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Monster Twin Cam Race Engines from JIMS

120-131-inch Twin Cam Engins With A Major Surprise

By Wrench, and JIMS Team
6/11/2010 9:16:41 AM

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This is a short and super-sweet announcement. Not only did JIMS develop an American Made, kick-ass twin cam Monster engine configuration with 131-inches of power, but it's approved by the factory and available through your local dealership. Hang on, there's more. They also developed a set of crankcases to allow any rider to install a 131-inch Twin Cam JIMS engine in an Evo frame back to 1991. Incredible.

Following are all the specs and info:



JIMS R&D Department has developed 131” and 120” Twin Cam Race Engines that bolt directly into Evolution motor mount style frames. Now the reliability and performance of Twin Cam technology is available for most OEM Harley-Davidson applications back to 1991, as well as most custom frames for Evolution engines.



Valve Train: Valve train loads are much higher in a racing engine like the JIMS 131” or 120” than a stock Harley engine. Cam lobe designs are more aggressive with higher lifts and acceleration rates. Valve springs must have higher rates and seat pressures for reliable control. And, these heavier, stiffer and more aggressive parts must run at high rpm. JIMS has been developing and manufacturing racing-quality valve train parts for decades and is using this experience in the JIMS Race Engines Kit.

Tappets: JIMS manufactures its proven PowerGlide II tappets to very high standards of fit and finish. The very close fit between the tappet body and hydraulic unit ensures that the tappet stays pumped up under the stresses of high rpm use. There is no higher quality tappet.

Rocker Arms: JIMS Roller Rockers overcome another racing valve train difficulty – side loads on valve stems and valve guides. High rpm and heavy valve spring pressures can result in high side loads which; in turn, accelerates wear. JIMS roller- equipped rocker arms reduce this loading.


Connecting Rods: JIMS connecting rods are enormously stiff, strong and reliable. They are forged from race- proven SAE 4340 steel. Every surface is then machined in CNC work centers to ensure that both static and dynamic balancing meets engineering design standards. The various heat treat, machining and grinding procedures are carefully followed by JIMS dedicated and independent inspection team to ensure the highest quality final product. JIMS also has exclusive use of the standard Harley-Davidson crank pin and crank pin bearings. These are the highest quality connecting rod bearings available.

Timken Bearing: JIMS uses the traditional Timken tapered roller bearing assembly on the left side of the JIMS engines. This bearing is more tolerant of the crankshaft flexing that is normal at high rpm. Experience in the field indicates that this traditional Timken back-to-back set is more durable.

Engine Cases: The JIMS Race engine cases are stronger, tougher and more versatile than a stock engine case. We didn’t simply add metal here and there. We considered the greater load requirements of the larger racing engine and designed accordingly. Our case set has thicker walls, stronger stud bosses and, larger radius corners.



The 131" features the same stroke as the JIMS 120" at 4-1/2”, but carries a larger bore diameter of 4-5/16". JIMS R&D Team has added many new features to further enhance the performance of this engine. The first step was to increase air intake into the 131” with CNC Ported Heads which were developed to flow air effortlessly. Next, we upgraded the oil pump to the high flow design found in all current production Harley-Davidson Twin Cam Engine Throw in a brand new JIMS Billet Cam Support Plate, which utilizes the new Harley-Davidson hydraulic cam chain tensioners, and finish it off with the latest in high-performance tappets, JIMS Powerglide II. As always, power delivery is as smooth off the bottom end as stock, with a wide powerband of roll-on punch. These enhancements, plus 130HP** and 135ft-lbs** of torque, take the 131” to an unmatched level of performance and reliability.

Here's the 131-B balanced configuration for Softails.

• Screaminʼ Eagle® Adjustable Pushrods
• ARP® Cylinder Studs
• JIMS® Pressed Flywheel Assembly
• H-D® Hydraulic Cam Chain Tensioners
• JIMS® Billet Cam Support Plate
• JIMS® Roller Rockers
• H-D® High Flow Oil Pump
• Screaminʼ Eagle® Cams
• JIMS® Forged Pistons
• Screaminʼ Eagle® Valve Springs
• JIMS® Powerglide™ II Tappets
• CNC Ported Heads
• Connecting Rods: 4340

• Horsepower: 130** • Cam Lift: .635”
• Torque: 135**
• Compression: 10.5:1 • Recommended Octane: 91
• Intake Valve: 2.080“
• Bore Size: 4.313” • Case Material: A356-T1
• Stroke: 4.500



Delivering 125 HP** and 121 ft-lbs** of torque is just the beginning. JIMS® thick-walled cases offer unmatched strength and are able to support a bore size of up to 4.800. This engine features pressed flywheels, forged pistons, Screaminʼ Eagle valve springs, forged 4340 steel connecting rods and the latest in high performance tappets, JIMS Powerglide™II. From the ground up, this engine has everything needed to stop the competition in its tracks, and the track is what this engine was designed for. Since 2004, JIMS has set the standard in High-Performance Twin Cam Racing Engines, and we are just getting started!


• JIMS® Forged Pistons
• Screaminʼ Eagle® Valve Springs • Screaminʼ Eagle® Cams
• Screaminʼ Eagle® Adjustable Pushrods• ARP® Cylinder Studs
• JIMS® Pressed Flywheel Assembly
• JIMS® Roller Rockers
• JIMS® Powerglide™ II Tappets

• Horsepower: 125**
• Torque: 121**
• Bore Size: 4.125”
• Stroke: 4.500”
• Compression: 10:1
• Cam Lift: .635”
• Intake Valve: 2.080“
• Case Material: A356-T1
• Connecting Rods: 4340
• Recommended Octane: 91


**Horsepower and Torque performance measured at the rear wheel with a Dynojet® Dynamometer. Your results may vary based on E.F.I. Induction (Non-carburated), camshaft and exhaust combination. This is not a street legal engine.

Does the JIMS team deserve a pat on the ass or what?

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Reader Comments

Interested in a 120.

Paul McPherson
Roanoke , VA
Saturday, October 1, 2022
Editor Response Hey Paul,

I hooked you up with JIMS. I'm sure they will reach out to you this week.
Had older 120 had a lifter come apart put in that is installed in newer 120's but can't find spec's that were sent with cams. Can you send them to me?

William David Davidson
Mcalester, OK
Friday, May 6, 2022
Editor Response Hey,

I will reach out to JIMS team.
I'm really considering replacing my '05 deuce twin cam 88 with a 120-inch JIMS. Does the 120 have the auto compression relief valves or do you have to have relief valves installed? Also would like to know the cost of these engines & if I ordered one can I get the jugs diamond cut? I know that would be extra.

I do realize I might need to change transmission over to the Screamin' Eagle race, would this engine require a high torque starter & the bigger 64mm intake?

If you can I'd like to get a quote on a 120 w/diamond cut jugs, & any information on anything else that would be require to change my bike over to the 120 engine.

Jeff Jewell
Robards, KY
Wednesday, March 8, 2017
Editor Response Someone from JIMS will contact you. You have a strong 5-speed trans and shouldn't need another, but I'll let the crew at JIMS handle your questions.
I have a 107 kit now needs to be rebuilt. I was checking up on up grades for every day riding (120).

Kenny Fitz
martinsburg, WV
Monday, March 3, 2014
Editor Response Here's a response from JIMS guys:

The 107 he has is a stock upgrade.

Our 120 is a completely different animal, with different head bolt pattern.
It would be a complete engine swap, NOT a rebuild.

120 kits intended for stock cases are not the best for durability.

Yes, the JIMS 120, if tuned and maintained, is GREAT for every day riding.
The parts are the best of the best (Thus the price tag), and additional room
in the cases and cylinders make for a longer lasting motor.

Street Legal, well that's a different question?



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