[joedls]

Originally Posted by BRUTAL64

So you are helping with the bail outs?

[Vettezuki]

Originally Posted by BRUTAL64

So you are helping with the bail outs?

Anybody who pays Federal Income Tax and is not receiving redistributed plunder, I mean tax money, is. My goal is to eventually slip the surly bonds of earned income tax, create progressively more, and give away progressively less (to the government).

Anywho, back to blown out piston rings. What's the difference between:
- checking cranking pressure
- compression test
- leak down test

[big2bird]

Originally Posted by joedls

Do you have a PCV valve on it or breathers? Also, I'd do a leakdown test before I pulled it apart.

Why. It's broken. Out it comes.

[big2bird]

Originally Posted by Vettezuki

Anybody who pays Federal Income Tax and is not receiving redistributed plunder, I mean tax money, is. My goal is to eventually slip the surly bonds of earned income tax, create progressively more, and give away progressively less (to the government).

Anywho, back to blown out piston rings. What's the difference between:
- checking cranking pressure
- compression test
- leak down test

A compression test should reflect near identical pressures in all cylinders. Lower numbers in adjacent cylinders identifies gasket issues. If the introduction of oil increases pressure, the rings are worn.

A leak down test identifies ring wear/failure to hold pressure.

[big2bird]

Originally Posted by BRUTAL64

I'm going. It'll be great to actually be among the GOOD cars.

You mean there will be some real Cobra's there?

[joedls]

Originally Posted by big2bird

Why. It's broken. Out it comes.

If he has a defective or plugged PCV system, it can cause excessive crankcase pressure.

Also, a leakdown test can help pinpoint where he is losing compression and exactly how much.

If he can clearly hear a whooshing/howling by listening at the oil filler cap during the leakdown test, he's losing compression through the rings.

If he can hear it (or even feel puffs on his hand) at the tail pipe, then it's his exhaust valve on that cylinder.

If he can clearly hear a whooshing/howling by listening at the carb/intake manifold, then it's his intake valve on that cylinder.

If he can see it bubbling in the radiator, it could be a head gasket, although it doesn't sound like that's it.

[big2bird]

Originally Posted by 94cobra69ss396

His crancking pressure should be higher than the Cobra's 155psi with 9.5 and a 111 lsa. To give another comparison, the Chevelle with 12.25:1 and a 110 lsa has 210-215psi.

The 454 engine I just refreshed for the Winnebago has 175lbs cranking pressure with 8.5 CR. Other than "relative" numbers, it means very little.

[94cobra69ss396]

Originally Posted by big2bird

The 454 engine I just refreshed for the Winnebago has 175lbs cranking pressure with 8.5 CR. Other than "relative" numbers, it means very little.

The cranking pressure is dependent on the compression ratio and the cam timing. More overlap equals less pressure. I'm sure your 454 with 8.5 also has a lobe seperation in the 115 or higher range which would give you good bottom end torque with your low compression. My 454 has a 110lsa that bleeds off some pressure but with 12:25 still has a high cranking pressure.

Ben, the whole point of the compression test, which is what gives you the cranking pressure we are talking about, is to determine if all cylinders are in the same range. Say you have 150 on all cylinders except one that is only at 80. Then you know that low cylinder is causing the problem. As Joe explained, by then doing a leak down test you can determine what the possible cause could be.

This is why I asked Adam what his compression and lsa were after he said he only had 135psi cranking pressure. If he only had an 8.5:1 compression ratio and a 106-108lsa I would say 135 could be an accurate range. However, if he does truely have 9.5:1 and a 111lsa 135psi is low.

[enkeivette]

9:1 with my thicker MLS
Hyd Roller .576 in .594 ex Lift 239in 245ex Duration @ .05 110LSA

Motor made 135 at 9.5:1 And it's always seemed to me like it's made about 20% less hp than comparable setups. It only made 520 crank with 5lbs, granted it was with a 14:1 afr, but still it should have made close to 500 without boost.

Once I sealed up the intake gaskets and tightened the belt after dyno day, it made 10lbs.

Not going to do any testing, time to pull the heads, and then the pistons. Pistons are coming out for sure, I can only hope that the cylinders are ok. I'd like to do this without pulling the motor. If the pistons are ok, I will resuse them. If not. I will get some blower slugs and drop my CR and order a smaller pulley when funds allow. It would be awesome to run 19lbs...

BTW, broken rings or not, I slaughtered the guy that I was racing. And I'd do it again, 60 psi in several cylinders or not. Watch out suckas!

[BRUTAL64]

Originally Posted by joedls

If he has a defective or plugged PCV system, it can cause excessive crankcase pressure.

Also, a leakdown test can help pinpoint where he is losing compression and exactly how much.

If he can clearly hear a whooshing/howling by listening at the oil filler cap during the leakdown test, he's losing compression through the rings.

If he can hear it (or even feel puffs on his hand) at the tail pipe, then it's his exhaust valve on that cylinder.

If he can clearly hear a whooshing/howling by listening at the carb/intake manifold, then it's his intake valve on that cylinder.

If he can see it bubbling in the radiator, it could be a head gasket, although it doesn't sound like that's it.

When I blew my 4 pistons, I'd take off the beather cap and it looked like a steam engine.

I did a leakdown just for grins. Man, you could hear it hissing thru the whole engine. Just plain sad. Yea, the engine just lasted 16 years.