rb26 leak down test, oh noes!

[Vkoslak]

I finally got around to seriously working on my rb26 I picked up last April that has been sitting on my engine stand.

I've been mostly working on cleaning off the old gasket material and any rust.

Today I took out the camshafts and used a 2 gal air compressor at 100psi attached to a spark plug adapter from a compression test kit. The air leaves really fast and feels like most of it is coming from the intake valves. It's a pretty good breeze. I also feel a little bit coming from the exhaust side.

I am doing this test correctly right?

I'm hoping it just needs the valves cleaned up. There is lots of carbon buildup. My fear is that the valves are bent.

[flatrate]

well with no cams in its super easy...

Some leakage is somewhat normal you may have carbon holding the valves open some...

Whats the leakdown percentage?? there should be 2 guages 1 being the amount of pressure being put in and the other is whats its able to "maintain" subtract them and thats the percentage

Hot and cold leakdowns are sometimes different as well

Putting oil in the cylinder will help you figure out weather you have damaged piston, rings etc

[Vkoslak]

Since I only have 2 gallons of air to use, it falls pretty quickly. It appeared to be within 10-15 psi.

Engine is definitely cold. No telling when the last time was it ran.

I'll try some oil in the cyls tomorrow.

[flatrate]

if your valves are leaking some and its at 10-15% thats exceptable no need to do a wet test (oil in the cylinders) unless you want a sweet cloud when you start that slut

[FAST-DATSUN]

Need constant air supply to get accurate test. Good engine should have less than 10% we use 3% on new and 5-8% on used to count as a really good motor

[Vkoslak]

So I'm guessing my 2 gal tank is not going to be anywhere close to enough. What size tank do you recommend? I know a few people in my local car club with larger compressors.

Also, I'm just using the 2 pressure gauges that are built into the compressor. One shows tank pressure and the other shows pressure after the valve for the outlet. I was going to head down to harbor freight and pick up a proper two gauge tester today just to eliminate any guessing.

I've been trying to avoid taking the head off the block so I wouldn't have to replace the head bolts or the metal headgasket that was on the engine when I bought it, but the more I mess with this engine, the more I think I need to.

[Vkoslak]

A quick follow-up.

So I bought one of those harbor freight leak down testers. Hooked it up to the rb26 tonight. It has the big green, yellow, and red bands for how bad the cylinder is leaking. They are all very close to each other and with a little bit of fiddling I got all the cylinders but #1 to go a little into the green zone. #1 was right on the edge of yellow and green and seemed to have a small leak on the intake side. Given that this engine has been setting for at least a year if not more, I think that is pretty good. I may still get a valve job, but I feel a lot better about the engine now.

Having the actual leak down tester was much better than what I was doing before.

[robbie2883]

unless the valves are bent just have them lapped in and you should be good