How To Retrofit A Hydraulic Roller Cam In A Big-Block Chevy

Words And Photos: Jeff Smith

In acting, timing is everything. The same could be said for performance engines. But instead of ignition timing, let’s talk about valve timing. While opening and closing points are critical, the secret to a strong performance valve lift curve is the aggressive combination of lift and duration. Duration is time in degrees of the valve event curve between valve opening and closing but lift is limited by the duration. Flat tappet cams are more limited in lift than their roller cousins. So, among other advantages, a roller cam offers much more lift potential for the same amount of duration. Combine the simplicity of hydraulic roller lifters with a roller lobe’s ability to crank up the lift and we now have better ingredients to make more power.

Recently the moon and stars aligned in such a way that we had the opportunity to underscore this hydraulic roller idea with a strong 0.030-over 454 street engine. This engine started life with a good solid foundation of SRP forged 10.25:1 pistons topped with a pair of factory iron oval port heads and a dated solid lifter flat tappet cam. The long block was sound so all it needed was a decent cam to awaken this engine’s potential power. The engine was going into a ’67 El Camino with tall street gears and an overdrive automatic. We consulted the COMP Cams Book of Armaments and decided on the retro-fit Xtreme Energy XR276HR with 224/236 degrees of duration and 0.510-inch lift.

COMP calls this a retro-fit cam as all the early small- and big-block Chevys were originally designed for flat tappet style camshafts. This means there are some important modifications that must be made in order to make a hydraulic roller cam work in these earlier engines. The first step COMP has already done for you. Roller lifters must always remain aligned to the lobe. It’s pretty obvious what would happen if the lifter was allowed to turn 90-degrees to the lobe so COMP attaches each pair of lifters with tie bars that prevent that from happening. The second step will require some minor installer effort. All helical cut distributor drive gears on a camshaft create a minor forward thrust. On flat tappet cams, this is counter-acted by a slight angle machined into the cam lobes. This angle accomplishes two tasks.

The first is to ensure that the lifters rotate in the bore for a more even wear pattern. This angle also counter-acts the cam’s natural forward movement. For obvious reasons, this angle cannot be employed on a roller lifter camshaft, so the thrust must be limited by some other means. On factory hydraulic roller lifter engines, this forward movement is limited by a cam thrust plate. Pre-roller engines do not have this feature, so a cam button is used to minimize cam movement to between 0.001 and 0.005-inch. COMP offers two different styles of cam buttons that we will look at as well as a very nice two- or three-piece billet aluminum timing chain cover for our big-block that offers several advantages. These covers also offer an ideal place to check the actual endplay.

Just for fun, we also put this engine up on the dyno, not really expecting to make great power with it. But this beast surprised us. The rest of the engine was configured with an Edelbrock Performer RPM dual plane intake and a Holley 850 cfm Ultra XP carburetor. We took the engine to Westech Performance Group and Steve Brule’ and crew quickly bolted the engine to the dyno. Since the engine had been previously run, we put a few minutes on the engine to warm it up, but didn’t have to worry about breaking in the cam and lifters. With water and oil temperatures stabilized, our first pull pushed the torque scale way up past 550 lb-ft and after finalizing the timing at 37 degrees and setting a lean-power air-fuel ratio, this big Rat bent the beam to 570 lb-ft of torque at 3,800 rpm with peak power a respectable 508 at a ridiculously low 5,200 rpm.

The peak horsepower rpm point was low because of the conservative nature of the cam as is the peak torque rpm point of 3,800 rpm. We plugged these numbers into a drag strip simulation program and with a 3,800-pound car with a 3.08:1 rear gear with good traction, this engine could run 11.50’s at 115 mph all day long. How much fun would that be? Stick this Rat in a lighter 1980 Malibu and it would be a rocket although traction might be a bit of an issue!

So if you are considering a retro-fit hydraulic roller camshaft conversion, take a few moments to walk through this installation with us. We’ll show you a couple of tricks that might save you some aggravation and reveal just how easy it is to update that flat tappet to a more modern hydraulic roller version. Then check out the power we made with a very conservative cam and you can begin to really see the advantages to a hydraulic roller cam.

Cam Specs

Cam – XR276HR-10 Adv. Duration (Degrees) Duration at 0.050 (Degrees) Valve Lift (inches) Lobe Sep. Angle (Degrees)
Intake 276 224 0.510 110
Exhaust 282 230 0.510

 

Hydraulic roller cam valve spring load recommendations

Camshaft Seat load Open load
Hydraulic Roller 180 420

Power Curve

RPM TQ HP
2,800 510 272
3,000 518 296
3,200 537 327
3,400 551 356
3,600 563 386
3,800 570 412
4,000 572 435
4,200 567 453
4,400 557 467
4,600 546 478
4,800 534 488
5,000 525 499
5,200 513 508
5,400 488 502
Peak 572 508
Average 539.0 424.3

Averages were calculated from the full dyno curve with data every 100 rpm.

Parts List

Description PN Source Price
COMP BBC Hyd. roller cam-lifter kit K-11-423-8 Summit Racing $911.97
COMP BBC hyd. roller cam 11-423-8* Summit Racing 290.97
COMP retro-fit hyd. roller lifters 854-16* Summit Racing 435.97
COMP valve springs, hyd. roller 911-16* Summit Racing 88.97
COMP timing set 2110* Summit Racing 37.97
COMP steel valve spring retainers 748-16* Summit Racing 54.97
COMP retainer locks 612-16* Summit Racing 22.97
COMP High Energy pushrods 7815-16* Summit Racing 44.97
COMP umbrella valve seals 504-16* Summit Racing 12.97
COMP nylon thrust button 205* Summit Racing 4.97
COMP Ultra-Pro rockers, 1.8:1 1828-16 Summit Racing 407.97
COMP aluminum 2 pc. timing cover 212 Summit Racing 257.97
COMP Hi-Tech pushrods 7663-16 Summit Racing 117.97
COMP Hot Rod 10w30 oil, each 1594 Summit Racing 8.97 ea.
COMP BBC valve covers 281 Summit Racing 205.97
COMP 8 oz. assembly lube 153 Summit Racing 8.97
COMP 7/16 rocker studs 4512-16 Summit Racing 56.97
COMP valvespring seat inserts 4697-16 Summit Racing 34.97
Milodon oil pan,6 ¼” depth, 6 qt. 30970 Summit Racing 252.14
Milodon oil pump pickup 18202 Summit Racing 56.95
Fel-Pro 1 pc oil pan gasket 1884R Summit Racing 28.97
ARP head bolts 135-3601 Summit Racing 84.70

* Parts included in the K-kit

Tools

We used the following tools in the process of this installation. Not all of these tools are essential and some you can make yourself.

Description PN Source Price
Powerhouse crank socket POW103055 Powerhouse Products $38.36
Powerhouse Pro degree wheel POW101600 Powerhouse Products 200.29
Powerhouse dial indicator POW151102 Powerhouse Products 61.57
Powerhouse dial indicator 2” ext. POW151112 Powerhouse Products 6.48
Powerhouse magnetic base POW151125 Powerhouse Products 30.33
Powerhouse cam handle POW101035 Powerhouse Products 32.46
Powerhouse height mic POW101200 Powerhouse Products 69.94
Powerhouse pushrod length kit POW101240 Powerhouse Products 66.04
Powerhouse crank gear installer POW101525 Powerhouse Products 21.26
Powerhouse balancer puller/installer POW300000 Powerhouse Products 138.56
Powerhouse degree kit POW101545 Powerhouse Products 146.13

Sources

Automotive Racing Products (ARP)
arp-bolts.com

COMP Cams
compcams.com

Federal-Mogul (Fel-Pro)
federal-mogul.com

Milodon
milodon.com

Powerhouse Products
powerhouseproducts.com

Westech Performance Group
westechperformance.com

 

About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
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