'98 Blazer Timing chain replacement
 

Hello,
I have a '98 Blazer, 186K miles, with a 4.3 engine. I would like to replace the Timing chain since I am replacing the water pump (pump failed) and giving it a complete tune-up.

I have never done a Timing chain and am a bit confused by the Haynes Manual on locating TDC for the #1 Piston. I have no timing scale near the Harmonic Balancer (don't know if there ever was one) except for the two "Lines" that are on it. When following the book It states to rotate the engine by hand waiting to feel a "puff of air" come out of the #1 cylinder (my book shows that to be the cylinder on the drivers side neareast the front) while watching the rotor line up with the mark I made for the #1 spark plug. The "puff of air" is never felt or heard when the rotor passes the #1 spark plug unless the person helping me is wrong about not feeling it.

The manual then states to rotate the engine again once TDC is found on the compression stroke 360 degrees before removing the chain.

Does this sound right or am I missing something?

Thanks for your help.

maybe this will help...https://blazerforum.com/forum/showthread.php?t=24373

If the timing chain has jumped, then you may not get the rush of air out the spark plug hole. At that point, you can just rotate the engine over until #1 is at TDC and hope for the best. Worst case, you'll have to rotate the engine over to get the cam back close. Once you have the old timing set off and the new one ready to install, you just have to line up the dots on the cam and crank gears.

Put the engine through two full rotations after you get the new timing set on, but before you put the cover back on to ensure that it keeps alignment properly.

Thank you for the quick replies. I'll try lining it all up best I can before removing the timing cover and then see where the timing marks on the sprockets are. In all honesty I don't see how it matter much If I were to make marks where the timing marks on the sprockets are along with some other refrence marks then put the new stuff on in the exact same place. Either way I'll do it the way the book and the two of you suggest.

Any thoughts on the book stating after getting to TDC to turn the engine another 360 degrees before removing the timing chain?

I would not bother with the timing mark. After the timing cover is off rotate the crank until the dots on the crank & cam gear line up. I doubt if it jumped time. If it did the dots will not line up. Just make sure the dots line up when you put it back together and you are good.

I do not know why it would say to do that... Haynes manuals often tell you to do things that are not necessary and leave out a lot of the necessary things though...:icon_doh:

In the end, that is all that is necessary. Just get the timing marks lined up and then put it through two full rotations of the crankshaft to ensure that the timing marks come back around.

My comment in regards to jumping time was to include that possibility in case the OP was replacing the timing set because of a stretched chain that has jumped already.

And please keep things in the open forum. So long as your question gets answered, who cares if there is a debate about how to do things correctly. In the end, the correct information will be presented and differing opinions will be ironed out.

Thank you for eveyones advice and help. It is all much appriciated.
David.

Hello all,

I am hoping for a bit more help.
I removed the timing chain cover to find what I was told is the "Oil Slinger" infront of the Crankshaft sprocket gear. It resembles the adapter that used to go in the middle of a 45 record (remember those).
It looks as if it comes with a Jaw Puller but I want to make sure before I go trying.
Thank you in advance.

I think what you are describing looks like a cup shaped washer that fits over the crank in front of the timing gear. I believe it helps keep oil from spraying on the seal. It should just pull off by hand and you can put it back on when you are done replacing the chain.

This is the CKP (crankshaft position) sensor reluctor ring (see the attached image). It should not be too difficult to remove. Be careful with it.