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Discussion and questions related to the course How to Degree a Cam
So I've followed the steps to find true TDC using the piston stop in the spark plug hole method. Once I verify where true TDC is by rotating the crank both ways and landing at the same degree (let's say I calculated both values and divided by 2 and it ended up being 6*), is this just where true TDC will be once I remove the piston stop and rotate the crank to have 0* line up with the pointer?
I guess I'm just confused because when i move the indicator to 6* that's with the piston stop is still in and therefore the piston isn't all the way up yet. And when I take off the piston stop and rotate the crank to line up 0* to the indicator my cam gear marks don't line up (off by about half a tooth or so. Wondering if there's something I missed or did wrong because in the next video Andre says that true TDC is found and the valves should be closed.
Use the stop so the piston is stopped a little way down. Then gently rotate it until the piston hits the stop and make a note of the position on the wheel, relative to the pointer, then rotate it in reverse until it hits the stop and note the position relative to the pointer. TDC will be the middle of those points, relative to the pointer.
Remove the stop, move the crank back 45 degrees, or so, and set the camshaft(s) to theirmarks and bring the crank up to the TDC mark - do it this way to prevent possible valve to piston contact it a piston is too close to TDC as the cam' is turned to position. Then bring the crank up to TDC and fit the belt/chain from the crankshaft working counterclockwise with the tensioner/adjuster backed right off. Then release the tensioner and set the initial tension. Turn the engine over by hand and if there is any sudden stop, or feeling of something stopping rotation, recheck the marks. You need to turn it over 2 or three complete revolutions to ensure the slack is taken out of the drive side, then reset the tensioner to correct for the slop developed, turn it over a few more times and recheck the timing is correct.
If it still seems like the timing is out, recheck and reset.
It's WAY past bedtime, so may have missed some steps, but you should get the idea.
So I just want to reiterate so I can try to better understand the process.
1. Without the belt installed yet set the crank to TDC using the mark on the oil pump.
2. Install the degree wheel and indicator and have the indicator point at 0 degrees.
3. Back up the crank about 20 degrees or so, install the piston stop, bring forward the crank to about 10 degrees, wind down the stop until it makes contact with the piston. Note the value.
4. Rotate the crank in the reverse direction until the piston contacts the piston stop again and note its value.
5. Add both values and divide by 2 which will yield the value where TRUE TDC is.
6. Adjust the indicator to point to the value. Rotate in the reverse direction and ensure that the piston makes contact with the piston stop at the same value.
7. Remove the piston stop and bring back the crank about 45 degrees, or so.
8. Set the camshafts (I assume this means have the marks on the cam gears facing each other and the dots or some indicators pointing up) and bring the crank back to 0 degrees TDC.
9. Have the tensioner on the loose setting and install the timing belt, starting at the crank working counter clockwise.
10. Release the tensioner and set the initial tension.
11. Rotate crank 2-3 times to eliminate the slack and then reset the tension.
12. Rotate crank several more times while checking on the timing.
OK, first my apologies, as I made a small error earlier (I think), as it's been a while and they were mostly 'head off', engines where the camshafts or rockers could be removed, non-interference engines, or in-line fours.
What is the engine?
Where possible remove the camshaft(s), the rockers/followers, or pushrods - basically remove the ability of the camshafts to lift the valves around TDC to avoid possible V2P contact. Basically a safety move for some engines - but you may not need to do it entirely.
With an in-line 4, note, if you have removed the head(s), camshafts, or whatever, some of this doesn't apply because the valves can't open.
1/ Before doing that, if the valves can be operated by the camshaft(s), leave the crank where it is if it's at positioned where the pistons are well down the bores, or carefully move it away from close to TDC or BDC, stopping if any contact is felt. This is so there will be adequate valve clearance as the camshafts are rotated to #1 TDC. Now turn the crank towards TDC, avoiding passing though BDC if there's risk of valve contact.
2/ Yes, you're using the marked TDC point is the first estimate.
3/ 45 degrees might be better, you want to make sure you can't force the stop into the top of the piston as damage can occur. With the stop in place, bring up the piston to the stop, don't force it, light contact is all that's needed - DO NOT try screwing the stop in against the piston!
Mark, or make a note of, the pointer position, eg 37 degrees BTc on the wheel.
4/ This is an important bit I missed. If required, with the crank in a position where all the pistons are down the bore, rotate the camshaft(s) by 180 - this is because as the crankshaft is swung through BDC #1 it will also move #2 and 3 through TDC and you want the valves at their TDC position for clearance as this is where both intake and exhaust are most closed.
With the valves safely clear, rotate the crankshaft through BTD until it contacts the stop again (if you feel any sudden resistance or contact, stop and check what might be causing it). Mark, or make a note of, this marker position, for example 41 degrees.
5&6/ In this example, there is 4 degree difference, so adjust the degree wheel to 39 degrees and recheck the two positions which should both be 39 degrees. Adjust and repeat if required.
When both values are the same, make a new crank TDC mark - I would also suggest making a note on the cam' timing slip, the engine manual, the build log (it's a good idea to record things as you go), and/or anywhere else it would be useful - you may not be the person who needs the info'.
7/ Yes, back the crank off so when you rotate the camshaft(s) to set the initial camshaft timing there's no possible v2p contact - or when the camshaft(s), rockers, or whatever that were removed to aid the process are re-fitted there can't be accidental contact and damage.
8/ With the pistons well down the bore, around 90 degrees B/ATDC is what I used to use, this is a good point for setting the vlave clearances, if required, as it's much easier to just turn the camshaft(s) with a spanner (wrench) than the whole engine. Different manufacturers use different methods, use the one for your engine to set the TDC #1 position(s) for the camshaft(s). If you're using vernier sprockets/gears set them to their 0 mark for this, this will be the base value for them.
9-12/ Yes, in operation the tension is from the crank' back, with the tensioner normally the last thing before the crank'. You need to rotate it several times, checking for any sort of resistance that may indicate V2P contact, then check the tension, it will usually need to be adjusted a time or two, and the camshaft timing is still correct. Oh, some engines run other things of the belt that are also timed, such as distributors and balance shafts, so don't forget to check everything - it's easy to have something jump a tooth. Remember, while drag will increase, so also be cautious about any feeling of contact.
I think that's about it, hopefully I haven't missed anything. Anyone else?
Thanks Gord! I'll try to follow these steps carefully. The engine being worked on is a Hondas B20B with a B16 VTEC head, so it should be very similar to the B18C motor that Andre demonstrated on in his tutorial.
And I guess I also want to be sure that once I find true TDC that the markings on the cam gears won't necessarily line up?
Hopefully I didn't miss anything, but should be very close.
Modern manufacturers have very good tolerances, especially Honda, but tolerances and things like skimming the head and/or block, or tunnel boring the mains, willslightly alter the timing, but it should be clear where the pulleys align to as a tooth is a long way out.
In theory, you should double check the actual timing and use verniers or offsetkeys if you want to go 'old school' to correct it.