Thanks again for the Kudos.  

Regarding comments by Verslagen & Dave, I won't be doing any port work with the head installed.  When I get to that point I intend to use my poor man's flow bench to monitor the alterations.  I want to check flow with the valves open in increments (probably .030" increments).  As I make small changes I can get a good feel if I'm going in the right direction.  I should be able to graph the results and end up with a bell curve (closed to open to closed).  I can then superimpose the modified curve over the as found curve.  I want to avoid having any portion of the modified curve below the as-found.  That might not be possible as flows at smaller opening points may tend to fall off as port volume increases.  I don't want to grind unless I can see what the changes are doing.  I've never tried using the poor man's flow bench for porting so it should be very interesting.


The insert I was describing would be a removable piece.  I believe one of you described this exhaust port as being like a broken leg that is broken in two places.  The floor of the port is smooth, but the roof of the port is very low and has an abrupt 90 degree ledge that travels straight up.  The mating header pipe has the inner pipe that forms this funnel.  The angle of the funnel is very shallow (probably on the order of 160 degrees or so).  So instead of making a long, gradual transition into the 1-5/8" inner pipe it's more like running into a wall.  I'm thinking that it might be possible to fabricate an insert that fits into the port.  The insert would be intended to smooth the transition from port to inner pipe.  I don't see any merit to having the hot gas run past the vertical edge of the port, expand in the small void between port & inner pipe, and then squeeze back down into the inner pipe.  I think it creates all sorts of turbulence and kills velocity.  The insert would be removable and no alteration of the port would be necessary.  If it doesn't work I can take it out and use it as a paper weight.  What do you think, is it worth a try?

The inner pipe has a 1.3” ID.

Another look

That spring seat is the root of all evil.  Start grinding away at the roof of the port and the wall below the spring gets thinner & thinner.  Pretty soon CRACK!  What a pickle.  I’m on it.  There’s gotta be a way to help this engineering nightmare.

Two things:
Want me to lend/send you the cutaway head pieces?
My seriously delusional though was to build up weld between the spring seats to allow the port roof to be raised.
Thanks again for testing and posting.
When you get to the point where you are pulling the top end, my guess is that paying attention to the squish band as well as the actual compression ratio will yield some serious results. Lance used a high comp piston, and cut the cylinder and the underside of the head. That tells me the compression ratio must be pretty dismal, and the squish band could be measured with a tape measure  

That is a mighty generous offer Armen.  I will send you a PM so we can discuss the details.

Dave had mentioned to me that there is essentially no quench on these engines (clearance at TDC too big to squish anything).  I generally like to run about .040” on a street application and about .030” on a race application.  Are those numbers achievable on the LS650?  I’m curious, how did Lancer deal with the cam chain?  Cutting the cylinder and underside of head should render the chain loose as a goose.

Jerry Branch does a weld build up on his Harley Evo heads.  He raises the port to eliminate the sharp bend/turn as the port interfaces with the valve seat.  I ran a set of his heads for awhile.  Ended up replacing them with Edelbrock heads because the Branch heads cracked.  He does alot of welding (ports, combustion chamber) and then lots of machining (bathtub chambers, larger intake valve seats, ports).  Not sure why the head cracked (at exh seat so lots of hoop stress) but I was no longer comfy with them.  They did look nice though.

I must admit that your pictures show how difficult it will be to improve the LS exh port.  Hope rings eternal.  If I have the cutaway I can probably make a dental casting of the port.  That will make fabrication of an insert a lot easier.

Both ports