Copper head gaskets

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Cyclops1862
Posts: 49
Joined: Thu Mar 03, 2022 8:22 am
First and Last Name: Jay Fetters
Location: Republic Michigan

Copper head gaskets

Post by Cyclops1862 »

When I was in my early twenties, I used to race karts powered by a Briggs raptor 3 (basically a 5hp Briggs given the barry bonds treatment) engine. We used copper head gaskets for 2 reasons. They were considerably thinner than oem type gaskets, increasing compression just a tad, and better heat dissipation. They would lower head temps by about 30°f. I am curious if anyone has ran them on the Kohler k series, or magnums. If you have, what kind of success did you have? I have also been told they seal better and last longer than oem type gaskets, but I can't personally verify this from experience as we did partial rebuilds after every race.

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Dave C
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Re: Copper head gaskets

Post by Dave C »

Ive heard these comments from years past. It may be a thing for the pullers. would have to ask some of those guys. Id be slightly concerned with clearance from the head to the piston.

Ive always run the good metalic heat gasket, sprayed with copper coat. Along with a good true head, top of block cleaned up and bolt holes countersunk. overtorque by 10 percent.... and never had an issue.
Trying to save cubs... one at a time.......

Cyclops1862
Posts: 49
Joined: Thu Mar 03, 2022 8:22 am
First and Last Name: Jay Fetters
Location: Republic Michigan

Re: Copper head gaskets

Post by Cyclops1862 »

I've never blown a stock gasket either, in my cubs. But as I was prepping my m18, I started thinking about a copper gasket. So I ordered some copper sheet that is .062 thick. With my measurements, it should have plenty of clearance for the piston and valves unless you neglect the engine and let the carbon get out of hand. When I purchased this oem type gasket, all I could find were standard gaskets. Where do you get the head gasket that has the metal ring around the inside? I've always called it a "fire ring".

mortten
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First and Last Name: Doug Anderson
Location: Peninsula, OH

Re: Copper head gaskets

Post by mortten »

A Stens 465-344 gasket has a fire ring.

Cyclops1862
Posts: 49
Joined: Thu Mar 03, 2022 8:22 am
First and Last Name: Jay Fetters
Location: Republic Michigan

Re: Copper head gaskets

Post by Cyclops1862 »

Thank you! Got them headed this way! :beer:

DaveKamp
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Location: LeClaire, Ia

Re: Copper head gaskets

Post by DaveKamp »

When I got my 109, the original engine was a replacement (black) engine with lots of hours, and getting tired... and the original owner still had the original engine, which had suffered a 'low' rod failure, meaning, it broke at the bottom end, with the piston mostly up. The remaining piece on the rod became a flail and smacked the little piece of rod left on the big end, and chipped a half-circle out of the bottom of the cylinder bore, so I thought it was toast, but after Don, and several other pullers showed me the big-end clearancing THEY did on their blocks, it was clear to me that the chip was of no consequence, so I decided to build it.

When I did, I used a new Stens piston and rod, and it took 0.030' to clean it up. I assembled the lower end, and checked piston height, then trued the head mating surface with a piece of glass and 600-grit paper. When it was done that far, there wasn't much space left for clearance. I did a rod-expansion calc and decided that pushing my luck with a thinner gasket was not gaining much in the scheme of things... even if the piston-top area was completely omitted, the limiting factor of performance is the big space over the valves... it's a flathead. That volume not only limits CR, it restricts airflow, so a big fight for more CR is rather high cost, low return. Guys do it, but if you're planning on 'working' it, it's rather fruitless.

Running a gasket with a fire ring is ALWAYS a good thing, and as noted, they do a GREAT job at transferring heat from the head to the block, especially in circumstances where you have an aluminum head, and an iron block. Thermodynamically speaking, it increases the heat transfer rate from head to block right along the ring's path, which isn't really a critical thing in a short-running motor, but it promotes equalization during CHANGE in temperature. The aluminum head is naturally going to expand in different ways, and at different rates, from the iron block... and the bulk of waste heat from combustion will be getting absorbed by the aluminum head. That copper ring will be effectively 'trapped' by clamping force on top and bottom, and combuston pressure from one side, with the rest of the gasket supporting it.

You could make a plain copper gasket... but IMO, a full flat copper is probably not going to seal as well, at standard torque, than a copper fire ring on a standard gasket... The fire ring is slightly thicker than the surrounding gasket, so when you start torquing the head on, the RING is taking essentially ALL the clamping force. Once you get to the last 20%, you're putting squeeze on the rest of the gasket surface, which is substantially larger. Sealing force being about a consistent barrier at high pressure, the copper ring is doing incredible work.

I didn't do it on any of my engines (my K241 rebuild was plenty strong for what I needed) but I've had guys bring me various sealing surfaces to cut O-ring relief surfaces in... and I've done it to several air compressors I've rebuilt. The material I used to O-ring my Brunner 4-cyl compressor was just plain old 18awg solid copper bell wire. I don't remember what I cut the groove to, IIRC, it was all by eye. I didn't cut the groove with the Bridgeport, or Cinci, or even lathe... I took apart an old printer, yanked out a roller-shaft, cut off a chunk and brazed the broken drill bit to it, then cut it to exactly the radius I wanted for the ring, and welded it on, then ground the drill bit into the proper shape and radius for the wire. To center it with the bore, I used a hole-saw to cut a half-dozen discs too-big-to-fit in the bore, then fed the printer rod through, stacked and glued 'em together and ran them across the belt sander with cordless drill spinning 'em, till they were a snug fit... and that little drill-bit cutter became a perfect bore-centered trepanning-jig. I used same cordless drill to scratch into the head 'till that copper wire was about half-sunk-into the head. I used a smidgen of super-glue to hold the wire in as a placed it, and then cut the ends of the wire SLIGHTLY LONG with clippers, then used a fingernail file to make it a zero-clearance butt joint.

Probably more than you wanted to know, but in case you're ever faced with a "How do I do that" moment...
Yes, I'm a Mad Scientist... but I'm usually happy, even when things ain't goin right.

Cyclops1862
Posts: 49
Joined: Thu Mar 03, 2022 8:22 am
First and Last Name: Jay Fetters
Location: Republic Michigan

Re: Copper head gaskets

Post by Cyclops1862 »

It's never more informative than I'm looking for. Thank you for a very thought provoking reply. I was thinking someday maybe making a copper gasket for the m18, I had heat transfer more in mind than compression gains. I was thinking that a cooler head is a better head, even if only marginally, but as you stated, the fire ring gaskets do a phenomenal job at their duty. After thinking on this for a bit, I think the engineers got the gasket material correct, and this little redneck isn't gonna argue with them, on a working tractor.

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