Previously reserved for only the highest tiers of competition engine building, camshaft belt drives were once considered to be out of reach of Joe the average engine guy. They’re expensive, difficult to install, and some even believed to be unreliable, when compared to the old standard double roller timing chain. Used to be the only high performance option beyond a typical dual roller chain was a bone-crushing, and ear rattling gear-drive. People were not satisfied relying on a flexible belt to turn their camshaft. But who was really missing the boat? Which technology is really the best for turning a camshaft today in our overhead valve, high power pushrod engines?
This is truly a case that defines the term “aftermarket” when referring to high performance parts adapted from improved OEM technologies. Because the OEM’s have been relying on dry belts to turn multiple camshafts for decades! Why wouldn’t racers want to rely on them for the very limited miles they actually put on their engines? If they’re good enough for the OEMs, can they be good enough for the rest of us? Follow along as we take a close look at belt drives with insight from CV Products.
Belt Drives Are Better
Truth be told, a belt drive is the ultimate way to turn your camshaft. And the additional costs of a belt drive are negligible when you factor in the added benefit of external adjustability, much less down time during cam swaps, and less wear and tear on other components. However, there still are a few things that could be considered draw-backs to running a belt drive. They very rarely can be bolted right onto an engine. You’ll typically be doing some grinding on the front face of your engine block to clear the belt drive’s mounting cover. And you may also be doing some grinding, or milling, to the back of the belt drive’s cover in order to get everything to fit. And that’s where you need to be particularly careful because there’s not too much material there and cutting a hole in the cover can be expensive.
If you’re swapping a belt drive onto an existing engine that had been equipped with a chain drive, you’ll have to swap out a few extraneous pieces on the front of the engine too. The timing pointer will most likely have to be changed. Your water pump may not clear the belt drive and may have to be moved forward using water pump spacers, (some belt drive kits even include water pump spacers in the box). And if you have to space the water pump forward, and you are driving it with a belt, that means that all your other accessories may have to be moved forward to realign the pulleys. If you’re running just a water pump and alternator on single V-groove pulleys, you may be able to get away with just installing a double V-groove pulley on the crank, and moving your belt to the forward groove, leaving the groove closest to the dampener empty. But, except for their more time-consuming installation requirements, there’s nothing better than a belt drive
“The captured cam hub/seal was designed to be very low drag and can take a lot of abuse. Once you bolt it on, the end-play is set which makes installation simple. Plus, it’s so stout that it creates less timing variations and even less wear on the distributor gear. All of that can be worth a few extra HP,” said Jeff Hickernell of CV Products.
The thing we like most about belt drives is the ability to advance, or retard, the camshaft for fast tuning. For most belt drives, we can have the necessary bolts loosened, the cam adjusted, and the engine fired back up in less than 5 minutes. The belt drives even feature degree markings on the cam gear to tell you how far you’ve moved. Although, said markings can be a bit hard to see in a race car.
The captured cam hub/seal was designed to be very low drag and can take a lot of abuse. Once you bolt it on, the end-play is set which makes installation simple. Plus, it’s so stout that it creates less timing variations and even less wear on the distributor gear. All of that can be worth a few extra HP – Jeff Hickernell, CV Products
Belt drives also make cam swaps much easier. On the dyno, we can typically have a cam changed out of a Chevy V8 in about 1 hour with a belt drive. And there’s very low chance of an oil pan/timing cover gasket leak after we’re done because you don’t have to break the oil pan’s front seal for the cam swap with a belt drive. Setting camshaft endplay is also easier with a belt drive. Most systems use a series of different thickness shim washers to move the cam fore-and-aft in the engine block, allowing the builder to fine-tune the cam’s end-play. If you’ve ever dealt with roller buttons on the nose of a cam, you’ll appreciate how much easier, and precise, cam endplay can be set with a belt drive.
A belt drive also offers a wear and tear advantage over gear drives and even chains because the belt transmits very little, if any, crankshaft harmonics to the camshaft. Which means a more stable high RPM pull and very low chance of damaging camshaft bearings due to vibrations.
When all things are considered, a belt drive might cost more up front. But it’s the time and money you’ll save with it in the long run that really makes them the best choice overall.
Tips: Removing The Cam Hub Seal Without Damage.
The belt drive’s cam hub has a small key pressed into it to locate the sprocket. Removing the hub seal without damaging it can be challenging. This tip will not only help save your hub seals, but will also make installing and removing cam’s faster.
Photo Courtesy Of: The Author
Using a camshaft installation handle makes cam swaps a breeze. But the bolts included with the handle are not long enough to work with a belt drive’s cam hub. So we got some 1-3/4-inch long, 5/16-18 thread socket caps screws from the hardware store. You may need shorter or longer bolts if your cam handle is different than ours from Proform Tools shown. Thread the long bolts into the cam and pull the hub just slightly out of the block.
This will then give you enough room to slide the seal back off its mounting studs, and then twist it off of the cam hub, moving it over the key without damage. You can actually remove the seal even with the cam handle in place. We just left it out for clarity in this photo.
Getting The Front Cover To Fit.
While most of the belt drive manufacturers have tried to make installation of their kits as easy as possible, with the aftermarket constantly introducing new blocks onto the market, none of them can keep up. So chances are very likely that your belt drive won’t fit without some clearancing.
If you’re lucky, you can just get away with clearancing the back of the belt drive’s aluminum cover, as shown here in the lighter shades of aluminum exposed after running it through the mill. Note how we even had to mill the oil pan’s front seal rail a bit to clear the billet steel front main cap on some blocks.
But let’s say that you’ve milled your cover and it’s still not enough. How do you safely clearance the block if it’s been assembled? The best answer is, you don’t. You tear the engine down to the block only, and clearance it properly. But, in a pinch, we’ve seen this method of sealing off the entire engine block as tight as possible and then just grinding through the tape as needed. Note the center circle drawn to indicate the opening hole of the belt drive’s plate. There’s no need to clearance inside this circle. Just outside of it. Most blocks, like the Dart iron small-block Chevy shown, will also need the oil galley plugs clearanced. We recommend removing them after all the grinding is done, and then cleaning them up on a bench grinder or in a lathe as we’ll do next.
We also tapped the oil galley plug threads a bit deeper into the block. There’s enough material up there for this not to hurt oil flow. But be careful trying this with other blocks, as it may cut-off oil flow. Always check the depth of the plugs vs. oil galley cross-passages. With the galley plugs trimmed flat and their holes properly chamfered, we screwed them in deep enough to clear everything. Also note how we even had to counter-bore the OE cam retaining boltholes on either side so the button heads of belt drive’s six mounting screws would clear. Overall, we clearanced about 3/16-inch of material all around the upper half of the cam tunnel.
The SBC built by Steve Morris Racing Engines features the CV Products XTS Elite Timing Belt Drive System to connect the custom solid roller camshaft to the Bryant crank. The 427 cubic-inch small-block cranks out over 1,800hp with help from a Vortech V-24 XI supercharger.
CV Products Elite Series belt drives feature a unique “captured” low drag hub/seal plate assembly for the cam. It has factory-set end-play, which greatly simplifies installation. The hub uses low-drag, precision-balanced bearings to reduce cam harmonics further and high-vacuum seals ensure no oil leaks. The back cover also uses an O-ring, instead of traditional paper gaskets, to seal against the block. Again, making installation a breeze compared to other systems.
Grooved or smooth front oil pan rail? Some builders don’t want to run a traditional oil pan gasket, or end seals, so CV Products has manufactured covers with, or without the oil pan end seal grooves. If you’re running a gasket with end seals, use the cover pictured on the left. If you’d rather just seal up your oil pan with silicone all around, use the smooth cover on the right.
One thing that will most likely need to be addressed when installing a belt drive is your timing pointer. Until now, there were very few options available to fit. Currently, CV Products offers these billet adjustable pointers made to fit their GEN 1 small-block Chevy covers.
Some might consider the belt to be the weakest link, but it’s actually stronger than a chain. Belts should be replaced regularly for safety though. It’s cheap insurance.
Not everything is Chevy. CV Products offers belt drives for small-block Ford Windsors, too. And other companies offer belt drives for most popular engines.