Better In Time: LS Cam Timing

Run on the dyno with the Comp cam in the 0 position, the modified LS1 produced 577 hp at 6,900 rpm and 463 lb-ft ft of torque at 6,000 rpm.

By Richard Holdener

One of the critical elements in any performance LS motor is cam timing. The cam all but dictates the character or personality of the motor. A stock LS3 is a perfect example, as the factory 6.2L motor is blessed with performance features that include lofty compression (for a street motor), impressive head flow and an effective intake design. In fact, these stock components would have been considered pretty racy not long ago. Despite what would be race components on a traditional small block, the stock LS3 drives like your uncle’s Malibu thanks to mild, stock cam timing. Combine these same attributes with a healthy cam profile and you completely change the nature of the beast. Thanks to changes in lift, duration and lobe separation angle, a typical LS3 (or any LS) will not only make more power, but do so with increased attitude. The only thing better than making more power is having a motor that sounds the part. When it comes to attitude and power production, it is all about cam timing.

Thanks to endless testing and articles, we all know that LS motors respond like no other to changes in cam timing. A cam swap on an otherwise stock LS3 can add 60-70 hp with no other changes except possibly a set of valve springs. That kind of gain shows that the rest of the combination is present and accounted for and all the combination needed was a proper performance camshaft. We know that other LS applications respond just as well or even better depending on the combination, but what about dialing in the cam timing? Regardless of whether you choose one of the many off-the-shelf performance or even custom grinds from COMP Cams, is there any extra power available from further adjustment of that camshaft? The fact that GM and many other manufacturers have gone to great lengths to apply adjustable cam timing to their performance arsenal lends credibility to the fact that there is definitely power to be had from advancing and retarding the cam. Along with testing cam phasing we also pose a theory about whether the results might indicate the direction for optimized cam timing.

In addition to JE Pistons and K1 rods, the 5.7L LS1 received a COMP 289LRR hydraulic roller cam. The healthy LSr grind  combined .624 lift with a 239/255 duration split and 114-degree lsa.

In addition to JE Pistons and K1 rods, the 5.7L LS1 received a COMP 289LRR hydraulic roller cam. The healthy LSr grind combined .624 lift with a 239/255 duration split and 114-degree lsa.

To illustrate the effect of cam timing, we needed two things, a cam and a proper test motor. Truth be told, the combination dictated the cam choice and for this test we wanted to err on the aggressive side of cam timing. The COMP 289LRR (54-471-11) cam offered .624 lift (in & ex), a 239/255 duration split at .050 and 114-degree lsa. This choice represented a healthy profile for our 5.7L, but we prepped the LS1 for the job by adding forged JE pistons, 6.125-inch K1 rods and Total Seal rings. This not only provided plenty of strength and proper sealing, but also the necessary valve reliefs for our healthy COMP Cam.

Rather than go the EFI route, we decided to run a pair of Holley 650 HP carbs. The Hi-Ram was designed to accept a range of different tops to accommodate both carburetion and EFI.

The aluminum short block was topped with a set of older CNC-ported RHS heads, a Holley Hi-Ram intake and dual 650 HP carburetors. The carbureted intake also required use of an MSD ignition controller. Rounding out the test motor was a crankcase full of Driven Oil, Meziere electric water pump and 1 7/8-inch Kooks long-tube headers. The two important components that made life easy for our test included a two-piece front cover and 3158KT adjustable LS timing gear set. The combination allowed easy access and adjustment of the new COMP camshaft.

Cam timing was adjustable via this eccentric on the cam gear. Loosen the three retaining bolts, insert an Allen wrench and dial in the cam position of your choice. Note the markings to indicate the various 0, advance and retard positions. We started with the cam in the 0 position (no adv or retard)

Cam timing was adjustable via this eccentric on the cam gear. Loosen the three retaining bolts, insert an Allen wrench and dial in the cam position of your choice. Note the markings to indicate the various 0, advance and retard positions. We started with the cam in the 0 position (no adv or retard).

With our test motor and cam at the ready, we started by dialing in the combination. The LS1 had been run previously on the dyno and needed no break in. For the first test, the cam was installed straight up or in the 0 position indicated on the adjustable cam gear. It is important to note that this early LS1 had no guides or tensioner on the timing chain and LS chains are notorious for their sloppy fit. We did not degree the cam for this test and instead relied on the cam position indicated by the timing gear.

 

After back up runs demonstrated the consistency of the motor, we adjusted the cam first by advancing it 4 degrees. This resulted in a slight drop in peak power down to 574 hp but the power was up everywhere else along the curve.

After back up dyno testing runs demonstrated the performance consistency of the motor, we adjusted the camshaft timing by advancing it 4 degrees. This critical tuning change resulted in a slight drop in peak power down to 574 hp but the power was up everywhere else along the curve.

After minor jetting and 32 degrees of timing, we were eventually rewarded with peak numbers of 577 hp at 6,900 rpm and 463 lb-ft of torque at 6,000 rpm. The aggressive cam allowed the 5.7L to exceed 100-hp per liter or 1.667 hp per cubic inch. Advancing the cam by 4 degrees resulted in peak numbers of 574 hp at the same 6,900 rpm and 466 lb-ft of torque at 6,000 rpm. Advancing the cam improved the output from 4,000 rpm to 6,700 rpm, losing out only the very top of the rev range. Retarding the cam by 4 degrees resulted in a slight loss in power near the peak, but otherwise the same curve as with the cam in the 0 position.

Conclusion

Running the cam straight up offered the most peak power, while retarding the cam offered the least. Advancing the cam improved the power output through the majority of the rev range right up to the power peak. For any application, the advanced position would be the best choice on this application, as this offered the best average power production. Using the dyno data, we calculated the average power production from 4,100 rpm to 7,000 rpm. The motor produced an average of 471 hp and 444.5 lb-ft of torque with the cam straight up (0 position), 475 hp and 448.6 lb-ft in the advanced position and 442.4 and 468.9 lb-ft in the retarded position. Even though the straight up produced the highest peak power number (by 3 hp), it was down by 4 hp in average production. One thing to consider here is that advancing the cam will decrease piston-to-valve clearance, so make sure you have plenty of room before adjusting the cam (we had .060).

Theory

After extensive testing (including this one), the following theory seems to hold true. If advancing the cam greatly improves power, then the combination might benefit from a milder cam. If retarding the cam improves power then the combo might benefit from a wilder grind. Of course the IDEAL grind is the answer, and the cam should tailored to the application and intended operating range, but the effect of advancing and retarding the cam can nonetheless be used as an indicator. If we apply this theory to our results, we see that the 289LRR COMP Cam seems plenty aggressive for the 5.7L combination. The theory and results of this test suggest that the combination is about maxed out in terms of average power production and that an increase in duration might bring increased peak power but will also result in a trade off in low-speed power. Had retarding the cam increased peak power, we might be tempted to go wilder on the profile. This general theory does not take into account changes in valve events (where duration changes are offset by changes in lobe separation angle).

Sources

COMP Cams/FAST
(901) 795-2400
www.compcams.com

Holley/Hooker
(270) 782-2900
www.holley.com

JE Pistons
(714) 898-9763
www.jepistons.com

MSD
(915) 857-5200
www.msdperformance.com

RHS
(877) 776-4323
www.racingheadservice.com

Total Seal
(800) 874-2753
www.totalseal.com

About the author

PPN Editor

Power & Performance News is the source for news, tech and products that help you get more performance from your vehicle. If powertrain performance projects and hardcore technical content are your interest, Power & Performance News is the publication designed for you. Our acclaimed editorial staff covers all aspects of engine and driveline upgrades with a mission of presenting information that is both interesting and achievable for the “average car guy”.
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