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4 Camshaft Selection Tips for Your Project
When rebuilding an engine, there are multitudes of parts to remove, clean, inspect, and potentially replace. A surprising number can often be reused, including the brain of the engine: the camshaft. While some engines have several and others just one, if the engine is halfway modern and runs on four strokes, there are a whole bunch of lobes controlling the air and fuel flowing through the combustion chambers.
It’s seemingly more popular than ever to swap camshafts during an engine rebuild or refresh, but picking from even just a couple of options can put any DIY enthusiast into analysis paralysis. Any camshaft has multiple variables that can be changed, and how they affect drivability and engine character can vary wildly. I know this because I recently started digging into replacing the camshaft on my Chevrolet LS engine build, and when I got overwhelmed with online research, I picked up the phone and called Matt Goins, CEO and owner of Tick Performance in Mount Airy, North Carolina. Here are a few of the tips he shared while helping me pick the perfect cam for my 6-liter V-8.
It’s About the Whole Puzzle, Not One Piece
The first thing you need to decide on is what the engine will be doing once assembled. This seems basic, but plenty of times I’ve heard people gripe about driving manners or durability due to a mismatch in what a part was designed for and what the owner wanted the final product to do well. Ordering new parts is exciting, but a lot of thinking should go into mentally assembling a package to ensure it will match your goals. Goins reminded me that this extends beyond the cam and into the rest of the valvetrain, too.
My plans on the LQ4 engine destined for my 1985 Corvette project involved getting better airflow in and out of the engine but also changing the cylinder heads. This meant it made sense to upgrade the springs and rocker arms as well, which then enabled even more lift without sacrificing reliability. If I had chosen to keep the heads on the engine and only swap the cam, I would have been far more limited in my choices.
There Is No Magic Number or Measurement
When picking a cam, Goins was clear there was no single magic number or measurement to pay attention to. “Yes, the lift, LSA (lobe separation angle), and duration play a pivotal role, but even with these numbers being the same between two different lobe designs, one lobe design can be much more aggressive than the other.”
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In short, it means that trying to extrapolate how a cam will behave by looking at only one part of the design is a fool’s errand. The different aspects like lobe separation angle, duration, and lift can each individually inform a small part of the character that a cam will give to your engine, but they need to be considered as a whole when comparing between differing options for your project. How quickly the lobe ramps to full lift and keeps the valve there is not immediately obvious when just looking at these measurements, so it is best to talk with the cam grinder or designer to ensure you select a profile that will meld well with the rest of your combination.
There Is More to Drivability Than You Think
In the old days, poor cam selection could mean a car that was nearly un-drivable for regular street use, but thanks to modern fuel injection and its fine tuning, being able to live with the characteristics that previously made for low vacuum or erratic idle can now be tuned out. This doesn’t help old-school carburetor-cars equipped with traditional distributors, but at least modern design has helped to evolve camshaft profiles to make even older engines more livable.
Goins pointed out that modern tuning is mainly the ability to adjust fuel and timing for specific sections of the tune, enabling that chunky lope that makes anyone at the drive-in or cars and coffee turn their head. He also notes that drivability is something highly personal. What I find tolerable in my stick-shift car might be absolutely insufferable to someone else in a similar setup, and totally tame to someone with an automatic transmission, where the torque convertor serves to significantly mellow the huck and buck that might come with a big camshaft and low-speed driving in a manual car. If you are looking for a guideline, Goins advised that the overlap of the camshaft is likely the best at-a-glance way to see how a cam will behave.
Installation Matters as Much as Selection
Installing a camshaft is comparable to installing many parts when assembling an engine: It can be as complicated or as simple as you want. Often, however, the results will display how much attention was put into the install. Taking the time to degree a camshaft once installed will confirm not only your work as the builder but also act as a final check that the part you are installing matches the specs you expect it to have.
Degreeing the camshaft involves placing a segmented wheel on the crankshaft and tracking the profile of the cam as the engine rotates via a dial indicator. This will easily confirm the max lift and also the opening and closing of the valves, but Goins believes intake centerline is also important to not only measure but understand. Intake centerline essentially tells where the the middle of the intake lobe is relative to the crankshaft position and thus the piston. Using an adjustable timing set or offset keyways can allow adjustment of the centerline, and advancing the intake centerline will often move the powerband lower in the rpm range, and vice-versa for retarding the camshaft timing.
In the end, I opted for one of Tick Performance’s camshaft kits, which helped ease my mind because everything was going to play nice together and also be durable and reliable. The other night I got Tick Performance’s own SNS Torquemax Stage 3 V2 grind camshaft inserted into my iron block, along with a new oil pump and timing chain. Once I finish the degreeing procedure to confirm the 237/242 degrees of duration and .633″/.608″ of lift on a 111-degree lobe separation angle, I’ll be on to the next step of the build for this engine and just that little bit closer to a test fire. Then I can drop it into the Corvette. That all sounds so close yet so far away …
I think your statements on cam selection can be made for an entire build. I have seen people go down the wrong road because they never decided what they were building to. My buddy restored a car with a lumpy cam and a high stall torque converter, and he HATED the high stall converter. Even though he was reliving the drag racing days of his youth, he was never going to actually drag race this car and probably should have thought things through.
I’ve personally had two cars with lumpy cams and didn’t really care for them. One of the engines is still in my garage – replaced with an engine with a marine cam (it was originally a boat motor after all). That marine cam delivers all the performance I want, and the engine is STABLE, which is more important to me than horsepower figures or sound effects.
I see people daily buy cams for sound vs true performance. Cool cams sound great but most are mid range and high RPM. This often leads to poor running cars and unhappy owners as they never match all the needed parts.
Then install many are not using break in oil or run the cam in as instructions state.
Even more we have people not adjust them properly or have lifter bore issues. They wipe a lobe and claim it is a soft lobe. The cam is all the same metal too often the don’t check everything they need to do. Then it often happens again as. The problem was not corrected.
One of the best questions I was asked buy my parts/HP advisor when I was hopping up my 1st car decades ago was “do you want it to sound good or pull good?”
The one thing you mentioned but didn’t list is one of the most important. Don’t be afraid to ask for help and ask questions. None of us can know everything and learning only through experience can at a certain point become pricey.
Very true!
Agreed. The #1 tip should be: call your camshaft manufacturer and ask them for a recommendation based on how you plan to use the car.
Sadly too many people think they know it all on cams and then get upset when things don’t work and you try to sort out the issues for them.
Cam company, speed shop or Summit Racing can guide to a correct cam if you can give them the correct info on the car and how you will use it.
The key is to look for the RPM range and the type of vehicle you are using the cam for, bigger is certainly not always better. If its a race motor that runs from 6000 to 8000 rpm in a light car then drivability is not as big an issue as a 3800 pound street car with an automatic. There are a couple of YouTube guys (one with the first name Richard- not promoting) who does a lot of power combos with LS engines- the different combos show that the key is not- as the article suggests- just the cam or just the heads or just the carb- but the entire package. Companies like Edelbrock make top end packages that take the mystery out of picking compatible components. Surprisingly (or not) sometime the smaller heads and smaller cam make a much more fun package for the street- maybe not as much top end power, but a lot more usable power. Just my 2 cents.
Your 237/242 duration is at .050″, right ?
The old rule of thumb still applies today; select the next smaller cam then the one you think you want.
The message here seems to be a complete crate engine swap is the safest course of action. An engine is a “ system”. Messing with a critical component of the system is asking for a less than optimal result.
Depends on the engine make and what you are using the car for. Racing? Cruising? Total restore or just make it run? Parts availability makes the difference these days for most ‘classic’ and ‘antique’ cars. If you are going to drive a lot, have a common Chevy, Ford or Mopar and can get a roller cam, go that route BUT use the best parts you can because the quality is mostly junk these days and has been for YEARS now and the oil today does not have the additives required for the old cams because roller cams have been used for 40 years now. If you can find N.O.S. that has been on someone’s shelves for decades, buy it as it is better than the chinesium junk today. OHC is another story.
There are oils on the market that are designed for older cars. Valvoline VR1 is billed as being designed for racing and classic cars.
George, In the cars that I rebuilt the engines, or had a crate engine installed, I have found that an old product from the 60’s works well. That is a pint of STP as it has far more zinc in the additive than just the oils containing the SM, SN designations. I still use those oils, but the STP is a little more assurance that the cam won’t die on me. My 68 Cougar 302 and the 84 Olds 307 have both been converted to the roller rockers and cams. The Olds went bad, but it was from a collapsed #7 piston that was Chinese junk. The rebuild got more attention to better parts. It was not built to be a hotrod, but a good cruising station wagon. That goes to the intention of the build in the article above.
Another consideration that I do not believe was mentioned here is if you have vacuum assist brakes and/or vents. You will need enough vacuum so the power brakes still work.
A very good mention. Thanks for adding!
I`ll never forget being I was a gearhead all my life. You could always tell the guys in high school and at the car shows that knew NOTHING about cars by the fact that he bragged his car had a 3/4 cam in it….
I would always ask how does it run without the other 1/4??
If they answered “Great” then it proved they were idiots.
Never heard that in my high school. The terms were always “1/4 race” or “3/4 race.”
Lots of words, zero information.
Agreed…..It was very generic with no specific information.
One of the main issues with large cam selection is low rpm loss of torque and horsepower. Now you need
lower gears, and have spool the motor more. Not great for street use. Not to mention carb and intake to match cam profile. Weight of car matters as well.
It would make for a real interesting article to take a somewhat heavy car, with highway gears, and have several people do a drivability test. Then swap a few things – one at a time – carb, cam etc. and see what the impressions are. Probably best done blind – driver would only know something was changed.
Being less weight and lower gears help cover up mismatches, they would be much more apparent.
What gets numbers on the dyno is rarely directly related to what most people would like to drive daily. An engine with a wider torque curve is much more enjoyable. RIP Myron Cottrell – I can remember a quote from a classmate (with a 1969 Dart with a big cam) – I’ve never seen taillights disappear so fast after you passed him leaving one day.
A very interesting “test” idea. Might have to see what I can make happen. Would be really fun to dive more into drivability like that.
Engine Masters series on Motortrend touches on this as they dyno test several different brands of the same components on a dyno engine. You touch lightly on part of the picture – cam choice is much more than just picking a cam. Gearing, weight, and tire size become questions along with how / where you intend to drive it.
Myron (before TPI) built a 400 SBC that appeared in Car Craft that had a huge flat torque curve for the street. Reliable, stout enough to move something without lots of weight reduction or gearing.
Feel – crisp, instant throttle response, especially off idle – makes for a ride you enjoy driving. Newer motors (like the LS you are putting together) can self adjust some to compensate. Something with a carb (tunable, easily changed for airflow), points (single, dual, then to electronic), stock manifold (then dual plane / single plane aftermarket), single exhaust (then duals, headers, muffler changes) make for a great learning curve. Think old 4 door G body platform….
Maybe a bit of what you go through ‘fine tuning’ your LS once in the car could be a primer. I imagine that fuel and spark curves could be best guess – and some adjusting will tell how good the guess was.
I rebuilt the 383 in my Roadrunner and opted for the Chrysler performance “Purple” camshaft. Didn’t like the loss of the low end torque and HP and ended up swapping it out for the stock cam about a month later.
I like my cams like I like my oatmeal… Lumpy!
While there is nothing that sounds quite like a lumpy cam… I selected what might the “smallest” BTR cam for my build, the “Truck Torque”. In a 3,200 pound pickup that will see towing duties.
If you bought too big of a cam, consider getting Rhodes lifters. They will calm the low end and lumpiness without actually changing cams. An additional benefit is that they are hydraulic but sound like solid lifters.
Always thought these would be a good idea, although also thought that if you are suppressing the valve lift early, you might be really shocking the valvetrain. Valves open slowly and this acceleration ramps up, same with closing. Does anyone have experience with these? Concern is that it can be hard and pound out the valve seats.
So it may help to some degree, but is more of a crutch than solution.
Kind of like running too much lash on a solid lifter cam. A little can help, but you can cross the line.