Rb25/30 Issue

[Turbsxr6]

I have just recently bought a rb2530 complete off another forum member with unknown specs. My issue is that I have just noticed that it is an a6 block and I just really want to know the best way of finding out weather it has been a forged Rb 30 intended for sohc and they have just slapped the 25 head on it or weather it is built for the higher cr for the 2530. I sorry I'm not very good at explaining what I'm trying to achive but besides paying for it to get pulled down and getting the compression ratio checked is there another way of finding out

[urtwhistle]

Only way I can think of with out pulling it down or installing it in your car is to put it on an engine dyno. sort the cam timing issues out (every 1 has them) and do a compression test. It will tell you if its high or low comp at least. nothing else

[Turbsxr6]

So now it's outta the car it will probably worth paying someone to pull it down ?

[KiwiRS4T]

You can check the compression ratio by pulling out spark plug and measuring the amount of fluid a cylinder holds at TDC compared to BDC.

[GTSBoy]

Not a valid test. Thin enough fluid to be accurate will slip past the ring gaps too quickly to allow precision. When you use a burette and kero/water to cc a head, you're looking for 0.1cc accuracy. That involves using a little grease on the valve seats and so on to make sure none leaks out.

[Turbsxr6]

So there is no way of telling if its got the lower cr of a turbo vl commo or it is in fact built for a 25/30 with forged na pistons

[GTSBoy]

If you used a thick enough oil to limit the leak rate, you could possibly do it accurately enough to determine THAT difference.....but I wouldn't rely on the answer to any great degree.

[scotty nm35]

Can you simply stick a scope down the plug hole and compare the crowns? You can pick the cameras up fairly cheap now.

[GTSBoy]

Yuh, lipstick cam on USB is only like $20-$30. But perhaps the rather wide angle lens on them is not going to give you a reliable image that you'd swear by, unless you had a couple pf other engines with known pistons in them to compare to.

Edited February 17, 2013 by GTSBoy

[PN-Mad]

Since the motor is out of the car,perhaps take the sump off and see what you see?

[Turbsxr6]

I can pull the sump off not a worry at all but what can looking from underneath do ? So if I fill it up with oil and try take a measurement of fluid that would be enough to work out if it is turbo vl or na forged ?

[Simon-S14]

Do a compression test and see how high they come up?