Testing compression, not a guage question...

[michael950]

When testing compression, do you have to have the exhaust connected? My assumption would be no, but you know what happens when you assume.


I just want to get confirmation on my assumption.

 

[sflsurfrider]

you do not need the exhaust manifold (or intake manifold) installed to check compression.

 

[Waste Land]

I would think yes but then again thats me. If the pipe acts as a forced induction component it should put more ait in the cylinder before the exhaust closes. Thats my idea but not sure how well that works in a "turning over" situation

 

[sflsurfrider]

youre overthinking jesse. thats a good thing.

if hes just putting a top end together and wants to make sure of the compression before he bolts everything up, he can check it without an exhaust.

compression begins after the exhaust port is covered by the piston anyway.

mike, youll be fine.

 

[Waste Land]

compression begins after the exhaust port is covered by the piston anyway.

I understand that. By the way a pipe works, as in forcing fresh air back into the cylinder via exhaust port, wouldnt that give it a bit more compression? Maybe not enough to count but im just talking now

 

[surferdude345]

Im no expert but i would think that just to make sure nothing is leaking it would be fine to just do it the way u have it.

 

[extreemthrottle]

I understand that. By the way a pipe works, as in forcing fresh air back into the cylinder via exhaust port, wouldnt that give it a bit more compression? Maybe not enough to count but im just talking now

only if it was running, and not enough to make a difference...

 

[Matt_E]

The compression difference gets big enoug to see when the engine is running. Not when turning over.

 

[Big Kahuna]

I understand that. By the way a pipe works, as in forcing fresh air back into the cylinder via exhaust port, wouldnt that give it a bit more compression? Maybe not enough to count but im just talking now

There is no fresh air in the exhaust..... only a sonic wave when the motor is running.

 

[Matt_E]

Regardless, the pipe increases dynamic compression.

 

[michael950]

The manifold is on, the chamber is off. I do not have a gasket, nor do I want to waste one to test compression.

How off will by numbers be? 1 PSI or 50 PSI?

 

[wetwolf]

1 psi if that

 

[michael950]

I just need to test compression before I pull the motor out of the ski, it will be going up for sale and wanted to test compression before I start pulling stuff off..

Thanks, that is what I needed to know.

 

[michael950]

Now it is a guage question:

I attempted to thread my compression tester on the Pro-Tec head and it will not thread easily. I get maybe 1.5 full turn and then major resistance. It will thread on the SJ no problem, and the plugs on the blaster will go on the SJ no problem.

So why am I having difficulty getting the compression tester (hose) to thread into the blaster protec head? I do not want to bugger up any threads.

 

[Matt_E]

So the plugs thread into either head, but the gauge will thread only into the stocker?

Clean both threads, perhaps? :dunno:

 

[michael950]

So the plugs thread into either head, but the gauge will thread only into the stocker?

Correct

Clean both threads, perhaps? :dunno:

You would think, I did that also. I also heated up the head a little to see if that would make a difference. Nope.