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#1 |
Registered User
Join Date: Dec 2015
Location: Westminster, CO
Posts: 26
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General Stock Cam Question
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!
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1978 K20 Camper Special, stock 350, TH400, np203, 265/75R16, GMC 10.5" rear, Dana 44 front 3.73, Q-jet. |
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#2 |
Registered User
Join Date: Dec 2011
Location: Yuma Arizona
Posts: 1,526
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Re: General Stock Cam Question
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.
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#3 | |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: General Stock Cam Question
Quote:
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 |
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#4 |
Registered User
Join Date: Apr 2013
Location: GUNTERSVILLE
Posts: 621
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Re: General Stock Cam Question
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. |
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#5 |
Registered User
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,541
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Re: General Stock Cam Question
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) |
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#6 |
Registered User
Join Date: May 2012
Location: horseheads,ny rust belt
Posts: 2,794
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Re: General Stock Cam Question
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.
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77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. Last edited by sweetk30; 12-04-2018 at 12:44 PM. |
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#7 |
Registered User
Join Date: Dec 2015
Location: Westminster, CO
Posts: 26
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Re: General Stock Cam Question
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.
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1978 K20 Camper Special, stock 350, TH400, np203, 265/75R16, GMC 10.5" rear, Dana 44 front 3.73, Q-jet. |
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#8 |
Registered User
![]() Join Date: Oct 2006
Location: Southern Kalifornia
Posts: 3,066
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Re: General Stock Cam Question
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.
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------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT |
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#9 |
Registered User
Join Date: May 2012
Location: horseheads,ny rust belt
Posts: 2,794
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Re: General Stock Cam Question
yep and other than center bolt valve covers it still looks like a reg old sbc . . .
__________________
77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. |
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#10 | |
Registered User
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 253
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Re: General Stock Cam Question
Quote:
Arthur in Alaska running a lot of gravel roads..... |
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#11 | |
Registered User
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 253
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Re: General Stock Cam Question
Quote:
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 !!! |
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#12 | |
Registered User
Join Date: May 2012
Location: horseheads,ny rust belt
Posts: 2,794
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Re: General Stock Cam Question
Quote:
__________________
77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. |
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#13 | |
Registered User
Join Date: Sep 2014
Location: Manley Hot Springs Alaska
Posts: 253
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Re: General Stock Cam Question
Quote:
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#14 | |
driving is in my blood
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,720
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Re: General Stock Cam Question
Quote:
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.
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
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#15 |
Registered User
Join Date: Oct 2013
Location: Maine
Posts: 2,356
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Re: General Stock Cam Question
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.
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76 Chevy K20 76 GMC K15 77 Chevy C10 77 Chevy K10 |
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#16 |
OutOfMyMind & I'llNeverKnowWhy
Join Date: Apr 2004
Location: Another world, some other time
Posts: 672
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Re: General Stock Cam Question
Can get adapters to run the perimeter covers too. Dipstick on the wrong side tho.
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-Justin-Out of my mind and I'll never know why 1976 Chevrolet Silverado C10 350 4bbl / TH350 Big10 longbed 1986 Pontiac Firebird T-Top 5.0L TPI 700R4 WS6 1992 Pontiac Firebird T-Top 5.0L TBI 700R4 My cardomain page ![]() I don't like to save, it's more fun to spend!! |
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