My response is/was to assist the OP ...

However, I wouldn't bet on that ... I've seen chains so loose they can be several teeth off. Why fight it, do it right the first time!

You are better off just to not rotate the motor backwards at all, especially when trying to assist a novice over the internet to install a distributer!

In reality it doesn't matter how you set the distributer as long as you have room to rotate the distributer to correct timing, most distributers are limited to the amount of rotational adjustment, so correct teeth match up is essential to ensure you have proper clearances to rotate the distributer to obtain proper timing.

-Enjoy
fh : )_~

 

IMO, if the chain is loose enough to skip teeth from rotating backwards then you'd be saving yourself a tow bill within the next few days if you make it jump out of time at home in the driveway.

 

Bashby, You are reading things that are not written!

Who said anything about the chain skipping teeth??? Not I!

The distributer can be off a tooth or two because of timing chain/gear slop... If the motor has been rotated backwards!

If the distributer is set a tooth or two off you'll have to rotate the distributer to compensate, most cannot be rotated enough because the vacuum advance pot or the like hits things.

-Enjoy
fh : )_~

 

The distributor can't end up a tooth or two off by turning the engine in either direction to line up the oil pump drive, as the way I described the gears are already fully meshed before you rotate the engine.
If rotating the engine backwards causes problems, that timing chain set is pretty much worn out and was going to fail in short order anyway. That said, it isn't a recommended procedure, however in many years of working on engines in general I have never had such an issue.
The distributor is timed off of the cam, so if it ends up out of time from that procedure, the cam is going to be too.

 

I agree, how you described to install the distributer and then rotate the motor to align the oil pump drive will not affect cam to distributer timing ... Due to the fact that the cam gear and distributer gear are already engaged, However, That method will cause major grief for the NOVICE installer! Trying to hold the distributer up (so it's not setting on the oil pump drive shaft) and CAREFULLY rotate the motor is a challenge.

However I do disagree (somewhat) with everything else!

Yes, If the chain is that loose there will be some slight cam to crank timing issues due to chain stretch, however that does not mean it's about to fail, I agree it's not good, but a loose chain can run for a long time, all this does is cause power loss.

However, the cam to distributer timing is another story, if they are not in proper time with each other the motor will run like crap.

And since you mentioned "however in many years of working on engines in general I have never had such an issue." ...

I'll say this, I used to own an engine replacement shop, the re-manufacturing outfit I bought motors from made me an offer I couldn't refuse, I went to work for them, I worked my way from disassembly to assembly to management!

I have set a lot of distributors in my 40+ years of motor building, I would have to guess in excess of 3 or 4 THOUSAND!

-Enjoy
fh : )_~

 

My bad, I did mis read that. It's a rbuilt engine and shouldnt have any play in the chain, so it shouldnt matter. I guess the best thing would be to rotate backwards then forward to check the slop in the chain and take it into account when dropping in the dist.