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If you’ve got a Stage 2 on your Twin Cam 88 but are still unsatisfied with your motorcycle’s performance, then it’s time to get serious and get a big bore kit.
A big bore kit can give your bike the extra power it needs to really pull ahead on the road, but with so many different kits available, how do you know which one is the right fit for your Twin Cam 88?
In this article, we’ll take a look at some of the best big bore kits for the Twin Cam 88, that will give you the extra oomph you’re looking for without sacrificing reliability.
The 3 Best Big Bore Kits for Twin Cam 88
 | 1. S&S Sidewinder 100" |
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 | 2. S&S 98" Big Bore Kit |
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 | 3. S&S 95″ Big Bore Kit |
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1. S&S Sidewinder 100″
Bigger cubes mean more power, and you can’t go any bigger than the S&S Sidewinder kit.
This legendary big bore kit will increase the displacement of your Twin Cam 88 all the way to 100″. You literally cannot get a bigger kit without having to machine the stock crankcase, which makes the Sidewinder the best big bore kit for the Twin Cam 88 for maximum horsepower and torque.
How much HP and TQ exactly?
Well, a 88″ to 100″ big bore kit will add +30 horsepower and around 20 extra torque. That’s a huge difference compared to stock.
Now, the best part about the 100″ Sidewinder is that it also slightly bumps the relatively low stock compression ratio to 10.5:1 (with stock 85cc heads), which is just about as high as you can go without having to use an octane booster or race gas.
This means great performance and throttle response for the streets without any drawbacks.
Lastly, you won’t have to worry about overheating your Twin Cam 88 as the cylinders are made from cast aluminum with a ductile cast iron sleeve inside.
The only real drawback to the 100″ Sidewinder is the price. If you’re looking for the biggest displacement possible, then this is the perfect big bore kit for you, but if you don’t need maximum HP, then it might be overkill.
2. S&S 98″ Big Bore Kit
If you want the absolute best bang for your buck (who doesn’t these days?), then we strongly advise going with the S&S 98 inch big bore kit.
The 98″ big bore kit is only slightly smaller than the 100″ Sidewinder kit, but it’s also a lot less expensive, and it makes a great base to move up from, even with stock compression. Though, we do recommend increasing the compression to 10.5:1 if possible.
Speaking of compression, one drawback of the 98″ is that it bumps the compression ratio only slightly to 9.7:1, which is nothing spectacular. You can also increase the compression ratio by milling the heads 79cc, which would give you a 10.7:1 compression ratio. Perfect for the streets.
Lastly, the 98″ big bore kit responds really well to good camshafts. To that end, we recommend pairing the 98″ big bore with Wood TW-6-6R camshafts.
This combo gives the Twin Cam 88 lots of pull to 5500 RPM with a really predictable torque curve.
3. S&S Cycle 95″
If you’re mostly looking to wake up your tired Twin Cam 88, then a 95″ big bore is probably all you need.
The S&S Cycle 95″ big bore kit will definitely wake up a tired Twin Cam 88 even with stock cams, and give the engine a nice boost in torque and throttle response as well. To be more exact, a 88 to 95″ big bore kit will add +10 horsepower, which is definitely enough to be felt while riding.
This particular big bore kit is perfect for those who want to increase the displacement of their Twin Cam 88 without going overboard, and it’s also one of the most affordable big bore kits on the market.
The 95″ responds well to cams and higher compression, but if you’re going to do that, then you might as well get the 98″ big bore too.
To that end, the S&S Cycle 95″ big bore kit is best suited for tired Twin Cam 88s that need a little bit more oomph. If you’re looking to make quite a bit of extra power, then you might want to look at the 98″ instead.
How to Choose the Best Big Bore Kit for a Twin Cam 88
Big bore kits cost a lot of money and they’re a pain to install, so you want to make sure you get the right one the first time.
Here are a few things to keep in mind when choosing the best big bore kit for your Twin Cam 88.
Boring OEM Cylinders at a Machine Shop vs Buying a New Kit
There are a few ways that you can increase the displacement of your Twin Cam 88, and they all have their pros and cons.
One of the more popular ways is bringing your OEM cylinders to a machine shop and having them bored to 95″ or more.
By doing this, you can probably save a little bit of money and the machine shop will make sure that the pistons are true to size, which is important.
However, the most popular way is simply buying a new cylinder kit. Bored cylinders from a reputable manufacturer will be stronger than OEM, and will last a whole lot longer. Furthermore, aftermarket cylinders usually have bigger cooling fins to compensate for the increased power and heat.
We strongly recommend going with aftermarket cylinders for extra reliability.
Choosing the Right Bore Size for Your Twin Cam 88
Bore sizes for the Twin Cam 88 range from 93 to 100, and it does get quite confusing when it’s time to choose one.
However, the only three sizes that are worth looking into are 95″, 98″, and 100″ – everything else is not worth it.
The 95″ big bore kits are the cheapest and are mostly used to spruce up tired Twin Cam 88s. They give a really nice power boost, but it could be lacking for some riders.
The 100″ is quite new and is only produced by S&S cycle. It’s designed for maximum horsepower and torque, but it’s expensive.
However, the 98″ is the perfect middle ground. It’s got enough displacement to give the Twin Cam 88 a really big boost, it responds super well to aggressive cams, and it’s pretty inexpensive.
If you’re looking for the best all-around big bore kit, then we recommend the 98″, but if you’re unsure – consider calling S&S cycle or FuelMoto, as they will be more than happy to help you decide.
Twin Cam 88 Big Bore Kit FAQ
Do You Need a Tune After Installing a Big Bore Kit?
Yes! We strongly recommend getting your Harley dyno tuned after you’ve installed a big bore kit.
It’s very important, as you will be wasting so much potential power if you don’t.
A good dyno tune will also make sure that your engine is running as optimally as possible. This means getting the most power out of your big bore kit, lower temperatures, and more MPGs.
While a dyno tune is the best way, it can also get expensive fast, therefore we also recommend using a Power Commander, or a similar off-the-shelf tuner.
Sure, it won’t be as precise as a dyno tune by a professional, but it will be pretty close to being so.
Do You Need Aftermarket Cams With a Big Bore Kit?
While it’s not completely necessary, we do strongly recommend installing new aftermarket cams alongside a big bore kit.
The reason for this is that the increased displacement will make your Twin Cam 88 really sluggish down low. While a 95″ big bore kit should work fine with stock cams, if you go with a 97″ or higher, then you will start running into problems.
Aftermarket cams can help with this by adding more power down low and in the midrange, which is exactly what you need.
Furthermore, aftermarket cams can really help unleash the potential of a big bore kit. If you want to make the most out of your new cylinders, then get some good cams to go along with them.
Final Thoughts
Installing a big bore kit on your Twin Cam 88 is the best way to increase the bike’s power and even its resale value.
However, it’s important to choose the right bore size for your needs, as well as get new cams and a dyno tune to really make the most out of your aftermarket cubes.
If you’re looking for the best all-around big bore kit, then we recommend the 98″, but if you’re unsure – consider calling S&S cycle or FuelMoto, as they will be more than happy to help you decide.
Thanks for reading! We hope this guide was helpful in your quest for more power.
Nick Kowalski is a diesel mechanic by trade, but his passion lies in motorcycles.
He’s been riding them since he was just a wee lad, and he loves restoring old Japanese street bikes and ATVs in his spare time.
Nick is an adrenaline junkie at heart, and he loves nothing more than hitting the open road on his motorcycle.