Seely 750/850 update

Kris Bernstein · Post by **Kris Bernstein** » Sat Sep 26, 2009 9:33 am

Finally got the "Pork Chop" crank back from Chris Applebee in the UK after it traveled over the pond three damn times. The crank was not so painful of an investment but the extra shipping costs really hurt. Naturally UPS denied the claim for damages, without opening the damn shipping container! It looks to be undamaged this time.

Got the close-ratio gear box all set up and straight cut primary gear on the clutch basket. R&D Motorsports in Fla. always does a great job.
FINALLY found three Yamaha VMAX snowmobile cylinders on ebay to cut the reed boxes off of. Those will be welded to the GT cylinder and some crazy porting will follow.

I have contacted Wassner Pistons in Germany and am set up to have some 850 big bore kits made. These will consist of two left hand pistons and one right hand. Also three rings (single ring piston), Wrist pins and circlips. Gonna' run about 250 bucks a piston and I would like to start with three complete sets. These will run in Nikasil bores and aluminum sleeves.

Anyone interested in an 850 top end kit?

Got a lead on a ' 73 GT750 motor and i snatched it up right away. It is complete (even has carbs!). and will provide spares as battle requires. Thanks Steve Ward!!!!!
Game plan is to have the second Seeley ready for the first Summit Point in May 2010!!!!

Oily Tom has been swamped with work in the UK and the first dry clutch kit is still a ways off. I'm to blame a bit as he made some gears for me for a damaged close ratio six speed...actually a Ducati project that is also waiting on the lift for bits to complete.

Kris

Suzukidave · Post by **Suzukidave** » Sat Sep 26, 2009 3:00 pm

Thats great news Kris that you have your chopped crank back in hand but i bet the trips across the big pond did run up a big charge . I see your going to go with the Yamaha reeds , any reason for your selection ? What are your thoughts on the " crazy porting " ? The big bore piston sets sound real nice but i am afraid they are out of my price range

Kris Bernstein · Post by **Kris Bernstein** » Sun Sep 27, 2009 5:38 am

I'm thinking about 198-205 degrees of exhaust duration is going to be about the limit. I would like to use a bridged exhaust port as I like the idea of a "T" port configuration like on the GT 1000 blocks from Austrailia. The transfers will be widened a bit and will also be bridged to help ring support.
If the sleeves are thick enough I woud like to carve sub ports going into the transfers, from the reedboxes but we'll have to see how that goes.
Obviously 360 degrees of intake duration. Will keep a bridged intake port as the rear skirt of the piston really does need the support on these motors.
Two boost ports on either side of the ring pin. These will be full width and port roofs will match the transfers as i will most likely use a flat top piston.
Flat tops are lighter pistons by design and allow for "colliding stream" transfer loop, which should help charging mixture. This aids power and also helps cooling a bit too.
Transfer duration(s) are still a matterof speculation we'll get there.
The head will receive new squish inserts matched to the flat top piston and will use the basic architecture of the modern TZ cusbustion chamber but with less compression, as the big piston will simply not allow it.
So we'll end up with six transfers, two exhausts and two sub ports into the main transfer pockets

Suzukidave · Post by **Suzukidave** » Sun Sep 27, 2009 4:09 pm

The sub ports from the intakes to the transfers would be a nice mod but from Teasers and my fiddling it looks like even with the stock bore there isnt room between the stud passages and the liner the way the cylinders are twisted and with your projected big bore i see that space taken up even more unless you have something up your sleave ? my answer to that problem is the lower ports i cut into the intake passage that open right near the lower transfer opening .... the rest of your plans sound very interesting , i cannot wait to see the progress pictures

Kris Bernstein · Post by **Kris Bernstein** » Sun Sep 27, 2009 4:42 pm

"...unless you have something up your sleave ?"

That is a very bad pun Dave!

"my answer to that problem is the lower ports i cut into the intake passage that open right near the lower transfer opening .... "

Did you post a picture of that, Dave? I'm really thick tonight and have'nt the smallist notion what it is that means!!??? Please help!

Kris

Suzukidave · Post by **Suzukidave** » Sun Sep 27, 2009 7:44 pm

Kris Bernstein · Post by **Kris Bernstein** » Mon Sep 28, 2009 4:22 am

I am going to have to publish a deminsional drawing because I am going to go in a differient direction. on my porting architecture.
By using a single ring piston and having the ring pin bare against the intake bridge, you can use two boose ports and simply cut them up the back of te cylinder wall, much like the achient TZ750 porting. I'm going to end up basically with two wide intake ports that will also serve as boost ports and avoid the second two windows at the bottom of the cylinder as the bridge should support the back of the piston.
Does that make any sense at all?

Kris

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 5:02 am

For my boost port i went with what i saw published and that was the port is directly across from the exhaust port . It looked to me if you used one above the other intake port it would direct the loop away from the exhaust port and more aimed at the transfer and i didnt think that was a good idea so i just went with the one .

tz375 · Post by **tz375** » Mon Sep 28, 2009 8:36 am

Dave's design is constrained by ring position and the fact that the intake port is radially displaced relative to the exhaust and transfers. Ading a second is possible, but flow balance is off.

You can dig two fairly large boost ports like a TZ. We tried that on a set of barrels but the gas flow in each are not the same. One is close to the carb and the other is way down the end of a long duct. If you have access to a good flow bench and smoke probe, you could tweak on those until they work by adding area to the deep one.

A better idea is to aim the flow upwards at 45 to 55 degrees from the boost port so it shoots at the plug from a single boost port. That way it's much easier to get a single flow stream pointing where you want it to go.

The exhaust can be bridged but that really isn't much or a help unless the studs are moved to allow more width. With stock stud positions, area and flow are compromised. Even a narrow bridge robs about 15% of the available area due to the way it flows, so you have to add that much back just to stand still.

I'm not convinced that the intake bride is needed but there's enough port area there to support about 150hp without much work.

Boyesen ports sound like a good idea, but those studs are an issue again. If you move some of the intake studs, that will open up all sorts of possibilities. Of course both sides will flow differently, so make the long one larger to compensate.

You can go pretty radical on the exhaust and while the liners are out, you can weld up the water jacket to raise the exhausts.

On the bottom of the barrel, Dave has done a great job of getting more gas into the crankcase. An even better way would be to fill the pockets on the top face of the crankcase and use that extra area for ports.

The transfers are odd but are quite large at the bottom. They can be opened up slightly there with weld or Devcon on the cases and barrel. At the top you can add about 6mm of width before you break out, but that can be welded up at the core joint line to release more area. More area at the top will help reduce the flow velocity which IMHO is too high on a GT.

I'm not sure about a flat top in such a large bore. I have not tried it, but it may sag on a road race motor unless you can control heat. You might like to think about reversing the coolant flow to start at the heads and around teh exhaust and working down. Some of the best modern motors work that way. And use a Davis Craig pulse electric water pump.

The water passages are a bit big and it would help to increase water flow speed to get rid of that heat. If you are thinking of using thick wall, wet liners, that might help.

Keep the pics coming.

water cooled · Post by **water cooled** » Tue Sep 29, 2009 2:41 pm

this one looks like a departure from stock...

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Suzukidave · Post by **Suzukidave** » Tue Sep 29, 2009 2:51 pm

Nice

where did that picture come from Kevin ?

Suzukidave · Post by **Suzukidave** » Tue Sep 29, 2009 2:54 pm

A look up the Hasse modified cylinder .

water cooled · Post by **water cooled** » Tue Sep 29, 2009 3:00 pm

Dave, I cant believe I actually found a picture that you dont have...its a miracle!

I thought it might catch your attention...

water cooled · Post by **water cooled** » Tue Sep 29, 2009 3:12 pm

Well...maybe not. Who is Haase?

Suzukidave · Post by **Suzukidave** » Tue Sep 29, 2009 3:13 pm

water cooled wrote:Dave, I think I actually found a picture that you dont have...its a miracle!

I thought it might catch your attention...

You do mean a picture i didnt have

Seely 750/850 update

Seely 750/850 update

Crazy porting.

Something upmy sleve....Ha!

Aaaaa, I remember now!

GT750 Porting - Modified