General Stock Cam Question

[learyw]

I'm going putting a new crate engine in my 78 K20 (part 809-12681429). Before I drop it in, I think I'm going to put in a mild Vodoo cam (part 10120701). This should give me a little performance bump.
This got me thinking. Why do stock motors come with such mild cams? What am I giving up by swapping out the factory cam? The engineers clearly designed that cam for a purpose? Why are they hesitant to put even a slightly more aggressive cam in stock motors? Fuel efficiency? Reliability? Cost? More generic so it fits multiple applications? There has to be a reason...Hoping someone had some insight. Thanks!

[SunSoaked]

In a word.. liability. Generally speaking the OEM's noticably limit the output of their engines for reliability. The bigger the safety factor the less likely they will push the limits of thier parts and end up in a recall. Recalls are expensive and can bankrupt a company. It doesn't mean the engine can't reliably produce more power (think about the LS). And that power cost money, otherwise we'd all be driving Denali's.

[geezer#99]

Originally Posted by learyw

I'm going putting a new crate engine in my 78 K20 (part 809-12681429). Before I drop it in, I think I'm going to put in a mild Vodoo cam (part 10120701). This should give me a little performance bump.
This got me thinking. Why do stock motors come with such mild cams? What am I giving up by swapping out the factory cam? The engineers clearly designed that cam for a purpose? Why are they hesitant to put even a slightly more aggressive cam in stock motors? Fuel efficiency? Reliability? Cost? More generic so it fits multiple applications? There has to be a reason...Hoping someone had some insight. Thanks!

It likely won’t give you any performance bump.
You need to raise the compression ratio at the same time.
The cam used has more to do with compatibility than reliability.
Here’s some reading for you.
https://www.crankshaftcoalition.com/..._compatibility

[Kudzupatch]

Keep in mind that they design for the majority, not the minority. Plus all the g'ment regulations on emissions and fuel economy. So it is finding the best compromise that will still sell.

Most people want a smooth running, reliable engine and probably only hit WOT once or twice a year.

There are lots of performance crate engines out there if that is what you want and that allows you to keep the warranty too.

[Dead Parrot]

When these trucks were being produced, they were having to deal with rapidly changing emissions requirements, evolving emissions equipment, lead being phased out of fuel, changing octane numbers, etc. Also, GM didn't know ahead of time if a purchaser would be using a truck/motor for heavy towing, in town delivery, suburban trips to the hardware store, or highway traveling. And it needed to start cold in -20* weather and hot in 120* weather.

Much easier to pick a specialized cam when you know your end use is for example:
80% highway towing with 87 octane pump gas (towing cam)
street drag racing using 91 octane real gas(higher RPM cam)

[sweetk30]

also dont forget you need to make bottom to mid range torque for a big heavy truck . not mid to high hp .

torque gets you rollin .

h/p keeps you rollin .

and if you didnt buy that engine yet look at a L31 engine 12530283 its a 96-03 vortec 350 . 250hp 330tq . just need new flex plate for auto as its a 1 peice rear seal / vortec carb intake / electric fuel pump . otherwise she bolts right in place . gets you roller cam and better flowing heads and more power for less money on engine purchase . then the few items i listed you are at your price you have in the engine part # you listed .

here is my engine question thread on the L31 http://67-72chevytrucks.com/vboard/s...d.php?t=763121 all the info you should need in here for the required parts .

pics of mine in a 87 frame / th400 trans / 89-95 serp belt setup / 87 exhaust manifolds all bolted up no problems.

[learyw]

Thanks for the replies on the factory cam. That makes sense to me. I figured, but couldnt find any information out there about it. SweetK30, that looks great. I have thought a lot about going L31 but my entire truck is original/stock. Im trying to keep it as original looking as possible. I already hate giving up on my original motor but the crate just makes so much sense. I can paint it factory original color and it will blend right in.

[manimal]

the L31 is a LOT better engine than the GM crate flat tappet engine. You get a roller cam and Vortec heads, you just need a Vortec intake and electric fuel pump.

[sweetk30]

Originally Posted by manimal

the L31 is a LOT better engine than the GM crate flat tappet engine. You get a roller cam and Vortec heads, you just need a Vortec intake and electric fuel pump.

yep and other than center bolt valve covers it still looks like a reg old sbc . . .

[akart]

Originally Posted by learyw

I'm going putting a new crate engine in my 78 K20 (part 809-12681429). Before I drop it in, I think I'm going to put in a mild Vodoo cam (part 10120701). This should give me a little performance bump.
This got me thinking. Why do stock motors come with such mild cams? What am I giving up by swapping out the factory cam? The engineers clearly designed that cam for a purpose? Why are they hesitant to put even a slightly more aggressive cam in stock motors? Fuel efficiency? Reliability? Cost? More generic so it fits multiple applications? There has to be a reason...Hoping someone had some insight. Thanks!

I put that same cam in my 1982 K20 and it definatly added some snort. Mild cam, just a (little) lump at idle, enough to sound good and to know you've got a different cam in there. Mileage is 12 mixed with no tuning I think I could do better will work on that this spring when I put on my iron 72cc Summit heads and Headman Headers. You will like this cam,well worth it.
Arthur in Alaska running a lot of gravel roads.....

[akart]

Originally Posted by learyw

Thanks for the replies on the factory cam. That makes sense to me. I figured, but couldnt find any information out there about it. SweetK30, that looks great. I have thought a lot about going L31 but my entire truck is original/stock. Im trying to keep it as original looking as possible. I already hate giving up on my original motor but the crate just makes so much sense. I can paint it factory original color and it will blend right in.

I like your idea of keeping it close to stock (same here) w/a cam swap that would run about 200 bucks as opposed to that 3K to 4K L31. Just make sure you run a ZDDP additive in you oil (All the Time) to protect that cam. That's what I do. My truck (1984 K20) jumps right up to 85 to pass and there's a lot left.
Crate engine w/an Edelbrock 1405 and an Eldebrock EPS manifold.
More to come this spring: 72cc iron heads, ported, headers,dual exhaust and an Eaton truetrac. Have fun !!!

[sweetk30]

Originally Posted by akart

I like your idea of keeping it close to stock (same here) w/a cam swap that would run about 200 bucks as opposed to that 3K to 4K L31. Just make sure you run a ZDDP additive in you oil (All the Time) to protect that cam. That's what I do. My truck (1984 K20) jumps right up to 85 to pass and there's a lot left.
Crate engine w/an Edelbrock 1405 and an Eldebrock EPS manifold.
More to come this spring: 72cc iron heads, ported, headers,dual exhaust and an Eaton truetrac. Have fun !!!

dude were you getting 3k-4k price on a L31 ? there 1895-2k all day long shipped to you .

[akart]

Originally Posted by akart

I like your idea of keeping it close to stock (same here) w/a cam swap that would run about 200 bucks as opposed to that 3K to 4K L31. Just make sure you run a ZDDP additive in you oil (All the Time) to protect that cam. That's what I do. My truck (1984 K20) jumps right up to 85 to pass and there's a lot left.
Crate engine w/an Edelbrock 1405 and an Eldebrock EPS manifold.
More to come this spring: 72cc iron heads, ported, headers,dual exhaust and an Eaton truetrac. Have fun !!!

Here's another thought:The Lunati cam you mentioned is rated best torque from 1,000 to 5,500 RPM. There is one below that (LUN 101207OO LK) which is rates Idle to 5,000. My truck has 4.10 rear end and @5K it would be doing 115 MPH. If I did it again I probably would have gotten the Idle to 5,000 cam as I doubt I will ever see much over 85 MPH. By the way it jumps right up to 85 w/plenty left. But like I mentioned I did put in the 10120701 and it works fine.

[Tom]

Originally Posted by geezer#99

It likely won’t give you any performance bump.
You need to raise the compression ratio at the same time.

There are tons, most likely hundreds, of just magazine dyno's showing that is not true in any way.

OEM's go with small cams for many reasons. EMISSIONS and gas mileage being big ones. They go with the smallest cam they can to still get the HP level they want to sell. If they can get 300hp from a tiny cam, then they don't need a bigger one.

[cadillac_al]

I always felt a huge boost in power when installing any average Rv type cam in a 350 Chev. Those stock cams are very tiny. I still use older Chevy engines because I prefer the simplicity of a mechanical fuel pump.

[Justins76]

Originally Posted by sweetk30

yep and other than center bolt valve covers it still looks like a reg old sbc . . .

Can get adapters to run the perimeter covers too. Dipstick on the wrong side tho.