Compression Test Results- Opinions?

Guess I need to make the best of it

Thanks again for the responses!

Ok, I have my head around pulling the top end apart. No question that needs to be done, based on your posts. And Adam, the pics of your reassembled top end is enough motivation to do so. Very nice! :TU:

Before I do so, I'll perform a leakdown test. I found several websites on building a tester. I work in a factory and we use lots of pneumatics on assembly equipment. I'm sure all the pieces required per those websites can be borrowed to piece together a unit. Dennis, thanks for your kind offer. I truly appreciate it. If I can't put something together that works OK, I may take you up on it. I just figure I can probably put one together today and try it tonight.

Mark and Larry I hear you on the coolant. Good theory. The car ran OK when parked long ago, so the coolant theory would provide an answer to the question of why a compression loss between now and then. I should see bubbles in the coolant/spray out the radiator with this test if that's the issue, correct?

Mark, should the pre-71 head gaskets be used? Anything better that could also give a slight compression advantage and still be reliable?

I'm trying to look for the silver lining here. If I can do some level of upgrading while it's apart, that would help dealing with the amount of time/$ I'm going to need to do this.

Thanks everyone. :TU:

 

Ken,
Don't know if there are any thinner head gaskets for the 350 that are still around.
TA may have something. There was a p/n for 68-69 350 that may have been thinner. The p/n was 1231136 and is not the same as the .045 thick ones that were used after that. The newer Felpro blue gaskets are good and don't have the leakage problems of the red ones GM used.
One other trick is to use long reach spark plugs. The plug extends into the combustion chamber taking up volume and thereby raising the compression.
I know this work on the 400/430/455 and may also work on the 350. The number for them is R44LTS. Don't know if there is an R45LTS.
You can always get the heads cut a bit to up the compression. Just don't want to cut too much or you will have intake manifold issues (lining up) and pushrod length issues too. A .025 cut should be ok with the .045 gasket.
Any 350 guys have any ideas?
Regards,
Mark

 

Hey Mark,

Ken's got a 455 under the hood of that beast!

 

Although it seems more like a six cylinder now. :gt:

 

Thoughts..

Ken,

IF the 4 corners of the head gaskets are weak or blown out, then here is an easy test..

With the radiator cool, remove the cap, and make sure it's full..

Leave the cap off, start the engine, and let it warm up to full operating temp.

Then, with the radiator cap still off, crack the throttle rapidly a few times, while carefully observing the radiator neck, (and don't stand in line with it..)

If you have that big a leak, it will shoot coolant out of the neck about 4 feet... all that compression has to go somewhere..

I doubt that's your problem, typically the car would be badly overheating by now, and filling up the overflow bottle.

I don't doubt that the head gaskets have suffered some ill effects from sitting that long. And steel gaskets would be just as bad, possibly worst.. there is a reason that the factory went away from that gasket, and it wasn't because the new gaskets were cheaper.. Part of the reason was it helped the compression reduction program for '71, but another part was they did have quite a few issues with steel shim gasket sealing. I have seen dozens of rotted out steel shim gaskets, on 430's and 70 455's.

And you certainly would not want to go to steel shim gaskets, without fresh cuts on the block and head surfaces. The surfaces have to be perfectly flat for those gaskets to seal properly.

I also doubt you have a valve problem. If an exhaust valve is burned, it will typically fire into the exhaust, and intake will fire back into the intake tract, and exit the pressure out the carb.

Either senario would cause a very audible "pop". This will be most noticeable under hard acceleration.

Considering the circumstances, I am willing to lay odds that you have 4 pistons with the compression rings stuck solid in the grooves, and the other 4 are partially stuck.

A leakage test is the best way to determine this, but considering you have basically no compression on 2 cylinders, it's not going to be tough to determine if it's a head gasket or not, long before you go taking the heads off.

My suggestion is this..

Do the above test, and if it does not spit coolant out the radiator neck like old faithful, then proceed to the leakage test. I bet that with 100 psi applied to the cylinder, you are going to have a tornado of air coming out of the crankcase. If that is so, then what you have is weak compression due to ring failure, and I would suggest that you enjoy the car for the rest of the summer, and then come fall, pull the engine out, and get ready for a learning experience.

Now, even if the head gaskets are blown, or you have a valve problem, you would not catch me pulling heads off in the car, with the motor installed.. not on a car like yours.

It's way too easy to rent a engine hoist, and round up a few buddies on the weekend, to yank the motor. And with the engine on a stand, it will be so much easier to work on, and you can throw a few fresh gaskets at it while your at it, and give it a nice, complete re-paint.

Even if you have to go thru the motor, as long as the cylinders are not rusty, and it just needs a re-ring, you shouldn't have to sell any of the kids to pay for it..

But I may tend to believe that you might have some rust damage to the cylinder walls... and then it's going to be more expensive.. You have have to lease a few of the kids out.. LOL..

Or maybe the wife.. :laugh:

JW

 

More info, if it's worth anything

Jim-

I'll try the coolant geyser method tonight. Easy enough to do. The car comes up to temp and stays rock steady there even if it's extended idling.

I hear you on the compression ring theory, but let me give you another couple observations and see if you still think the same thing. When it was first noticed that #1 was not performing, Tom Telesco and Carl Rychlik were over the house helping me out. One of the things Tom did was to pull the PCV valve out and check for pressure. He didn't note anything being pushed out of the crankcase. same for opening the oil fill and pulling the dipstick out slightly (all done separately). They were both thinking that ring problems (blow-by) might not be a factor unless it was also coupled with a valve issue (stuck valve). I hope I remembered that correctly.

In terms of backfiring, the car hasn't backfired through the carb at all. I was having difficulty starting it and got some backfiring through the exhaust. It doesn't backfire through the exhaust once it's running, so I'm thinking it was just dumping gas into the exhaust while I was cranking it to get it going???

Does any of this additional info change your probable diagnosis? Or does it add further to the compression ring theory?

Anyway, I know it's hard to diagnose from so far away and without seeing/hearing it, but I appreciate any further thoughts you might have.

Thanks,

Ken

***************************
Something else I just thought of- you can hear the sound of compressed air escaping through the exhaust in rythmic bursts. Best way I can describe it.

 

(CWREIP) Child / Wife Reduction Engine Improvement Program:
Sounds like something we could get a government grant for, also sounds like a "win win" situation to me.

 

Not four foot, but still a gusher

OK-

Filled the radiator as it was a bit low. Started the car and had some coolant spilling out of the filler neck. It would surge out every five to ten seconds or so. Enough for me to catch it in some shop towels as it was starting to pool on the floor. It got to a point where enough had spilled out that coolant would disappear from view, then surge back up. Not old faithful, but spilling over the top. This is while the car was idling and before the thermostat opened. I made a little dam on the garage floor while I was waiting for it to warm up. ou:

Once it warmed up a bit, I got in and gave the gas a couple of stabs. Once I let off the gas, I'd get a gush about a foot to eighteen inches high coming out of the radiator. Now at idle it was already losing coolant, so I was starting somewhere less than full. Did this a couple of times, shut it off, then called the EPA. :Brow:

Thoughts?

 

Update

Made a set-up today at work to put air into the cylinders. It consists of a male quick disconnect into a brass T with a gage on one port and a ball valve on the other that leads to a female quick disconnect. On the outlet side I hooked the hose for the compression tester with the check valve removed. Ahead of this whole set-up I have a regulator and another gage.

I have to borrow a friends compressor, but used a junky one I have that can only make about 50 psi. It does have a tank, so there's somewhat of a reservoir.

Anyway, I hooked this up to the number 1 cylinder and brought the motor to TDC. I pulled the valve cover and made sure the valves were not moving when I turned the crank slightly back and forth. After doing a visual on the valves I looked at the timing mark and it was a whisker off of "0".

I turned the valve and dumped air in. I could hear it, but not from the crankcase or the carburetor. My wife helped and could both feel and hear it from the exhaust pipes.

I know I need to do this with a "real" compressor, but just listening seemed like a lot of info as suggested in a post above. Once I borrow a compressor I'll put a regulator upstream of my tester and do all cylinders.

Seems like the exhaust valve ain't doing its job. How does relate to the 12-18" gusher I noted above???

All help and advice appreciated!

 

I kep wondering where the coolant in my car was going. I was topping it off once a week. Then it dawned on me that I was losing it through the laeks in the head gasket. But the leak was minor enough that it was all evaporating before it got to pool in the cylinder.

I finally noticed the white smoke one morning when I went to work in the car.

Drove it straight back home and into the garage.

 

Adam-

I do have a small coolant leak that dampens the garage floor, so it's hard to tell if the low coolant issue is related to this leak or a faulty gasket. I haven't been able to figure out where the leak comes from yet.

Anyone else have any comments? Jim, is it ok if I call you today for a quick consultation? I know you're a busy guy, so no problem if you don't have the time. I can send pictures of the wife and kids for that swap. I figure they're worth at least one of them fancy $10k motors you put together. :laugh: J/K

 

Ken,
Did you happen to leave the radiator cap off when you did your air test? If you had seen bubbles or surge during that test it would have been conclusive prove of head/head gasket problems. Your above symptoms are a bit inconclusive, could just be normal water pump surge, if the "gusher" had occured before the engine was warm and during acceleration then just as JW said it would have been a slam dunk head gasket leakage problem. With the gusher occuring with the engine decellerating (sp?) and with the engine partially warmed you may have just been seeing the effects of the water pump slowing and the suction side water backing into the radiator.
Definately want to be sure on that head gasket issue, you can do some damage quick if its the problem, if its just valves or gummed up rings I'd drive it, add some Marvins Mystery Oil or some Seafoam to help clean it a bit maybe.

 

Hey Len-

Thanks for the response. I was thinking that because the gusher occured upon decelleration that it might have been normal as suddenly you're slowing down the coolant flow and might get a pulse backward. Sounds like you're thinking the same way.

I did leave the radiator cap off when I did the leak test on #1. No bubbles that I could hear and the tank on my lttle compressor emptied quickly. I suppose I need to finish the leak down with a proper compressor to be able to assess what's happening in all cylinders, particularly the corners.

 

Bad head gaskets will also make the radiator hose feel real hard when started because of combustion pressure and it will make bubbles in the overflow tank with the radiator cap on and warmed up. Tom