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> TDC, On the compression stroke
nsyr
post Apr 29 2005, 01:11 PM
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How do you determine the TDC on the compression stroke for piston 1 after putting the engine together?
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tat2dphreak
post Apr 29 2005, 01:14 PM
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QUOTE (nsyr @ Apr 29 2005, 02:11 PM)
How do you determine the TDC on the compression stroke for piston 1 after putting the engine together?

chopsticks...













(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)
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nsyr
post Apr 29 2005, 01:17 PM
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But if the camshaft rotates half the speed as the crank there would be two TDC's for each piston, correct?
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ThinAir
post Apr 29 2005, 01:19 PM
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I've been wondering the same thing so that I can confirm that I really got my distributor put in correctly - before I try to fire it for the first time.

Chopsticks will tell you that you are at TDC, but how do you know for sure that you're on the Compression stroke and not the Exhaust stroke?

Perhaps it's by looking at the position of the rockers on the other cylinders? (My rockers aren't on quite yet - maybe tomorrow!)
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ArtechnikA
post Apr 29 2005, 01:22 PM
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help us help you, 'cause there are a few different methods depending on what you're actually asking, and what engine...

T-IV ? Porsche flat-6? V8? something else?

is your question about finding -A- TDC, or is your question about determining which TDC is #1 compression?

there are a few methods for finding TDC, but the short version for a Porsche engine is: look at the flywheel or crankshaft pulley - it's marked on one or the other (depending on what kind of Porsche engine you're dealing with).

you *should* be able to tell by the distributor position, because installing the distributor is done when the crankshaft and camshaft positions are known...

#1 TDC compression is when both valves are closed. you need to tell us what engine you're working with and exactly what you're looking to find out before we can be too much more detailed...
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ThinAir
post Apr 29 2005, 01:23 PM
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Oops... mine is a Type IV 2.0L

My distributor was installed when the piston positions were known, but I'm a little paranoid about this and was thinking that I'd like to check it one more time.

This post has been edited by ErnieDV: Apr 29 2005, 01:27 PM
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nsyr
post Apr 29 2005, 01:25 PM
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It's a stock 2.0 The dizzy is off and I am not sure which #1 tdc is compression.
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tat2dphreak
post Apr 29 2005, 01:28 PM
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the chopsticks comment was a joke, please do not put chopsticks or anything else into your head... search for chopsticks here and you'll know why...

the pelican article on valve adjustment has handy info regarding finding TDC...

http://www.pelicanparts.com/techarticles/9...alve_adjust.htm
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Type 4
post Apr 29 2005, 01:34 PM
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Pull valve cover.
Look at the slot on the underside of the bell housing.
When both valves closed on #1 and the line on the Flywheel is visable thru the slot you are at TDC.
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nsyr
post Apr 29 2005, 01:37 PM
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Let's say i am reassembling the engine and i am to the point that the case is together and the heads are on. I have nothing in the way of dizzy or dizzy drive gear to tell me that I am on the compression stroke or exhaust. There will be two different positions that the camshaft will be in at #1 TDC. How would I tell which is compression and which is exhaust.
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ThinAir
post Apr 29 2005, 01:37 PM
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QUOTE (tat2dphreak @ Apr 29 2005, 12:28 PM)
the chopsticks comment was a joke

I wondered about that, but using something long and slender like a plastic straw didn't seem unreasonable as a way of noting when the cylinder had reached the top. I figured you just needed something that was long enough that you could hold onto the end and it could not possibly slip through the spark plug hole and get stuck inside the cylinder.
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ArtechnikA
post Apr 29 2005, 01:37 PM
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QUOTE (nsyr @ Apr 29 2005, 02:25 PM)
It's a stock 2.0 The dizzy is off and I am not sure which #1 tdc is compression.

okay, cool.

there is the easy way: if you can assume that the distributor drive shaft was installed correctly, you're home free, because the dizzy drive slot is offset and the distributor can be installed (correectly) only one way.

lacking that, pull the valve covers and look at the rockers. if you're on #1, both valves will be closed, and on #3 (your only other possibility) there will be at least one open, a lot.
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nsyr
post Apr 29 2005, 01:42 PM
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QUOTE (ArtechnikA @ Apr 29 2005, 02:37 PM)
lacking that, pull the valve covers and look at the rockers. if you're on #1, both valves will be closed, and on #3 (your only other possibility) there will be at least one open, a lot.

Pretty much the answer I am looking for!!! (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

Thanks
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