I think that point has already been made ":>)

 

I guess I will jump in here. I would not stroke it unless your going to bore it just a waste of money and time. that's just me I never do anything half way.

 

Yep, rebuild it with quality, proven components, break it in right and take good care of it and it will provide the reliable service the OP is looking for.
I will note that I have seen a stroker or two that were really fast (for a shovel) when they were running.

 

Yet... Back in the day, Drag Race sanctions had to separate Shovels from Ironheads due to Performance differences.. if combined...a Shovel would Never Win.. Hell Evo Big Twins had troubles, unless modified

 

Personally I’d go 4 5/8 or even 4 3/4 and leave the 3.5 bore cylinders. Additionally I’d also consider Ultima and T&O wheels.

I’ve built a dozen or more stroke only motors leaving stock jugs. Some tips:

Clean up the heads, do it yourself or have it done. Don’t be afraid to very mildly clean up any flashing with a 60 grit cartridge roll. Get a GOOD valve job.
run enough spring pressure but be as conservative as you can.

Time your breather

Make sure your cam clears in the cam chest and in the rocker boxes

Run the shortest lifters you can find and use longer pushrods.

Shovels hemi chambers are not efficient, DONT think like a modern build.. waist some Air and fuel… you want violent turbulence because the heads suck.
DONT buy a cam based on head flow… buy a cam that matches your mechanical compression and rpm target range, but way more lift.

think like this… say you buy S&S stock shovel heads and they tell you they flow a max of 550… ok, Engine builder Jonny come lately says ok… buy a cam that maxes at 550 cause that’s all they flow… idiot. Here’s why. If the heads max at 550… you want them to flo 550 for as long as they can. Lifting the valve past the heads max of flo still allows the head to flo the max longer. Imagine a M grind 590 like this…. 300, 350, 400, 450, 500, 550, 550, 550, 450, 400, 350, 300… get it. Because you took the valve to 590 past 550… you flowed at max longer. That’s different than duration. And if you have lots of duration you need more and more compression, you want to avoid that. Sometimes duration is our friend, but you want an early valve closing… win through lift.

All street bike including dressers I built motors for I ran minimum 10:1 compression… but here’s the rule. Run the lowest dome you can with the highest mechanical compression possible. To do this DO NOT dual plug the heads. There is ZERO benifit unless your running a dome so tall the spark can’t ignite the other side… and by then you need even a taller dome to offset the added CC’s the dual plug added to the chamber.

Do everything you can about minimizing carbon build up that causes hot spots and detonation. Get that fire ring with compressed gasket to right around 1 to 1,5 thousands from touching the spicket groove in the head. This will make your chamber far more efficient. (I run 11.7:1 in Florida heat with pump gas).

Don’t waist your money on valve geometry past low lifters. It’s a rabbit hole that waists thousands and yeilds nothing.

Search for pistons with some skirt and a low dome. This is key… the “old” 1800 series S&S were great, but the new ones raised the dome to lower the ring… not as good.

I’d shoot for a cam around 250-268 duration… lift around 550 to 600. You WILL need to clearance the rockers and cam chest, but not a big deal. Lifter blocks “might” need clearanced too.

feel free to pm me with questions. If you think I’m full of nonsense don’t listen to me. Been doing theses motors for over 30 years.

 

If you go shovel get dirty, go mean.. don’t be afraid of those EVO’s and Twinks.. you do have some advantages. First your stock cases are stronger. In another thread we ponder 90hp 80” EVO’s… as I mentioned there, there probably are some. But not a lot. One of the reasons is guys who tried to build over 85 or so ponies from the stock evo cases grenaded them. I personally saw two come apart at the track… messy. Shovels… heck take them to 103 at 12:1 with that 5” arm and those cases would hold.

Another advantage… the new guys wit their EVO’s and Twinks like to think smug like they have the best tech… in some ways they do. But let’s clear some air… Harley didn’t replace the Hemi because the EVO out flowed them… nope Harley changed to the EVO because all of a sudden Gas sucked. That’s right it wasn’t about power or power potential, it was about gas. Hemi’s can kick but. But they need good gas and good compression.


Another underdog advantage, most don’t realize is cube for cube.. Shovels, EVO’s and Twinks make the same power up to 103”. At 103 the shovel stock case is done. (Don’t get me started on 3 13/16 leaking jugs… not practicle with stock cases at all) Shovel heads just can’t support past that 103 “ volume. So don’t be afraid of that 88” Twinkie. An 88” Shovel will make just as much power.

 

A really simple nice running engine is the 86” 10:1 B grind super light valve spring motor. Lighten up the wheels, put it in a light bike and man that’s a fun combo.

3 1/2 stock jugs with 4 1/2 stroke= 86” 80-90hp
3 1/2 stock jugs with 4 5/8 stroke = 89” like adding 7-8hp more
3 1/2 stock jugs with 4 3/4 stroke = 91” like adding 9-12hp more

 

Or...for what it costs for yer Shovel to Keep up... You could have simply bought a Sportster... Now ya got One Each

 

You just gotta be willing to push your daughter off of it so you can ride it.






















I kid.. I kid.

 

I kid you Not...You Gotta Catch Her!!!