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Increase L82 HP

 
Old 09-04-2018, 12:48 PM
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JoeManuele
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Default Increase L82 HP

I do not want to change the engine in my '78, it has only 42k miles on it and has been well maintained all it's life. I would love to improve the HP from 220 to 300. Any suggestions?

Last edited by JoeManuele; 09-04-2018 at 12:55 PM.
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Old 09-04-2018, 01:05 PM
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HeadsU.P.
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That's a very vague question. What is your speeding budget? Is it $500 or $3500? (Heads alone could be two grand)
What cam do you have now?
Do you have headers now?
What is the estimated compression ratio you have?
What intake & carb do you have?

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Old 09-04-2018, 01:13 PM
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[QUOTE=HeadsU.P.;1597921059]That's a very vague question. What is your speeding budget? Is it $500 or $3500? (Heads alone could be two grand)
What cam do you have now?
Do you have headers now?
What is the estimated compression ratio you have?
What intake & carb do you have?[/QUOTE

The engine along with the rest of the car is completely stock and original. I would not want to spend more than $1500 on it.
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Old 09-04-2018, 01:14 PM
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The engine along with the rest of the car is completely stock and original. I would not want to spend more that $1500.
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Old 09-04-2018, 01:23 PM
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toddalin
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Have the heads "pocket ported." Easy 20+ hp and undetectable.
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Old 09-04-2018, 01:32 PM
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HeadsU.P.
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H-m-m-m-m. You need to rob a bank or settle for less.

Flat Tappet Cam & Lifters, timing chain, gaskets, etc: $300
Headers, gaskets, bolts, etc: $400
Better intake: $270
Better carb: $450? hard to say.

No money left for heads. Keep in mind a simple add-on could result in unforeseen costs. For example, headers. You will need gaskets, special bolts and likely different plug wires so as not to burn them. May have to completely change the exhaust pipes beyond the collector. This could really dip into the budget.
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Old 09-04-2018, 01:33 PM
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C3DeedlyDee
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More details on car. Is it completely bone stock?
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Old 09-04-2018, 01:37 PM
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You could start by changing the vacuum timing over to ported vacuum source. Recurve the timing so that initial is more in the 15-17 btdc range with a total of 36*.
rebuild the carb or have it done by Lars.
install headers and a true dual exhaust system.
​​​​​​these things will get you noticeable better performance without having to take heads off.

otherwise the best performance enhancement would be changing the heads as well as the other items.
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Old 09-04-2018, 01:43 PM
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Originally Posted by C3DeedlyDee View Post
More details on car. Is it completely bone stock?
Yup...no upgrades or modifications. I think I am hearing what I basically already knew. Either put in another engine that will be compatible with the original 3 speed automatic tranny and 3.51 rear or just enjoy the car as is.
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Old 09-04-2018, 01:46 PM
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Originally Posted by REELAV8R View Post
You could start by changing the vacuum timing over to ported vacuum source. Recurve the timing so that initial is more in the 15-17 btdc range with a total of 36*.
rebuild the carb or have it done by Lars.
install headers and a true dual exhaust system.
​​​​​​these things will get you noticeable better performance without having to take heads off.

otherwise the best performance enhancement would be changing the heads as well as the other items.
I did remove the catalytic converter and redid the exhaust making it a true dual exhaust which definitely helped. I've rebuilt the carb as well but would still love to increase the hp a bit more.
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Old 09-04-2018, 01:47 PM
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Originally Posted by REELAV8R View Post
You could start by changing the vacuum timing over to ported vacuum source. Recurve the timing so that initial is more in the 15-17 btdc range with a total of 36*.
rebuild the carb or have it done by Lars.
install headers and a true dual exhaust system.
​​​​​​these things will get you noticeable better performance without having to take heads off.

otherwise the best performance enhancement would be changing the heads as well as the other items.
i think you mean going from ported to full manifold vacuum on the distributor. 👍
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Old 09-04-2018, 02:51 PM
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Originally Posted by speedreed8 View Post


i think you mean going from ported to full manifold vacuum on the distributor. 👍
yes that is what I meant , thanks
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Old 09-04-2018, 02:56 PM
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Originally Posted by JoeManuele View Post
I did remove the catalytic converter and redid the exhaust making it a true dual exhaust which definitely helped. I've rebuilt the carb as well but would still love to increase the hp a bit more.
so timing and headers will help.

but really to really increase the HP in a significant way it’s gonna take a change of flow to the engine. Ie change the heads.

fotunately the L-82 has flat top pistons and forged bottom end components so it can take a decent bit of HP increase as is.

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Old 09-04-2018, 03:06 PM
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I'm not understanding your train of thought.
Everything can be compatible with that your TH350. You can shove over 400 horse through it easily. Rear axle ratio is fine.
And putting in another engine is sure not going to be cheaper than your $1500 upgrade budget.


So you are good-to-go on the exhaust situation if you install headers. Sinking any money into those old heads is just not money well spent. Because the spending never stops there. Then someone wants to do a valve job, then new springs, retainers, seals, valve guides, and on & on & on. They are still big chamber, low flow, limited valve lift, heavy iron heads.

Last edited by HeadsU.P.; 09-04-2018 at 03:08 PM.
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Old 09-04-2018, 03:37 PM
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Start with an L-82....You need to install 64cc chamber aftermarket heads and thin head gaskets gaskets to get 10.4 compression ratio. Change carb jets and re-curve the existing distributor. No cat and free flowing exhaust already....you just built an old school 1969 L-46 350/350 engine....and you are still in budget. No cam swap required because it is already in there.

Its a great Corvette engine. My 1980 L-82 has been modified with this exact recipe and I have no plans to change it.
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Old 09-04-2018, 04:59 PM
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+1 On what everyone else said.

1. Long tube headers
2. Tune what you have- needed after the headers anyway (ignition timing & carb)
3. If you have the money left: Get a more modern grind flat tappet cam like the Lunati Voodoo 256/262 or 262/268 & new timing chain set (you might need new springs for the heads, too to control the steeper ramped cam lobes)
4. Start planning for buying new heads with the next round of cash infusion (or just get a higher stall torque converter so the car FEELS more powerful and fun- TH350 TC's are cheap)

You do #'s 1-3 and you should get better fuel economy, too. -Sell it to your wife/S.O. that way "I love driving the Corvette, but I need to make some changes to improve the fuel economy" (Long tube headers +torque +mpg; more ignition timing down low +torque +mpg; faster ramp cam = higher dynamic compression ratio +torque +mpg.)

Adam

Last edited by NewbVetteGuy; 09-04-2018 at 05:05 PM.
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Old 09-04-2018, 06:07 PM
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Start with an L-82....You need to install 64cc chamber aftermarket heads and thin head gaskets gaskets to get 10.4 compression ratio. Change carb jets and re-curve the existing distributor. No cat and free flowing exhaust already....you just built an old school 1969 L-46 350/350 engine....and you are still in budget. No cam swap required because it is already in there.

Its a great Corvette engine. My 1980 L-82 has been modified with this exact recipe and I have no plans to change it.
AND

.1. Long tube headers
2. Tune what you have- needed after the headers anyway (ignition timing & carb)
3. If you have the money left: Get a more modern grind flat tappet cam like the Lunati Voodoo 256/262 or 262/268 & new timing chain set (you might need new springs for the heads, too to control the steeper ramped cam lobes)
You can easily go from the stock 220 NET HP to 300 Net HP with the L-82 potential as it is now. How do i know?

My totally stock L-82 4 speed with no emissions, 2.5 inch duals, and Shorty (NOT LTH Headers) headers with a Holley 4175 650 CFM vacuum secondary Qjet replacement carb along with performance timing 1.52 roller tipped rockers, and a 180 operating engine temp did 233 RWHP with a weak compression #6 cylinder. 233 RHWP is about 275 Net HP. Karol on the forum with his L-82 4 speed with just true duals and no emissions with stock cast iron manifolds did 248 RWHP on the same dyno as my L-82 with weak compression. 248 RWHP is about 292 Net HP, NOT Gross HP like the Lt1/L46's

As others have noted even mediocre cylinder heads and a slightly more modern performance flat tappet cam will easily get you to 325-330 Net HP which is substantially more Net HP than an L46 350/350 Gross HP or even the 330 Gross HP LT-1's. Good heads with a compression bump with a .015 head gasket along would get you to about 10.2:1 compression and an easy 375 Net HP. The L-82 is the last of the great Gen 1 SBC from GM....

Last edited by jb78L-82; 09-04-2018 at 06:16 PM.
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Old 06-10-2019, 09:26 PM
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Default change heads

sounds like a dam broken record change heads change the heads
ever hear of building something other than just be a part changer
pp head do real good little work low dur cam port and undercut stems on valves bump compression a little shim gasket cut head s nice daily drive
buy more heads more heads dam
DAM BROKEN RECORD LONE HIM
2 GRAND JUST TO START BUY MORE HEADS THIS GUY
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Old 06-10-2019, 10:28 PM
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7t9l82
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300 horsepower? Give it a performance tune up. The national hot rod association, you know the guys the sanction drag races nationwide said the L-82 factored out at 312 h.p. but all the suggestions are worthwhile.changing the cam is the last thing I would do.
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Old 06-10-2019, 10:43 PM
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Originally Posted by joey bunker View Post
sounds like a dam broken record change heads change the heads
ever hear of building something other than just be a part changer
pp head do real good little work low dur cam port and undercut stems on valves bump compression a little shim gasket cut head s nice daily drive
buy more heads more heads dam
DAM BROKEN RECORD LONE HIM
2 GRAND JUST TO START BUY MORE HEADS THIS GUY
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