compression test of Studebaker engine-Method??

[James Caspi]

Three days ago, I demanded that I be shown the compression tests done on my newly rebuilt straight 6 engine.

I discovered that the 'supposed correct and normal method' was to remove all spark plugs, and have someone crank the starter --each time a pressure gauge had been screwed into one of the cylinders.

The several very troubling things were that if the cranking went 4 times or 5 times the pressure continued to build so the reading was a "hit and miss" ordeal of guessing what the reader said. Is it possible to be more accurate than that?

I firmly believe that the guy who decided what the gauge read could have controlled what he says he read as much as he pleased.

Is there a more accurate and absolutely standard way of doing this??

Jim

James Caspi
1950 Champion Regal Deluxe-2 dr.
New York, NY.

[Mike Van Veghten]

Actually...he was "close".

There will also be a difference in cranking compression when the engine is warm vs. when it's cold.

Anyway -
1. Remove all spark plugs
2. "Block/wire" open the choke, fully
3. "Block/wire" the throttle open, fully
4. Install tester (no leaks!)
5. Spin the engine UNTIL...the tester stops climbing. This can take 3 to 6 revolutions, depending on a lot of variables.
REMEMBER..the number of revolutions, and do the same thing to all cylinders. If a cylinder varies some, go ahead and add a rev. or two....NOT a problem.

Note...if yor engine is NEW and "unstarted and broken in"...this testing can be VERY bad for the cam shaft, DON"T do it.
IF...the engine has at least 500 miles on it, not only will the cam and lifters like you better, SO..will the compression gauge. You have to break in the rings to get a true reading...!

Mike

[Tom Bredehoft]

Compression test taken from 55 Commander Shop Manual, page 66 Engine.

"Use a compression gage to determine the compression of the cylinders. Remove the spark plugs and insert the gage in the spark plug hole of each cylinder in turn. With the carburetor throttle wide open, crank the engine several revolutions with the starter motor and record the maximum pressure indicated on the gage."

It continues to describe oiling the cylinders and comparing with unoiled, and finding blown gaskets between cylinders when to adjacent cylinders both have low readings.

The gages I'm familiar with have a check valve so that the cumulative total pressure is recorded, not guessed at by the reader.

Seems that the test was done according to the prescribed method.



[img=left]http://www.alink.com/personal/tbredehoft/Avatar1.jpg[/img=left]
Tom Bredehoft
'53 Commander Coupe (since 1959)
'55 President (6H Y6) State Sedan
(Under Construction 571 hrs.)
'05 Legacy Ltd Wagon
All Indiana built cars

[sals54]

I would do the test again. If you are in doubt of the outcome, a repeat performance is not difficult. If you do not have a gage, they are quite cheap to purchase. Be sure to follow the prescribed methods as stated above and you will know for yourself. Remember that the pressure reading is important, but consistency through all cylinders is at least as, (some would say more), important. You want the readings to stay within 5 lbs of each other to be ideal. 10 lbs would not be life threatening tho.

sals54

[PackardV8]

Mike is correct, but for engines with high spring pressure. A Stude six runs such comparatively low spring pressure, it is doubtful the lifters would be harmed by a compression test prior to break-in.

If one is as concerned about the condition of cylinders as Mr. Caspi seems to be, understand the readings will not be conclusive until the rings have seated. This usually takes a couple of hundred miles for cast iron rings. It is possible, but unlikely chrome rings were used, but they take as much as a couple of thousand miles to completely seat.

Also, a leak-down test is generally considered to be more indicative of ring seal than a compression test.

thnx, jack vines

PackardV8

[bams50]

This from James' previous thread, toward the end, here:

http://forum.studebakerdriversclub.com/topic.asp?TOPIC_ID=26121

After having 1000 on the new engine which included oil pump gears, new pistons with new rings and bearings, slightly polished cylinder walls before putting the new rings and pistons in them, new freeze out plugs after cleaning out the whole engine of any sludge--and she still consume oil somehow.. What should I look for now? We even did a compression test both dry and wet (with oil).

My mechanic said we didn't bore out the engine which would have taken a huge extra amount of work including removing the engine block from the car.

We are hoping there is still more breaking in period to run the engine so this might be the cause of the oil loss.

Please help me figure out why I'd loose 1/2 quart of oil in one tank of gas at highway speeds?

I suspected faulty cylinder measurement and less-than-proper preparation; and suggested a compression test and a leakdown test would be a starting point.


Robert (Bob) Andrews Owner- Studebakeracres- on the IoMT (Island of Misfit Toys!)
Parish, central NY 13131

"Some people live for the rules, I live for exceptions"- 311

"Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"

[James Caspi]

Yes, you guys are ALL OVER THIS, and correct.

The new engine does have cast iron rings, has 950 miles on the newly reworked engine, (I let it break in for the first 500 miles and changed the oil and filter and torqued the engine head down also at the 500 miles), then continued to drive it up to 1000 as of today. On a weekend trip (around the 600-850 mile mark) I was at 50 to 65 mph for maybe 100 miles, obviously also was checking the oil frequently, as well as 150 miles at more normal driving speed of 20 to 50 mph. I am sure I used a 1.25 quarts over the weekend and some.

Funny thing about that check valve pressure gauge you all talk about, is that YES, it did have one of the release valves too but the mechanic would not let the pressure accumulate beyond the 4 cranks because he said it would keep going up and up etc. I watched it go past 100 lbs and who know what pressure?!!--but the mechanic told the other guy on the starter button to stop cranking so he released the pressure from the gauge with a button on the side of the gauge and they both started again.

It was a dialogue between sitting mechanic and engine side guy like this-- "crank, no hold it--too many times, start again (releasing the pressure) crank etc. -performance!! I didn't think it was very consistent at all.

You guys ask such good, accurate questions and I want to present every fact I can remember.

Of yes, one more, the owner of the shop borrowed (from a machine the machine shop that does machining on engines) the special gauge "a special sounding measuring device" of some sort to measure the cylinders walls both for taper and out of round and said they were all within range!

Have I shed any light on your questions? One thing for sure, I'm learning a heck of lot I didn't even think of before. Had I ever realized such a thing as boring out the engine cylinders, I would have done it in a second so that this job was done ONCE AND CORRECTLY!

Jim

James Caspi
1950 Champion Regal Deluxe-2 dr.
New York, NY.

[curt]

Should this test not be done on a warmed up engine? I always drive mine about 10 miles before compression testing.I would be interested in a vacuum test, they say a lot about an engine.

[gordr]

I would doubt the validity of a compression test if the operator arbitrarily stopped the test while the pointer on the gage was still rising.

As far as oil consumption goes, Champion engines are known for wear on the valve lifters and their bores, which allows excessive oil to spray around in the valve chambers. Some of this gets sucked up through the intake valve guides and burned, and some sprays on the lower part of the cylinder bores, and can get past the rings and be burned.

There are supposed to be stamped steel deflector plates that fit in the valve chambers to direct some of this excess oil away from the valve guides, and some rebuilders leave these out.

One other point: you spoke of "polishing" the cylinder bores. I hope NOT. They cylinder bores are supposed to be honed with stones that provide a uniform matte surface with a cross-hatch pattern. That holds a little oil in the pores of the metal and helps the new rings to seat. Rings might never properly seat in cylinder bores that were really polished.

Gord Richmond, within Weasel range of the Alberta Badlands

[drnittler]

So would this deal where lifters and bores many be worn cause son oil to spit out the oil cap?
My engine was redone, I reused the same lifters, new rings, honing, bearings, etc...I have 4000 on the rebuild with some oil comsumption. What is this metal plate your are talking about?
Thanks.

David G. Nittler

[James Caspi]

The cylinder bores were not polished but uniformly rough exactly so the real seating could take place with the cast iron rings doing that work.

I also have some oil that seems always to be smoking out of the oil fill cap when the engine is turned off when hot.

A lot of information being circulated and it is very helpful. thanks again.

Jim

James Caspi
1950 Champion Regal Deluxe-2 dr.
New York, NY.

[skyway]

IMHO installing those missing deflector plates should be the first step to controling oil usage in any otherwise healthy stude 6. You'll find them shown in the parts book in an exploded view of the engine. There are 2 of them, one for each tappet chamber. They kinda perch against the bottom of the chamber, and are trapped in place by the 2 bolts that secure the tappet covers.

I think they were standard on all flat Champion engines, but may not have come to the Commander engines until the 245. (Note Champ and Comm plates differ in size)

My then fresh 226 Commander was using too much oil until I installed them. Seems like that engine went from using a quart every 600/800 miles to more like every 1200.

[drnittler]

I don't remember these deflector plates for the OHV 6 engine.

David G. Nittler

[53k]

quote:Originally posted by drnittler

I don't remember these deflector plates for the OHV 6 engine.

They weren't needed on the ohv engines.


Paul Johnson, Wild and Wonderful West Virginia. '64 Daytona Wagonaire, '64 Daytona convertible, '53 Commander Starliner, Museum R-4 engine, '62 Gravely Model L, '72 Gravely Model 430

[skyway]

My bad, I meant only the L (flat) heads.