bobs65

Hi folks -

Was searching through old threads looking for some info from "Lars" about distributor tuning etc...and came across this post:

Lars's Tuning Secrets: The Common Tuning Tour Observations and Fixes

He mentions before doing any sort of carb tuning to first tune the ignition system. I am just about to finish up with my Carter rebuild and before I install and tweak, it looks like I should be pulling the dist and checking it out? I still have a recurve kit from Lars that I'd love to install.

I guess the first question is, can this be done by a newbie? or should I farm this out? Can someone point me to some good articles/docs/pictures of a dist rebuild/recurve. I recall Lars kit coming with a lot of documentation.

thanks as usual,
Bob

BarryK

go to my Tech Articles page here:

http://www.lbfun.com/Corvette/Tech/vettetech.html

click on the title header called "Timing & Vacuum advance"

read the following articles for everything you need to know about timing and setting up your distributor.

Timing 101
by: John Hinckley

Mapping Advance
by: John Hinckley

Timing for Peak Performance
by: Lars Grimsrud

Vacuum Explained
by: Lars Grimsrud

Vacuum Advance Specs
by: Lars Grimsrud & Duke Williams

chris ritchie

Lucky you! I wish I had one of those Lars kits. Lars stopped doing distributors.

I assume the kit is either little springs, weights, or both. Take your distributor cap off and then take the rotor off. The springs and weights live under the rotor. You can replace them without removing the distributor. Loose one of those springs and you'll hate yourself.

The articles listed in the previous message will tell you all you need to know about checking your new curve. Check the articles, but I believe you'll need a dial back timing light to check the curve. The articles will tell you for sure. A dial back light will certainly make the checking and setting the timing easier.

If you need to replace the vacuum advance, it is possible to replace it without removing the distributor. But it's tricky.

bobs65

I recall the kit having springs,weights and the vacuum advance. Having never messed with a dist, should I even be attempting to pull it out...or can I use this as a learning experience and it isn't that bad?

In other words, should I have someone around who's pulled and installed one?

Bob

BarryK

refer back to my tech articles page under the "Ignition System" section. There is an article by Lars on how to install the distributor after you removed it

62Jeff

Bob, if you read the articles hosted on Barry's site, take notes, and remember that we're here to help, you should have no trouble doing this.

The biggest challenge I would imagine someone having, is putting the distributor back in the correct way. If you use the orientation of the distributor rotor and vacuum can for reference before you remove the distributor, and then later install it aligning those two reference items with wherever they were aimed when you pulled it out, you should be close enough to get it started.

0Willcox Corvette

I agree with you guys. Read, Read, and Read some more! So many people do not understand timing and advance curves! Having the correct kit is important as long as you have the right distributor shaft. I don't know what Lars sent you but I'd bet it is on the money and a tried and true fit.

If you can't figure it out then send it to me. I have the old sun machine and can dial it in for you.

Willcox Inc.

bobs65

Thanks everyone and I certainly still don't fully understand timing and advance curves. The kits Lars sent has:

1 Shim kit w/2 - .010, 2 - .020 and 1 - .053 hardened shims
1 Brass Centrifugal Advance Stop bushing
1 Custom Calibrated Black Centrifugal Advance spring
1 Custom Calibrated Silver Centrifugal Advance spring
1 Custom Calibrated Vacuum Advance Control Unit

...no weights like I initially thought, but Lars explains why. So it looks
like I have everything I need in this kit.

Bob

chris ritchie

I just saw this thread after posting to another one started by you.

Make sure you fix your carb before attempting this. Don't fix the distributor and carb at the same time. That's because if you screw one up, you won't be able to diagnose what's wrong.

bobs65

Thanks Chris...no doubt I have no plans in touching the dist until I get the carb going. I guess I got ahead of myself...it all went back together so nicely, so the confidence of slappin her back on and firing her up was high...

Bob

bobs65

Hope everyone had a Merry Xmas!!

Ok with my carb rebuild done I've moved onto the distributor. I'm at the point of installing Lars recurve kit, but read some stuff about packing the oil well with gauze and a plastic seal? Mine did not have a plastic seal and there wasn't much left in the oil well.

Is the plastic seal important? and can I just pack the oil well with something else?

Bob

BarryK

the "packing" in there was kinda like sawdust. it's use was to hold the oil for lubrication. If any was left at all you were in pretty good shape.
I'd clean it out well and use a 3"x3" piece of gauze and saturate it with 20wt non-detergent motor oil.
Install a new plastic seal - they should still be available thru your local Chevy parts counter. GM part number 1950569 for 10-pack.

JohnZ

Yes, you need the seal - that's what keeps the lube for the upper bushing from drying out (that bushing gets no engine oil from below - it's only lubrication is from the lube well below the plastic seal). I prefer the packed/oiled gauze as Barry noted, but you can also use wheel bearing grease or gray moly lube. Don't forget the oiled felt washer that goes on top of the seal - that lubricates where the breaker plate pivots on the O.D. of the upper bushing.

bobs65

Thanks John and Barry.

I was able to find a seal at my local vet shop and packed the well with a soaked gauze....what I just realized is I put back the original felt washer(in good shape) as is...didn't soak it in oil?

..and now the dist is installed and ready for the timing part of the show.
Do I need to pull it back out?

Bob

JohnZ

I'd pull it out and oil that felt washer - without lube, the breaker plate will eventually start to bind on the upper bushing; it moves hundreds of times per hour, every time the vacuum advance moves.

bobs65

Ok, pulled it out, took it all apart and oiled up the washer as suggested. I put it all back together and now she won't start?

I'm pretty new to this, but am thinking the points are toast...here's why. One of the steps in Lars recurve kit was to rotate the dist and listen for a "snap" which are the points opening as a spark jumps the point gap.

Now I don't hear or see this happening like before. Can points just fail like that?

thanks,
Bob

BarryK

first, make sure the distributor is in correct, it's easy to get it reinstalled one tooth off.
than make sure the ignition wires are indexed correctly on the cap (correct wire in the correct place).
one thing to double check is the black ground wire that is the ground wire from under the breaker plate to the negative terminal on the coil. This wire because of all the constant movement of the breaker plate can fail causing no ignition spark. Check it carefully for cracks, broken wires or faulty connections at the terminal ends.
The points shouldn't "just fail". If you didn't touch them they should be fine but if you removed them and reinstalled them they may need to be re-gapped. If you don't have a feeler gauge you can use a paper matchbook cover - it's close enough to the proper gap thickness to get it working. Also, a quick run of a file over the points ends will clean off any oxidation or pitting causing a poor contact.
It could also be a simple case of the distributor rotated too much out of correct timing position. Did you mark the distributor housing against a reference mark on the motor to make sure it was reinstalled referenced back to those marks? If you did you should be close enough on the timing for it to at least start before resetting the timing with the light. If you didn't put reference marks to reinstall it back in against the position may just be out far enough to set the timing off enough to prevent starting.

bobs65

I did mark both, but lost the dist mark when I cleaned it up. Lars recurve documentation had a pic of the wires and how the dist/rotor points at the #1 wire.

So when I initially put the dist back in the first time when it finally dropped in, the rotor had moved over a few notches and was then pointing to the #8 wire. The documentation talks about "walking" the rotor back around to the #1 position, but I could never get it to work.

I then moved the oil pump shaft a little clockwise so it lined up with what I remember it looking like when it went in before and it seemed to work(the rotor was pointing to the #1 wire).

The black ground wires seem all connected and fine. When I initially took off the dist, the back wire from the vacuum advance to the breaker plate was broken and just hanging there. I re-stripped the breaker plate end and crimped it down to the existing place. There is another ground from the points to the coil which is fine.

I removed the points/condenser 3 times during this whole process. Once when I initially took the dist out and apart, then again after putting in the plastic seal and today after needing to soak the felt washer.

Bob

BarryK

ok, you covered the black ground wire, and if the rotor is pointing to the #1 terminal you are probably installed OK.
Most likely it's just a rotational timing setting issue (position of the distributor). you can actually use an Ohm-meter to get yourself pretty close, probably within 1-2 degrees of correct timing, more than close enough for it to fire up.
try Lars paper here:
http://www.lbfun.com/warehouse/tech_...stallation.pdf
look at step #7 in this article. He describes how to do it and it saves me all the re-typing

Oh, and forget what I said in my last post about the points gap. I had a major brain fart last nice and not sure why I said removing and reinstalling the points would change the gap, it won't. If it was fine before you removed them the gap should still be fine now, the only thing that changes by removing/reinstalling them is the dwell setting.

JohnZ

Dwell setting = points gap. When you adjust the dwell, all you're doing is changing the points gap.