twincam 4 3/8 stroke 103

[bobo]

I want to build a 103 and use existing S&S 585G what would be a good compression number? this is a touring bike and is usually single rider, primary is 24/37 super meg 2 into 1 exhaust either 44 or 51 CV i have both, heads have been done by Headquarters cc is unknown at the moment. I will buy screaming eagle pistons and this is the question which compression do I buy.

[FXDBI]

Headquaters ( Doug Coffey) set there heads at 83cc unless ordered different,  S&S 585 @10.7 gives u approx195-200ccp.  Cam is very happy there, I run the 585 in a 110@10.7 with a set of dougs heads. Its much happier there than it was in a 95@220ccp.   Bob

[bobo]

thanks for the feed back
10.7 is this static or corrected comp. heads will be measured after disassembly

[shindig]

Get with Don at HD Street Performance.  He sells some really nice KB pistons that are better and probably cheaper than the SE ones you are looking at.

[FXDBI]

thanks for the feed back
10.7 is this static or corrected comp. heads will be measured after disassembly

Static compression, the S&S 585  bleeds off compression ,  my 110 ends up approx. 195ccp, using Dougs heads (83cc) a .030 head gasket and the Harley drop on cylinders/piston kit. piston were .005 in the hole. On the big boyz calculator it comes in 195ccp.  I used the EZ starts and have a 720 amp Anti gravity battery stock cables and starter doesnt even know there is a engine there, never a problem.  I would suggest you install some comp releases.  The Harley drop on 110 kit comes with Mahle pistons and is a good bang for the buck, saves the expense and time boring your cylinders.  Bob
 

[bobo]

FX the heads already have comp. releases this is a 1999 standard when the crank blew up we put in a welded 4 3/8 and went to 107. Bike now has 277000 klms  and is using oil. So I found a set of stock 88 in. cylinders and just need pistons so was thinking 10.25 or 10.5 harley pistons. To go 110 cu in would have to split engine again and this time around my brother wants to go least amount of $$$$ possible. 200 ccp would be good for this cam?
thanks 

[Ohio HD]

To go 110" you can use S&S drop in 110 cylinders.

[Don D]

I am an S&S dealer, consider harleys 110 kit. Be aware for either you may have some counterbore issues that may take a little massage.

[RoadKingKohn]

Get with Don at HD Street Performance.  He sells some really nice KB pistons that are better and probably cheaper than the SE ones you are looking at.

When buying parts remember this one thing.  ALL Harley-Davidson parts are purchased based on the low bid.  Not on the highest quality but on the lowest price.  KB pistons will be cost less simply because they are lacking the HD 200+% mark-up.

[Don D]

A few facts about the KBs.
They can be Line2line coated for a nominal added cost
The STD., not OS, pistons, most of them, are .001 OS so if a little cleanup is needed to those HD cylinders they can be brought right in to straight and true. S&S lately are very far off and the HD steel liner stuff is better but nothing to write home about.

[Hillside Motorcycle]

I want to build a 103 and use existing S&S 585G what would be a good compression number? this is a touring bike and is usually single rider, primary is 24/37 super meg 2 into 1 exhaust either 44 or 51 CV i have both, heads have been done by Headquarters cc is unknown at the moment. I will buy screaming eagle pistons and this is the question which compression do I buy.

The best compression for that .585, would be a .570 set at 10.3.....

[bobo]

just found out the newer con rods are wedge or tapered and Harley does not supply 103 pistons for my square ended
rods. Would it be okay to mill the 96 pistons inside to fit square or straight  rods? We do not want to go 110 and want to do this as inexpensively as possible.

[rigidthumper]

That works fine.

[bobo]

sorry has any one done this, mill the inside of newer Harley pistons to fit the old square end rods

[topcat3815]

Hobans brothers in Wis. will mill your pistons for the non tapered rods

[bobo]

thanks for your help mill pistons it is

[Don D]

Use KB pistons and move on. they offer several at different compressions and they will take the standard rods fine without mods and the valve relifs are in the right place and deep enough to accomodate OS valves Doug used.

[kd]

   Sounds a pretty cost effective fresh start too. 

[Hillside Motorcycle]

just found out the newer con rods are wedge or tapered and Harley does not supply 103 pistons for my square ended
rods. Would it be okay to mill the 96 pistons inside to fit square or straight  rods? We do not want to go 110 and want to do this as inexpensively as possible.

The pistons are mounted in a vertical mill,(we have a fixture) and with the use of a ball end mill, the wrist pin pillars are simply milled, equally, to accommodate the rod.
Easy, peasy.

[bobo]

thank you for the great info I will try it. If it works great, if not buy pistons what have I too lose just time. Its winter up here in the great white