M-38 First Startup After Rebuild/Sitting for a While

MoxM38 · Post by **MoxM38** » Sun Dec 27, 2020 2:53 pm

Fellas,
Now that my starter issue appears to be resolved, I am focusing my attention on properly getting the engine running. When I was preparing to start it up the first time in October (before the starter issue brought it to a grinding halt), I followed the procedures contained in several posts for first startups. However, those preparations were done two months ago and the engine has been sitting.

My steps for oil priming and first startup in October:

1. This was a total engine rebuild with engine dipped and painted, new pistons/rings, valves/guides, new cam, etc. etc. Engine bolted in and torqued to specs. I verified all items torqued to TM specs (flywheel, clutch, crank, etc.).

2. Oil Priming. I "soaked" the new oil pump in 30W oil, spinning the shaft to ensure completely full and inserted into the block. I synched up the distributor to the oil pump per exact instructions found in one of Wes's previous posts. I am confident the timing is correct. I also filled up the oil filter canister and poured oil down the center tube as it feeds the timing cover. I also syringe fed oil through the hose from the side of the oil filter to the block below the fuel pump. I pushed oil through until it squirted out the oil pressure sender hole. I then squirted oil all over the valves behind the valve cover. I then filled the oil pan to the specified level.

So, one big question: is this oil priming that I did two months ago good after a couple months? Did I miss something initially that I should do to lubricate the engine for this first startup?

I went through a lot of work to get this thing rebuilt...I don't want to screw it up now! When I turned the motor over several times (perhaps about 5-8 seconds of turning over), I did not register any oil pressure....would that take a while to build up the pressure?

Thanks in advance and Happy New Year!!

Rick

OKCM38CDN · Post by **OKCM38CDN** » Sun Dec 27, 2020 5:37 pm

You should be good to go, all the oil will leave a film to cover everything till you get it fired up. It will take a good 30 seconds or so to show oil pressure.

You have prepped it well IMO...

Understand your thinking, getting ready to fire up an F-134 (M-38A1) after the tank comes back from the shop.

Good Luck...

MoxM38 · Post by **MoxM38** » Sun Dec 27, 2020 7:31 pm

Thanks Hal, I have been turning it over tonight to get some oil flowing. It's on the battery maintainers tonight and tomorrow I'll hook up the plug wires and introduce some gas to see if it will fire.

I used to be stationed at Tinker AFB back in the day, I'm an old AWACER from the 552d. Great memories there!

Rick

OKCM38CDN · Post by **OKCM38CDN** » Sun Dec 27, 2020 8:54 pm

Retired from the 3rd Mob in 1994...

MoxM38 · Post by **MoxM38** » Tue Dec 29, 2020 8:30 pm

Uh oh, big problem (potentially) on my first startup on my rebuilt motor. As I've got the engine turning over, I have noticed a couple of disturbing facts:

1. The engine turns over rather roughly, it seems to bind up a bit as it turns during a particular stroke. It's doesn't sound good. The binding doesn't stop the motor, just slows it up considerably during a particular part of the stroke at a regular interval.

2. Compression is not looking good. TM calls for 90-110 psi per cylinder, I'm getting about 75 on cylinder#1, 70 psi on #2, 65 psi on #3, and 60 psi on #4. It is an old gauge I'm using but the trend is not promising.

I get no engine turnover other than what the starter provides. Lack of compression seems to predict that. Sigh.

I contacted the builder and he stated he will have time to discuss next week. What do you think if possibilities that are not as apocalyptic as I am imagining?

RonD2 · Post by **RonD2** » Tue Dec 29, 2020 9:57 pm

Timing not set correctly.

Valves not properly adjusted.

Good luck!

danrothe2001 · Post by **danrothe2001** » Wed Dec 30, 2020 6:58 am

Don’t be too concerned with the low compression on a new motor. Depending on the cylinder wall finish and the ring set it is not uncommon for compression to be a little low until you run it and the rings start to seat. You have enough compression for it to run. As was suggested, make sure everything else is set right. I am more concerned that you say it turns over unevenly. How does it feel turning it over by hand with a socket on the front? Are there tight spots doing that or does it feel smooth?

Dan

MoxM38 · Post by **MoxM38** » Wed Dec 30, 2020 4:34 pm

Today's status: I hit the starter and took some measurements. The binding seems to have subsided, I did not really notice it this morning. That's promising. I also did another cylinder compression test, I get about 75 psi across all cylinders now (#3 & #4 are a couple psi less).

I also did a spark test and verified that all four spark plug wires are delivering spark, however I have one bad spark plug. Ordered one right away.

I will check the valves tomorrow.

MoxM38 · Post by **MoxM38** » Fri Jan 01, 2021 6:57 pm

Valves checked today, it appears the machinist set them to 0.014" instead of the M-38 TM clearance of 0.016" (is 0.014" for earlier MBs?).

I am awaiting a new spark plug, realistically I should get four new ones. I was able to clean up the offending plug and resurrect some spark out of it for testing. All plugs are 4.5 years old.

I still feel some occasional binding/tightness as I turn the crank, but I am able to do it by hand with the help of a pipe on the end of my breaker bar. Some strokes turn pretty easily (#1 at TDC) but others pretty hard (#3 and #4 at TDC). I am chalking this up to tightness due to a fresh rebuild?

Also, one question on my crank nut. In all the posts I have read, I see varied opinions on crank nut torque. I have mine to 110 lbs based on a general "consensus"... what's your recommendation?

Xamon · Post by **Xamon** » Sat Jan 02, 2021 8:51 am

Okay regarding the drag I am perhaps going to confuse things a bit but....
TM 1804A pg. 62 item 51 and pg. 88 item 84

In regards to item 84 the piston rods and the pistons themselves are directional so installing either incorrectly could cause drag. At least that is how I read things. I am sure Wes will correct me if I have this wrong.

MoxM38 · Post by **MoxM38** » Sat Jan 02, 2021 11:13 am

Okay, something to look at. Also, it won't fire at all. I verified the timing when I installed the oil pump and distributor together...matched all the instructions exactly. Then I verified four good plug wires and four plugs that produce spark (one was a little fouled, I cleaned it up to get some spark). I even poured gas down the carburetor.... I'd have thought I would get at least a little chug...but nothing....only the starter turns the motor over.

I hope I'm not out of my league at this point....

Post by **wesk** » Sat Jan 02, 2021 2:10 pm

(is 0.014" for earlier MBs?)

Yes.

I am chalking this up to tightness due to a fresh rebuild?

The tightness check is to be performed with the plugs removed. You should be able to rotate the crank/rods/pistons/cam easily by hand or with a regular socket and 1/2" drive ratchet. If stiff then requires further investigation. Fresh rebuilds are normally unpredictable on resistance approaching TDC on compression strokes. If the starter will turn the engine at least 400 RPM then investigate the condition of the starter / batteries and their proper circuitry / grounding.

I have mine to 110 lbs based on a general "consensus"... what's your recommendation?

The industry standard on determining correct torque values is you use the manufacturer's recommended torque if one is published. If not published use the standard torque value for the diameter/pitch and grade of bolt or nut used. The Army did not published standard torque charts as part of their vehicle repair manuals until the later 50's / 60's. What I have always done is read the applicable service manual's installation instruction. If no specified torque is listed in the assembly instructions or in the spec's page then look up bolt/nut size (dia/thread pitch) then I go to the Willys Civvy Factory Manual (in this case SM-1002) and look in the assembly section & spec sheet for a specified torque (there is no specified torque for that nut in the SM-1002). Finally I refer to a standard torque chart for a 1 1/16" x 16 NF nut standard torque value.

The images listed below are from my photo album and the larger more readable files are on page 3 of my album:

Note these Torque Table Instructions found in an aircraft service manual.

More info

Just google General Torque Charts.

MoxM38 · Post by **MoxM38** » Sun Jan 03, 2021 7:33 am

Thanks for the responses. As for the crank nut torque values, I've seen the chart regarding different grades if nuts, bolts, sizes, etc....and frankly it blew my mind a bit. Hasn't anyone here had to torque their M38 crank nut down? What torque value did you use?

Post by **wesk** » Sun Jan 03, 2021 3:24 pm

http://www.willysmjeeps.com/v2/modules. ... _album.php

.014 chain drive cam L134's. .016 gear drive cam L134's.

Finding any torque chart with a 1 1/16"-16 thread size has been very difficult. But Lo & Behold! I found a reference for the crankshaft damper nut torque in my Old Chilton Jeep CJ 45-84 manual, 65-75 Ft Lbs.

I checked my 1940's and 1950's Motor Repair Manuals but found nothing. My 1960's issues though show 100-130 Ft Lbs for the crank damper/pulley.

MoxM38 · Post by **MoxM38** » Mon Jan 04, 2021 2:50 pm

We'll, look at that! I'll keep this for reference for sure! I've a mechanic coming to take a look/feel at the engine turning over to ensure I don't screw something up. Better safe than sorry.... I'll keep everyone posted.