Building a bike to run in hogs gone wild, gonna be a grudge bagger type bike
i have 4.250” piston/cylinders from Solenbergs (Delkron)
has anyone run 4-1/4” bore and what was your experience with them?
engine is getting 110 heads that we put av&v 2.150 intakes and 1.650 ex valves in. Flows 300cfm and maybe a hair more after final vj
heads pretty run out at .600” and don’t pick up but few cfm after so I’m also making final decision on cam grind. Any advice? This is all out dragrace engine, don’t care about street drive ability.
Pistons are flat tops btw
havent fully decided if staying with 4-3/8 stroke or going to the 5/8” stroke if I can make it work with these cylinders/pistons. I come from jap bike dragracing (4 cylinder Suzuki stuff) world where we use spacer plates under the cylinders when changing strokes, not sure how applicable that is to these vtwins. Pistons do have the pin moved up into the oil ring and use support rails which is exactly another way we do it with the integral top case/cylinder jap bike stuff. I build my own engines and do my own machine work/fab work except the cylinder head porting and cylinder boring (our cnc prototrak/Bridgeport clone isn’t stiff enough to bore cylinders precisely IMO). Got into the Harleys over the last few years as I get older (I’m almost 50) and have built several street motors using stock or bored 103 jugs, but haven’t built a big one like this.

Thanks for any replies

only pics I have on my phone right now but I take some better ones of the parts I have compiled so far when I get to the shop later

 

Don't bother with the 4.375 crank.. Build the 131"er and those heads won't get you all out.. Hell my Evo heads flow 284 cfm (Hillside).... Use a woods w68 cam....

 

Thanks for the reply, but what do you mean by the comment about the heads won’t get you all out? As in they aren’t enough for an all out race motor? If that’s what you are referring to, yeah I would like a set of b2 heads but that’s another $2500 approx that can go towards other things on the build. But yeah I agree if that’s what you meant. With the right cam, or that woods you mentioned, what kinda power should that combo make with the 3/8 and/or 5/8 stroke?? Will have HPI’s biggest TB with the big 1.900” manifold opening. They are local to me, I’m in Indy

 

You said you wanted all out.. So money should not be an issue..

 

Poor choice of words, was referring to all out dragrace only engine no regards to how it would run in a street bike. Didn’t mean all out as in unlimited budget.

 

If you plan on running with hogs gone wild you need to be wild also. B2's..

 

If you’re ok with running in the mid/upper tens then using parts listed could get there, right cam, compression, tune, venting. Better heads if wanting more, even those 110s should flow better than 300.

 

You did not say which year cases you'll be using.

It's more than likely the cylinders are cut to some length for a particular stroke. I would go with whatever stroke your cylinders support and not use plates. 4 1/4 bore cylinders have pretty thin spigots and if you end up jacking them up 1/4 inch for say a 4 5/8 stroke there may be to much stress on the spigot.

I'd use a 3 gerotor oil pump like Thayer or SnS.

SnS or stock HD cylinder studs. Diamond head bolts. Make sure you use the latest Cometic 4 1/4 bore head gaskets. You can tell by looking at the center piece, It will be embossed. I use a little case sealer on the base gasket behind the tappet covers and where the cases meet on the base gasket.

If running stock cases, don't drill out the scavenge hole that goes into the crankcase.

For sure check the valve reliefs. They will probably be off.

Make sure to pay attention to intake manifold spacing. Rocker box clearancing (bottom for springs, top for roller rockers). Make sure the oil returns from the heads are good. Cam clearancing.

Plan of a fair sized oil catch. Some have had good luck with adding a breather to the oil tank.

You will need to have a crank built or go with SnS.

If a later TC, plan on a upgrading the tranny. Clutch for sure.

I'd let whomever does the heads pic the cam.

Do a Burns pipe kit.

 

semi off topic and idle curiosity:

IF you did add plates how do you get the intake to mate up across the greater distance ?

Thanks

 

The easiest is way to get a longer manifold. HPI sells them, SnS sells D and G manifolds that are longer. So does Ultima. SnS probably sells them for their throttle bodies.

Not sure if Jim's still makes them but you could buy about a 0.080 spacer with an O ring sealed up against the head.