Distributor retard

Pritchard · 08-21-2000, 04:27 AM

This is a follow up on a previous post. I have a '74 2.0 L with a stock engine except for pointless ignition.

After checking everything associated with the FI system and finding nothing out of spec, I started examining the distributor. I found that the retard side of the advance/retard mechanism (is it called a dashpot?) will not hold a vacuum. The advance side will hold the vacuum. Yes, I have both advance and retard nipples on the throttle body and on the dashpot.

My question is: should the retard side hold a vacuum? If so, could this be why the engine will not keep running?

The number on my distributor is: 039-905-205

I also noticed that the springs for the centrifugal advance down in the dizzy were different from each other. Neither is broken, they are just different. Is this normal?

Thanks in advance for your advice.

Pritchard

John Rogers · 08-21-2000, 06:06 AM

If the retard side of the distributor vacuum pot won't hold a vacuum, that is a small vac leak which will throw off the idle settings but more importantly the timming won't retard to the value it is suppposed to be at idle which will make the engine run erratic, possibly stalling at idle. The springs may in fact be different looking so I wouldn't worry about them.

Pritchard · 08-21-2000, 06:55 AM

Thanks John. That answers a lot of questions about my engine.

Now, what do I do about it? Can I repair/replace the dashpot? Or am I looking at replacing the entire distributor? If the answer is choice #2, what dizzies are available for FI other than the expensive OE dizzy?

Thanks again

Pritchard

bowlsby · 08-21-2000, 08:45 AM

I have a very low serial number 74 2.0 as well (Aug 1973). Look at the retard nipple on your throttle body very carefully. I have heard that the 73 cars had a retard nipple that was open and funtional, but on the 74 cars the retard nippple was eliminated. Mine has a nipple but it appears to be soldered shut. I figure the factory just hadn't yet opened the box of 'updated, nippleless" throttle bodies, so they just closed mine off.

The hose from the retard side of the diaphragm is connected to the nipple on the throttle body, but obviously it does not function to retard the timing. I think that is the Deceleration valves funtion, which is mounted over by the pressure sensor.

On the cars without a nipple, the factory reputedly just ran a short section of hose under the throttle body/plenum without connecting it to anything. Satisfies the smog checkers I guess.

John Rogers · 08-21-2000, 10:20 AM

You are stuck with the stock distributor I think. Try putting a little pressure on the retard side and use some soap solution to look for the leak and you might be able to seal it with Goop sealant. Since one side holds and the other one doesn't I imagine the diaphragm is okay so it might be a crack in the body or where the little nipple attaches. Patching is not as elegant as a new distributor, but a lot cheaper. Good luck

Pritchard · 08-21-2000, 10:46 AM

Thanks for the advice guys.

The retard nipple is definately functional. I can feel the vacuum at idle, until the engine dies, of course.

I will look for cracks/leaks tonite and seal them if possible.

Pritchard

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Bowlsby, it's the other way around. The 73s have both advance and retard. Some or all of the 74s have the distributor with both fittings on it, but no *advance* fitting on the throttle body. That's the one that points right-front, and goes to the distributor fitting pointing away from the distributor.

The vaccuum unit (I think it is called a dashpot) is available separately. Ask for part number 039.905.271 . Hopefully they're not NLA...

--DD

scriabin · 08-21-2000, 10:19 PM

The one small question remaining unaswered: to my knowledge, yes, the two springs on all the distributors I've peeked into have appeared slightly different from one another, with different spring rates I'd always imagined (never encountered specific literature covering the matter).
Anyone out there possess this knowledge?

Does their movement 'overlap' in deployment to smooth the advance curve? And, I've wondered, what would happen to total advance if the two were ever accidentally swapped during a rebuild?
Hope this is not frivolous, I'm interested to know.

--John Lambert

Pritchard · 08-22-2000, 03:51 AM

Hey that's good news to hear that the dashpot is available separately. I disassembled/forced mine last nite. I did find where the base of the retard diaphram had a slight tear. Hopefully this was why it wouldn't hold a vacuum.

Just in case you're curious, there is a separate diaphram for both the advance and retard.

I have tried to make a repair. I have no idea if it will work. It involved the use of a latex glove and some very sticky glue. Everything looks like it will work, I'll be putting it all back together tonite. Cross your fingers for me.

Thanks for the input.

Pritchard

Pritchard · 08-23-2000, 04:04 AM

Well, I reassembled the dashpot last nite and had some degree of success. The repairs I made held together long enough to let me know that the problem is the vaccuum unit. The engine started up and idled smoothly (after setting the timing). However, after a few minutes, the glue started to let go and the poor running was back. I was happy to finally know what the problem was.

Now I have to find a replacement for the vaccuum unit. I have e-mailed Tom at PP on the availability of a new part. Just in case PP can't get the part, anyone out there willing to part with a vaccuum advance unit for a 039.905.205 distributor?

Thanks for all your help.

Pritchard

bowlsby · 08-24-2000, 09:42 AM

Well Dave D once again, YOU DA MANNN!

I was remembering a similar discussion from about a year ago with the other 914 brain trust...Brian Kumamoto (where is that boy, did he sell his car and get away from 914's after it was published?)

I went and checked my early 74 model (Aug 73) car and sure enough, it has both retard and advance nipples on the TB as well as on the dizzy vaccuum diaphragm. Both diapgragm nipples have hoses connected, and the retard function operates. The advance nipple on the TB is soldered shut however and the advance hose is only connected for looks and to keep dirt out of the dizzy diaphragm case I suppose. I have heard that some 74 owners have put 73 TB with the functional advance nipples on with improved performance...(quicker acceleration?).

Does anyone know if I can replace that advance nipple on my TB with an open one..are they available? Are they screwed in or pressed in? I am afraid to just heat up the solder or drill it out for fear of damaging it somehow.

Advice?