The Learning Never Stops

The Learning Never Stops

By 1976, I was a rookie racing in the National Pro Stock ranks. Being a hands-on owner/driver (Old School Pro Stock days) I had to learn – sometimes the hard way – what went on with the moving valvetrain parts when running big roller camshafts at mega rpms.

In 1969, I started drag racing at sanctioned drag strip events as a young mechanic and hot rodder. Formerly, my racing had been illegal on county roads. Amazingly, in my first sanctioned effort, I won a trophy in the 1D Hot Rod class at Oswego Dragway in IL. What I learned in the next 50 years would pale in comparison to what I knew in ’69, and the learning never stopped.

By 1976, I was a rookie racing in the National Pro Stock ranks. Being a hands-on owner/driver (Old School Pro Stock days) I had to learn – sometimes the hard way – what went on with the moving valvetrain parts when running big roller camshafts at mega rpms.

I learned about cam timing, valve-to-piston clearances, spring pressures, rates, coil bind limits, retainer and keeper options, spring locators, and shims. I also learned about valve seat materials and angles, valve seal types, how to grind stainless and titanium valves, the best valve guide materials and clearances, using lash caps correctly, types of rocker arms and ratios, rocker arm geometry, rocker arm girdles, special shaft rockers, pushrod deflection verses spring pressures, and what diameter pushrods to use.

(Note-If using canted or hemi heads with big lift cams, such as I did, check intake-to-exhaust valve clearance when valves pass closest to each other. Spec is .030˝ min.) 

Common Mistakes

Rocker arm geometry is one of the biggest mistakes I find in modified engines. Incorrect geometry can cause premature wear on valve guides and stems and cause horsepower loss.

The second biggest mistake I find in modified engines when using bigger lift cams is valve stem seal clearances, especially retainer to seal and also inner spring clearance. 

Most of the things I mentioned can be found in “how to” books, cam catalogs, online, (careful there) or from instructions enclosed with new parts. 

Most hot rod heads need special valve seals. With older, original heads the seal bosses will need to be cut to a lesser diameter and height for special valve stem seal fit. Machining the spring seats may be needed for larger outer and perhaps added inner valve springs.

If using inner spring it must clear the seal shoulders a minimum of .075˝. Those springs bounce all over – even when contained by lower spring locators and upper retainers. 

Checking the retainer to seal clearance is easy with the cylinder head off or on. If the head is off, put an intake and exhaust valve in the head. Install seals on the guide bosses. Put retainer and locks on top of the valve stem, and keep the retainer tight by pulling up so the valve seats.

If the head is already installed, just remove springs and retainers with lighter test springs. A good machinist ruler is usually all that is needed. Measure the space from the bottom of the retainer to the top of seal and record that distance. Then, subtract gross cam lift. That is your valve seal to bottom of retainer clearance. I like .090˝ minimum.  

If building the engine, and the cylinder head is still off, mock up #1 with both valves, install the head on the block and torque (with used head gasket if possible since this is only a mock up). Install the lifters, pushrods and rockers. 

Set the rocker adjustments at recommended lash, then turn the engine over slowly a couple times, rechecking valve lash. 

When the rockers are at lash, the rocker should be fairly horizontal. Roller on tip should be slightly inward on top of the valve. Next, turn the engine over until the valve is at half gross lift. The roller tip should now be on top center of the valve stem. When it goes full lift, the roller tip will move slightly inward and then back on return. 

Animal Jim Feurer has been passing his engine knowledge on to other engine builders, telling countless racing stories and churning out engine builds as only he can for decades.

If the geometry is off, use the adjustable pushrods to obtain the proper length to correct geometry as needed. Then, order the proper length, diameter, hardness and strength pushrods.

Sometimes including a lash cap on the valve stem will correct a geometry problem. (If using lash caps, use 10-degree retainers and keepers with step for lash caps). Cap should sit on valve stem, not on keeper step.  

Another frequent mistake is clearance spec for the bottom of cap to bottom of keeper shelf. It should be .005˝ minimum. 

This would also be a great time to do a primary check of valve timing. If you’re smart, have clay on the pistons to check valve-to-piston clearance. Be sure to put a coating of oil on top of the clay so it doesn’t stick to the valves! 

As my learning has continued over the years, I’ve been fortunate to be able to pass my knowledge on to my engine customers.

You May Also Like

It’s Racing Season!

Well folks, racing is officially back! And that means engine builders, tuners, transmission builders, chassis builders, and racers have all been hard at work these past few months getting things ready for the track. . Every year it seems the off season will take forever on paper, but in reality, we’re back racing again in

Well folks, racing is officially back! And that means engine builders, tuners, transmission builders, chassis builders, and racers have all been hard at work these past few months getting things ready for the track. .

Every year it seems the off season will take forever on paper, but in reality, we’re back racing again in the blink of an eye. From the time the industry gears up for PRI in Indy to the time some of the first races of the year take place, that time goes by incredibly fast. And, it seems these past few years have carried much more excitement for racing across the board, which is always a good thing!

Don’t Put the Cart Before the Horse

Happy New Year everyone! I trust you all enjoyed the holiday season and are hitting the gas full throttle now that we’re in a new year and January is already flying by. Personally, I’m not generally big on making resolutions – at least not ones that require tons of effort or ones I know I

Changing the Narrative Surrounding the Automotive Industry

Every now and then, one of my local radio stations in the Cleveland area invites people to call in who recently got ghosted after a first date. For those who need the definition of ghosting, it’s when someone cuts off all communication without explanation. The radio station tricks the ghostee into telling their side of

Brand Loyalty – is it a Thing of the Past?

Well folks, it’s late September and summer has officially come to a close. If you’re like me, you’ll miss those warm weather days and longer hours of daylight, but it’s been a great few months of race events, car shows, seeing customers, visiting shops, and of course, creating tons of content. In fact, one of

Engine Builder Attends SBI’s 40th Anniversary Gala

If there’s anything that these past couple years has demonstrated, it’s that nothing is for certain in life or in business. In these days of such ever-changing environments, economies, consumer habits and the like, it’s more than impressive when a company reaches a major milestone. In July, the team at S.B. International, located in Nashville,

SBI Gala

Other Posts

Turbocharged 414 cid L8T Engine in a Honda S2000

As we’ve mentioned in other Sick Week interviews, there aren’t tons of import cars at the annual drag-and-drive event in Florida, so when we see something like RC Flint’s Honda S2000, we take notice. Upon further investigation, RC opted to forgo the 4-cylinder for a 414 cid L8T engine, and we got the full scoop

L8T engine
Wagler CX Billet 6.7L Cummins Engine

The Cummins engine is a powerhouse in the diesel world, but even the mighty Cummins can be improved upon. And who better to do it than Jeremy Wagler and Wagler Competition Products. The shop’s new Wagler CX billet engine is based on the 6.7L, but utilizes some different attributes for big power and performance.

Wagler CX billet Cummins engine
Honda S2000 Sports a Turbocharged L8T Engine

Following a fire with his Honda S2000 in December 2023, RC Flint spent five weeks in a mad dash to get his turbocharged L8T engine and the car back together in time for Sick Week 2024. Even with the setback, the S2000 had lofty goals. Check it out!

Honda S2000 L8T engine
Dodge 2500 with a Turbocharged 6.7L Cummins Engine

Tim Krueger’s current pride and joy is a 2004 Dodge 2500, a truck with a turbocharged and nitrous-boosted 6.7L Cummins engine that has been fine-tuned at Tim’s shop, TK Truck Performance. Check it out!

6.7L Cummins engine