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24 September 2006

Everyone wants more power. Well,everyone who has (or thinks hehas) a performance car, that is.Naturally, if were consideringgaining maximum streetable pow-er, this usually involves removing

the original engine and either modifying it or re-placing it with an already-built mega-pony motor.

Since engine removal and any subsequent en-gine rebuilding may not appeal to busy shops

(the dead car will tie up floor space during thebuild), in this article well focus on those modifi-cations that, theoretically, can be performedwithout the need to vacate the engine bay. Sincemost owners wont want their baby stored out-doors, well assume that the vehicle must remaininside your shop during its stay.

Camshaft UpgradeSince the camshaft dictates when valves open andclose, the distance of valve opening and the periodof time valves are open, the camshaft choice canhave a dramatic influence on engine horsepowerand torque. When selecting a camshaft, dontdrive yourself nuts by trying to choose among possi-bly dozens of choices. Follow the camshaft makers

r ecommendat ion ,based on what youhave to deal with(make/model/year, anyother existing or plan-

ned modifications) andwhat the customerwants to achieve (morelow-end power, moreon the top end, morepulling power fortrailering, etc.).

When a choiceexists between flat-tappet and rol ler

cams, again, followthe cam makers ad-vice. A roller cam(so named because

its designed to use roller-bear ing lifter s orfollowers) may provide quicker engine re-sponse, the potential for higher engine speedand increases in power and torque, but maynot be ideal for all applications, dependingon what the customer expects. Spend sometime reading the cam makers tech informa-tion regarding their various offerings. Anyquality camshaft maker offers a technical ad-vice line, so real-live-person advice is only a

phone call away.In this day of affordable digital cameras, its awise move to first photograph the entire enginebay before teardown commences, to serve as ahandy reference during reassembly, especiallywhen servicing a vehicle make and model withwhich youre not familiar.

Since we dont have room here to detail everytype of engine application, well offer a few gen-eral guidelines. For in-block OHV camshafts:

When removing rockers, pushrods and lifters,keep all parts in order.Note:Whenever replacing acamshaft, always plan to replace lifters as well.The reason to keep all original parts in order is toallow inspection (checking each lifter and its corre-sponding cam lobe for wear, damage, etc.) and asinsurance, just in case the customer ever wants toreinstall the original cam.

To prevent damage to cam bearings, thecamshaft must be removed with extreme cau-tion. The use of a specialty camshaft handle or

a 5-in.-long bolt that threads into the cam snoutshould be used as a helping hand. Do notallowthe cam lobes to drag across the cam bearings.Even slight scratches or gouges in the bearingscan cause a severe reduction in oil pressure.

Always test-fit all new lifters in their bores. Aclean-oiled lifter should slide into its bore with-out sticking. If in doubt, check the engine servicemanual for lifter bore clearance specifications.

When select ing the new camshaft

(whether obtained by you or the customer),its advisable to always purchase both the camand lifters from the same manufacturer, as aset. This ensures that the metallurgy of the

MikeMavrigian

Significant engine performance modifications can be made

without removing the engine. The following upgrades wont tie

up a service bay and can be completed at a respectable profit.

mmavrigian@motor.com

Performance Perspectives

Whenever possible, its preferable to select a

complete camshaft kit from the cam maker. Thiswill ensure that the correct lifters and valvesprings are installed to match the camshaftsand the engines speed requirements.

Photos:MikeMavrigian

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cam lobes and lifter faces is compatible. Before installing the new cam, carefully coat all lobes using

the break-in/assembly lube specified by the cam maker. Usual-ly this is supplied with the cam kit. The camshaft journals maybe coated with either the same break-in lube or a quality en-gine oil (30 W is usually a good choice). Avoid using syntheticoil at this time. All lifter faces should be coated with break-inlube as well. This is especially true if the lifters are the flat-tap-pet type. If the lifters feature roller tips, you may be able touse engine oil, but always follow the cam makers recommen-dations for assembly lubrication of all parts.

If you have the time, or if the customer insists on obtain-

ing maximum potential of the cam, consider degreeing thecamshaft. This allows you to verify the cam timing profile, andto tune the camshaft timing in relation to the crankshaft. Adegree wheel kit will be needed for this task.

Check pushrod length s, especially in the case of acamshaft that features a substantially higher lift as comparedto the original cam. A pushrod checker tool, available fromany good speed shop, will make this easy. This allows you toverify that the pushrods are not too long for the application.

The following comments apply to OHC camshafts:

If cam caps are featured , pay close atten tion to thecam bore saddles and caps. Some may feature replaceablecam bearings, while others will feature no removablebearings. In either case, inspect the bearing surface. Ifbearing inserts are worn/damaged, they may be replaced.If no replaceable bearing inserts are featured, and theparent aluminum bores are worn or damaged, the cylin-der head may be reconditioned by a competent machineshop by align-boring.

Depending on the make and model of the engine, it mayfeature lash caps/lifters (under the lobes) or shaft-mountedcam followers only. Always inspect all parts for wear or dam-age and correct as needed.

Regardless of the type of engine, always apply thecamshaft assembly lube specified by the cam maker.

If the camshaft(s) require timing adjustment for optimumperformance (such recommendations should be supplied bythe cam maker), adjustable cam sprockets are available througha variety of performance aftermarket suppliers, allowing you toeasily advance or retard cams for peak performance.

Valve SpringsIn some cases, you might get away with reusing the originalvalve springs. In other cases, the cam maker will recommenda specific valve spring that must be installed along with itscamshaft. Depending on the camshaft profile and the specificengine application, a higher valve spring pressure may be re-quired to complement the camshaft.

Be aware that, if the springs must be replaced, this may beaccomplished (carefully) with the cylinder head on the block.However, if the springs feature a larger diameter than the OE

springs, the spring seats may have to be machined according-ly, in which case the head(s) must be removed.

Always adjust all valves to the engine makers specificationsbefore attempting to start the engine.

Performance Perspectives

Circle #20

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Fuel/Ignition/ExhaustGenerally, any OE fuel system can be

upgraded to enh ance performance,provided air intake, ignition and ex-haust are coordinated to work as acomplete system. Boiled down to itsbasics, the more fuel and air you al-low an engine to ingest, the hotterthe spark and the less restrictive theexhaust must be.

If the engine is carbure ted, its ob-vious that aftermarket carbs are read-

ily available. What many enthusiastsdont understand is carb size. Biggeris not always better, especially forstreet use. The carburetor cfm (cubicfeet per minute) size must bematched to the engine dis-placement and must per-form at peak efficiencyalong with the other fuel-and air-related components

such as cam, heads and ex-haust. The most commonmistake customers make isto choose a carburetorthat s simply too big fortheir application.

Its usually best to followthe carburetor manufactur-er s advice when picking acarb size and model. Carbu-retor makers suggestions arenot, as many may assume,very conservative. If a Holley,BG, Edelbrock or othermakers tech advisor suggestsa 650-cfm unit for a small-block Chevy engine thatsoutfitted with stock cylinder heads, adual-plane intake manifold, mild camand street headers, hes probably right.Ignoring his advice and instead select-

ing a big, fat 800-cfm carb may lookcool, but itll likely result in bogs, stum-bles, an overrich condition and all-around terrible driveability.

If the engine features OE electronicfuel injection, dont assume that nothingcan be done. Larger volume injectorsare available, along with less restrictiveinjector fuel rails. To take full advantageof higher-flow injectors on a computer-

controlled system, the performance af-termarket offers an increasingly widerarray of control options. Depending onthe application, this might involve an

OE computer upgrade or a replace-ment ECU (many of which are pro-

grammable). The purpose of the ECUupgrade is to provide fuel delivery dura-tion and optimized spark control.

Making substantial engine changessuch as cams, air and fuel delivery maynot provide much of an improvementif the original ECU doesnt like what itsees and tries to limit fuel and sparkdelivery. Generally, if you plan to makea bunch of changes, the ECU issue will

likely need to be addressed. Other-wise, you may not realize the full po-tential of the upgrade parts.

An easily installed and very popularupgrade involves air intake. Even

with an otherwise unmodified engine,a less restrictive air supply system canwake up a motor to the point wherethe customer can feel (or at least

hear) a difference. If the engine ismodified in terms of fuel enrichment,cam upgrade and a more free-flowingexhaust, an aftermarket open intakesystem will be mandatory.

Obviously, carbu retor s provideboth intake air and fuel delivery man-agement. When electronic injectionis involved, air is managed via thethrott le body. So, if the goal is to pro-

vide the engine with better breathing,consider stepping up to a larger-diameter throttle body. Again, re-member that one change alone wont

provide the ultimate p erformancegoal. A sensible starting point might

be to move to an aftermarket air inlet(open air filter and free-flowing airduct to the throttle body) along witha larger throttle body.

An efficient ignition system is amust. Generally, todays later-mode lengines are already equipped withfairly strong spark systems (althoughaftermarket hotter-spark systems areoffered). Older carbureted engines

can definitely benefit by the additionof more robust dist r ibutors andstronger spark delivery. Performancedistributors, high-voltage coils, moreefficient spark plug wires and spark

control/storage boxes pre-sent sensible upgrade con-siderations.

Dont ignore the exhaust.Remember, what comes in

(in terms of air/fuel intake)needs to eventually go out.A restrictive exhaust systemcan choke power and resultin a r ich fuel cond ition.Depending on the vehicleapplication, a performanceupgrade might involvetubular tuned-length ex-haust headers, aftermarketperformance (less restric-tive) mufflers and larger-than-OE exhaust pipe.When dealing with emis-sions-era vehicles, the up-grade might be limited to acat-back exhaust (replac-

ing the pipe/muffler assembly whileleaving the converter in place). Mov-ing to tubular headers can pose achallenge on late-model vehicles, for

a number of reasons. Headers mightnot be available for the vehicle athand. Also, carmakers have done areasonably good job of improving ex-haust flow with superior OE designs.

Regardless of what type of exhaustchanges are planned, a good rule ofthumb is to opt for either stainless-steelor specialty coated components to en-hance appearance and longevity. A daily

driver vehicle might not warrant thisadded expense, but its a safe bet that anenthusiast would prefer corrosion-proofcomponents where available.

26 September 2006

Performance Perspectives

When installing aftermarket camshafts, where the customer maywish to fine-tune camshaft timing for optimum performance,pitch the OE cam sprockets in favor of aftermarket adjustablesprockets. In the case of the DOHC Honda engine, this allows indi-vidual advance or retard of both the intake and exhaust cams.