Jackshaft rotational play

[paulbell6]

Hi, when I rebuilt my engine the gears on the Jackshaft and Distributor (which had covered 57,000 miles) were very shiny on the surfaces that were in contact with one another and if I ran a finger nail over each area there was no noticeable ridges showing signs of wear. Thinking back to my Engineering days I do know that meshing gears by design have a certain amount of "backlash" built into them, so I would imagine that this is what you are experiencing. I assume that you are measuring the two millimetres on the outside of the Jackshaft sprocket, if you are measuring off the Jackshaft itself then it may indicate a problem.

Good luck

Paul

[MLCstag]

Hi, when I rebuilt my engine the gears on the Jackshaft and Distributor (which had covered 57,000 miles) were very shiny on the surfaces that were in contact with one another and if I ran a finger nail over each area there was no noticeable ridges showing signs of wear. Thinking back to my Engineering days I do know that meshing gears by design have a certain amount of "backlash" built into them, so I would imagine that this is what you are experiencing. I assume that you are measuring the two millimetres on the outside of the Jackshaft sprocket, if you are measuring off the Jackshaft itself then it may indicate a problem.

Good luck

Paul

Yes, at the outside edge of the sprocket. Now going to get the jack shaft out for peace of mind.

Thanks

[Stagsongas]

You might find this thread useful;

http://www.stag.org.uk/forum/showthread.php?22234-It-s-Broke-(&highlight=It%27s+broke

Regards

Steve

[MLCstag]

The distributor drive teeth do wear on the jackshaft, but don't normally fail catastrophically like the water pump teeth.

I have had to replace the jackshaft on my project Stags engine due to wear on the distributor drive teeth, the water pump teeth were perfect, just like on the spare jackshaft I have got that I took out of a scrap engine.

Neil

Neil / All

Can someone help me identify exactly what excessive wear is? The jack shaft is out and the distributor gear teeth on the jack shaft are shinny but are they worn? The edges are still parallel and not sharpened (see pictures). The same is true of the gear teeth on the distributor. If I buy a new jack shaft and distributor shaft, will the play still be there as it could be "normal"? If I do buy a new jack shaft are they well engineered and are all suppliers providing from the same manufacturing source?

Incidentally the jack shaft water pump teeth are also shinny but may not be excessively worn. The water pump teeth are perfect.

Dist copy.jpgJackshaft dist gear copy.jpg

[staginhiding]

They don't look too badly worn ..always tricky from pics.
Are the shiny bits still relatively flat i.e not hollow across the tooth..

Sam

[staginhiding]

Have you checked the very front bearing surface in the block for wear,usually in the form of a ridge..

[MLCstag]

They don't look too badly worn ..always tricky from pics.
Are the shiny bits still relatively flat i.e not hollow across the tooth..

Sam

Appreciate its difficult to see from a picture. I also find it difficult to detect any hollow across the tooth so it could be reusable? If it wasn't for the play I would reuse

[V Mad]

It looks OK to me.

Talking of play, My car ran for a couple hundred miles with no lower bearing in the pump. Yes that's what I said, no bearing at all; the PO had forgotten to fit the bush. So I would not worry about a 2mm backlash.

[milothedog]

Appreciate its difficult to see from a picture. I also find it difficult to detect any hollow across the tooth so it could be reusable? If it wasn't for the play I would reuse

A simple way to check that any case hardening on working surfaces is still good is to try and score it with a sharp tool, it should just glide over it and leave no mark.

Ian.

[flying farmer]

Those teeth look pretty good to me. If there are no obvious ridges or hollowing of the teeth, and the flat bit on the top of each tooth is not worn narrow, then the shaft should be good for reuse.

One of my engines has over 150,000 miles on a jackshaft and pump, if they were hardened properly in the first place they seem to last a long time.

Neil

[MLCstag]

Ian / Neil

Thanks for your comments. I'm coming to the conclusion that the jack shaft can go back in. Just need to clear my head about the pump option. I try the scratch test tomorrow. Need to overhaul the distributor whilst its out too.

Brian

[MLCstag]

Sorry didn't mean to ignore all the other comments from everyone else. I very much appreciate them and will take them into account.

Cheers Brian