When Replacing A Timing Chain On A Small Block 350 Chevy Original Motor?

Question

At first, the car backfired badly through the carb (flames) which made me feel that it jumped timing. After that, it has done it a couple more times. When doing all this, we have checked and the distributor is not 180 degrees off. Used a timing light and checked when my friend had his finger on the number 1 plug hole. When it blew, we aligned it to TDC and dropped it in. Still backfired. And then, we checked compression. Before, all were about 145 and now, more than half are around 90-100. My friend and I didn't touch the rings, the pistons, block, valves or anything. We even checked the valves. Check out fine. The lifters are pumping and everything seems fine. So anyway, backfire badly, low compression, and having a hard time starting, my friends and I figure that when it backfired first, it jumped and may have gotten worse or worn out. So anyway, I decided to replace it. Good insurance anyway. Might as well do it now rather than wait and wait if it is even good. I have a new chain sitting right next to me haha. So I'm going to put it on tomorrow.

Well anyway, if it did jump or is worn, then how can I be sure the pistons, valves, cam, crank and all that align? Do I have to align it at TDC and then remove the heads and then set the cam and crank correctly and then set the chain? Or is there no need for that? Hope not haha. Well, what all do I do. If it jumped or is worn, what are the steps? Granted, I know how to get to it and take it off, but I just wanna get an insight on how to install to insure everything is fine. Thanks

1972 Chevelle 350.

Answer 1

CAN'T COUNT THE 350S&400S&454S THAT HAS BEEN BLT IN MY FAMILIES SHOP,THE FIRST THING I'D CK,IS THE GEARS ON THE CAM & CRANK,MAKE SURE YOU ARE LINING THEM STRIGHT UP&DOWN FROM EACH OTHER,IT WOULDN'T HURT TO GET IT TDC FIRST,AFTER THAT SET THE DIST. DWN IN THE GALLY,TAKE A PIPE WRENCH AND A SHOP TWL.(PUT AROUND THE CRANK)MOVE THE CRANK BACK&FORTH JUST ALITTLE,THE DIST. SHOULD SET DOWN IN THE GALLY,PUT THE RETAINER ON THE DIST. THEN BUT FINGER TIGHT ONLY,THEN BEFORE YOU PUT THE PLUGS BACK IN TURN IT OVER WITH THE STARTER A COUPLE OF TURNS,(2OR3) JUST TO MAKE SURE EVERYTHING SEATED.BRING IT BACK UP TO TDC&CK. YOUR ALIGHNMENT ON THE TIMING CHAIN(GEARS)AGINST THE DIST.&TDC,IF EVERYTHING CK'S BUTTON HER UP AND KICK THE TIRES AND LIGHT THE FIRES,SHE SHOULD FIRE W/O ANTY PROBLEMS,YOU MAY HAVE TO ADJ. THE TIMING SOME TO GET IT JUST RIGHT,BUT NO BKFIRES,GOOD LUCK LET ME KNOW HOW IT TURNS OUT.I'M A CHEVELLE OWNER ALSO,1965 SS Z16

Answer 2

I never did a Chevy timing chain but I did a SB Ford. Everything had a little dot on it that was supposed to line up to get it close. All the signs of what you have going on sounds like that.

To rough time things once you have the timing gears indexed, there is a trick a friend showed me.

He took a distributor cap and cut a hole where the #1 plug wire went in. We put the distributor where we thought it should be and used a pencil in the spark plug hole to find #1 TDC. Just make sure it is on the compression stroke and not the exhaust. That's easy to do if you have the valve covers off.

When we used that system to check things out, we got it to fire as soon as we turned the key. It was a pretty cool deal.

Good luck man. I know how frustrating this kind of stuff can be.

Answer 3

Ive been working on this car for a very long time (i lost count by now) and i say sell it and buy a 69 Camaro or 78 Trans Am :)