Engine: Low compression on 3,5, and 7.

[Mcwicki51]

Hello,

I am new to the world of studebaker. I just purchases a 1963 Studebaker Cruiser with a 289 V8, flightomatic and factory power disc brakes.

Over the weekend I performed a compression test and was disappointed to find out that #3,#5 and #7 are all down with readings of 90, 100 and 120 . The other cylinders are between 140-150.

I put some MMO in #3 and rechecked the compression with no change in the compression.

All the old plugs looked good.

I have posted a picture of the plugs with associated readings.

I have no history on the engine and I have not adjusted the valves. I am considering picking up another set of head to work on while I drive the car around. I am assuming that my problem is with either the valves or potentially a head gasket.

I am not loosing oil. It is clear. I am also not smoking out the tail pipe. No loss of coolant and it is clear.

I am stumped. Any ideas?

Thanks,
Steve

[DEEPNHOCK]

The Autozone up in Woodland (or those in Sacto) should have a radiator tester on their tool loaner program.

http://www.autozone.com/loan-a-tools/pressure-tester-adapters

[thunderations]

I think you are on the right track. Something with the heads is probably your problem. Might be as simple as a valve job and good to go. Head gasket would usually give you the same reading as the cylinder next to it.

[jclary]

I like the way you have laid out the plugs and have written down the respective pressures. If you still have that laid out...how about, taking the valve covers off, and write down the clearances, on those solid lifters. As I have posted before, some mechanics can't accept the natural "clatter" of these solid lifters and keep cranking down to quieten them. It might not be your issue, but would be an interesting exercise.

Especially for those of us who don't have to get our hands dirty, and strain our low backs, bending over fenders to accomplish the task.

[karterfred88]

Before getting carried away-torque the intake, adjust the valves. Then do a leak down test, using a compressor to pressurize the cylinder, that will help identify a problem if there is one.

[Mcwicki51]

Thanks... I will definitely get do all the things that you have suggested. I will repost with the valve clearances. I will look into renting a radiator tester and a leak down tester.

Steve

[karterfred88]

And just a quick suggestion, depending on how much use this car has had, I'd put new plugs in it after adjusting the valves and resetting the timing, go out and drive it "hard" for a few miles, hard acceleration and deceleration for a tank or so of gas. Carbon can and does flake off the piston tops and valves sometimes holding a valve from fully closing, a good hard run will sometimes surprise you in the difference in readings.

[RadioRoy]

I have noticed a tendency for 3 and 5 to have lower compression on the "used" V-8 engines I've worked on. Always wondered why those particular cylinders would do that.

[Mcwicki51]

Driving it "hard" with the Flight-o-matic seems to be challenging. It likes to just cruise a long.... My downshift is not working. I thought that I would sort out the engine first.


Any thoughts on the Lisle Combustion Leak Detector? Would this be helpful to figure out head gasket versus valve adjustment? Should I use some MMO or seafoam after confirming that I do not have a head gasket issue?

Thanks, Steve

[karterfred88]

Driving it "hard" with the Flight-o-matic seems to be challenging. It likes to just cruise a long.... My downshift is not working. I thought that I would sort out the engine first.


Any thoughts on the Lisle Combustion Leak Detector? Would this be helpful to figure out head gasket versus valve adjustment? Should I use some MMO or seafoam after confirming that I do not have a head gasket issue?

Thanks, Steve

Sure it will help, but a cooling system pressure check is almost as good-pressure disappears, pull plugs one at a time. Won't find a cracked head but cheaper. Even watching the coolant with the t'stat out and running at idle with cap off should show bubbles of exhaust at no cost. Usually a head gasket into combustion chamber failure will show as white deposits on plug tips, exhaust into coolant passage as bubbles in the radiator, to oil galley , baby poop look to oil. Have fun- the 5-7 is usually a valve problem, they fire one after the other and I believe this causes a leaner mixture for them--not 100% sure of that though.

[jackb]

??-how much driving has this engine seen in recent weeks, months, years ???

[Mcwicki51]

Hello, It was not driven much over the past 18 months, but I have put about 300 miles in the last month after purchasing it. It runs well with not problems with temperature. I actually drove it from Davis to Nevada City in a 95 degree day (75 miles and 3000 ft of elevation change). The engine only moved past the midpoint on the gauge. Coming home it never reached the half way mark on the gauge. I changed the oil, filter, plugs, cap and rotor. She is running like a top except for the rocking of the car at idle while sitting at a stop light. This is what caused me to check the compression in the first place. Thanks, Steve

[Mcwicki51]

To adjust the valves... How many folks would recommend the procedure that I see that seems very easy. Half the valves with #1 at TDC and the other half with #6 at TDC. This is the order:

With Pointer and engine on Number 1 firing position adjust valves

EXHAUST Number 1, 3, 4, 8

INTAKE Number 1, 2, 5, 7

With pointer at Number 6 firing position adjust valves

EXHAUST Number 2, 5, 6, 7

INTAKE Number 3, 4, 6, 8

It seems too easy. I am planning on doing it cold and setting them to 0.026" lash.

Any other tricks or is the method in the shop manual substantially better to use.

Thanks,
Steve

[karterfred88]

Nope, that works for me, but I do set 1/2 with the engine hot (to the hot dimensions), put covers back on (yes they leak) get it hot again and do other half. New gaskets, run away and cross my fingers (I hate fixing valve cover leaks).

[JoeHall]

"...rocking of the car at idle..." is a good indicator the valves are too tight. Odds are, you will find all of the exhaust valves a bit tight, but real tight on #3, 5 & 7.

How was the gas mileage? If MPG is OK, with oil mileage and temperature OK as you said, I'd button it up and drive the snot out of it. (Once the valves are adjusted.)