Engine rebuild recommendations

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Seff
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Engine rebuild recommendations

Post by Seff » Wed May 23, 2018 12:30 pm

My engine stopped running at the last meet, right after a long drive. I removed the spark plugs to check compression. Number two had no compression. Called AAA at that point.

The ring ridge is not very pronounced - but at what point do you hone/bore the cylinders?

This is the result, after removing the head. Picture of the number four valves for reference.
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artificer
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Re: Engine rebuild recommendations

Post by artificer » Wed May 23, 2018 11:12 pm

Number 4 exhaust insert was not fitted correctly/properly [loose] is an evident issue & this may be so on all exhaust valve inserts including number 2.
These will all need resizing & fitting correctly sized for the next go inserts....frozen then tight fitting is recommended.
This problem you had may have absolutely nothing to do with rings or the cylinder condition.
As it is now I recommend getting all your valves right, reassemble then re-check compressions.
You'll find you have probably nailed the problem/s experienced & no big $$$'s required.
Do not rebuild an engine when current mechanical condition/s fixed will last one's lifetime with little current outlay to get everything right.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

Seff
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Re: Engine rebuild recommendations

Post by Seff » Thu May 24, 2018 3:10 am

Roger - don't fix something that ain't broke.

Machinist says to disassemble the engine completely for cutting valve seats and valve guides, so I'll be taking the rotating assembly apart no matter what. That'll give me a good view of the bearings.

Seff
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Re: Engine rebuild recommendations

Post by Seff » Thu May 31, 2018 12:26 pm

The cylinders still have hone crosshatching. The pistons have the tiniest bit of skirt wear, but nothing that looks bad. Ring ridge isn't bad at all.

The engine was renovated by the French army in 1985 - and has gears instead of a timing chain. The cam lobes are also very pointy?

Chuck Lutz
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Re: Engine rebuild recommendations

Post by Chuck Lutz » Thu May 31, 2018 12:53 pm

artificer's post is probably an excellent suggestion for this problem since your lack of compression is probably due to the loose insert.

With that in mind, I would now suspect that the others were not installed correctly and would want to either replace them all or at least check to see if they are seated firmly. Since you mentioned a possible worn cam, and you are planning on disassembling the motor to do the machining. You are at a crossroads with this engine. If you find that there are issues with tolerances and worn parts, now would be the time to sort that out. While you might get by with just new inserts....where do you stop?
1) Has it been "rebuilt" since the French Army did it?
2) If so, who did it and possibly this is why the insert(s) are loose.
3) If you suspect shoddy work (poorly fitted inserts) you should, in my opinion, check EVERYTHING before reassembly
4) I am a big fan of having the pistons & rods as well as the crank and flywheel balanced when you have the motor torn down. It will run smoother and not vibrate at low or high rpms and won't beat itself to death early.
5) Would this be a good time to mill the head and deck the block to insure a good, tight head gasket seal? Sure, why not?
6) We don't know the history of this motor, do you? How many miles does it have? Did the Speedo odometer even work?
7) Does it burn oil or does the rear main seal leak?
8) If it does leak, inspect the rearmost section of the crank where the seal rides and if it is not a shiny as the rest of the journals, have is machined/cleaned so it does not tear up a new RM seal.

Again, you may be OK to just have the Stellite inserts replaced so they are TIGHT, and that lone will be OK.....but it is up to you and your assessment of what you are finding in that motor to decide to stop there or go "Whole Hog" and rebuild it....and it is you who will be paying for this so it is something to at least consider.
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
GPW 108552 4/17/43 Louisville, KY. USA 20371278 (DOD est./Tom W.)
Bantam T3 4582 10/29/42 USA 0173499 (est.)


Seff
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Re: Engine rebuild recommendations

Post by Seff » Tue Jun 05, 2018 11:48 am

I have loaded the block into the back of my car, and will be delivering it at the machinist tomorrow morning. There are several other valve seat inserts, and I don't trust any of them.

1.) Not that I know of. All parts were WOF, which indicates an army rebuild. But no real way to tell.
2.) N/A
3.) Will do. The block is stripped at this point.
4.) I'll inquire about balancing the rotating assembly. This is a longevity build, so that's definitely a priority.
5.) I milled the head 0.1" (yes, 2.5 mm) two years ago before installing it - so that should be good.
6.) No idea of miles. It's a 0.030" overbore, with all WOF pistons. There's a rebuild plate in french on it. I can snap a picture of the plate if that helps.
7.) Neither. Oil looked milky (maybe burning water), which a block mill and a new head gasket would hopefully fix. Water pump is also getting a new gasket. I'll also have the machinist check the block, and particularly the cylinders, for cracks. But, I haven't noticed a loss of coolant when it was running.
8.) Rear main seal doesn't leak. The rest of the journals look smooth. No "record" ridges.

Seff
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Re: Engine rebuild recommendations

Post by Seff » Wed Jul 11, 2018 9:30 pm

The fiber gear on my cam doesn't have a timing mark. Is it possible to time the cam from the keyway?

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