O-ring motors, best way to raise compression?

[LakeFever]

I’m considering an o-ring motor and wondering what the best route is to bump up compression. I know the heads can be cut and re-grooved and I know the block is taller (+ 0.0040” iirc )

I don’t know if it’s as simple as shaving some gasket heads down small and running a gasket or if decking the block is best. Best in this reference is easiest/cheapest way to achieve. I like the idea of o-rings simple because I don’t have to keep buying head gaskets but obviously the ease of machining is a pita. I can get the block decked but not having a mill I have to farm this out which is time and unknown cost. Anyways just curious to start a discussion on the best route to take here. Thanks

[skialot2]

If you want to use Orings instead of gaskets the best way to bump compression is to cut the heads and have them regroved. From what i have heard, if you deck the block you need to use gaskets or the pistons can hit the head.

[25two.stroke]

Cut heads and have the oring land re-cut. If you shave gasket heads and then put even the thinnest head gasket your squish will be WAY too much and the motor won't be happy. If you deck it 0.040" and then run gasket heads then you can do whatever chamber or squish you want...but at that point you probably should not have started with an oring motor lol

[LakeFever]

Exactly the point. Wondering who has done it and what method they chose. Deck the block isn’t a huge deal during a full engine rebuild with fresh pistons and whatnot. But if it’s a runner and not nec to peel it apart cutting heads is the way to go I guess. Either that or just live with low compression. I guess the moral of the story here is so far no one knows an easy recipe to accomplish compression increases on an o ring mota if there even is one that is. The deck height is 40 thou taller correct?

[VkingMike]

I built an O-ring motor and opted to have the heads shaved and regrooved by a gentleman in NC recommend by Jay Smith. The block is 40 thou taller, but I didn't want to cut the block down or run regular gaskets. Cutting and regrooving the heads has $400 I think, which was worth the money to me.

https://www.screamandfly.com/showthr...t=o-ring+heads

[LakeFever]

Thanks Mike I know Jay he’s a great guy. I remember you working on the oring motor I didn’t recall you getting the heads done thanks for reminding. What compression did you end up with?

[VkingMike]

The guy was very knowledgeable and cuts a lot of O-rings heads, so I took his suggestions. I told him I wanted 145 psi and he said " I know exactly what to do then" One of these days I'll get around to actually bolting this motor on and running it lol

[rob@umt]

The guy was very knowledgeable and cuts a lot of O-rings heads, so I took his suggestions. I told him I wanted 145 psi and he said " I know exactly what to do then" One of these days I'll get around to actually bolting this motor on and running it lol

I appreciate the complement Mike! My notes say that I cut .070 off of your heads and ended up with the compression chamber .460 deep. I've worked with Jay for 25 years or so and have cut a truck load of heads taking them from 130 lbs for some people to 300 lbs for others and recessed them for over bored stroker motors.

[rob@umt]

And Mike I just noticed that we joined S&F on the same month of the same year. That must show our age

[LakeFever]

I appreciate the complement Mike! My notes say that I cut .070 off of your heads and ended up with the compression chamber .460 deep. I've worked with Jay for 25 years or so and have cut a truck load of heads taking them from 130 lbs for some people to 300 lbs for others and recessed them for over bored stroker motors.

thats solid! Do you cut the o-ring channels deeper or swap to a different o-ring?

[VkingMike]

thats solid! Do you cut the o-ring channels deeper or swap to a different o-ring?

I know I got the 225x O-rings that were recommended. They have a better sealing surface if I remember correctly

[rob@umt]

Yes, generally unless someone specifies differently I'll put a 225X sealing ring in the combustion chambers of the 280 heads. It's a question that I always ask, but I've put 200 plus lbs on many 280s with stock o rings and I've never been told that they failed so I don't know that its a have to do.