How to find TDC on a Hemi

[Mopsquad]

New to Hemis and I need to find TDC to configure and install the EFI distributor.  Usually, I just feel compression with my finger on the spark plug hole.  With a hemi of course, Its covered.  What's the procedure(s) to get TDC on these motors?

Thx!

[BIGSHCLUNK]

A dowel rod will get it done just keep an eye on it

[Mopsquad]

A dowel rod will get it done just keep an eye on it

Thx!  Safe diameter?

[RUNCHARGER]

I pull all the plugs. Then I run a bolt into the plug hole of #1, make sure the bolt has a deburred end on it and is not that long so it stops the piston maybe 3/8" from the top. Rotate until it stops, mark it on the balancer (against the pointer of your choice) then rotate it the other way and mark it. TDC is half way between those marks.
Honestly I do it with a dial indicater before the heads go on, but your's is obviously assembled already.

[LinceCuda]

Go to your local Auto parts store and spend $6.00 on a piston stop and follow runchargers instructions.

[Mopsquad]

Go to your local Auto parts store and spend $6.00 on a piston stop and follow runchargers instructions.

Ok.  I assume the valve cover comes off?

[Chryco Psycho]

not nessisarily , more difficult on the hemi but can be done with the cover on , you can also go from #6 cyl too if that cover is easier to remove , , I would just use a long 1/2 bolt & gently turn the engine over as Sheldon said , you will be very close

[Mopsquad]

not nessisarily , more difficult on the hemi but can be done with the cover on , you can also go from #6 cyl too if that cover is easier to remove , , I would just use a long 1/2 bolt & gently turn the engine over as Sheldon said , you will be very close

Thx,  I will use a long bolt or long dowel.  The balancer has no marking so I'll have figure it out.

[1 Wild R/T]

Ok, the short version...  If you want an accurate TDC location a dowel isn't gonna do it... If you want a rough idea of TDC the dowel is fine....   Thing is the piston stays at TDC for 7-10 degrees of crankshaft travel because the crank throw is moving side to side but with virtually no up & down travel....

So to do it accurately you need to stop the piston at least 1/2" down the bore which is where the piston stop LinceCuda mentioned comes in.... Or the bolt Runcharger mentioned... Personally I have an old spark plug with the center knocked out & a 1" long shaft welded into the center.... 

I would suggest removing all the spark plugs so the engine turns over easily, if it's hard you wind up having to use allot of effort & that could cause you to be forcing the crank to turn just as the piston hits the stop.... Probably wouldn't hurt it but it could so pull the plugs....

Once you install the piston stop don't even think about using the starter, major damage awaits....

Ok, so plugs out, piston stop in, carefully turn the engine over with a breaker bar on the crank..... When the piston contacts the stop make a mark on the damper at the TDC pointer.... Not using the breaker bar turn the engine backwards till you contact the piston stop going the other way....  Again mark the damper at that point....   Remove the piston stop....    Now turn the crank to get those two marks in an accessible spot..... Measure the distance between them... divide by two... now mark the damper in the exact middle of the two marks.... You have true TDC....  Clean off the first two marks....  Done...

[Mopsquad]

Ok, the short version...  If you want an accurate TDC location a dowel isn't gonna do it... If you want a rough idea of TDC the dowel is fine....   Thing is the piston stays at TDC for 7-10 degrees of crankshaft travel because the crank throw is moving side to side but with virtually no up & down travel....

So to do it accurately you need to stop the piston at least 1/2" down the bore which is where the piston stop LinceCuda mentioned comes in.... Or the bolt Runcharger mentioned... Personally I have an old spark plug with the center knocked out & a 1" long shaft welded into the center.... 

I would suggest removing all the spark plugs so the engine turns over easily, if it's hard you wind up having to use allot of effort & that could cause you to be forcing the crank to turn just as the piston hits the stop.... Probably wouldn't hurt it but it could so pull the plugs....

Once you install the piston stop don't even think about using the starter, major damage awaits....

Ok, so plugs out, piston stop in, carefully turn the engine over with a breaker bar on the crank..... When the piston contacts the stop make a mark on the damper at the TDC pointer.... Not using the breaker bar turn the engine backwards till you contact the piston stop going the other way....  Again mark the damper at that point....   Remove the piston stop....    Now turn the crank to get those two marks in an accessible spot..... Measure the distance between them... divide by two... now mark the damper in the exact middle of the two marks.... You have true TDC....  Clean off the first two marks....  Done...

Thank you for the very detailed write up!

I'll pull the plugs, maybe not #7 (booster blocks proper access).  Is there a certain piston stop applicable to hemis?  Or...do I pull the valve cover and use a generic one. 

I see that Mancini has one in their catalogue. 

http://www.manciniracing.com/matdcinto.html

[1 Wild R/T]

The one Mancini sells is fine but Summit would get you one quicker.... Valve covers can stay on....

https://www.summitracing.com/parts/sum-900189/overview/

[Mopsquad]

The one Mancini sells is fine but Summit would get you one quicker.... Valve covers can stay on....

https://www.summitracing.com/parts/sum-900189/overview/

Thank you!  Wasn't sure if I need a hemi specific part.  I have a 14mm stop already for my Ford.

[ratroaster]

Ok, the short version...  If you want an accurate TDC location a dowel isn't gonna do it... If you want a rough idea of TDC the dowel is fine....   Thing is the piston stays at TDC for 7-10 degrees of crankshaft travel because the crank throw is moving side to side but with virtually no up & down travel....

So to do it accurately you need to stop the piston at least 1/2" down the bore which is where the piston stop LinceCuda mentioned comes in.... Or the bolt Runcharger mentioned... Personally I have an old spark plug with the center knocked out & a 1" long shaft welded into the center.... 

I would suggest removing all the spark plugs so the engine turns over easily, if it's hard you wind up having to use allot of effort & that could cause you to be forcing the crank to turn just as the piston hits the stop.... Probably wouldn't hurt it but it could so pull the plugs....

Once you install the piston stop don't even think about using the starter, major damage awaits....

Ok, so plugs out, piston stop in, carefully turn the engine over with a breaker bar on the crank..... When the piston contacts the stop make a mark on the damper at the TDC pointer.... Not using the breaker bar turn the engine backwards till you contact the piston stop going the other way....  Again mark the damper at that point....   Remove the piston stop....    Now turn the crank to get those two marks in an accessible spot..... Measure the distance between them... divide by two... now mark the damper in the exact middle of the two marks.... You have true TDC....  Clean off the first two marks....  Done...

How do you know it's on the compression stroke so the dizzy isn't off 180?

[1 Wild R/T]

Ok, the short version...  If you want an accurate TDC location a dowel isn't gonna do it... If you want a rough idea of TDC the dowel is fine....   Thing is the piston stays at TDC for 7-10 degrees of crankshaft travel because the crank throw is moving side to side but with virtually no up & down travel....

So to do it accurately you need to stop the piston at least 1/2" down the bore which is where the piston stop LinceCuda mentioned comes in.... Or the bolt Runcharger mentioned... Personally I have an old spark plug with the center knocked out & a 1" long shaft welded into the center.... 

I would suggest removing all the spark plugs so the engine turns over easily, if it's hard you wind up having to use allot of effort & that could cause you to be forcing the crank to turn just as the piston hits the stop.... Probably wouldn't hurt it but it could so pull the plugs....

Once you install the piston stop don't even think about using the starter, major damage awaits....

Ok, so plugs out, piston stop in, carefully turn the engine over with a breaker bar on the crank..... When the piston contacts the stop make a mark on the damper at the TDC pointer.... Not using the breaker bar turn the engine backwards till you contact the piston stop going the other way....  Again mark the damper at that point....   Remove the piston stop....    Now turn the crank to get those two marks in an accessible spot..... Measure the distance between them... divide by two... now mark the damper in the exact middle of the two marks.... You have true TDC....  Clean off the first two marks....  Done...

How do you know it's on the compression stroke so the dizzy isn't off 180?

in this case we are identifying TDC to mark the damper.... So it doesn't matter... To determine #1 compression stroke you either look for cylinder pressure or watch the valves.....

[RzeroB]

How do you know it's on the compression stroke so the dizzy isn't off 180?

in this case we are identifying TDC to mark the damper.... So it doesn't matter... To determine #1 compression stroke you either look for cylinder pressure or watch the valves.....

Or if the dizzy is out, you can use a small inspection mirror in the dizzy hole to watch the lifters on the cam, which is essentially the same as watching the valves, but without having to remove the valve cover.