I am considering installing a Crane Adjustable Vacuum advance on my 1970 455. The part can be seen at:
http://www.summitracing.com/parts/crn-99601-1/overview/

Has anyone had any experience with this product?

Thanks, Peter

 

It's a very easy upgrade, just follow the directions.

 

If you don't need the Mech. Adv. springs, there's a $10 less alternative


Your local speed shop may have such a kit for a similar price also.

Easy, and if you need to tailor the spark curve due to engine mods [like my very non-stock 403] it's a good idea and not real difficult to do.

Be aware that the "adjustability" of the VA unit is generally ONLY how far it travels, not what vacuum at which it starts to move.

Google search for other articles describing the vast array of VA choices and how to select the right one, or contact me if that proves futile.

 

To add to what Chris wrote, be aware that changing to an adjustable vacuum advance is not an "upgrade" in that the change by itself really won't result in a performance increase (unless the old unit was non-functional). What it will do is allow you to tailor the vacuum advance to better match the needs of the engine based on any other mods you've made or on today's crappy gasoline.

 

Joe is correct. It will also allow you a bit more initial timing and a way to limit your cruise timing to compensate.

 

Thanks, I understand. The primary result I am looking for is to be able to better adjust timing to deal with pinging under load at 2300 -2800 rpm (climbing West Virginia hills, or passing at crusing speeds), while still having enough advance at low rpm for idle and around town driving.
I was planing on trying out stronger mechanical advance springs and then adjusting vacuum advance.

Separately - I understand that I can replace the springs and vac advance with the distributor on the engine. What if I notice that the weight bushing is worn - do I have to take the distributor apart to change that?

 

use a vacuum pump to check it when adjusting it more then once also. I had one before it worked great but it was touchy to adjust especially the crane unit. I also had better mileage and better performance with it.

 

Hi JFB - can you explain how it was "touchy" to adjust?

Thanks, Peter

 

I had a lot of advance for only a few turns of the allen wrench on mine pcard this could spell detonation problems just check it a few times to avoid problems. my advance after a few turns was 50 plus degrees.