Help - Cam swap horsepower/torque change 383 - Chevelle Tech
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post #1 of 17 (permalink) Old Feb 15th, 20, 11:27 PM Thread Starter
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Help - Cam swap horsepower/torque change 383

Hello all
Looking for advice and estimates of power increases if I change cams. Many years ago I had my 383 with EFI built with the intention of daily driving it. UDHarold spec’d me a 274 hyd roller, 219* @ .050 and .525 lift on a 112 lsa. It dyno’d 424hp and 440tq. It’s a pretty mild cam, but made decent power.
If I swap cams to something bigger maybe in the 227* @ .050 and similar lift, and LSA to maintain vacuum for EFI how much will that change my power and power bands?
Thanks

1969 Malibu
EFI 383/700R4/3.55
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post #2 of 17 (permalink) Old Feb 16th, 20, 3:59 AM
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Re: Help - Cam swap horsepower/torque change 383

hi
efi brand
manifold type/brand
cylinder head spec / cc / brand / model
static compression ratio
exhaust
auto, stall or manual gear box ??
Basically is the engine built to handle more cam???
If the engine is restricted more cam is needed to achieve the same goal .
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post #3 of 17 (permalink) Old Feb 16th, 20, 8:12 AM
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A 383 w/233,241 roller, 10.5 compression, aluminum heads, air gap, well tuned Holley DP, properly set up ignition, open, tuned headers,
will get you around 500/500. All in a streetable package.

IMO, machine work is critical to HP and longevity. Is rotating assembly balanced to less than 2 grams ?, plate decked ?, crank journals polished ? Hi quality cylinder hone ?

All above is for naught if you’re gonna harness this to a 700r and 3:08 gear.

Question: EFI doesn’t work on low vacuum cams ? Someone school me on this !
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post #4 of 17 (permalink) Old Feb 16th, 20, 9:13 AM
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Re: Help - Cam swap horsepower/torque change 383

Hi
For 383 /400 to achieve 500hptq with a conservative combo is difficult
most dyno sheets 460-490 hp/tq
pending cylinder heads pinch point/port size/ valve size. 2.02 valve 180cc wont do it, alloy or not
195 /215cc head with 2.08 valve
single plain vs d/plain
comp min 10;1---10.5;1
torque plate hone
1.6 rocker min
1/16 inch rings or thinner
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Last edited by swampy 6x6; Feb 16th, 20 at 9:34 AM.
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post #5 of 17 (permalink) Old Feb 16th, 20, 9:39 AM
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This close enough ? 😁

(Forgot to give credit:
“Horsepower courtesy Skip White Performance”. 👍
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Last edited by Reelysalty; Feb 16th, 20 at 10:00 AM.
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post #6 of 17 (permalink) Old Feb 16th, 20, 10:49 AM
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Re: Help - Cam swap horsepower/torque change 383

ok for a 250ish cfm head

Quote:
Freedom is not caring what others think of you
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post #7 of 17 (permalink) Old Feb 16th, 20, 11:40 AM Thread Starter
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So it seems I left a lot of information out. Engine specs are:
- Edelbrock pro flo 4 EFI, going to replace pro flo 1 and trying to decide what hp level based on the cam.
- Edelbrock rpm 60899 heads with minor port and polish work by the builder. 195 runner 64cc chambers.
- compression I’m guessing is 9.88-1. I don’t know exactly because I can’t find the piston part number he wrote down. He wrote srp 138013, but I think he meant 138130.
- the short block is decked and honed and the rotating assembly is balanced and forged but only 2 bolt main.

I’m not really looking for 500hp/tq as my tranny is a built 700r4 and still have the 8.2 10 bolt with 3.55 gears. But if I can get another 25 hp out of it, i think it’s worth the money and time.

Thank you

1969 Malibu
EFI 383/700R4/3.55
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post #8 of 17 (permalink) Old Feb 16th, 20, 1:26 PM
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I doubt you’ll feel 25 HP w/any drivetrain, and especially what you have.

Be happy w/what ya got !
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post #9 of 17 (permalink) Old Feb 16th, 20, 1:33 PM
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Quote:
Originally Posted by cuisinartvette View Post
ok for a 250ish cfm head
You could always call them and offer your services as a consultant? 😁


https://www.youtube.com/watch?v=oMRXjYkijRI

👍
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post #10 of 17 (permalink) Old Feb 16th, 20, 4:58 PM Thread Starter
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Quote:
Originally Posted by Reelysalty View Post
I doubt you’ll feel 25 HP w/any drivetrain, and especially what you have.

Be happy w/what ya got !
Thanks for the honest answer. I’ll put the funds into something else!

1969 Malibu
EFI 383/700R4/3.55
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post #11 of 17 (permalink) Old Feb 16th, 20, 5:23 PM
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Re: Help - Cam swap horsepower/torque change 383

"maintain vacuum for EFI"

That is odd, EFI isn't dependent on vacuum in the ports.
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post #12 of 17 (permalink) Old Feb 16th, 20, 6:45 PM Thread Starter
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Quote:
Originally Posted by Dave Ray View Post
"maintain vacuum for EFI"

That is odd, EFI isn't dependent on vacuum in the ports.
It has to do with idle vacuum so the computer knows how much fuel to maintain a smooth idle and I think off idle transition. Edelbrock recommends 10-11” of vacuum. To me, that’s one of the bummers with fuel injection, running anything less than 110 lsa can potentially/maybe/might cause drivability trouble so you lose out on some of the lopey cam sound. When my engine was l first built 17 years ago with the pro flo 1 system, The builder used a cam with 107 lsa and it sounded good, but only pulled 10” of vacuum at normal idle and would stumble a bit coming to stop lights and acceleration, anything more aggressive and it probably wouldn’t idle at all.

1969 Malibu
EFI 383/700R4/3.55
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post #13 of 17 (permalink) Old Feb 16th, 20, 6:59 PM
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69 Vette said “, The builder used a cam with 107 lsa and it sounded good, but only pulled 10” of vacuum at normal idle and would stumble a bit coming to stop lights and acceleration, anything more aggressive and it probably wouldn’t idle at all.”

Wow, I just had a friend pull off efi and go back to Holley. Calls to Edlebrock were no help. Every stoplight, on a 4 speed, same mess you describe !

Another reason not to run efi 😁
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post #14 of 17 (permalink) Old Feb 16th, 20, 7:27 PM
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Re: Help - Cam swap horsepower/torque change 383

hi
230-236 112 LSA is about as far as I would go with your efi combo

I`m doing the same at the moment 230/236/110 to 236/242 /110 with carb and I no vacuum might be an issue even thou my engines a 400 cu-in. I would like a vehicle that has good street ability for brakes etc etc
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post #15 of 17 (permalink) Old Feb 17th, 20, 4:19 PM Thread Starter
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Out of curiosity, what HP gain would/could I see with my combo if I went to a 230/236 duration cam?

1969 Malibu
EFI 383/700R4/3.55
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