges1]

Is the vac barb fitting on the inside of the diaphragm (towards the distributor) or the outside, or both?

Outside

 

[Grayscale]

Outside

So, which of Pighead's distributors? Retard or advance?

 

[Grayscale]

It is a vac retard (below). Akin to Pighead's black-painted distributor. Clockwise breakerplate rotation Disconnect the vacuum source.
Post #9 Not running right - https://forum.ih8mud.com/threads/not-running-right.1345855/

 

[andrewbridges1]

It is a vac retard (below). Akin to Pighead's black-painted distributor. Clockwise breakerplate rotation Disconnect the vacuum source.
Post #9 Not running right - https://forum.ih8mud.com/threads/not-running-right.1345855/

What do I do to cover the nipple on the carb? Some sort of plug?

 

[Grayscale]

Vinyl vac caps at the auto store. I've never made good use with the rubber ones if it is exposed to fuel vapor.

Or, Vintage Teq might have something better. That is where I got my factory vac caps.

 

[charliemeyer007]

Stick a bolt in the tubing for now. Tape up the nipple on the dizzy for now.