A few thoughts on the head gasket problem?
Yes please. Thank you
It's at a very hot spot - the exhaust seat, and far away from the cooling influence of the intake tract.
Besides gasket integrity, there are 3 other possible contributors to the failure:
1. the cylinder's head-gasket surface is not flat at operating temperature due to local temp-induced warping.
2. the cylinder is not flat due to leverage from valve spring tension (the springs are far outboard of the bore center, and have mechanical advantage).
3. you may have borderline clamping force at the failure point.
1. I don't know of any fix except thermal barrier coat inside the port. Is the exterior fin surface bare? Painted? Coated? I have a feeling that the entire upper end could be held flat by a stiffening plate secured above the head on stand-offs using longer bolts. It doesn't have to be really thick if it has a "dorsal fin" extended across the center span (it's also another heat convection dump, and air scoop).
2. I'm trying to make a "rev kit" fixture for my SV to load some spring tension against the crankcase rather than the cylinders. It can be a substantial steel plate under the cylinder base, extending to the right with "eyeglass" holes to permit the valve covers to work around it (lucky me - I need stroker plates anyway). If it can't be stiff enough, it can be braced to an extended top motor mount (vertical post).
3. The bolt hole looks like it perforates the cylinder? If you spot-face the bottom, you can use a fine-thread bolt and a big flanged washer on the bottom and a nut on top for more compression. You can also add the next smaller size bolts (if 3/8-16 NC, use 5/16-18 NC or 8.0mm-1.25mm, etc.) in-between the existing adjacent to the failure point.
Brilliant Lars, you did it!
Thanks Chris.
Panic, I like your idea of adding more bolts, I'm seriously thinking of making a pair of heads for my own Indian (I was about to contact Moen at IPU to scrounge a scrap head to use as a pattern). The heads on my motor are the only part I'm not happy with, but mostly because loads of fins are bent or broken.
Lars
It is super to see you make it here and participate.
Not a motorbike guy, but have loved watching your build and finally running such a unique machine.
The design and materials of the cylinder head gasket that failed is NOT the most robust for any engine, particularly a boosted motor.
If you would like, send me a PM and I can offer opinions/suggestions.
Rick@RBMotorsports.comAgain Congratulations for your successful trip. You have a lot to be proud of.
Thanks for your offer and for your kind words Rick.
I will contact you
but also; please post any advise here
If you have room in the cylinder casting, you can just up-grade all the bolt sizes (not to mention most of the threads aren't too fresh...). To remove minimal metal, you want a pitch very close to the original: if 3/8-16 NC (a std. thread), it becomes 7/16-16 NS, which isn't std. but it's common - use H-D 45 or UL bolts. If already 7/16-14, the usual fix is 1/2-13 but 12mm × 1.75mm looks a bit better (removes less ID, and pitch is only .5 away).
I'd make the head thicker everywhere, taller fins, longer perch distance to the bolt surface. Leave a generous seating surface for 3/16" or more thick washers at the bolt holes. Extra mass slows down overheating slightly. Put the plug closer to the exhaust valve. I'd try to figure out how much pop-up I need before figuring casting thickness, you want at least .200" thick over the dome, plus the quench distance.
OK:
The gaskets.
All in all I'm quite happy with my bike considering my limited economical and mental resources.
In particular I'm very glad that it felt safe and "tight" to ride, and that the whole blower set up ( the big unknown )
seamed to work pretty fine.
Obviously there's a lot of things that I want to improve and modify,
the head gaskets being the first thing that comes to mind.
I'm surely not the first one to run into this problem
and this is not something I have dealt with before
so all advise is highly appreciated !Here's what happened:
Close up
front gasket
and rear gasket
Here's some of the suggestions folks have presented:
..no gasket. Period.
..no gasket. Paint a "gasket" with aluminum-paint
( let it sit in the can for a while. Use the thick stuff at the bottom of the can )
..form a thin strand of stainless steel wire and use as "gasket"
..make a groove in the top of the cylinder. Lay a thin 'rod' of copper,
(that stands proud a few thous of the grove) in the groove.
I don't think there's room for that on mine, as the distance between
the bolt-holes and the cylinder-bore is so small.
BTW: This seams to be a weak point , gasket-wise, on my engine judging from the above photos...use copper gaskets.
I'm not sure such a thing is available for my bike.
but it shouldn't be hard to fabricate.
I have some for my BSA ...
...and I take it that I should use
the 'solid' type, not the one with the white stuff in between two thin
pieces of copper
...which reminds me that someone mentioned that the type of gasket I was running
was problematic as they served as a heat-insulating layer between cylinder and top,
so the two pieces were moving ( expanding ) in different manners
and thereby "rubbing" the gasket, and weaken it.
Panic:
I'll come back to your informative detailed comments later today
but just for now: ( and this goes for Chris/desperate too):
I'm not sure how to read it, but the rules states that:
for Vintage Class one shall
"...
retain the O.E.M. heads......originally installed at the time of factory production.."
I'll have to find out exactly how this should be understood
....if, and how much, one can 'modify' the heads.
One thing tell me that there's NOT a lot one can do as the rule also states
"...
exact reproductions may be legal in vintage class if they offer no competive advantage..."
Anyone knows ?
