Well I was in the process of adjusting the timing and found out that I have way to much mechanical advance, 13btdc and total mechanical is 49, so 36 degrres of mechanical advance is alittle much here, and I would like to run alittle higher than 4btdc like 10-12 and still be all in around 36-38. some one had obiously at one time advanced the unit at idle and didn't recurve it for the advance of initial and put the total way to far over. They didn't know what else they were changing by doing that, I assume. So none the less I decided to pull the dizzy and change the limit bushing to find it crack and worn. No suprise. I went ahead and disassembled the distributor to check the rest of it out aswell while its out of the car. It is the factory 68 TI that came in the car and has seen about 40,000 miles. The tach gear hasn't worn the back wall if the distibutor too much yet, with a pick i can barley feel a ridge where the tit is in it. The tac does bounce a bit when revving up and down though. I feel like i should upgrade to the teflon button? Im not sure i want to drill a hole in the unit for the button though, or if it would affect clearances for the tac gear too. I dont want the brass button on the end of the gear anyhow, they seem like they could cause other isses that I dont need. Just looking on some input on what other people would do here. I do need to get a new limit bushing and the seal that goes over the cavity for the upper bushing. It was still filled with the factory dust like whatever it is oily material all clumped up. One artical I read said to use a 3x3 piece of gauz and roll it up and pack it in there? Good....Bad?

Is there a spec on tach gear movement also? .010? Is that just at the end where the tach drive goes in and just put a dial indicator on it and try to pry it back and forth? I'm also not 100 percent sure what I would need to do to this housing to install the Teflon button if that is in the end the way to go

 

If you are curving your dizzy for performance, you don't really care what the 'initial' timing is. You adjust the distributor for max mechanical advace of 36 deg. with the vacuum plugged off (this should occur between 2600-3000 rpm or you need to change springs on the mech adv. weights). Then, when you go back to engine idle, you can just check where the initial advace is; but as long as it is under about 16 deg., you should just leave it that way. The idling engine will likely run cooler and idle better than at 4 deg., anyway.

 

That's what I'm looking to do, but I'm going to need a new or maybe larger limiting bushing to achieve this. That's the reason I would like to get the initial timing/base up somewhere around 10 to 12 (roughly). Like you said, to help some some minor cooling issues and help the idle smoothness. Im guessing Im going to end up using a little larger than stock size limit bushing in the end. Thanks for the reply

I really want to get this tach drive figured out and what I should/need to do there?

 

Measure the length of your limit slot with a pair of calipers - in most cases, the slot is too long to produce a good performance curve even with the limit bushing in place. Weld the end of the slot and grind it to shape to produce a slot that is no longer than .365". This will give you the timing numbers you want.

If you have very little wear on your housing thrust surface, simply grease up the end of the crossgear and re-install it. Don't use the brass thrust button - it will get chewed up quickly, and all the brass debris will destroy your lower bushing.

Pack the upper greasewell with wheel bearing grease. This will slowly "ooze" over time, providing a nice time-release lube for the upper bushing.

There is no spec on crossgear endplay - just make sure you do have some play so it's not locked up... It's exact position with relationship to the mainshaft gear is irrelevant, as long as it's fully engaged. The length of the crossgear gives you over 1/8" of float in either direction to maintain full contact.

Lars

 

That's perfect. If there's no need to install the Teflon button then that saves me the time doing that and wondering exactly how aswell. I'm guessing by filling the slot your using the factory limit bushing? Is that a rubber one? Or are you changing to a different one? Thanks alot for your knowledge

 

For filling the slot, I'm using a TIG welder and a high speed grinder to shape it after welding. In addition to welding it, you may still need to use the limit bushing on the stop pin. It doesn't matter if you use the factory-type rubber bushing or if you use the brass bushing in the Mr. Gasket 928G kit - they are both the same diameter. Use of the bushing by itself, without welding the slot shorter, will typically result in an advance curve that is far too long for a good performance application: You'll only be able to run about 6-8 degrees initial with 36 total in most applications with only the bushing installed. On your engine, you want to be able to get your initial up in the 16 to 18 range, and then have 36 total.

See my paper on How to Set Timing for instructions on how to calculate the slot length requirement. E-mail me for a current copy.

Lars
V8FastCars@msn.com

 

Email sent thanks again man