/// 273 Commando Teardown Help ///

[Bossanova5]

Hello All,

I know there have been many posts on here about this subject, but due to the length of some of the threads it's hard to find direct answers.

Tearing down a greasy/tired 67 273 Commando. Cylinders 4,6, & 8 compression were lower than the other cylinders.

Please comment on the pictures:

1) Appears to be OEM pistons with the "DCPD" logo embossed on the piston skirts. I don't know what 'B" means stamped on the top of the piston?
2) Head gasket appears to have been on there a very long time. Advice on removing it? (Don't want to scrape it and risk gouging the head or block surfaces) as it is stuck to head and the block deck has material stuck to it as well.
4) Both valves on cylinder #4 leak like sieves. Valve job and new veal seals intended for both heads.
3) Any other observations or recommendations welcome.

I haven't measured the pistons or bore sizes yet, but from looking at the cylinder walls there is cross hatch lines visible on all of the cylinder walls.
I hoping to clean and reuse the pistons, re-ring them and hone the cylinders. Are there decent piston rings still available for the OEM bore size? (Assuming it hasn't been bored before)
Was probably going to order some custom Cometic head gaskets? as I would like to keep the compression ratio as high as possible. I'm not looking to build this thing other than to make it a reliable street engine.

Thanks in advance

 

[Newbomb Turk]

@toolmanmike

 

[toolmanmike]

Hello All,

I know there have been many posts on here about this subject, but due to the length of some of the threads it's hard to find direct answers.

Tearing down a greasy/tired 67 273 Commando

Please comment on the pictures:

1) Appears to be OEM pistons I don't know what 'B" means stamped on the top of the piston?
2) Head gasket appears to have been on there a very long time. Advice on removing it? (Don't want to scrape it and risk gouging the head or block surfaces) as it is stuck to head and the block deck has material stuck to it as well.
4) Both valves leak on cylinder #4. Valve job and new veal seals intended for both heads.
3) Any other observations or recommendations welcome.

I haven't measured the pistons or bore sizes yet, but from looking at the cylinder walls there is cross hatch lines visible on all of the cylinder walls.
I hoping to clean and reuse the pistons, re-ring them and hone the cylinders. Are there decent piston rings still available for the OEM bore size? (Assuming it hasn't been bored before)
Was probably going to order some custom Cometic head gaskets? as I would like to keep the compression ratio as high as possible. I'm not looking to build this thing other than to make it a reliable street engine.

Thanks in advance

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This might be a tough response. I'm watching a movie with the wife right now so bear with me.

Those are nice high compression pistons. They look like the originals but so do all the aftermarket ones. Measure the bore. It could be standard. Crosshatch is common. Mopar had high nickle blocks and they just don't wear much. They will develop a ridge and slight taper at the top of the bore. I will try to look closer at the head gaskets but they don't look like the originals which were embossed steel shim. The stockers had a strange shaped chamber that wasn't round.No need to use Cometics. Their thinnest aren't any thinner than the composite gaskets Summit sells. Let's see. What did I forget?

 

[toolmanmike]

The head gaskets should just pull off. If they are stuck, there is another clue that they are not originals. Pull them off and you can use a gasket scraper or putty knife to get under them it won't hurt the deck or heads.

273 Head Gaskets

Pulled the heads off my 273 for the first time in it's life and noticed that the head gaskets aren't round anymore like the cylinder bores, but rather misshapen. Any idea what might cause that? Notice in the upper right hand corner Chrysler even stamped the penstar on their head gaskets.

www.forabodiesonly.com

Get the heads surfaced, the guides checked and repaired if/as needed.Get the valves and seats ground. New valves may be needed. Have the springs checked or replaced as needed. New valve seals of course.

 

[Richard Sweet]

Are you going to do any of the work? Are you going to leave the engine in the car or pull it out?

Are you going to calculate the compression ratio and cc the heads and get them checked for cracks? What are the casting numbers on the heads?

Maybe check out the main and connecting rod bearings.

Maybe check out the cam and lifters.

Check the timing chain and gears.

Did the engine hold coolant and pressure OK? Any cooling issues? Is the radiator coming off?

What's the min and max budget?

 

[circlepilot]

When you get your heads done, have the machinist install hardened valve seats. Unleaded fuel can cause the valves to beat the OEM seats to death.
Norm

 

[junkyardhero]

those aren't OEM commando head gaskets. they look like possibly some NOS (which would've just me NS at the tme) units or some composite 318 jobbers.

 

[RustyRatRod]

those aren't OEM commando head gaskets. they look like possibly some NOS (which would've just me NS at the tme) units or some composite 318 jobbers.

Yup cause the originals were steel shim, plus they didn't have round bore openings.

 

[66fs]

Factory Commando pistons. Yes, you can reuse the factory pistons and re-ring that engine unless you find something wrong. I have an extra of factory standard rings if you want them. Look like original 273/318 head gaskets. How thick do they measure? Keep the lifters in order if reusing the cam. Cast iron is tough to gouge, a standard gasket scraper, single edged razor blade and lacquer thinner should get the decks clean. What head castings do you have? I'd run stainless exhaust valves and skip the hardened exhaust seats. Get new valve springs, good gaskets, seals, brass freeze plugs, and a double roller timing set.

273 Head Gaskets

Here is the straight scoop on 273 head gaskets. There is no use in getting a smaller diameter head gasket since the closed combustion chamber, 64-67, measures about 3.97" at the widest point and 4.04" at the original steel shim head gasket witness marks. Since the gaskets need to be sandwiched...

www.forabodiesonly.com

 

[toolmanmike]

Factory Commando pistons. Yes, you can reuse the factory pistons and re-ring that engine unless you find something wrong. I have an extra of factory standard rings if you want them.

Please send him a pm on the rings if you are offering.

Look like original 273/318 head gaskets.

Not original but replacement gaskets. The original ones were steel shim.

How thick do they measure? Keep the lifters in order if reusing the cam. Cast iron is tough to gouge, a standard gasket scraper, single edged razor blade and lacquer thinner should get the decks clean. What head castings do you have? I'd run stainless exhaust valves and skip the hardened exhaust seats. Get new valve springs, good gaskets, seals, brass freeze plugs, and a double roller timing set.

273 Head Gaskets

Here is the straight scoop on 273 head gaskets. There is no use in getting a smaller diameter head gasket since the closed combustion chamber, 64-67, measures about 3.97" at the widest point and 4.04" at the original steel shim head gasket witness marks. Since the gaskets need to be sandwiched...

www.forabodiesonly.com

 

[66fs]

Please send him a pm on the rings if you are offering.

Not original but replacement gaskets. The original ones were steel shim.

Yes sir

They may be original to that engine, or not. Definitely not steel shim gaskets.

 

[toolmanmike]

Yes sir

They may be original to that engine, or not. Definitely not steel shim gaskets.

Curious if they still used steel shim in the 68 and 69 2 barrel engines. Not to sidetrack but did the 318's and 340's use steel?

 

[66fs]

Curious if they still used steel shim in the 68 and 69 2 barrel engines. Not to sidetrack but did the 318's and 340's use steel?

Not that I have seen. They were all composite, but I have not had any virgin "68" 340's. The 340/360 combustion chambers were a little wider than the 273/318 combustion chambers. I have only seen the steel shim gaskets on 273 Commando/Charger engines.

 

[Bossanova5]

PM sent to 66fs for the rings

 

[junkyardhero]

Curious if they still used steel shim in the 68 and 69 2 barrel engines. Not to sidetrack but did the 318's and 340's use steel?

they did not.

i've had virgin 68/9 318 2bbl and 340's open and the steel shim is unique to the 273

ETA: i should've been more pointed. i *know* the steel shim with the unique shape is specific to the commando motor. i'm unsure on the 273 2bbl motor in that NOS gaskets i've come across are composite. however, when i tear down the unsullied 273 in the 68 dart i'll report back.

more to the point though, the OP's gasket looks like the fire ring is a big larger so i'm *guessing* it was open at some point. it seems reasonable that somebody would just knock on a set of 318 gaskets because they were widely available probably cheaper and they likely wanted to lower the compression slightly to be more gas friendly.

although, that's mostly a somewhat educated three raccoons in a trench coat guess. do with it what you will.