WHAT MAKES A TURBO CAM A TURBO CAM? HOW MUCH LIFT, DURATION, LSA AND OVERLAP CAN YOU REALLY RUN? 

I must thank you again Richard, I'm guilty of worrying about overlap because that's what I was previously lead to believe. I value your experience and knowledge.

Yes use a good low rpm cam then let the rising boost curve take care of the power on top. That way you can max your power across the rpm range based on what your hard parts can handle.

GREAT information that can save people many dollars and much frustration! PS the "Baaaaaaah" power sound effect on the motor pic was golden!

Based on Richards advice I chose a "stage 1" turbo cam and a "long runner" stock style intake with my 7875 turbo. I bet the car is way more fun than if I went with a stage 3 cam and short runner sheet metal intake. Most people ignore the advice and just buy cool "race car stuff" and slap together.

Richard as always your the man!! Your cam game is top shelf for sure!! Thanks for the videos and daily talks!!

I sure do appreciate your videos Richard. I'm new to this LS stuff stuff at 53 yrs old.

Pressure ratio of exhaust/intake is very important. Everything that he said is true when you have the same backpressure in the exhaust as boost in the intake. That means that the turbine size is most important, as that is what determines the exhaust backpressure. Most oem turbo engines have higher backpressure for better response while most aftermarket turbochargers are bigger and build boost at higher rpm and make more top end power with the expense of lower end rpm.

Texas Speed sold me a "Stage 2 blower cam" for my 13 Silverado 5.3L w/P1SC1. 224/228/.600 lift 114 LSA. That was about 5 years ago. Now, that same cam is listed as a Cleetus McFarland Dumpster Fire cam. Their "Boost cams" listed for my truck now are way different.The truck sends 600+ to the wheels so it works!

The cam in my turbo LQ4 I got used from a friend who ran it in a Maggie charged LS1. Specs were good for what I wanted didn't care that it was a blower cam . Works great

My wife was inspired by your introductory music. I enjoyed it so much, i played it again and again...and again. Great video, dude

I rely on chatter of what others are finding out, including you and mostly can get an idea of what parts are working for certain applications. Reputation is a factor as well in picking parts, as you said before BTR was making cams that you thought would test out differently and now you are a believer. I bought from BTR for that reputation.

Your reasoning (and experience) makes sense. The back pressure from a turbo balances the effect of boost during overlap. I'm guessing that a belt driven supercharger is a different story due to the lower back pressure, and would send more raw fuel out of the exhaust at high boost.

I don't think anyone would argue with the statement that adding boost from a turbo will increase power output over not having boost from a turbo. What would be more interesting to see would be to run a group of builds comparing everything from a single pattern narrow lsa cam with lower lift to what colloquially would be called a "turbo cam" with a dual patter, wide lsa, high lift cam and maybe even a reverse pattern cam for funzies, and look at percentage of increase for n/a vs 2psi, 5 psi, 10 psi, etc to see if one makes better use of boost. I get that the variables would be hard to isolate and head characteristics would play a big factor, but I think there would be some themes one could gather from such a comparison. I would think that there is such thing as a cam that operates more effectively with a turbo than others. Would you disagree?

The LSA and duration split absolutely effects the curve, you can see even on your dyno sheet that N/A with the Truck Norris cam the power is holding on all the way to the edge of the sheet, yet boosted the power is starting to drop off and you pull the pin early, its dropping off because there isn't enough blow down time beyond that rpm point to clear the cylinder of the extra combustion gasses, there is only a certain speed the exhaust gas can peak at before it can't move anymore volume, this then becomes pumping losses. If you took that cam and just widened the LSA only then that power drop off point would move further up the rpm rage before you get to the same issue again, then its looking at duration, opening and closing events of the exhaust valve to control cylinder pressures at different points of the rpm range to make sure your not lifting the head and blowing head gaskets or worse all the time. So much more to the science of a camshaft in reference to boost for the best efficiency, performance and longevity.

As far as I can tell in the DOHC world the terms “supercharger, turbo cam” compare differently to the “n/a cam” mainly with the event dynamics and not necessarily the lift or duration. The ramp rates being symmetrical vs asymmetrical will make differences too. When they refer to turbo cam is designed to help where the turbo lacks such as down low and opposite with the blower cam. It will help the blower up top when it needs more help. That’s the only thing I can tell that would be different when marketing the terms for the cams. However I completely agree with this for pushrod engines.

Totally agree . Look at turbo/ supercharging as an atmospheric pressure or air weight multiplier . In automotive terms this was thrashed out in 1980s Europe with the introduction of turbocharged 1.5 litre engines to compete with the Cosworth DFV V8 engine . Bhp required to win say 650 . 1.5 litre NA unlimited race engine at 100bhp/litre , 150 + bhp @ 9000 rpm with established reliable cams . X 4 Bar boost = 600bhp with lighter weight advantage made the Renault cars competitive with their 4 cylinder engine at the beginning of the era with mechanical fuel injection . At the end the end of the era cams were limited only by the physical dimensions of the cylinder head or cam carrier space they occupied and fully mapped fuel 8njection , efficient charge cooling and unlimited boost the 1.5 litre V6 engines were making 1200+ bhp @ 11-12 000 rpm in practice allowing the turbocharger to control the boost without a wastegate and anywhere around 850bhp in regulated boost race trim . The BMW iron block 1.5 4 cylinder was making around 1300 bhp in practice with engines and boost levels deliberately designed to last only 4 laps running on the edge of total destruction. On qualifying these engines were removed , retired to the scrap pile after analysis and a race engine installed to actually compete . Rinse and repeat for every race . Totally unsustainable and running out of control . In aeromotive terms this is called normalising . This was thrashed out in the 1940s when both types of supercharging were employed to replace the air weight lost at altitude to preserve the power levels achieved by the air racers at normal sea level , with boosting in war emergency/ take off mode with the introduction of 2 speed superchargers as war and development progressed .

When investigating the longevity of 440 Bus engines for Chrysler in the 70s we found that overlap/ exhaust close had a big effect on EGT Stock 440 cam bad and 440 HP cam worse In addition you have to keep the exhaust valve on its seat to cool as much as possible the really long closing ramps killed these motors, exhaust manifolds glowing cherry red on medium pulls and even on our test Cordoba How long do you want to live? changing cam and going to quench pistons lowered EGT 800 degrees That said, as Richard says, start with a cam designed for your usage and torque curve needs then shorter is usually better unless you are really light and short bursts

In my experience the turbo cams are better on the starting line on a drag strip, with big turbos. Anywhere else you're correct, the turbo multiplies the na power.

I'm building a blower motor, and I chose the old school 327/350hp (.447lift/223dur. 114 lsa) Cam. My thinking is that supposedly blower motors like more duration and LSA, and if that Cam can help a NA motor make more than 1 hp per cubic inch surely it would multiply that even better under boost. I hope I'm right. I don't want to end up building an old slow dog.

Overlap with a high back pressure in a vehicle will restrict the timing your able to get out of the engine without detonation. I chose a low overlap cam for this reason. If I had twins or a turbo that has a 1:1 back pressure ratio I wouldn't be scared of overlap at all. Even on high back pressure setups I'm not scared of high overlap cams I just know not to get carried away on the timing especially on a pump gas deal.

On N/A engines tighter lobe separations make more power vs wider lobe separations.

I see it as a simple solution. Spec your cam for average power in your desired rpm band for your application.

As turbo cam sales drop like Bank stocks this week.... I'm using the BTR torque cam with the 202/ 202 duration in my twin turbo build. Early Spool, super strong mid-range, no need for over 6,000 RPM. Just look at the n/a power curve and decide which one works best for your application and then imagine it multiplied and that's how you pick your cam.

We learned back in the 80s and 90s that there wasn't alot of gain from using a turbo specific or nos specific cam. And only about 20 hp gained from the bigger cams. Bloodviking

Simply put, cams no matter the make for what engine will idle,spool and give better low end drive ability with smaller digit specs. But with larger digit specs will teeter-tot the dyno graph upwards in favour of power at the sacrifice of low to mid range torque,spool & response.

People's minds revolt when you tell them it's as simple as buy the cheapest one that doesn't require more changes than you want to make, i.e. Valvesprings/converters... No no no , this one has a cool name, that one has a cool social media endorsement, this one is custom just for me because my little mass produced engine is different from the hundreds of thousands of others just like it.

So it seems the real question is: Is there anything that makes a cam better for a turbo application than a non- turbocharged application?

Boost is just a extension of na if all is equal.....but try splainin dat to the coyotards and modular guys

You need to decide if you want an engine that makes power and low to mid range rpm or higher range and gear the car accordingly. A 4500 to 8500 rpm cam would need 4.11 to 4.88 gears. While a mid range cam would start out at 3500 rpm.

Fantastic wealth of info you provide to the sport

I love this video, this is what I was thinking and your data confirmed it thank you !

Howdy great videos all the time can't wait for the next one.! The cad company videos were #1 got a 85 suburban with the pro street heads 4x4 1 ton rears straight cut gears th400 . Anyways what weight/ color springs would you recommend on distributor sbc 383 11 1/2 1 comp xr282 Mickey Thompson cross ram Holly 650s . Runs great but no advance set at 24° really appreciate your awesome work on here.

Great video, I’m running a comp 287/303 advertised. 227 int./ 241 exh. @.500. 0.557 int./0.539 exh. With a 107 LSA seems to work fine with my twin rear mount turbos.

I sometimes dis agree with your tests, but this I can agree with %100

Still learning from your videos, Richard. Good stuff, man.

I cant comment on LS engines as we dont have much of them here. While you tested for full throtle, which is ok for drag racing, things may be different when driveability and more boost is factored in. We mostly do high boost DOHC inline 4s here, and high revs NA. The turbo cams usually run "high lift" 10.25mm cams with 270 duration and 30+ psi boost, up to 9000rpm, most power produced with about 115 separation. The NA engines run something between 300 and 330 duration, and rev to 12,000. Pretty sure the turbos would not run great with that much duration, since they cant rev that high.

To answer the question in the title. Look for the package that says," Turbo Cam." LOL. I couldn't help it. It seemed funny. I'm scrolling while charging my headphones. It's been a hard day.

If your intake and exhaust pressures are equal then forced induction is just like operating at 10000ft below sea level. But, if your exhaust pressure is higher than intake, as turbos have, then with increased overlap you decrease VE. That changes with rpm, thus your “multiplier” will change by rpm. This is why turbo cams benefit from lower overlap than supercharger cams.

So what is the reasoning or claimed benefit for the cam manufacturers to offer turbo cam profiles? Just for the sake of having more part#’s to list in a catalog? Not trying to start a debate, genuinely just asking.

It's possible to build an engine that builds loads of tork in real usable vehicle speed. If you can make almost all your power at say 75 mph would be alot of fun. At 5252 rpm at 65 mph could be interesting.

N/A engines don't use different cams when running at high and low altitude tracks even though the intake density changes. Why would you change cams just because the altitude changed artificially?

A good all around cam for the street would be at about 1800 plus rpm. A radical street cam will be rated at 3500 plus rpm.

A good gear ratio for your differential would be 3.50 on a streetable car. For top end mostly I'd go with a 320 degree cam and a 3.23 gear with o d. Major top end there.

Overlap makes power

Most engines are over cammed by home builders thinking more is better. A 3500 plus rpm cam is radical and I've seen street cars with these solid lifter cams.

Good work Richard

With your turbosystems that makes more backpressure than boost and are not very powerful anyway, a " turbo cam" would make power.

More overlap leads to reversion before boost, once boost pressure is greater than exhaust back pressure it then does something different. It pushes out fuel in the exhaust and messes with your true cylinder AFR. If that fuel was pooling behind the intake valve some of it is going to go out the exhaust. The wideband will read what the system saw (average), but not what the cylinder saw. So in this case you usually have to add more fuel than normal to get it right in the cylinder, even though the wideband says otherwise.

Ok we all know that you can add boost to any motor with any cam, but we in the know !know that it’s the overlap that’s different on a turbo, or blower cam, even the factory changes the overlap.. a NA MOTOR NEEDS TO Scavenge on the exhaust side to pull the air in, but you don’t want the exhaust hung open too long while the intake is open why, because you simply push the boosted air out the exhaust so the less about of time the exhaust is open on a boosted motor the more power it will make..so your not totally right, other than yes boost will just increase the power, but the right cam will do it better..

Personally I blame squirrels.....

Damn I love that intro music!!! Always puts me in a good mood. Lol

Why did GM make the cam that has 122 LSA for their supercharger. BTW, I agree with you 100% I have a Magnuson Supercharger and the cam is nothing like a *blower* cam.

I knew guys who used wrinkle wall tires on the street to hook up all that power.

I was under the impression pressure pre-turbo is what matters with relation to duration and overlap. When you are only running 7-8psi you aren't going to see enough back pressure to cause an issue. So the power curve will mimic the NA curve as you say. Get into the 2:1-3:1 back pressure levels and higher overlap camshafts will run into detonation issues. Where a smaller cam with high negative overlap @.050 will not. With the 1.10 T4 S475 I'd see 2.8:1 back pressure levels at 26lbs. The turbo was tapped out and of course not the best unit for the job. But I believe it stayed together and ran "ok" at those levels because I ran a camshaft with -24* of overlap. Similar to my old DSM motors seeing into the 3:1 back pressure ranges on the baby 16g turbos. If you run a setup that will run at 1:1 or better (twins) you run what ever cam makes the most power where you want it. Just as you say. I ran a "big" MS3 cam on my twin 5.3 setup. Worked well!

Who would believe forcing more air and fuel into a motor makes more power ? 👏😆

Why not test cams with different dimensions and see the differences then. Example a 215/230@.050 with a 108lsa vs a cam with 215/220(or 215/215) with 108lsa. Then change lsa in same cams and see differences......

What I’d like to see was sloppy stage 2 228-232 cam but 108lsa against exactly the same at 114lsa and see what happens NA and boosted

How does the Summit Big Nasty cam perform compared to the truck Norris and chopacabra?

Thats exactly what I did I'm building it the way I would build a good NA package and when I'm happy with that then ill pop the Turbo on If I can make 600-700 NA I won't need to push the Turbo, the cam I picked turbo didn't come a consideration. im not building a full on race car im after a tough daily

Love your videos, can you do some tests on the effectiveness of Velocity stacks and or carb spacers effect. I saw a couple videos you touched on about spacers but a dedicated video on these would be great, there are alot of myths in these areas running around with carb guys.

How did u test 5 non-turbo cams? Where did u find them? If all cams r turbo cams? 🤔🤔

I run a stage 2 on a 1KZ Toyota LN106 Hilux , over 200 HP. And the extra torque I get is insane... Auckland Camshafts /NZ Call Henry ... he knows the game! Real power just a phone call away!

I’ve seen too many boosted motors do cam swaps and make more power !!!! We all know lift has the greatest effect on power, so we leave lift about the same same duration,and just split it different and swap the over lap and watch it increase in power why, less air is leaving why the exhaust and intake aren’t open together as long pushing air out..

Hey Richard. Curious if you have any videos of you running that Holdner/Happel “best cam”?

Why not test it with the power / boost formula in mind? Does a “turbo cam” make the engine any more efficient from a % of gain standpoint versus a non turbo cam at similar boost levels? What about potential backpressure differences at these same levels? I think it would make a good test. Also, what about boost threshold (minimum RPM where the turbo spools)? Or response rate (time it takes to spool at higher RPM)? Might be hard to test on a dyno versus in a car but also be interesting to see if the “turbo cam” changes anything.

Richard I have btr stage 4 in my 6.0 with 76mm turbo it’s happy at around 13lbs but when adding more boost it makes less power Data looks perfect Full exhaust 3/12 to 4 inch no muffler Any idea why

Hi richard! Building a 408 with +18cc dished pistons.Looking for a good street cam. car weights around 3,400lbs through a 4apeed auto and 3.73 gears. What would be a good btr cam to go with ? Im all ears !!! Thanks!!

4:25 had me looking for someone

When in doubt go smaller. A fairly stock engine with a 296 cam will suck.

You ever thought about using better legends and line colors on your charts? All I see are multiple red and blue lines and then a legend that says all red lines...

Have you ever done a 4.8 crank and rods in a 6.0 or 6.2? I'm curious if it's possible and what pros and cons it would have.

Makes sense. So then why do manufacturers have them categorized as “turbo” and “blower” cams?

Kinda hard to read the graphs cause the legend color coding is all red... And: the claim "it just multiplies" does not hold true in all of the graphs. The curves are not the same. For sure the boosted graphs are higher, but the paths are not the equal but shifted. The multplier changes.

Moral of the story is, don’t overcam.

Could you do a cam comparison for a good street combination. A turbo sized for the street, so it will be responsive, but it may have a higher pressure ratio (intake to exhaust) when comparing to a drag race application for example. Then compare a well matched cam profile with different amounts of overlap, with three different boost levels for each cam. 15, 20, 25 psig. The goal would be to see which one performs best under this test. You made the point, but overlap provides a scavenging mechanism, but the heads, headers, intake... have to support also, otherwise overlap can lead to excessive residual exhaust gas left in the chamber or possible flow reversal into the intake. The question is not that you need a "turbo" cam, but the profile, timing, and overlap can be optimized and optimal is not the same for NA to turbo, or big turbo to small turbo, and... or maybe it is, but a dyno comparison would tell the tale.

Bain Racing from Oz, I feel like you and them would make beautiful music together.

The turbo cam needs to match the turbos. If you've got small restrictive turbos that give instant boost then a long duration cam is no good, you need a short duration cam.

Hi Richard I have a couple 2.6 and 2.9 ford v6 and some the Yamaha sho engine how do I select the right cam for these engine? My goal would be more tq from idle and still run smoothly and if possible to make a bit more power is there an equation like you guy use for the v8? Thank

Some racing cams have a terrible short rpm power band, race only type.

how about a 6.0 n/a build combo vid. no power adders. Diff heads and cam combos maybe diff compressions

What kind of camshaft can I run on a Chevy 6.0 with some chop that will still spool up pretty fast?

Is every cam a nitrous cam too?

But what about a RV cam? Or the 3/4" Race cam. 😊

When He some Day build engine that make over 400nm torque/ per 1Litre, then he make new video 😅, like he's t-shirt wrong cam. Show must Go👍

How long does it take to get oil through the pushrods on a dry LS? I did a cam swap and a few other things I’ve primed the pump and rolled it over but no oil through the push rods.

Will a stage 2 turbo cam with a turbo cause the oil dipstick to come out because of pressure?

3/4 turbo cam😅

New to the Turbo game, been an N/A Nitrous guy for decades. Very impressed with your method of presenting information, it is much appreciated and bound to save me $$$ in my new endeavors. I live at 7000 ft. elevation and would like to see some advice on what to look for in working with thin air for daily driver stuff and also spooling/power at the track. Albuquerque and Denver specifically. Thanks for all the help you've given already.

I wonder if summit will let me return my stage 3 twin turbo cam? Lol

MPG - save money on fuel with my 5.7l to buy a turbo kit - what do you suggest for an MPG cam lol

So I can run my reverse split TR230 that's a 230/224 on a 111 LSA and this principle would still apply? I love everything about the cam, so if I could turbo it and it would mimick its manners has now, but with more power, I'd be ecstatic.

Hello Richard, Please help; can i use BTR .660 dual valve springs with a .656 lift camshaft?

Hey Richard, another great video on turbo charging as this is my first foray into turbocharging. You happened to actually do a full video on my Comp Cam 35-518-8 that was also massively informative. My question is on power peak rpm. I have a 363 Ford with this cam, (AFR 1492 heads)and on the dyno the power peaked at just over 5100 rpm. The cam spec says it should peak at 6200. Is that due to the extra displacement over the 302? Or what other factors would there be? TKS!

No offense or anything, I just don't understand what does he means by saying "it works well". Of course any engine that runs N/A makes even more power boosted in case of decent A/F ratios, ignition timing, etc. I would like to know what cam benefits the most. I don't see the point comparing the N/A engine to the boosted. Why doesn't he compare the boosted engines to each other? That would be more useful.

Are these same scenarios true for centrifugal blowers and PD Blowers?

So if a turbo simply multiplies the N/A torque curve, what does a supercharger do? Does the same concept apply to superchargers, or do superchargers perform better with supercharger cams?

we need runs all the way down at 1500~2k rpm and there about, unless you run a auto that change every time you get a bit there is a lot of unseen changes i feel

What about the 2.7 high output Chevy 4 cylinder that has a variable Camshaft 3 different lobes.

The question from a noob now becomes, do I use same valve springs that come with the NA cam or will a turbo make the springs weak and have valve float?

What's the best cost friendly cam to buy an where can I get it