Compression Test Results


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Post Sat Jan 27, 2018 6:07 pm

Compression Test Results

Ran compression test today on my GRD 214. Results as follows:

1 - 78
2 - 76
3 - 80
4 - 77
5 - 78
6 - 80

Good news is all of the results are close to each other. Bad news is that according to the Thompson Guide for GRD engines, the optimum results should be between 110 and 120 psi, and it states that the results should NOT be below 90 psi.

Oh well, by the amount of oil burning and blowby I’ve been seeing, this is pretty much what I expected. I’m just happy that there is no single cylinder that is much worse than the others.

What are you guys seeing on your older engines?

John

"Cornelius" - The "Rolling Restoration" of a 1939 IHC D-2 Pickup - 113" WB
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Post Sat Jan 27, 2018 11:31 pm

Re: Compression Test Results

Few weeks ago I gave the old HD213 a tune up and the compression tested at 110 psi.


Tony
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Post Sun Jan 28, 2018 2:57 pm

Re: Compression Test Results

Ok - I’m Green Diamond green with envy :-)

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Post Wed Jan 31, 2018 3:49 pm

Re: Compression Test Results

IHC factory manual lists compression on a new GRD motor at 6.3 approximately 95 lbs. Your engine is probably fine, GRD are a low compression motor, even reading is more important than how high it pumps up the compression tester, many variables can affect a compression reading,

Thompson guide isn't the best source of information compared to factory manual,
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Post Wed Jan 31, 2018 4:24 pm

Re: Compression Test Results

Should have checked the factory manual too! 95 makes me feel quite a bit better 8-)

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Post Wed Jan 31, 2018 4:28 pm

Re: Compression Test Results

That's even compression.

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Post Wed Jan 31, 2018 5:03 pm

Re: Compression Test Results

I suppose the engine was cold and the cylinder were dry. A little ATF on the cylinder walls should help boost the pressure. Maybe C89 can verify the warm engine thing.
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Post Thu Feb 01, 2018 11:59 am

Re: Compression Test Results

I have a freshly rebuilt GRD 214 in my panel, hasn't been started in maybe 3 weeks or more,

I will do a cold compression test, then start and run to operating temp and do another one,

My truck is 6v. so I will also do each test with the 6v. battery and then with a 12v. just to see if cranking speed has any effect,

Probably early next week, stay tuned, this is just for my curiosity, no claims or contradicting others intended.
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Post Thu Feb 01, 2018 4:06 pm

Re: Compression Test Results

Sounds interesting! My test was completed at operating temp., 6V.

John

"Cornelius" - The "Rolling Restoration" of a 1939 IHC D-2 Pickup - 113" WB
New Website - "Restoring Cornelius"
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Post Sat Feb 17, 2018 7:39 pm

Re: Compression Test Results

OK, finally got over this nasty flu, And it stopped pouring rain, a non garage owner in the NW. Hmm,

so background on the motor, GRD 214 was rebuilt in 1991 and never started, I got it in 2013, took off head, new 30 over pistons fresh honed cylinders, new valves/seats, etc., holes 3 & 4 had some corrosion as there was never a carb installed and moisture got into intake, cylinder walls cleaned good, 3 & 4 intake valves removed & refaced and seats were refaced in the truck, did nothing to other pistons, valves as it was all new, inspected bearings, all crank/rods turned with new bearings,
everything reassembled,

the motor has probably 30 miles and 5-6 hrs. on it, so broke in? probably not, rings seated? probably,

test done with fully charged 6v. and 12. batteries, 12. connected with jumper cables directly to starter, brand new compression tester as my 30 yr old one was giving wacky readings, carb held in wide open position,

6v. cold 1=98, 2=95, 3=88, 4=85, 5=85, 6=98

12v. cold 1=108, 2=102, 3-95, 4=98, 5=99, 6=110

then I ran the truck for about 1/2 an hour, up to operating temp on gauge, block was hot to touch, not super hot,

6v. hot 1=98, 2=90, 3=95, 4=85, 5=90, 6=100

12v. hot 1=113, 2=110, 3=105, 4=100, 5=103, 6=115

conclusions:
to me compression tests can vary greatly, so I wouldn't get hung up on number rather than even across the board,

all old mechanics manuals tell you variances in castings of combustion chamber can affect reading by 10lbs,

12v. tests can make you feel better about your 6v. motor's health by giving you about 10lbs. higher reading

I plan to do another compression test after I drive it a couple hundred miles or so,
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