1995 4.3 timming chain help

[michigan man]

looking for the right timming installion .my book say cam at 6oclock,and crank at 12 oclock with @4 piston at tdc firring,

i have been told from gm mechanic,@1 piston TDC,cam at 12,crank at 12,and #4 firing,

so which one is right

[michigan man]

im still looking for timing set up help for chain and sproket.what sequence

i have been told my book is wrong.

[Mikado14]

Michigan man,
I doubt that anyone on this forum could quote you what you are asking without referring to a book or they just finished one and it is fresh in their mind.

I will be more than happy to post here tomorrow night after checking at work tomorrow.

Better yet, when you get the timing cover off, rotate the engine until the cam is at 12 o'cock. See where the crank is at and reinstall the new chain and gears exactly as you took them off.

[michigan man]

im trying to help a friend out,he has taking his off before it was properly aligned,and have been told the way he put it back together ,with the chilton book is wrong,or 180 degrees off.
my book said #1 piston at tdc,#4 firing and timing marks at 6 oclock on the cam,and 12 on the crank,

but i have been told the gmc manual for this is 180 different./#1 at tdc,#4 firing or compression stroke,and gear marks at 12,and 12.

so we are trying to find which one is right before putting back together

[BlazerLT]

I don't even see why you need this info.

Take the chain off and put a new one on exactly like it came off.

Why do you need to change anything?

[quaddriver]

the smaller gear is keyed to the crank, there is only 1 way it can go on, the larger pulley is located to the cam via a little nub cast on the end of the cam, there is only 1 way it can go on, as long as they are on and the little 'notches' on each point at each other, you are set.

[Rick Norwood]

I hope you have NOT moved either the Crank shaft or the Cam shaft AFTER the chain was removed.

If either one was moved, do not try to start this engine until you are absolutely certain that it is back where it belongs or you could destroy your engine.

If neither shaft has been moved, put the new chain and sprockets on the way they came off. You can now rotate the engine and make sure the distributor rotor is pointing to the correct firing cylinder.

[michigan man]

as i mentioned it has been turned,and chain and sprockets taking off,and yes you can be off,and you dont just line up timming marks.so im looking for a real mechanic,that knows the sequence,we have two books saying two things,

if you read my first post to this you would understand. its either ,#1 at tdc,at compression stoke,and cam and crank at 12,or it is #4 piston,at tdc for firing,and 12,and 12,.its one or the other only,jim

[Mikado14]

Ok michigan man, follow closely:

IF the distributor HAS NOT been removed, do the following:

Install your crank gear, you have a key way so it only goes on one way. The crank must be rotated so that the mark is at the 12 o'clock position. This should put #4 and #1 at top. DO NOT DRIVE CAM GEAR ON WITH A HAMMER, ALLOW THE BOLTS TO PULL IT ON OTHERWISE YOU CAN KNOCK OUT THE WELCH PLUG IN THE BACK!!!!There is a dowl pin on the cam that fits the cam gear so the gear only will go on one way. The mark at the cam will be at the 6 o'clock position. If the distributor HAS NOT been removed, the rotor should be pointing at the #4 wire. Button the job up, you are timed properly.

IF the distributor HAS BEEN removed, rotate the crank, with the timing chain all in place. Continue to rotate the crank until the crank mark is at the 6 o'clock position and the cam is at the 12 o'clock position. #1 cylinder should be at TDC and ready to fire, you may now install your distributor.

PS: The directions in our manual at work is also unclear. The directions go on in a long string sentence and appear to be incorrect. What you have been stating is a mixture of distributor not removed and distributor removed.

[michigan man]

thanks for the information.the disributor had been out and cleaned.today he put it at 6oclock on cam,and 12 on the crank,and #4piston on compression stroke,with it pointing to number #4 at dis cap.
was installed 180 off
now with it all apart and in line its going to a friends and the mechanic can check it.
it originally quit going down road,no spark,so he thought it jumped time,and started there,it did need a chain.has 181000 miles on it and had been running great

it is still blowing through throtle body yet,even with out any spark

[Rick Norwood]

Michigan Man, This forum is full of real mechanics that want to do nothing but help you. I truly understand your frustration, but you need to understand that we just can't spit out information on a whim. We need to truly understand your problem completely before we can advise you. Remember, you are there looking at the problem, we're not.

If you have the chain on and timed properly, and your still getting blow back through the Throttle body, you might have bent a valve. Have your mechanic check it out.

[michigan man]

going on trailer tomarrow to have mechanic check it out ,now,no spark

[quaddriver]

Originally Posted by michigan man

as i mentioned it has been turned,and chain and sprockets taking off,and yes you can be off,and you dont just line up timming marks.so im looking for a real mechanic,that knows the sequence,we have two books saying two things,

if you read my first post to this you would understand. its either ,#1 at tdc,at compression stoke,and cam and crank at 12,or it is #4 piston,at tdc for firing,and 12,and 12,.its one or the other only,jim

Who is telling you this crap?

your 4.3 is a chevy.

without fail, all chevys have the crank gear keyed and the timing gear located.

unless it is a special cam gear that allows it to be clocked 0, +4, -4 it will only bolt on one way (unless you use a large hammer) and note, even the gears that allow such clocking ONLY allow such clocking.

so to reiterate:

if the gears are pressed and bolted on, and the crank has its mark at 12, and the cam gear at 6, then the valves are in time. Period.

that bears repeating:

if the gears are pressed and bolted on, and the crank has its mark at 12, and the cam gear at 6, then the valves are in time. Period.

as for re-timing a distributor, it is also not the rocket science people claim it to be. As you are facing the motor, the norm is to have the tower for #1 be to the right of the centerline (imagine a line drawn thru the dist from the front of the engine to the rear), but the tower can be ANYWHERE as long as the rotor points to it when #1 is TDC. As for timing off of another cylinder, its one of those 'I have to be different' things people do when they time a chevy V8 off 6. they dont know why it works, they jsut accept that it does and somehow they are avant garde. Shop elsewhere.

1 and 4 on the v6 have TDC(F) 360* from each other. If the crank turns twice for one cam rotation then you can deduce that if #4 is at TDC(F) at 12Cr/6Ca then #1 MUST be at TDC(F) at 12CR/12CA, or else someone used that large hammer.

I happen to have a 4.3 rebuild on one of the stands right now so just holler if you need to see pics.

[michigan man]

thanks also quad river

i was sent information,that said,#1piston on tdc,#4 firing,and 12 and 12.

which was wrong,its exactly as you say.6,12 with #4 firing.

is it possible to hit a valve ,if motor was turned with it 180 off,thats way he had it and turned it over,and does blow through throtle body,every now and then.
the car lost spark ,is what started this,so its on the way to shop today,jim

[Rick Norwood]

yes it is possible to hit a valve if the crank and cam are out of time.