Should I check TDC?

[davepl]

Originally Posted by geezer#99

You still haven’t answered the question.
Likely because you don’t know.

If you want to be off 10-20 degrees on your timing, so be it.
It’s only a few holes in pistons.
No biggie.
It’s not your dollar being spent.

Your question made no sense. You said "How many crankshaft degrees does the crankshaft turn when the piston is at tdc?"

I don't even know what that means. I'd argue that the crankshaft turns 1:1 with the crankshaft.

If you meant cam, it's half the crank speed obviously. But by definition when something is at TDC it's not turning any degrees, it's sitting at TDC, so I still have no guess.

[jocko]

Originally Posted by superhondaz50

The engine didn't have any balancer, so nothing to compare to unfortunately.

AH! Duh. Ok, got it now - thanks

[jocko]

I'm gonna go out on a limb and assume that what was being asked (by geezer) was how much crankshaft rotation occurs (in degrees) with an almost unnoticeable amount of piston movement near the top or bottom of the stroke (i.e. as it reverses direction) - yes there is some number of degrees near TDC where the piston moves up/down less and less as it approaches TDC - therefore, the number of degrees of rotation equates to proportionally less and less piston movement in the cylinder until it reaches TDC (or BDC) and reverses direction in the cyl. I get the question, and it comes down to being accurate or being good enough. Good enough is, well, good enough - but why not be accurate when it's about the same amount of effort?

To be honest, while finding TDC is a bit simpler than degreeing a cam - it is indeed a first critical step. If the OP is trying to determine if his timing tab is correct with his new balancer, then I'd submit, yes, a few degrees matters. So, while it may work, I would not use a pencil - why risk even breaking a chunk of lead off after the heads are on? Would it matter, not likely, but I doubt any of us would purposely throw a chunk of lead or sliver of wood into our cylinder just before slappin the heads on for grins.

Anyway... OP did the right thing, used an inexpensive piston stop, found true TDC, nice job.

[geezer#99]

Good answer Jocko!
Likely 5 to 10 degrees is normal depending on the stroke.

Some people want to be accurate, some close enough.
I got no problem with that.
I got a problem with people who want to teach others that close enough is better. Makes for poor results.
Rant over!

[Killer Bee]

Originally Posted by geezer#99

You still haven’t answered the question.
Likely because you don’t know.

If you want to be off 10-20 degrees on your timing, so be it.
It’s only a few holes in pistons.
No biggie.
It’s not your dollar being spent.

first off, I not only answered your irrelevant question, I defined what it actually is and what it's called, and gave a decent explanation how it actually doesn't affect the OP's objective..

remember him, the guy that was asking for help, and YOU posted absolutely NOTHING informative or useful..

Originally Posted by geezer#99

Hilarious stuff!
So, killer bee I got a question for you.

How many crankshaft degrees does the crankshaft turn when the piston is at tdc?

Originally Posted by geezer#99

Good answer Jocko!
Likely 5 to 10 degrees is normal depending on the stroke.

Some people want to be accurate, some close enough.
I got no problem with that.
I got a problem with people who want to teach others that close enough is better. Makes for poor results.
Rant over!

furthermore, you accused me of not knowing what piston dwell is although I'm the only one using the term and YOU do NOT know what it is if you think a piston STOP tool measures it!

a piston stop tool absolutely does not measure piston dwell! it stops the piston on compression stroke before reaching TDC then just short of a full rotation of the crank in the opposite direction it stops the piston at the exact same place on exhaust stroke [which is why the tool manufacturer recommends loosening the rockers on #1] just before reaching TDC.. NEITHER OF WHICH ARE TDC or PISTON DWELL measurements.. actually these marks are BTDC and ATDC theoretically equal from TDC.. the person using the tool splits the difference of those two marks to calculate TDC, which in this case the OP stated was 2 DEGREES off from his balancer.. loosening the fasteners holding the scale will probably give you that much movement..

the tool works in an infinite number of positions short of TDC, as a matter of fact, no exact position is usually mentioned.. it only creates two reference points close enough for the user to measure and mark the center of..

so smart guy, what is the piston dwell on the OP's engine? c'mon, I'm sure we'd all like to know.. cuz it sure the hell isn't 5-10° per your post..

here's a brief conversation a little more in depth about it..
http://www.stevesnovasite.com/forums...p/t-94282.html

Agreed true dwell is so infinitesimally small that we don't have instruments that can accurately measure it.

why don't you show us a reference to a piston dwell measurement for a stock SBC? I'd like to see it..


I furthermore defined the reason such a minimal amount of zeroing accuracy will never be realized in a STREET level engine build.. but I suppose your ego was still preventing you from reading it.. If you think the OP is going to have less than 2° resolution with a handheld timing light through a stock timing chain, cam gears, street distributor, etc., you must be joking, or ignorant of how that works as well.. 10-20° timing variance and holes in pistons? yah, ok



the OP, remember him, was asking for help and not interested flying it into space.. I gave him an ABSOLUTELY valid method in simple terms to getting him ready for static timing and making smoke and stand behind every letter of what I posted..

you however contributed absolutely nothing but childish jabs and jeers and showed us your lack of understanding of a subject you brought up..

please go on to tell us all how ignorant I am approaching the 30th year of my career as a professional mechanic and how much smarter you are

now wise guy, my rant is over.