Technical Rattle in Crab Distributor (brake piston perhaps?)

Hi All

Running a flatty with crab distributor and petronix module and car runs fine, but have an issue with a rattle noise coming from crab distributor that is connected to manifold vacuum, mostly at idle.

Have removed the distributor several times to check for damage, and all looks good, and believe it may be the brake piston rattling when high vacuum and the piston may be pulled away from advance ring, and its just rattling in the tunnel sleeve it sits in the distributor.

Have wound the preload on the spring down three turns after what feels like it starting to get tension, but think ill keep giving it a few more turns to see if the noise disappears (more spring tension to fight vacuum at idle)

Has anyone else ever experienced this? At first i though it might have been vacuum escaping out the cap, but believe its the piston rattling.

Also if vacuum is pulled from the distributor, the noise disappears, which has lead me to believe its the piston.

Couldn't find anything on the web or searching, surely I'm not the first to experience this.

cheers Julian

 

Does it still have a piece of leather on it and is it hard as a rock? Bubba had a rebuild post on here many years ago and he was using the leather from an old weight belt for rebuilds.

 

Hi Oldtimer, yes still has the original leather, and is hard but i soaked in oil for a week and it softened up somewhat.
i do have an old toolbag with thick leather that im thinking of punching a circle out of to replace the leather pad.

 

to those that are interested, i ended up finding the advance plate had a wobble in it (years of wear i guess) and when the vacuum was high (idle) and the piston would rise, the plate was wobbling thus rattling the piston in its slot.

I put a shim behind the advance plate and put the distributor all back together and now all good.

cheers Julian

 

Thanks for checking back in. I'll be rebuilding one these distributors this winter so any info is helpful