Leak down testing

[vectorizer]

How is everyone holding piston at top to do leakdown testing.

[Jay Smith]

Flywheel holder by Snap-On is what I use !

[red hott]

me to snap on fly wheel holder
tray

[Tom D.]

Clamp on to the edge of the fly wheel with 2 pairs of vice grips. 1 pair on each side of the starter.

Tom

[Barefoot Bob]

But I just use a half inch socket and breaker bar on the flywheel nut

[sosmerc]

I use a breaker bar on the flywheel nut....but I bring the pressure up slowly to about 40 lbs and "find" by feel top dead center...at that point it doesn't take any effort to hold the flywheel and you can then turn the pressure up to 100psi for testing...but be prepared for the flywheel to want to jump to one side or the other. It takes a little practice and it can be pretty dangerous if you are not careful.:D

[gaineso]

Socket and breaker bas on flywheel nut. That way I can let it dow to exhaust port to check entire cylinder. Just be prepared as it comes off center. A 3" bore will have 700 lbs force at 100PSI. You gotta have a good grip.

Great way to see condition of the motor. That's what finally gave me the confidence to take my little I6 back out and run it. And it runs great since I got the timing fixed and premium gas.

[Balzy]

what SOSMERC and gaineso said !!!!!!!!!!!!

[ProComp]

Haven't used mine yet but I talked to my buddy who is a mechanic and he claims if you have it at TDC, there should be little torque on the flywheel as it is balanced.

He also went on to say if you don't have it a TDC and you use too much air pressure you could possibly bend a rod. Anyone care to comment?

ProComp

[Barefoot Bob]

And a shop owner for the last 6 years. I dont think you have to worry about bending a rod.

[aircraftman]

youll end up bending your rod when the mota pulls you into the transom!:D

the best way is to use the breaker bar (long 1/2 or 3/4 inch model) so you can move the piston up and down.

i wouldnt say that letting the thing go while under pressure is good for the mota but i dont think it would hurt it.

[Balzy]

bend a rod when you run more compression than that? No way. He is right about the fact that if you get dead nuts on TDC it will stay there all by itself. Damn hard to find it dead nuts though. Just pull the piston up with a breaker bar on the flywheel nut at 20 PSI or so and when you start to feel it finding TDC increase the pressure. As you add pressure it gets easier to tell where TDC is. If you are close to TDC you can hold it real easy. Just don't go over TDC or will wanna take off on ya !!!!!!!!!

[ken medendorp]

put indicator in spark plug hole bring it to TDC then hook up tester It'll stay with out holding it and you won't get hurt

[halveb]

I like that last idea cause knowing me I'd find a 1000th of an inch beyond TDC and get the transom face-lift. Where can on buy a TDC indicator that indicates on a Merc V-6 or are they adjustable, etc?

[Balzy]

Jay Smith makes a way cool TDC finder piece. It's on his website.

http://jaysmithracing.com/

New! Piston Top Dead Center (TDC) Gauge
Forget the clumsy old methods of finding the piston's top dead center location. Use the new JSRE TDC Gauge for easy, accurate, and quick results. Will fit standard plug threads, however, other threads can be made. A high quality instrument for the serious performance enthusiast.

Piston Top Dead Center Gauge ........$40.00
(Plus freight)


I have one on the bench in the shop. Hee hee !!!!!!!!

http://jaysmithracing.com/images/TDC%20Tool/TDC%201.JPG

[gaineso]

I got one of JSRE's TDC indicators. Really cool deal, works great on my inline and I'm sure better on a V-6.

I was in a hurry and I asked him to overnight. I paid shipping of course, but I got it next day. Everything good you've heard about JSRE and Balz to the Wall is true.

[vectorizer]

Thanks for all the answers. Matt Ludwig

[racer]

A true and acturate leak down is more than just at TDC if you want to see your cyl condition and not just the rings. The piston should be moved up from port opening with several pauses and back down to port opening with several pauses. A variation in the percent of leakdown shows a cyl problem.