OK, understood. I will try to fix the tester or get another one.

 

I wonder what size the port is inside that leakdown tester.
A carburetor jet might be an easy fix, if you can find a 1/4-32 tap.

 

Great minds and all that. I have a Holley #44 jet, but discovered that they are 1/4-32. So I have that tap in my wish list at Amazon and just haven't pushed the button on it.

And one of the reasons a commercially available orifice is good is that the angle of the approach and exit is very important. In fact, somewhere I read that those are spec'd by the Fed's for aviation engine testing. So using a jet would let us replicate testers and results, where just drilling the hole won't. In fact, it probably makes the unit overly sensitive.

 

Holley parts!?!
Really Gary, what are we going to do with you??


Yes it would make for an easily swappable orifice that could be replicated anywhere..

 

I think all of the parts cleaning and powder coating have made him go a bit nuts! Holley parts, eh?

As for the OP, those compression numbers are good. My 351W only has 30-40,000 and mine are 150-155 PSI all across the board for reference.

 

More likely it is the brake cleaner I use to get the parts ready for powder-coating. Just bought another case of it yesterday. As for the Holley jets, my thinking was that while the power valves, accelerator pumps, and gaskets leak I don't think the jets will.

(Now will you leave me alone? )

 

That brake cleaner can sure give me a headache after a while of using it. You might be able to save money if you buy one of those refillable spray cans and buy it by the gallon from somewhere. I know where my dad works they get a gallon of it for $8 a gallon.

 

ok I purchased this:
It seems to work better. With 100 psi on the high side I can observe 0 psi (or 100% loss) on the low side with no problem. OK, great.

Unfortunately, the results appear to be very bad.

cylinder 1: 100 psi high side / 16 psi low side / 84% loss / noise in valve cover vents and oil dipstick tube
cylinder 2: 100 psi high side / 30 psi low side / 70% loss / noise in valve cover vents and oil dipstick tube
cylinder 3: 100 psi high side / 15 psi low side / 85% loss / noise in valve cover vents and oil dipstick tube
cylinder 4: 100 psi high side / 30 psi low side / 70% loss / noise in valve cover vents and oil dipstick tube
cylinder 5: 100 psi high side / 16 psi low side / 84% loss / noise in valve cover vents and oil dipstick tube
cylinder 6: 100 psi high side / 32 psi low side / 68% loss / noise in valve cover vents and oil dipstick tube
cylinder 7: 100 psi high side / 30 psi low side / 70% loss / noise in valve cover vents and oil dipstick tube
cylinder 8: 100 psi high side / 20 psi low side / 80% loss / noise in valve cover vents and oil dipstick tube

 

Well, I would bet that is a good tester. And those are BAD results. I've never seen any that bad. But I am having a hard time believing that the engine is that bad, and especially that all of the rings are gone, which is what that indicates.

However, let's make sure - you are bringing each piston to its Top Dead Center on its firing stroke? How are you finding each TDC?

 

Given the okay compression test numbers I can't see it.
Dry 135-150
Wet 160-180

I don't know what size orifice OTC is using.
If it were TINY those leakdown numbers might make more sense

 

I apologize, I also feel like I must be doing something wrong. To find TDC I rotated the engine looking into the spark plug hole and stopped when the piston reached its maximum. This is by eye so I'm sure I could be a bit off. I then tested using the leakdown tester. I then rotated the engine until it was back up to TDC and tested again. I figured this way I would hit the firing stroke, but for some reason unknown to me I got similar results regardless on both positions.

I also tried the test at BDC (as I heard one can also use BDC) and I got similar results -- but I only tested this on cylinder 1.

How would you recommending finding TDC on the firing stroke? Could I have damaged something?

 

If you don't hear anything from the intake or exhaust I have to assume you are at TDC compression (with both valves closed)

On the first page a few of us said everything seemed good.
That you seem to be having problems with your leakdown testing procedure doesn't change that.

Personally, I would check for timing chain slop and clean the pickup screen while you have good access.
Maybe pull the valve covers and see if it is really gunked up in there.
Flush the block and heater core with a garden hose.
Remove the blower motor and clear any leaves, mouse nests etc from the plenum/blower resistor.
Replace any hoses you can because they are likely soft unless they are new.

That's all the advice I can offer.

 

I am now in this same situation. I just bought a Chevy Tahoe for $400. The engine is making bad noises is why I got it at such a low price.

What I was able to do is run this engine and evaluate it from the tailpipe emissions, and the sounds it's making. I can tell the bottom end is very sloppy with lots of bearing noise. I have a choice; Either lift the engine up, pull the pan, and try to do surgery and stick new bearings in it, or go ahead and pull the engine and go through the whole thing.

After thinking about it, I am going to pull it and check the whole thing out. I want to use it to go on trips and pull my camper, so I want to check the whole thing out for any troubles. Hopefully the bores are good and I can re-ring it. If the crank is scored I will go ahead and have it turned.

You need to decide the same thing. If you really do not have any money, and time is on your side, you might just as well just run the engine like it is, and evaluate it from there. And then pull it later if you need to.

If you have a little money, and want it to be right, why not go ahead and pull the engine down and go through the whole thing. If you pull the heads you can see right away how much wear it has, by how much ridge is at the top of the cylinders. I was looking at kits for the Tahoe, and I can get one with gaskets, bearings and rings for about $350 or so. I can't remember if that includes pistons or not.

 

I certainly understand where Jim is on this, and would have to agree that the compression #'s look good. But I'm at a loss as to why the leak-down #'s are so wonky.

Eyeballing TDC is probably good enough as engines have the valves closed for quite a few degrees before and after that point, and the only thing critical is that the engine won't turn from the air pressure. So you must be getting it close enough. However, the air escaping from the sump boggles my mind. That suggests you have massive leakage past the rings in every cylinder. And that brings to mind several questions. Like, how long since this engine has been run? Any chance there was water sitting in the cylinders for a long time? What does the oil look like?

 

His rings could be stuck in the compressed position. Had that problem on a 352 FE. Nobody ever changed the oil, rings were stuck compressed. Had tons of blow by, but it only had 100 PSI in every cylinder. Which he does not have. Took a chisel and a hammer to get the rings off - they were that stuck! most of them are still sitting in the floor with rings on them. Only 1 out of 8 had free rings. So, he could have a problem similar, but the compression readings don't really show it.