Change the cylinder head gasket

[Roofus]

Hello !

I have to replace the cylinder head gasket of my 49 chrysler, what are the traps I have to expect ?

Edited September 6 by Roofus

[Ivan_B]

Stuck bolts, warped head, burnt valves, difficult to clean deposits in the chamber. Sounds about right? Flatheads are rather very simple to work with, some people even carry a gasket with them as a spare part.

 

later: oh yes, clogged coolant drain at the bottom of the block 😅

Edited September 5 by Ivan_B

[Sniper]

41 minutes ago, Ivan_B said:

later: oh yes, clogged coolant drain at the bottom of the block

 

Yes and a mess of coolant to clean up once you get it clear.  I usually end up putting in a draincock with a nipple so I can use a hose to direct the flow to a bucket.  Might be time for a good flush and drain before you put in fresh coolant.

[Dave72dt]

You'll have to do all the standard checks if you're replacing the gasket because it's blown plus several retorques after it's been through some heat cycles.

[Ivan_B]

57 minutes ago, Sniper said:

I usually end up putting in a draincock with a nipple so I can use a hose to direct the flow to a bucket. 

I am also doing this with the stock drain. A small fuel/air line hose, with one layer of electrical tape over it, fits right into that drain hole. You just need to hold the hose in place while opening the drain.

[Veemoney]

In addition to what was mentioned so far I would add the following:

• You will likely be pulling the coolant bulb for water temperature if it is still intact from the head. Small tubing so be careful not to kink it and also removal of the bulb from the head may require some patience and rust dissolver. If it is the stock device it contains ether which is flammable. 
• I would plan on having a machine shop mill the head mating surface to up the compression if it has not been done yet. 
• If you had any overheating issues it would be a good time to look at water pump and distribution tube.

[Roofus]

I hope I wouldn't have all these problems at the same time 🫢

[keithb7]

Consider watching my 3 part series on You Tube. I replaced my cylinder head on my ‘38 Chrysler. Any time a head comes off, checking valve seal-ability is best practice. 

 

 #1 video starts here:

 

Part 1: Flathead Mopar Cylinder Head Crack!
https://youtu.be/vlb2q9w0vGk

Edited September 5 by keithb7

[Sniper]

2 hours ago, Ivan_B said:

I am also doing this with the stock drain. A small fuel/air line hose, with one layer of electrical tape over it, fits right into that drain hole. You just need to hold the hose in place while opening the drain.

 

Some of us are old and fat and won't be able to stand back up if they lean over that long, lol.

[Sam Buchanan]

Some of us are old enough that we just have to stand there and let it dribble.........we are accustomed to that...........  😛

Edited September 5 by Sam Buchanan

[rustyzman]

Spray coat your new head gasket with Permatex Copper Spray, on both sides before you install it.

https://www.autozone.com/sealants-glues-adhesives-and-tape/sealant/p/permatex-copper-high-temperature-spray-a-gasket-sealant-9-oz/520940_0_0?cmpid=LIA:US:EN:AD:NL:1000000:PER:19332030449&&CATARGETID=120054150001286384&CADevice=c&gad_source=1&gclid=EAIaIQobChMI4bHmoaauiAMVzEX_AR33oQxPEAQYASABEgJk9vD_BwE&gclsrc=aw.ds

 

I seal the head bolt threads with thread sealer.  My personal preference is this one:

https://shop.advanceautoparts.com/p/permatex-high-temperature-thread-sealant-1.69-oz.-59235/16160026-p?product_channel=local&store=7134&adtype=pla_with_promotion&product_channel=local&store_code=7134&&&&&gad_source=1&gclid=EAIaIQobChMIpou-tqauiAMVv0H_AR03PwgYEAQYCSABEgKCIfD_BwE&gclsrc=aw.ds

 

Gently clean out all the head bolt threads on the block, as well as any of the mounting bolt threads on the head with a tap.

 

Torque the bolts properly, in steps and in sequence.  Retorque them again when the engine is hot.  If you have any head studs vs head bolts, realize that they are not the same torque.

 

Perfect time to shave the head a little too.  I took .030" off mine.  Lots of opinions on how far to go to raise compression vs. retaining some squish area between the plug and piston.  Anything will help a little, our engines are very low compression generally.

 

Paint the head if you like, perfect time.

 

Use proper body mechanics lifting it on and off.  It is heavier than it looks, but it is totally manageable.  

 

Remember to have fun!

[Roofus]

23 hours ago, keithb7 said:

Consider watching my 3 part series on You Tube. I replaced my cylinder head on my ‘38 Chrysler. Any time a head comes off, checking valve seal-ability is best practice. 

Your videos are precious, thanks to them we feel less alone😉

[Sniper]

3 hours ago, rustyzman said:

Spray coat your new head gasket with Permatex Copper Spray, on both sides before you install it.

 

That is applicable to an all copper head gasket.  If you are using one of the newer copper on one side, composite on the other then only spray the copper side.

 

3 hours ago, rustyzman said:

Gently clean out all the head bolt threads on the block, as well as any of the mounting bolt threads on the head with a tap.

 

I would use a thread chaser, not a tap.  Taps can take added material off the threads and loosen up the fit.  Thread chasers are specifically designed to not do that.

 

3 hours ago, rustyzman said:

Lots of opinions on how far to go to raise compression vs. retaining some squish area between the plug and piston.

 

Next time you have a plug out, look down the hole.  The plug is not above the piston.  Squish refers to the distance between the HEAD and the piston top.  In our flatties you are going to need to mill the head AND the block to get anything useful out of squish.  Since most common head gaskets are are around .080" thick and squish fades about above .050" gap your going to have to either deck the block a lot to get the piston above the deck or find a custom, thinner gasket.  Or custom pistons that stick out the deck.

[rustyzman]

I still recommend the spray on both sides, even with a newer style gasket.  My personal preference and experience suggests that with a less than factory perfect surface on either side, this can help with sealing. 

 

A tap of the correct class of fit, used properly, will not remove additional material.  Chasers are OK as well, but a correct tap is a perfectly fine tool for the job.

 

I am aware that the plug is not above the piston.  Perhaps my wording was less than ideal on what I am trying to get across.

The issue I am suggesting to avoid is removing so much material from the head, that area of transition area between the plug, which is above the valves, and the top of the piston is not narrowed too much to get a clean, quick burn transition.  Again, your opinion on how much is too much to take off may vary, but if that physical transition area between the plug and the piston is narrowed too much, it limits how quickly the ignited air/fuel mixture will propagate into the area above the actual piston.  It is one of the reasons that Fire-Slot style high compression heads existed in small racing flathead applications, to attempt to correct a severe narrowing of that area in high compression heads by providing a direct ignition propagation path to the piston.  We of course want more compression to improve the overall power of the engine, but there is a physical limit of how much can be removed from the head or block before adverse effects show up.  That is what I was trying to say.

 

 

[greg g]

Make sure you use the proper sequence when torquing head bolts and remember  to retorque after a run up to proper operating temp.

[BayArea48Deluxe]

I just recently redid my gasket on 230. And I don’t know if you have like blown head gasket or anything but I got my head magna fluxed and milled and then freeze plug .. got double sided copper gasket and adapted it with permeated gasket spray. Re tapped holes to clean em up. Cleaned cooling holes because they were filthy. All the normal things. Got a nice tip for putting it back. Went out and bought two bolts identical to the head bolts cut the head off and put one in the front one in the back so when I placed the gasket and the head they were all lined up. Then put my bolts down and torqued and re torqued after I ran engine. Came out good I think 

[BayArea48Deluxe]

And #2 non hardening for the head bolts as well. 

[Roofus]

Finally thanks to you all, I had no problem, my diagnosis was good.

[BayArea48Deluxe]

Roofus, what gasket you going with? Copper ? Or composite? 

[Roofus]

There is a copper surface and an indeterminate material surface

https://www.ebay.fr/itm/186033058247

[Roofus]

Quote

later: oh yes, clogged coolant drain at the bottom of the block

The drain tap was not blocked, but seized, I had to unscrew the tap and I took a glycol shower

[BayArea48Deluxe]

Looks good roofus.. you getting that head milled sir? 

[keithb7]

The thinnest block section between the siamese’d pair with no coolant flow between. Not surprising as I have heard if its going to happen this is usually where it’ll happen. 
 

Have decided if you are going to test your valves for leakers?

[Roofus]

I have like you, poured liquid on the valves and this one did not pass, so I deduce that they were waterproof.

Edited September 27 by Roofus

[Roofus]

I just noticed that the cavities of the 2 cylinders concerned were well cleaned by the unrude fuel.