Hi,

History:
Bought an '88 with 230k on the truck, PO said ~150k on the motor. Ran fine.

Then check engine light, shows TPS failure, I replace that but have trouble dialing it in to make the light go off. Can't set it right. Told to set the ignition timing, I try to do that but find it's way off. I'm in a hurry, so take the truck to the shop.

Shop looks, says the timing chain must have stretched (he says probably because of using nonToyota oil filter) and jumped a tooth, because it's off a tooth. Says I was lucky it didn't snap and tear up the valves etc. So he recommends a new timing chain kit.

I'm in a hurry and don't know much about timing chains, so I tell him to go ahead. *&#$ expensive. Now I have someone tell me that these chains don't ever jump a tooth, if they stretch that much, they just break.

Anyone ever know of these chains stretching and jumping a tooth? Or was my timing put together wrong at some point and the chain was fine? I brought this up at the shop and the tech asked the mechanic whether the guides were broken. They were not.

Please any commments appreciated. Feel like I got hosed for the price of a new kit ($270).

Thanks,
Bryan

If $270 was for the kit with installation, it's an awesome price. If just for the kit, you need to bring vaseline in with you when you pick up your truck.

The basic kit from engnbldr is $54, and $64 gets you a kit with a steel rail guide (rather than the stock nylon guide).

It's possible for a chain to jump a tooth, just unlikely. Especially with the guides still intact. I call BS on the diagnosis. The truck would run like crap with the cam off a tooth (either real strong off idle, but flat on it's face above 3,000 rpm, or no power until above 4,000 rpm).

The reason the timing looked so far off was the fact that the TPS was out of adjustment... It would be around 12* BTDC without the jumper (or with jumper but TPS out of spec), and 5* BTDC with jumper in place.

A good way to get everything close enough is to loosen the TPS, install the jumper, and rotate the TPS until the idle drops. Set the timing to 5* BTDC at 600 rpm. Then wiggle the TPS back and forth until you find the closest adjustment between low and normal idle. Tighten it down, remove jumper, and drive.

Get your truck away from these hacks! <img src="/forums/images/graemlins/scared.gif" alt="" />

Anyone ever know of these chains stretching and jumping a tooth? Or was my timing put together wrong at some point and the chain was fine? I brought this up at the shop and the tech asked the mechanic whether the guides were broken. They were not.

Please any commments appreciated. Feel like I got hosed for the price of a new kit ($270).

Thanks,
Bryan
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>>>*While it is possible for the side plates to get hot enough for the metal to actually "stretch" my feelings are this is not what actually happens.

There are several wear points, the outer roller spins on an inner pin so the pin can wear, the inside of the roller can wear, the outside of the roller can wear and the side links can become loose and add to the total.

Considering there are 96 links on the late design and 98 links on the early, we can see quickly that this can stack up to a LOT of added length.

I have seen chains that are pretty long, those I can tie into knots. A new tight chain can't be, they won't flex that far.

So if a chain is running way too snug for some reason, like we will see if a 20R or 22R head is on a late 85 & up block without enough metal milled off, then it can and will wear quickly.

We know the chain will elongate, that is why the system incorporates a tensioner in the first place. If it didn't, there would be no reason for one.

Of course the tensioner has limits, and if the assembly gets worn enough, it can jump teeth rather than completely breaking...*EB

Hey thanks guys for the comments, that's helpful for sure. Yea the $270 was just for the chain kit; another $500 for labor....

Thanks again, great knowledge on this list, and it's really appreciated.

Bryan Pon