Friday, July 17, 2015

Piston Pressure

<This post is part of the 'New Engine Rebuild' project>
Everyone should have a mate called Dave. If you haven't got a mate called Dave, you are missing out and really should consider seeking one . I have a mate called Dave and he has kindly loaned me his piston compression gauge.

Best put it to good use...

It's pretty self explanatory what you do with it, and if you can't work it out, the instructions are on the back of the card so there is really no excuse to get it wrong. It's a simple job of finger tightening the end of the gauge into the spark plug hole and crank the starter motor a few times.

If the engine is in the car then you would need to find a way to stop it firing up, so taking all the spark plugs out would be helpful. As my engine is still on the floor of the utility room, there is no danger of it firing. If it did fire up, I would find out how, patent the secret and make my fortune selling engines that ran of fresh air!!!

It is worth noting that I have a new camshaft and it has yet to be broken in, so I don't want to be cranking the starter for too long, so I tried to keep it under 10 seconds per burst. Don't want to knacker my new cam!!

Anyway, enough waffle, the results were as follows, piston 1 being the one closest the the fan end:

Piston 1 - 186 psi
Piston 2 - 183 psi
Piston 3 - 182 psi
Piston 4 - 189 psi.

I'm pretty happy with those numbers for 2 reasons: one the pressure is nice and high, and two, the numbers are very close to each other. I have read that you are looking for a deviation of less that 10% between the numbers. So in my case 10% would equate to about 18 psi. As you can see the biggest deviation is between piston 3 at 182 psi and piston 4 at 189 psi, at just 5 psi which is well below 18 psi threshold, so very promising numbers.

Let's hope this translated into a smooth running engine...

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