Got some new 3 1/2 S&S pistons that fit 4 1/2 to 4 3/4 for my shovel. The comp from S&S says 10.8. My Cam is Andrews 6. i have programable ignition & Voes. That comp seems way to High for a shovel. Any one used this Combination. Or advice to lower comp it has New S&S heads . Yet to build it. Any Advice appreciated
Is the comp given for 4 1/2" or 4 3/4" stroke?
Piston part number?
I don't think S&S made that high of compression on either one of those stroke for off the self pistons,maybe special order. :potstir:
xlfan has a valid question. The same pistons will provide different compression with each stroke.
Mike, I built a 4.5 " stroke early shovel with one of the first kits S&S produced. I don't remember all of the ratios offered but I built mine at 10.5 with the TRW pistons supplied. I did a few freshen-ups after that and bought 10.5 TRW's from S&S each time.
The first order of business when running Shovels at 10:1 and higher is duel plugging the heads. That Andrews #6 won't be happy with anything less than 10:1.
Quote from: JSD on April 05, 2022, 01:56:15 AMGot some new 3 1/2 S&S pistons that fit 4 1/2 to 4 3/4 for my shovel. The comp from S&S says 10.8. My Cam is Andrews 6. i have programable ignition & Voes. That comp seems way to High for a shovel. Any one used this Combination. Or advice to lower comp it has New S&S heads . Yet to build it. Any Advice appreciated
I have not used the combination you speak of, heck, I don't even know what combination you have, but have run plenty of shovels with high compression. That Andrews 6 and 10:1+ plus compression makes for a high reving engine. For a shovel, that also means greatly reduced cylinder life because of the increased piston speed that comes with the longer stroke. My days of owning, riding and working on shovels are long past, but if I were to have a shovel I would build it to be the low RPM torque monster that is at its very root. Mild compression, short cams, modern electronic ignition, CV carb and any exhaust other that straight pipes will make for a fun shovel. If you proceed with this high compression stroker, be aware that there will be issues with cranking it over. Best of luck.
:agree:
That seems awful high c/r for a shovelhead. I have not run that either, but didn't they used to make longer cylinders, or at the very least, stroker plates for builds like that? Is this a drag bike, or intended to be ridden on a regular basis on the street?
-JW
Pistons fit 4 1/2 to 4 3/4 stroke stock bore part number from S&S site 106-5779. Compression ratios from site
4 1/2 = 8.4-1
4 5/8 = 9.4-1
4 3/4 =10.8-1
I imported the bike and have receipts for motor work. It is 4 3/4 stroke has a broken fin on rear head so i have new S&S heads cylinders and above pistons. The crank is factory balanced for those pistons. TRW 2900 series that havent been used for 20 years came in at 9.1. So the piston kit S&S sell is one size fits 3 Strokers. Yes i would have liked a low comp stump puller like my last Shovel. Piston company's offer plenty of range in 3 5/8 but not stock bore.
The bike is a 68 Genny i purchased hasn't been ran for a while as owner pasted away and i bought it off his son who shorted the Mallory Disy . i have a All balls hi out put starter. I am pulling bike apart for a refresh so i know what i have. So there's where i need help with those damn pistons. If i Mill the Crowns to lower comp then the balance will be affected. Make thicker Base plates then Manifold issues. Help
S&S does sell lower compression pistons for stock bore strokers.
(https://i.imgur.com/PDHV8ZM.jpg)
Quote from: JSD on April 05, 2022, 10:24:19 PMQuote from: Ohio HD on April 05, 2022, 09:59:52 PMS&S does sell lower compression pistons for stock bore strokers.
(https://i.imgur.com/PDHV8ZM.jpg)
S&S Have not got those been trying everywhere to purchase those 920-0085 picture's come up on Google as the old TRW with Teflon piston pin retainers. The shops that advertise them if you read full description Have part Number 106-0085 i have Emailed them and told them so.
Go to an S&S dealer. There must be shops in Melborne that are S&S suppliers. It's a current part number.
Or ask the suppliers on this site, see if they'll ship to you. Or ask S&S who in OZ sells their products.
920-0085 S&S (https://www.sscycle.com/products/low-compression-forged-stock-bore-stoker-pistons-for-1936-84-hd-big-twins-3-seven-sixteenths-inch-point-060-inch-oversize/)
S&S Supplier in OZ
Rollies Speed Shop (https://rolliesspeedshop.com/our-brands/)
Thanks for replying. Rang Rollies no stock rang all dealers in Australia no stock. Redgrave Sydney have old TRW 2900 but up to .50 oversize. So if someone can get my part number i pay and shipping. It would be a good build at 9.1 comp i could get a milder cam 514 S&S or so. Bit limited being a 68 slab side.
Quote from: JSD on April 06, 2022, 02:29:43 AMThanks for replying. Rang Rollies no stock rang all dealers in Australia no stock. Redgrave Sydney have old TRW 2900 but up to .50 oversize. So if someone can get my part number i pay and shipping. It would be a good build at 9.1 comp i could get a milder cam 514 S&S or so. Bit limited being a 68 slab side.
You can of course do what you wish. I'm just showing you they can be gotten. Rollies is a large S&S authorized dealer. They can get them from S&S.
The CP pistons I use in my 124" motors aren't off the shelf items. CP has to make them to order. Anything can be done when you contact the right business. This last time it took me 15 weeks to get them.
Thanks mate for all your help had contact with Branko AU and he has sent S&S a email. Let you know when i now more. That Storm is Wicked.
Given that your cylinders are 5.330" gasketface to gasketface, you could get close to 8.4:1 with strokerplates of 0.100" and the pistons you already have.
Quote from: Ohio HD on April 06, 2022, 02:57:23 AMRollies is a large S&S authorized dealer.
that he is ...... it's been near on a decade since my shadow last darkened that askholes doorway
As XLfan has said maybe try stroker plates or cutting down the piston domes.
Good news i havee 920-0085 9.1 as Ohio HD sugested and a 514 S&S cam ordered. Thanks for help should pul from 2000 rpm so should be good. Keep you informed when tested. Thanks again