I've got this old TR-6 engine out of the TVR, and I'd sure like to know a bit more about it's condition. Was thinking a leak-down test would be the way to go.
Any issues with testing it with it sitting on the floor?
Have to lock the crank somehow to prevent rotation, maybe?
Would I be able to properly hear the various leaks? Valve leaks out the head would be easy to hear. What about ring or head gasket?
Anyone done it?
No problem. Easier, actually. Just pull the spark plugs, hook the tester up to #1, set #1 at TDC on the compression stroke and go. Then do #2, etc. HF sells a tester pretty reasonable. Directions for it are a bit light, but it works fine.
Cool. Any worries about the crank rotating, or is that no big deal?
Should I give the cylinder bores a squirt of oil or not bother? Supposedly the motor hasn't run since 2011.
No oil. Crank won't rotate from a little air pressure so don't worry about it.
I did the 4th gen 3SGTE before I swapped it into the RAV4. WIth a grenaded turbo as it came from the JDM importer, I was concerned I might be swapping in something with a hole in the piston, so I checked it with the leak down just to make sure. Hook it up and then turn the crank and you can watch the valves close on the gauge. Leakage will go from like 100% to low to 100% as the valves close and open.
Awesome. I might have enough misc pneumatic parts to put together my own tester. Would just have to turn a spark plug adaptor.
I disagree, the crank will want to rotate from the air pressure. I had to put the car in gear and chock the wheels last time I did a leakdown.
I put a rubber glove over the exhaust, vale cover oil-inlet and the carb trumpets...the one that gives me the five finger salute tells me what is going on.
How much air pressure are you pushing in there? You're not trying to start it. If it does move, then just put a flywheel lockdown thingie on it.
In reply to Dr. Hess :
about 100 psi if I recall. The gauge had an indicated test pressure if memory serves.
And locking down the flywheel is what I do when I do this on a stand. Big fan of the leakdown test as an indicator of how healthy an engine is.
spinning it with a starter can give an Idea about compression Equality but to do a correct Leak Down then you must Pressureize the Cylinder. this is why they have Two Gages.
Typical leakdown tests are done at 100psi. The engine will absolutely want to rotate if you're not at TDC. Many an airplane mechanic has been struck by a moving propellor when doing one.
If you have it precisely at TDC then the crank won't rotate because the rod is straight up and down so it's balanced. If it's slightly off then the 100 psi will definitely rotate it. A piece of angle iron with a couple holes in the right places bolted to the flywheel will fix that.
Has the engine been sitting forever? I always disregard, or downplay, at least, compression and leakdown tests on an engine that has been sitting for quite a while, because carbon softens up and flakes off and catches under valves and stuff. My Camaro that sat for six years would have failed miserably, based on the sound while it cranked, and how much boot I had to put to it to get all eight working again. I didn't particularly care about that engine, but it is actually working pretty well now.
In reply to Streetwiseguy :
Yes, according to PO the car last ran in 2011. What I've found for condition would certainly support that the vehicle has been ignored for a long time.
In reply to USERNAMETAKEN :
Is it in a condition where you can fire it up through the use of jerry cans and jumper cables? Run it for 30 seconds and see how it sounds.
Rust will happen on valves and seats on a sitting engine. Run it first, maybe five minutes or less to clean the valve sealing surfaces. Particularly on an engine that sat for seven years. I wouldn't even attempt to do a compression or leak down test otherwise. Ask me how I know. BTDT.
It's not really in a place where it can run now.
It never really was anywhere close to being able to run. Even when I just got it. Hence the bench leak-down test.
I really just want to get a feel for the health to better evaluate the value. I figured if it has a good leak-down then maybe it would be considered more like a runner rather than a builder. Maybe I just can't assume that.
It was built in England. At the very least, it needs a set of hardened valve seats to deal with modern gas, plus a good de-coking is required on a regular basis.
Streetwiseguy said:It was built in England. At the very least, it needs a set of hardened valve seats to deal with modern gas, plus a good de-coking is required on a regular basis.
The PO said he did put in hardened valve seats. The motor got a full build with a bunch of racy parts back in the early 90's. He had a T4 turbo on it, pulling thru a big SU carb. Said it was running 12 psi on pump gas.
If his story is true, it could be a nice builder. If I take into consideration the condition of the rest of the car, then probably the engine also needs a total rebuild.
he wouldn't be the First to put all the money in the Engine.
How good of a compressor do you need for this? I need to see if I bent the valves in my VR6 after doing the timing chain, but don't own a compressor. Would something in the 8-gallon range be sufficient or do you need something beefier?
A smaller compressor should be fine. It is not the "gallons" as much as the "CFM"'s. However, the leak down test doesn't take much air. If it is not leaking, it doesn't take hardly any. If it is leaking, then it takes air, but that gave you your answer anyway. You can also use your built in compression tester which is the short fat stubby appendage on the device on the end of your arm. Pull the plugs, have your helper crank the motor while you put your thumb over the spark plug holes. If it doesn't pop your thumb off the plug hole, you have a bent valve or a really big hole in the piston.
Dr. Hess said:If it doesn't pop your thumb off the plug hole, you have a bent valve or a really big hole in the piston.
Thanks! Sounds like the wife and I have a project for this weekend! :)
Just say bore is 4 inches and stroke is 4 inches (big cube v8). If the Piston is exactly between tdc and bdc, 100 psi:
4*3.14 (call it 3 for easy numbers) = 12 sq inches, times 100 is 1200 lbs. Divide by 3 (4 inch stroke is 1/3 foot) means 400 ft lbs of torque on the crank. You bet it'll rotate...
But get the Piston at tdc first and it won't take much to hold it still.
When I had my SBF out of the car, I just pulled the rocker arms and tested it with the piston at the bottom. Back the air pressure off to where you can rotate the crank, and you can see how egg shaped your cylinder walls are.
Turn crank to BDC, Pop off the push rod to the valves, do leak down test. Yes you might miss some bore wear with it not being at TDC but it will tell you if rings are healthy or and if valve leak. This way you don't have to lock the crank at TDC.
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