Any experience or feedback WRT subj ...? I am fairly pleased with where I'm at for now, but just laying the groundwork for the way ahead ... sometime in the near future (next week or next summer ... depending on how attractive the options) ....

* * *

I've never been too big a fan of my silver powdercoat motor ... but, the '09 Street Bob look really grew on me (silver engine block and trans with black cylinders and heads) ....

Am kind of thinking of CP-Carrillo 98-3 forged pistons for a 10:1 CR and swapping my jugs and heads for bored Street Bob/Fat Boy Lo cylinders and heads in black (without the machined fin edges) ... a multi-angle valve seat grind and maybe a mild port job and high-lift springs (not really needed with my TW37B cams) ....

If I went that route suppose I would need a manifold and throttle body then (since post-'05 the heads changed the intake manifold flanges) ... had been thinking of maybe going with a Screamin' Eagle 50MM T/B H-D P/N 27623-05 ....

For now, I am okay with my the rest of my setup: ThunderMax w/ AutoTune ECM/EFI, Andrews TW37B cams, Goodson A/C and Paughco 2-into-1 pipe ....

* * *

I am kind of on the fence about the whole deal with heads and T/B ... with the additional displacement and increased compression, I'd probably be about as happy as I would ever be with a mild street build and hopefully be around 100 ft-lb torque ....

And I am rather budget conscious ... that was why I have also been looking at some take-off parts in the classified ads, craigslist and e-Bay ....

Just going with someone else's 95" jugs and pistons may be a little more economical perhaps ....

* * *

Any thoughts or feedback ...?

THX ...

R/
'Chop

 

Bore for 98" (3.932") Wiseco flat top pistons, BigBoys street port job for your cams; forget the throttle body, the stock TB will support the build. Should be good for 100+ TQ and HP with the a good tune. Spend the $$ you would have spent on a TB on a better pipe. Oh yeah, you don't need a new manifold, just the intake flanges.

 

According to page 13 and following of Wiseco V-Twin "Complete Catalog" at http://www.wiseco.com/Catalogs/VTwin...eteCatalog.pdf ... the flat top piston yields [static, I assume] 9:1 CR ... largest flat top is 95" +0.020 for a calculated displacement of 95.322 CID ....

Am I missing something ...?

As I understand stock CR is somewhere around 9.5:1 ... would rather not go to a lower CR if I'm going to go big bore ... unless the Big Boyz street port job includes decking the heads to increase CR ... then, guess I'd just have to be sure of valve to piston clearance ....

Maybe G2 MotorSports / Star Racing would be an attractive alternative ... http://www.starracing.com/documents/98-107Pistons.pdf ... their flat top yields 9.5:1 CR and is 98 CID ....

Axtell's 3.932" flat top pistons yield 9.6:1 CR with stock 85cc combustion chamber ... the 0.140" dome piston bumps CR to 10.6 ... [also available in 3.937" which they still refer to as a 97" motor vice 98"] ... guess it is what it is ....

CP's 3.937" FT yields 9.5:1 CR ... the 3cc domed variety yields 10:1 CR ....

* * *

Was thinking of just foregoing the TB ... maybe even just stick with stock heads ... as long as CR is at or below 10:1 am thinking I'll be okay without compression releases ...?

 

Why not go to a 103, I have the perfect set up for you. I promise to save you some $$. PM me.

BD.

 

Not suggesting you lower your CR and yes, you are missing a couple of things. The advertised CRs are based on a stock chamber volume of 85ccs and stock head gasket thickness. However, factory tolerances are not that consistent and chambers can be smaller or larger (I have seen 84cc to 89ccs). Stay with a flat top; no need to go to the aftermarket for 98"; save yourself some $$ and go with SE cast flat tops; about half the price of aftermarket forged and there are about a gazillion of them running trouble free.

There are compression calculaltors (there is one on the BigBoyz website) that you can use to sort this out. Select a piston and use the calculator to find out how much you would have to cut to achieve the CR you need. You would set up the calculator with the bore, stroke, head gasket thickness (you want .030" Cometic MLS gasket up top), chamber volume at 85cc and play with the "dome" volume (there is a value even for flat top pistons) until you get the static CR advertised for the piston. Then reduce chamber volume to produce the CR you need. Forget about static, you need to be looking at corrected CR (a function of the intake valve close) and cranking compression. A corrected compression of 9.0-9.3 and a cranking CR between 180-185psi is a good target. You know the intake valve close of the 37 cam and that will control corrected and cranking CR. You can work backwards from the chamber volume to see how much the heads will have to decked to achieve the desired CR. Don't worry about valve to piston clearance unless you have larger inkake valves installed, which you really don't need. Compression releases are cheap and I would recommend installing them even if your static CR is marginal for CRs; they will extend battery and starter life.

Actually Axtell is using Wossner pistons now, I think; they don't manufacture their own pistons. I believe Wiseco makes a 3.932" piston for Hillside Cycles. Scott woud be happy to bore and fit the pistons for you, I am sure.

Stock CR varies with chamber volume but will run 8.9 to 9. If you are going to do this, I would recommend head work; BigBoyz would be affrodable and produce good results. You have a good cam, one of the best, to build around, fuel management, A/C and pipes. Another $300 for boring and pistons and about $550 for headwork, call Zippers for a starter map for the new configuration and let the TMax do the rest; you will be impressed.

BTW, you can't get from 88" to 103" without case boring.

 

Wiseco manufactures our 98", (#HMM VT-1767, not in their catalog, exclusive to us) as well as our 107" piston kits,(#HMM VT-1768) which come with a complete Cometic engine gasket set. We set/install rings when boring those cylinders.
The 98" have an 8,5cc dome, and the 107" have a 4cc bump.
Both can be juggled to flatops,(no charge) at which point yield a -2cc, from the large 2.100" valve reliefs.
We hardly ever go to 95", or 103" anymore.
Scott

 

Unless I'm missing something ... which, again, I may well be ... to make an 88" into a 103" I would have to 'split the cases' to either (i) replace the crank with a 4-3/8" 'stroker' or (ii) machine the cases to take bigger cylinders ... my understanding is that '98"' is as big as you can safely go without boring the cases ....