Solid Copper Engine Gaksets....?

[Snickare]

I've been building an '82 CB750. Turns out my gaskets were discontinued by Honda. In the search for new gaskets, I have had several people recommend that I use my CNC to cut solid copper replacement gaskets. I have the patterns for several of the gaskets now, and was wondering what the consensus is from people that have more engine building experience than I.

Would a solid copper head gasket and base gasket work well? Is there any interest in producing these for other people? I could start cutting them out in stacks and providing all sorts of models for those with discontinued gaskets....

Any input would be appreciated. Thanks

Todd

 

[Tim]

Copper is good for a head, not 100% sure about the base. I just used a copper gasket for the top end of an XS650 engine I'm building.

As I understand it the benefits of copper are it does not compress as such, so it can be re-used making top end rebuilds on race motors easier. It can also be of varying thicknesses allowing you to adjust compression ratios with the thickness of the gasket.

I'd suggest some who run copper head gaskets run without a base gasket which is a common method to increase compression ratio without machine work.

So far as cutting your own, I have no clue what goes into it or where you'd source appropriate material. I'm 99.9% sure there are simple aftermarket gasket kits out there for your CB750 and likely existing copper options ready to go. They're not expensive.

 

[Snickare]

Thanks for the feedback. The material is easy for me to find, there is a local metal supplier that has lots of copper I could source. And the fabrication of it would be easy for me, as I run a shop with a CNC router. All I have to do is input the design into my programs, and out pops a gasket.

As it turns out for my bike, the factory gaskets have been discontinued, and Honda will no longer make them. The only option left is the aftermarket gasket sets. However, the aftermarket stuff is cheap thin and paper. The OEM stuff is rubberized and metal reinforced. There is a very big difference. I've hunted down the OEM gaskets for my now second rebuild. The first rebuild wasn't successful because of the gasketry. I got tons of leaks that started small and worked their way up to bad enough to try again...

I've been prodded on to make copper gaskets but don't know the benefits, or the adaptability... Any more feedback would be great, before I grab up some copper and start making a handful of gaskets.

 

[Rich Ard]

Re: Solid Copper Engine Gaksets....?

As was pointed out in your previous post, the gaskets are unlikely to have been your issue...

 

[Snickare]

So what would be the issue then Rich...? The surfaces were flat and clean. I prepped them myself. The assembly was a bit touch an go, as my mechanic had never done a cb750 before. Not to mention the thin paper gaskets are very lite duty. But the guy building the motor builds blueprinted race engines... He's pretty adept at motor building. He was not very happy to build the motor with aftermarket gaskets, and then not overly surprised by the leaks when it didn't work out so well. He also did quite a lot of research with local Motorcycle builders. Id say he did a damn good job, minus the leaks...

And, I'm not trying to get into the reasons for the leaks and the gaskets here, I'm really thinking of making a run of Copper head gaskets, that's if they are a good alternative...? I don't know much about them.
Honda doesn't make OEM gaskets any longer, and the aftermarket are visibly inferior. I'm not saying they wont work, just that they are visibly inferior to the OEM... SO would copper be a good alternative? Is there interest if I start making some? or should I just not even experiment? Motors are not my thing... But CNC'ing copper gaskets would be easy for me... Is there a market? I've got the CB gaskets in my hands right now. I could easily start producing them.

 

[mg42gunner]

You have to take into account crush on your cnc gaskets compared to the original gaskets. You may already know this but I'll type it out just in case. 'Crush' is the thickness you lose by torquing down on a metal gasket that cannot be recovered. This is a major problem on head gaskets for the sole reason is if you have too much crush in the gasket your valves and pistons will start playing tag with each other. Just because the copper is the same thickness as the original gasket doesn't mean it's right. I'm not sure if this is as much of an issue on the cycle engines as it is on an automotive, but I've heard of more than one guy flaking his engine because he didn't know he had just lost .01 of an inch on his head/cylinder block clearance.

The benefits of copper gaskets are more than fiber/metal combination. They are reusable for multiple torquing sequences if you're constantly rebuilding the top end of the engine, they handle overheating better which for an air cooled engine is awesome, they actually crush more than a fiber gasket because the fiber gaskets have little steel or graphite rings around the bolt holes and chambers which lowers the combustion chamber to the piston face increasing compression (Minute amounts most of the time but compression is free power), they don't blow out unless you do a damn fine job at wanting to. We run them on the Sprint car for the reasoning of the constant tear down of the top end.

 

[kopcicle]

Okay now for the bad news .

No one mentioned that along with the ease of use and re-use that you will be reusing the copper head and base gaskets frequently . One of the drawbacks to copper is that it will not absorb and swell in the presence of fluids . Also in the presence of repeated heat cycles copper will move , no matter how it's torqued or located . Copper is just not a 30.000mi fix , 10k maybe , less if you don't get it .
http://www.hylomarsealant.com/ is your friend .
http://www.permatex.com/products/product-categories/gasketing/gasket-sealants/permatex-high-tack-spray-a-gasket-sealant-detail is also a godsend .
http://www.amazon.com/automotive/dp/B008BYPRRI is a unbranded suzuki bond .

You will have to make adjustments to the O-rings around the camchain tunnel and the cylinder studs .
It is a a drastic change from the install and forget composition gaskets you are used to .

All that said I use copper in a variety of UJM fours twins and singles . Each individual application is just that , individual . All have a learning curve . Rarely will you get it completely sealed the first time . I feel that despite the issues copper is worth the effort .

~kop

 

[Snickare]

Wow. thanks for the great input. Lots to think about. I'm not going to do copper on my build, but I will be taking the measurements for the gaskets, so I can have them on hand in case I try to cut a few out. There's a lot more to them than I have time to indulge with at the moment. First thing is to get my bike running again.

 

[Rich Ard]

Re: Re: Solid Copper Engine Gaksets....?

And, I'm not trying to get into the reasons for the leaks and the gaskets here...

You have two open threads addressing that point - hope you get your engine sorted out.

 

[Snickare]

Thanks Rich. This thread was not in relation so much to MY gaskets, as it is to test the waters for my production of copper gaskets. I appreciate all the help, from anyone that has something to share. However, siting that you've stated elsewhere that I have problems, is just plainly not helpful. Especially when that is not what I was discussing here. I'm sure you have much more experience with motors and cb750s than I do, and I appreciate your help to identify the issues I do have. But realistically this thread is not about those leaks, and totally about the advantages, and application of copper gaskets, which I have gotten some really great info on. I figured while I have the gaskets, I could take the measurements and start cutting copper. And, I may just make a handful of them for some people locally.

My main interest is if I should go about trying to make a few, or if there may be a good market for a larger production. As I've stated, I don't know what the benefits and/or downfalls to copper are. Through the info provided by some great responses here in this thread, I figure I may take down all the measurements and store the file away for later work. But I did surmise from the help offered, that it may take more research as to designing the gaskets properly, rather than just cutting plain copper.

Thanks Rich for your concern, and if you do have any ideas as to what may be causing my leaks; I welcome your input in the other thread. I just got the motor pulled apart on the bike today, and will be posting some pics in the other thread of what I've found. Maybe you could help by putting in your thoughts there.

 

[Scruffy]

Read this section of another forum I belong too, lot's of vintage wrenching information. The factory engines from said vehicles shipped with copper head gaskets... http://p15-d24.com/forum/20-technical-archives/