Top/Bottom End Alignment
#11
10-13-2019, 05:59 AM
Ah, all of that save for the Alternator, Steering Pump, etc, have all been removed a long time ago, its been sitting the garage for several years like that now. And im going to assume i need to remove the valvecover if the pump and alternator are coming out (what with being right over the top of it). And just to be sure i dont botch it - Exhaust valve full open with #1 At Top Dead Center?
- Is the engine out of the truck? (aka sitting in your garage?)
That means that somebody did mess with the engine. Has removed all the stuff in the front and also removed the camshaft chain cover.
Normally the camshaft and the assembly do have specific marks which put them in line with the crankshaft. (Dot or Arrow on both the crank sprocket and the chainwheel on the cam).
If no other adjustment is made or needed (we are talking all OEM components, are we!?) it will simply align the camshaft in relation to the crankshaft.
With this you will have two positions where the crankpin of the #1 piston is on it's TDC. If, as you state in the quote, the exhaust valve is open at that point, you are not at the compression/ignition stroke but most probably off by 1 turn. (Remember: Camshaft turns at half the speed of the crank. To complete all 4 strokes the crank turns twice.)
Indeed, removing the valve covers is a sure method on getting it right, as you can observe both valves open and close until you get it up to TDC with both valves closed. All other parts being in the right order, now you have a sure position from where to start working the ignition.
#13
10-13-2019, 07:55 PM
Just a question:
- Is the engine out of the truck? (aka sitting in your garage?)
That means that somebody did mess with the engine. Has removed all the stuff in the front and also removed the camshaft chain cover.
Normally the camshaft and the assembly do have specific marks which put them in line with the crankshaft. (Dot or Arrow on both the crank sprocket and the chainwheel on the cam).
If no other adjustment is made or needed (we are talking all OEM components, are we!?) it will simply align the camshaft in relation to the crankshaft.
With this you will have two positions where the crankpin of the #1 piston is on it's TDC. If, as you state in the quote, the exhaust valve is open at that point, you are not at the compression/ignition stroke but most probably off by 1 turn. (Remember: Camshaft turns at half the speed of the crank. To complete all 4 strokes the crank turns twice.)
Indeed, removing the valve covers is a sure method on getting it right, as you can observe both valves open and close until you get it up to TDC with both valves closed. All other parts being in the right order, now you have a sure position from where to start working the ignition.
- Is the engine out of the truck? (aka sitting in your garage?)
That means that somebody did mess with the engine. Has removed all the stuff in the front and also removed the camshaft chain cover.
Normally the camshaft and the assembly do have specific marks which put them in line with the crankshaft. (Dot or Arrow on both the crank sprocket and the chainwheel on the cam).
If no other adjustment is made or needed (we are talking all OEM components, are we!?) it will simply align the camshaft in relation to the crankshaft.
With this you will have two positions where the crankpin of the #1 piston is on it's TDC. If, as you state in the quote, the exhaust valve is open at that point, you are not at the compression/ignition stroke but most probably off by 1 turn. (Remember: Camshaft turns at half the speed of the crank. To complete all 4 strokes the crank turns twice.)
Indeed, removing the valve covers is a sure method on getting it right, as you can observe both valves open and close until you get it up to TDC with both valves closed. All other parts being in the right order, now you have a sure position from where to start working the ignition.
#14
10-13-2019, 08:39 PM
The motor is still in the vehicle, and pretty much everything is OEM save for typical maintenance items like the plugs and wires. So both valves need to be closed at the top of the compression stroke on #1, with both marks aligned at eachother? a bent valve and/or damaged piston is the last thing i'd want to end up with.
#15
10-15-2019, 06:05 AM
Correct. I guess that your ignition is off. Therefore it may be necessary to remove the valve covers to make sure your are at TDC compression stroke and set the ignition from there.
Expanding a bit on the issue.
Now we just had to make sure you have an OEM camshaft and cam timing chain set.
If it was aftermarket with various keyways to advance or retard the cam one would need to have the install instructions from the manufacturer.
One needs to understand the inner workings of an engine to do this properly. I.e.:
- An exhaust valve cannot be open during the power stroke - period. (You simply are not at TDC compression stroke)
- All is related to the camshaft. The crankshaft "only" needs to be in the correct position towards the camshaft - timing gear marks. (So the piston is actually up when it should be)
- Ignition has to be correctly set towards the camshaft - period. (Again this means TDC compression stroke #1 cylinder for the Blazers)
The last one means that the ignition event in fact only needs to be correct in relation to the camshaft - assuming the camshaft is in the correct relation to the crankshaft. Obviously when your timing gear is off only by a couple of degrees you will wreak havoc inside the engine.
The rotating assembly (crank, rods, pistons) have the chain sprocket indexed by the keyway on the crank and the sprocket. This mark will put your #1 cylinder at TDC when your camshaft chain-wheel mark is aligned with the crankshaft mark. (see video in the link above)
This is the first adjustment and only relates the camshaft to the crankshaft.
What about jour ignition.? The ignition can still be off by any amount.
Why is that? Because the distributor ignition is dropped into place by a meshed gear without any marks.
For the deeper understanding: It would not be necessary for the ignition to be in a particular direction or point. You could use any position which would bring the finger of the ignition close to one of the points in the cap at the engine being TDC on the ignition stroke and you could adjust from there by fitting the ignition wires in the correct firing order and adjust the timing from there. Unfortunately this is normally not feasible because the manufacturer has decided to give you only that length of wiring. So the distributor on the Blazers normally points in a discreet position when all is correctly set up, and all wiring and spark plug wires can be nicely nestled on the distributor.
Now on an engine which runs fine, when you remove the distributor cap and not the position of the spark wire to #1 cylinder, when you turn the engine over until the TDC mark on the crankshaft pulley/damper lines up with the mark on the block AND the distributor finger points to the #1 spark wire (cap button) you are at TDC #1 cylinder in the compression stroke.
Most of the time people screw up because they pull the distributor and do so without taking into account that the shaft on the inside (with the finger) turns when pulling the distributor out.
Even when you have marked the distributor outer casing people forget to mark the finger at the position before pulling it and after pulling it.
As the gear down there on the camshaft is a helicoidal gear pulling up straight on the distributor will turn the distributor shaft.
I do it like this: Turn the engine until on TDC compression stroke on cylinder #1 (It's important to understand TDC vs. TDC compression stroke! - This is where removing the valve covers comes in.). Then mark the distributor at the adjustment ring vs. engine block AND at the same time mark the position of the finger against the edge of the distributor casing. Then loosen and remove the bolt and the clamp at the block. Pull out the distributor straight up for about 1 1/2 to 2 inches which should pull the gears apart. Remove the distributor without turning the finger. Mark the new position of the finger against the distributor.
When you have to drop in the new distributor or this one back in after whatever repair you did, align the finger with the second mark. (Still assuming nobody has turned the engine.) Then drop the distributor back in the same way you pulled it. Chances are good, that you will hit the gear again in the same spot. While lowering the distributor back in the finger should turn back to the first mark on the distributor case and you are done. Eventually even the oil pump will align nicely and you are done. Can be a 5 minute thing can end up in your nightmare.
What can go wrong:
Somebody turns the engine
Dropping the distributor back it does not engage in the oil pump slot and people turn the finger to make it fit.
Off by one tooth on the mesh between cam and distributor
Not being on the TDC compression stroke #1 cylinder
I hope it didn't confuse you. Anybody correct me or expand.
Expanding a bit on the issue.
Now we just had to make sure you have an OEM camshaft and cam timing chain set.
If it was aftermarket with various keyways to advance or retard the cam one would need to have the install instructions from the manufacturer.
One needs to understand the inner workings of an engine to do this properly. I.e.:
- An exhaust valve cannot be open during the power stroke - period. (You simply are not at TDC compression stroke)
- All is related to the camshaft. The crankshaft "only" needs to be in the correct position towards the camshaft - timing gear marks. (So the piston is actually up when it should be)
- Ignition has to be correctly set towards the camshaft - period. (Again this means TDC compression stroke #1 cylinder for the Blazers)
The last one means that the ignition event in fact only needs to be correct in relation to the camshaft - assuming the camshaft is in the correct relation to the crankshaft. Obviously when your timing gear is off only by a couple of degrees you will wreak havoc inside the engine.
The rotating assembly (crank, rods, pistons) have the chain sprocket indexed by the keyway on the crank and the sprocket. This mark will put your #1 cylinder at TDC when your camshaft chain-wheel mark is aligned with the crankshaft mark. (see video in the link above)
This is the first adjustment and only relates the camshaft to the crankshaft.
What about jour ignition.? The ignition can still be off by any amount.
Why is that? Because the distributor ignition is dropped into place by a meshed gear without any marks.
For the deeper understanding: It would not be necessary for the ignition to be in a particular direction or point. You could use any position which would bring the finger of the ignition close to one of the points in the cap at the engine being TDC on the ignition stroke and you could adjust from there by fitting the ignition wires in the correct firing order and adjust the timing from there. Unfortunately this is normally not feasible because the manufacturer has decided to give you only that length of wiring. So the distributor on the Blazers normally points in a discreet position when all is correctly set up, and all wiring and spark plug wires can be nicely nestled on the distributor.
Now on an engine which runs fine, when you remove the distributor cap and not the position of the spark wire to #1 cylinder, when you turn the engine over until the TDC mark on the crankshaft pulley/damper lines up with the mark on the block AND the distributor finger points to the #1 spark wire (cap button) you are at TDC #1 cylinder in the compression stroke.
Most of the time people screw up because they pull the distributor and do so without taking into account that the shaft on the inside (with the finger) turns when pulling the distributor out.
Even when you have marked the distributor outer casing people forget to mark the finger at the position before pulling it and after pulling it.
As the gear down there on the camshaft is a helicoidal gear pulling up straight on the distributor will turn the distributor shaft.
I do it like this: Turn the engine until on TDC compression stroke on cylinder #1 (It's important to understand TDC vs. TDC compression stroke! - This is where removing the valve covers comes in.). Then mark the distributor at the adjustment ring vs. engine block AND at the same time mark the position of the finger against the edge of the distributor casing. Then loosen and remove the bolt and the clamp at the block. Pull out the distributor straight up for about 1 1/2 to 2 inches which should pull the gears apart. Remove the distributor without turning the finger. Mark the new position of the finger against the distributor.
When you have to drop in the new distributor or this one back in after whatever repair you did, align the finger with the second mark. (Still assuming nobody has turned the engine.) Then drop the distributor back in the same way you pulled it. Chances are good, that you will hit the gear again in the same spot. While lowering the distributor back in the finger should turn back to the first mark on the distributor case and you are done. Eventually even the oil pump will align nicely and you are done. Can be a 5 minute thing can end up in your nightmare.
What can go wrong:
Somebody turns the engine
Dropping the distributor back it does not engage in the oil pump slot and people turn the finger to make it fit.
Off by one tooth on the mesh between cam and distributor
Not being on the TDC compression stroke #1 cylinder
I hope it didn't confuse you. Anybody correct me or expand.
#16
10-16-2019, 02:24 AM
While i had to reread it a couple of times due to the 'odd' english i got the gist of it, Both valves closed with #1 on TDC Compression stroke, meaning it will be on its exhaust stroke the first time the motor turns over, correct? The distributor was installed by a Mechanic and was in proper alignment and has not been removed, so its only as far off as the camshaft itself is, Though that info will be useful next time its due for replacement/if i can find a company that manufactures a compatible electric distribution system for conversion. We're not talking about ignition timing here, only the Cam/Crank alignment.
#17
10-16-2019, 04:48 AM
I always thought it to be a lot easier for people to fix something once you know "all" on how it works. This will enable you to figure out what the problem is.
Your correct, the compression stroke is also the ignition and "work" cycle. Once the crankshaft has turned towards 180 degrees (piston is nearly full down) the exhaust valve opens.
Have to work on my English thou - "odd".
No wonder, as English is not my mother tongue.
Your correct, the compression stroke is also the ignition and "work" cycle. Once the crankshaft has turned towards 180 degrees (piston is nearly full down) the exhaust valve opens.
Have to work on my English thou - "odd".
No wonder, as English is not my mother tongue.
#19
10-26-2019, 12:51 PM
Alright so as im sure i didnt quite get across what im trying to do
Red marks the Crank gear timing mark which isnt visible on camera, In bringing both back to pointing at eachother i'd like to avoid the possibility of bending the valves. I should have stated so earlier that im not sure how far out of alignment everything is so turning the motor at this point to me seems dangerous without understanding where everything is.
Spoiler
#20
10-26-2019, 05:51 PM
Huh, looks gross.
Funny cam drive.
You're in for a valve cover and rocker arm removal.
I stand corrected but as far as I know no way to align that cam with the crank without the risk of hitting the valves when the rocker arms are in place.
Les... you have a good way of doing this without removing the rocker arms?
Funny cam drive.
You're in for a valve cover and rocker arm removal.
I stand corrected but as far as I know no way to align that cam with the crank without the risk of hitting the valves when the rocker arms are in place.
Les... you have a good way of doing this without removing the rocker arms?