Maximium bore on 74" shovel : V-Twin Forum: Harley Davidson Forums

atrick · 03-08-2009, 01:46 PM

I wonder if anyone knows the maximium bore/cubic inch you can go on a 74" shovel without boring out the cases for bigger jugs?

sljb4 · 03-08-2009, 03:24 PM

I'm pretty sure if they are 74" jugs you can bore up to .080 over and if they are 80" jugs you can bore .040 over if you pass those specs it's time for new ones.

springer- · 03-08-2009, 03:29 PM

Boring to the max just to get the biggest bore possible isn't recommended. Takes away the ability to go to the next over size if needed. If you are already bored out that much and you need to know if you can go bigger to correct issues in the cylinder then disregard my comment.

strokerjlk · 03-08-2009, 03:58 PM

Quote:

Originally Posted by sljb4

I'm pretty sure if they are 74" jugs you can bore up to .080 over and if they are 80" jugs you can bore .040 over if you pass those specs it's time for new ones.

true statement

atrick · 03-08-2009, 06:38 PM

I got stock cylinders and its time for a rebuild. I'm trying to decide whether to bore out the stock cylinders or get big bore cylinders but I don't want to bore out the cases with big bore cylinders. If I got to do a complete rebuild which it needs as there's 45000 mi on the original rebuild which was overbore to clean up cylinder, andrews B grind with solids, lifter oil holes plugged , new valves and valve guides which was done in the early 80's, so its time for a upgrade plus in 29 years parts and technolgy has come a long ways.

springer- · 03-08-2009, 06:50 PM

I would consider just boring to the next oversize and calling it good. This can leave you additional material if you ever need to bore it again. The purist in me no longer sees any advantage to boring out stock cases as they can never be "unbored" back to original. If you want to go bigger consider aftermarket cases designed for that purpose and save yours. JMO

atrick · 03-08-2009, 07:08 PM

I don't want to bore the stock cases because I bought the bike new in 78 and have all the original parts even tho I've changed a lot of things on it, I can still put it back completely original. I want some more power right now just to play as this isn't my primary ride so I can play with this one and have fun and someday put it back stock and sell it. Overseas people like those old completely stock bikes.

Sarge7 · 03-08-2009, 07:55 PM

Buy a new or used set of jugs and save the orginals. And .080 is pushin the max good chance of seeing the pistons depart the engine at hi revs. Been there done that.

Hillside · 03-08-2009, 08:12 PM

If more is wanted, bore next over, with Wiesco 9:1's, deck the cylinders also, and install a Wood 6. I would also reccommend a valve job, and related as well.
Very good gains to be had.

06roadglide · 03-09-2009, 12:29 AM

Quote:

Originally Posted by Hillsidecycle.com

If more is wanted, bore next over, with Wiesco 9:1's, deck the cylinders also, and install a Wood 6. I would also reccommend a valve job, and related as well.
Very good gains to be had.

This is what I have in my shovelhead. S&S heads and a thunder header. It made 68 hp in a .010 over 74". The dyno operator couldn't believe it was still 1200cc motor. The throttle response is awesome. Gets 48 mpg too!

Hillside · 03-09-2009, 07:25 AM

Quote:

Originally Posted by 06roadglide

This is what I have in my shovelhead. S&S heads and a thunder header. It made 68 hp in a .010 over 74". The dyno operator couldn't believe it was still 1200cc motor. The throttle response is awesome. Gets 48 mpg too!

That is a snappy 74"er!!
Ex-employee(thank God!) here had my brother Craig and I work over his 80" Sturgis, with modified S&S heads. Dyno report on our site. I believe it marked close to 85/85. Thunderheader as well.

Scott

06roadglide · 03-09-2009, 08:55 PM

Quote:

Originally Posted by Hillsidecycle.com

That is a snappy 74"er!!
Ex-employee(thank God!) here had my brother Craig and I work over his 80" Sturgis, with modified S&S heads. Dyno report on our site. I believe it marked close to 85/85. Thunderheader as well.

Scott

Impressive!!

There's alot in them ole shovels if you just look in the heads.

rosascycle · 03-10-2009, 07:42 PM

Take a look at the 86to 89 cuin 4.5/8 S&S flywheel kits, No case boring uses your stock cylinders and adds more power than the 3.5/8 cylindres will. When it comes to shovel head kits not many have done the amount we have, my opnion 89cuin 4.5/8 wheels mild head work, Serdi Valve job, cam's, pipes W/baffles, you will have a real good runnin shovel

DD Slider · 03-12-2009, 07:50 AM

You can get a ton of horsepower out of a stock bore and stroke motor, what you have to keep in mind is air in air out. The more efficient you accomplish this the better your motor will run...
There are hundreds of variables between air in and air out, such as cam lift, duration, timimg, flow thru the heads and exhaust.