port timing

[jmester]

What is the best way to figure out port timing? With a degree wheel or dial indicator.
Also what is the best way to measure piston to head clearance.

 

[cheshire cat]

What is the best way to figure out port timing? With a degree wheel or dial indicator.
Also what is the best way to measure piston to head clearance.

I'm a bit new but I guess the disc is favourite remember tho' there's +/- approx 5deg at top and bottom dc with no piston travel so a depth guage would be good too for a starting point re squish I found soft solder wire as good as any hope this helps p.s was in Frederrick once (at All Type?) if think must have had a good lunch that was thirty years ago, unfortunatly never got to come back --- great country!!!!!!

 

[trappermike]

Yes,use a degree wheel with a dial indicator to accurately find TDC,then find out your port timing.
Using the degree wheel is explained in here many times.
Also described in here is how to find out your squish clearance with solder.

 

[trappermike]

You are right Chesire,there is little piston movement for several degrees near TDC so having a dial indicator is ideal,but there are other methods that can be used alternately. Your TDC measurement should be accurate or else all your other measurements could be off also.

 

[Stumpys Customs]

Heres a link to a thread that explains it. http://www.arboristsite.com/stickies/177311.htm
Sorry aboput the pics, They some how turned off the HTTML code on the thread so they don't show up. Somebody redone the pics later in the thread.
Just a word of caution. If you use a dial ind. to find TDC you could be off a degree or two possibly more.

 

[trappermike]

Maybe if you have a cheap dial indicator or don't zero it properly... Even a few degrees before or after TDC the piston IS still moving up or down relative turn the crankshaft's arc of rotation,and a quality indicator properly used will indicate that exactly,my indicator has a small roller bearing so friction cannot squew the reading. Common Stumpy this method is used by race engine builders all over the world,are they all wrong or mis-informed?
For every degree of rotation near TDC my indicator will show piston movement up or down exactly.
I know some people will use the "stopper" method,but it is not more exact,just handier in some instances.
The idea that the piston is not moving up or down near the top or bottom of the stroke is not correct,just the movement IS trickier to detect.

 

[Stumpys Customs]

Maybe if you have a cheap dial indicator or don't zero it properly... Even a few degrees before or after TDC the piston IS still moving up or down relative turn the crankshaft's arc of rotation,and a quality indicator properly used will indicate that exactly,my indicator has a small roller bearing so friction cannot squew the reading. Common Stumpy this method is used by race engine builders all over the world,are they all wrong or mis-informed?
For every degree of rotation near TDC my indicator will show piston movement up or down exactly.
I know some people will use the "stopper" method,but it is not more exact,just handier in some instances.
The idea that the piston is not moving up or down near the top or bottom of the stroke is not correct,just the movement IS trickier to detect.

I got ya, Just speaking from my experience. may wasn't being patient enough.

 

[trappermike]

Thanks Stumpy,but I think I must agree with your words of caution.:msp_thumbup: If not properly used or in some circumstances(Like the spark plug hole is at quite an angle-not straight down over the piston)then the dial indicator may not give an accurate reading.
I'm wondering if you are thinking of the piston stopper method as an alternate to find TDC,which may be better in some cases,and doesn't require having a dial indicator.

 

[Stumpys Customs]

Thanks Stumpy,but I think I must agree with your words of caution.:msp_thumbup: If not properly used or in some circumstances(Like the spark plug hole is at quite an angle-not straight down over the piston)then the dial indicator may not give an accurate reading.
I'm wondering if you are thinking of the piston stopper method as an alternate to find TDC,which may be better in some cases,and doesn't require having a dial indicator.

Alot more variable come into play with a dial ind. My thinking was that as the piston is @ TDC the crank has to break over which takes a few degrees of movement. I'll try to set up something & maybe a vid. I never used a dial ind when building auto engines either. In all my research of the subject through the years a positive stop & rotating the crank back & forth is the most accurate method of finding TDC. Several different ways to skin this cat.

 

[mdavlee]

I use the drop valve method for timing on P pumped cummins. That way I know for sure as most of the timing pins are a little off from being bent or broken and missing. Hard to mess that up. If I remember right there's a good bit of rotation between them. SOmething like 9" on the balancer. I've messed around with a dial indicator but usually a stop is easier.