/// Another Bunch Of 273 Commando Rebuild Questions? ///

[Bossanova5]

Hello All,
In the midst of the teardown and I have a few questions.

1) Piston #8 has a few light scoring marks near the top of the side of the piston. Looks like it might of sucked something in. The cylinder wall shows no damage and neither does the valves.
What do you think this is from?

2) I have been using the Berryman gallon carburetor cleaner dip to clean the pistons. It works ok, but not too the cleanliness that I'm looking for.
Any better ideas to clean the pistons?

3) I initially thought that the inside of the block and heads had a lot of grime. But it appears that the castings on everything from the heads, block lifters etc. are really rough and look like grime. I posted below a picture of the inside of two lifters, one cleaned and one dirty. The casting marks a really rough as well.
Is this pretty common?

4) The firewall side of the intake manifold's sealing edge almost looks like the casting broke off.
Is this lack of the metal surface being present going to be a sealing issue?

Thank you in advance.

 

[junkyardhero]

1) Piston #8 has a few light scoring marks near the top of the side of the piston. Looks like it might of sucked something in. The cylinder wall shows no damage and neither does the valves.
What do you think this is from?

if no damage anywhere else, i'd guess carbon build up that broke off and rattled around in there. dress the rough spots and ship it.

2) I have been using the Berryman gallon carburetor cleaner dip to clean the pistons. It works ok, but not too the cleanliness that I'm looking for.
Any better ideas to clean the pistons?

media blast, but that's a dangerous game. maybe an ultrasonic cleaner with an aggressive cleaner but tough to do with aluminum.

3) I initially thought that the inside of the block and heads had a lot of grime. But it appears that the castings on everything from the heads, block lifters etc. are really rough and look like grime. I posted below a picture of the inside of two lifters, one cleaned and one dirty. The casting marks a really rough as well.
Is this pretty common?

yeah, looks normal.

4) The firewall side of the intake manifold's sealing edge almost looks like the casting broke off.
Is this lack of the metal surface being present going to be a sealing issue?

it's not broke. sometimes they just look like that from the molds. it'll seal up fine there's plenty of meat.

ETA: if you're just doing a hone/re-ring/bearings & reseal on the motor, i think that piston looks plenty clean.

 

[Dana67Dart]

The firewall side of the intake manifold's sealing edge almost looks like the casting broke off.
Is this lack of the metal surface being present going to be a sealing issue

If you want to dress the casting to be more eye appealing go for it.

 

[Bossanova5]

Below is a picture of #7's rod bearing.
Pretty strange wear marks. Debris or something must have got itself in somehow?

There are no ridges on the crank journal,
I'm hoping this can be polished away?

It appears I have different sets of valve springs on each head.
I have green on one side only. Anyone know what the green color valve springs are?


Piston cleaning came out good, seven more to go.....

 

[JDMopar]

Seems like I remember seeing green springs on a few 340 heads over the years. Somebody may have swapped them to the 273 head you have.

 

[toolmanmike]

Below is a picture of #7's rod bearing.
Debris must have got itself in somehow?

There are no ridges on the crank journal,
I'm hoping this can be polished away?

It appears I have different sets of valve springs on each head.
I have green on one side only. Anyone know what the green color valve springs are?


Piston cleaning came out good, seven more to go.....

View attachment 1716386217

View attachment 1716386220

View attachment 1716386235

View attachment 1716386255

View attachment 1716386256

View attachment 1716386257

I would recommend checking the crank out. It may need a polish or may be a turn. That's not normal wear. May be check the rods too.

 

[Bossanova5]

Very nice polished crank and rod

 

[toolmanmike]

Very polished crank and rod

Done right

 

[furrystump]

What is the goal of the build? Just a rering /bearing and seal or a rebuild? What block machining is planned if any? Do you have a bottle brush kit? If it were me, and because it is apart and an “unknown” Depending on how the cam bearings looked. If they need replacement I would remove all the plugs in the block and have it cleaned professionally. Then when you get it back scrub it with bottle brushes. Then scrub it again…..then again. You will need to dingle ball hone the cylinders at least if they are straight and round. Nothing wrong with using a dingleball hone for what it is designed to do. Give you the correct surface finish NOT the correct bore size or geometry. After that take a rag with ATF on it and wipe the bores and see if the rag comes out clean. ATF has serious detergents in it. If the bores are glazed you really need to break the glaze to get the new rings to seal if boring the block is not in the cards or needed. Things really can’t be too clean.

 

[furrystump]

Oh, are you replacing the cam and lifters? If you weren’t planning on it, have you kept track of which lobe each lifter was on? If not, you will need to replace or reface the lifters. They developed a wear pattern to each other and they are now a mated pair.

 

[furrystump]

Have you read this thread? Might help.
How to Rebuild a Small Block Part 1: Block Prep (Updated 1/30/2025)

 

[Bossanova5]

I have been reading the thread you mentioned about rebuilding a small block.
Very informative. Thank you

My plan for the engine is the following:
1) Re-ring (Using Chrysler new old stock 273 rings) using the cleaned OEM pistons
2) New rod and crank bearings and cam bearings if needed.
3) Valve job. (Exhaust and intake valves are leaking on #6 & #7 cylinders) The machine shop mentioned to install all stainless-steel valves in lieu of hardened seats
4) Have the block checked for any issues, possibly decked if required.
5) Reuse the cam. I am tagging and bagging each lifter and associated pushrods to clean and install in their original locations
6) Hone and deglaze the cylinders. The bore and piston measurements so far are within the factory spec.
7) Remove all freeze plugs and oil galley plugs for cleaning (With brushes, wire wheel etc.) with a both a pressure washer and or a thorough cleaning at the machine shop.
8) Crank polished, hopefully it won't need to be ground.

As for the cleaning, that's the worst part. I fully understand about making everything surgery clean before assembly.
This engine had so much grime on the exterior and horrible carbon buildup on the pistons. It's as though the thing was being ran without an air cleaner for years. It's taking me close to 1 1/2 hours to clean each piston removing carbon from both the head and ring lands

The goal is to make it a great running reliable street engine without spending a fortune.

Thanks for your input.

 

[1973dust]

FYI, I did what you are doing to an 100,000 mile 84 318 a number of years ago and it worked out great. I didn't even have anything done to the heads, although I'm sure I should have. I know what you mean about the time it takes cleaning the old parts.

 

[JDMopar]

Don't be afraid of a 10-10 crank if it needs to be turned. Also, you might be able to buy new Scat I beam rods cheaper than having yours resized and buying ARP rod bolts. The Scat rods already have ARP cap screws instead of bolts and they come all weighing exactly the same thing on both ends and total. That's what I did on my 273, and it was about the only place I saved any money...lol. Good luck with your build. That's gonna be a nice little motor for your car.

 

[furrystump]

Sounds like you’re well on your way. No mechanical fear of using a ground crank. Just machining cost and make sure you get the correct bearings.

 

[furrystump]

Not sure how a stainless valve is going to stop the seats from getting pounded out of the head with unleaded fuel.

 

[furrystump]

Heat really helps with cleaning, can you feed your power washer warm/hot water? That helps a bunch, but the block will flash rust almost instantly. Wipe/spray any machined surface with WD-40

 

[66fs]

Not sure how a stainless valve is going to stop the seats from getting pounded out of the head with unleaded fuel.

It is not the pounding that kills the exhaust seats. It is the interaction of high heat, cast iron, and the standard exhaust valve material that causes the cast iron to transfer to the valve which becomes a rotary file. That is why you don't need hardened seats on the intake side using the same cast iron and spring pressures.

 

[Bossanova5]

I picked up this Old Stock OEM Head Gasket set for the 273.
Part number 2806984.
From what I read, these will work on the 273 and are close to being as thin as the original 273 gaskets.
Comments please on using this head gasket.
Will these work and not lower the compression?
Thanks

 

[stroker402]

compression with those composite gaskets will be lower than steel shim gaskets.

 

[Bossanova5]

Thank you.
I guess I will pass on using them.

 

[AJ/FormS]

The goal is to make it a great running reliable street engine without spending a fortune.

The compression change for this application, is relatively meaningless. 3cc on a 10.5 engine is worth a half a point of compression.
At WOT, from zero to 60 mph, I doubt you could measure the difference in ET.

 

[66fs]

I picked up this Old Stock OEM Head Gasket set for the 273.
Part number 2806984.
From what I read, these will work on the 273 and are close to being as thin as the original 273 gaskets.
Comments please on using this head gasket.
Will these work and not lower the compression?
Thanks

2806984 head gasket has a 4.01 bore and is about .031" compressed thickness at head bolt torque of 85 ft lb, .3915 cubic inch volume, about as good as you can get for a 318 or 273 anymore. I would not use those steel shim intake gaskets though.

 

[Bossanova5]

Would using a set of Mr Gasket 1121G's be a better option?
Thanks

 

[66fs]

Would using a set of Mr Gasket 1121G's be a better option?
Thanks

They are 4.140 bore x .028", .377 cubic inch volume. So not much difference, your choice.