Rusty Bowtie

General Category => General Discussion - Intros => Topic started by: 28chevyguy on November 10, 2020, 12:30:33 PM

Title: How much timing chain slack is TOO much
Post by: 28chevyguy on November 10, 2020, 12:30:33 PM

Still trying to fix this 71 Cutlass  ( with 350 engine)  .   Used to run like a raped ape.  Now it bogs under load and back fires through the carb like it ain't getting enough fuel .   Changed a ton of parts for no reason and then swapped all the original stuff back on ... because it didnt fix it.   Its NOT the carb ,  distributor , plugs or wires. 

So I tried checking Timing Chain Slack today by pulling the cap and drawing a mark on my crank,  going back and fourth to see how many degrees before the rotor wants to move... I GOT ABOUT 18 DEGREEs before the rotor wanted to move.  They say 10 is the most you'd expect.  Does anyone want to inject their opinion here??    I want my burnout machine back .

Title: Re: How much timing chain slack is TOO much
Post by: TFoch on November 10, 2020, 12:50:45 PM

I had a 70 Nova with a 350 that we bought used.  It started to pop back through the carb and run like crap.  Couldn't set the timing to the factory specs because it wouldn't run right.  Changing the timing chain solved the problem.  I don't know about the Old engines but the 350 Chevy's had that white plastic over the cam gear and some of that had chipped away.

Can you pull the timing cover without pulling the oil pan.  If yes it could be an easy fix.

Title: Re: How much timing chain slack is TOO much
Post by: EDNY on November 10, 2020, 12:54:31 PM

Years ago I had a guy stop by with an Olds 350 that was backfiring etc.  He said it used to run great..changed plugs etc.  Took a water bottle and squirt water around intake to heads area...the vacuum sucked the water right in!

Don't know if the intake was warped or if it had bad intake gaskets...but he said he would take care of it and never came back.

Title: Re: How much timing chain slack is TOO much
Post by: 28chevyguy on November 10, 2020, 01:32:52 PM

Thanks for both the replies.    I hope it is the timing chain, similar to Tfoch"s experience...that would explain the lack of power now adays and the backfire through the carb .  Now that you mention it , although this is going back a few months now , i feel like i DID have to clock the distributor in slightly more advanced than the book wanted , otherwise the idle was stumbling and not so smooth.

   Ed,   im pretty confident its not a intake leak,  I did get plenty of Vacuum with my test gauge.   Idles nice and low.  Pretty sure its just a bad part somewhere I just want to find the dang thing and change it .

Title: Re: How much timing chain slack is TOO much
Post by: 28chevyguy on November 10, 2020, 02:57:23 PM

The Last thing im going to do before tearing down and replacing timing chain... I just ordered a 3/8 inline Fuel Pressure Gauge to see if its getting enough fuel to begin with .

Title: Re: How much timing chain slack is TOO much
Post by: EDNY on November 10, 2020, 08:21:22 PM

Water in a plastic bottle is a very inexpensive test ;D ;D ;D ;D..you may have great vacuum at idle..but  I suspect it's not backfiring at idle.  May not be intake leaks but a couple of squirts and you can rule it out muy pronto!

Title: Re: How much timing chain slack is TOO much
Post by: RoarsRods on November 10, 2020, 09:28:27 PM

Maybe a wiped out cam or broken valve spring or a bad plug wire!
If the chain is worn put a timing light on it and see how much it bounces around while holding the rpm up steady!
RoarsRods

Title: Re: How much timing chain slack is TOO much
Post by: 28chevyguy on November 11, 2020, 09:58:45 AM

OK Ed , Gotcha.  will do . 


thanks RoarsRods  .    will do .

Thanks