1980 L48 upgrade
Thread Starter
Racer
Joined: Nov 2020
Posts: 265
Likes: 76
1980 L48 upgrade
Hello All,
I have a 1980 all stock with an L48 that runs really well. I'd like a little more pop from the motor so I'm considering either upgrading to Aluminum heads, intake manifold and headers or going to whole new crate engine. Question is: If I'm looking for 40-50Hp increase can I get that with the new heads and manifold? Considering that the engine I currently have runs so well not sure I want to invest $3k on crate engine if I can get some more HP out of this motor with the upgrades.
I appreciate the advice.
I have a 1980 all stock with an L48 that runs really well. I'd like a little more pop from the motor so I'm considering either upgrading to Aluminum heads, intake manifold and headers or going to whole new crate engine. Question is: If I'm looking for 40-50Hp increase can I get that with the new heads and manifold? Considering that the engine I currently have runs so well not sure I want to invest $3k on crate engine if I can get some more HP out of this motor with the upgrades.
I appreciate the advice.
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
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Cruise-In VIII Veteran
Headers and a good true duels exhaust, performer intake and decent 64 cc 180 runner heads with correct recurving of your distributor should get you in the ball park of 100 HP. IMHO.
Race Director
Joined: May 2000
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Headers won't really improve performance of an engine like L-48 with a low overlap cam, but the biggest problem you have is the exhaust systems It's very restrictive. Dave McClellan in his book stated that the single catalyst exhaust increased back pressure "half and atmosphere". That's over 7 psi and you add that to the modest 3 psi of the pre catalyst system.
So most of what you gain from better flowing heads, bigger camshaft, etc. is going to be eaten up by additonal exhaust pumping loss. A modern monolithic converter offers less restriction, but it rally needs two,
Duke
So most of what you gain from better flowing heads, bigger camshaft, etc. is going to be eaten up by additonal exhaust pumping loss. A modern monolithic converter offers less restriction, but it rally needs two,
Duke
Le Mans Master
Joined: May 2007
Posts: 5,018
Likes: 1,118
From: North tonawanda NY
to get 50hp increase you can get a set of 64cc heads, these will boost your compression ratio and help make more power with your dished pistons. Add a better flowing exhaust manifolds or headers and a better flowing exhaust, with a mild 262 or 268 cam. (might as well do this if you still have the plastic stock timing chain setup timebomb in your engine) you can replace the intake for an additional possible 10-15hp or so.. from the dyno testing I recently seen done you can gain between 20-30hp by just converting to electric raditaor fans vs the stock fan and clutch system our cars came with. This should net you a minimum of at least 50hp possibly much more depending on actual components chosen.
Last edited by augiedoggy; Apr 10, 2021 at 12:22 PM.
Le Mans Master
Joined: Jun 2019
Posts: 7,649
Likes: 2,466
From: Indiana
I would ....
invest in 2.5 inch dual exhaust drop cats if you can..this modification will be needed whether you go crate, headers , heads etc..i would keep manifolds for now and remove the heat flapper valve.
time the engine 36 total and re curve the distributor....
consider rehabbing carb and tuned..
look up Lars timing papers and carb advice for last 2.
then assess how it feels and go from there with minimal wallet damage or waste.
other options i like
180f thermostat
cap egr
i bet you will be where you need to be
invest in 2.5 inch dual exhaust drop cats if you can..this modification will be needed whether you go crate, headers , heads etc..i would keep manifolds for now and remove the heat flapper valve.
time the engine 36 total and re curve the distributor....
consider rehabbing carb and tuned..
look up Lars timing papers and carb advice for last 2.
then assess how it feels and go from there with minimal wallet damage or waste.
other options i like
180f thermostat
cap egr
i bet you will be where you need to be
Thread Starter
Racer
Joined: Nov 2020
Posts: 265
Likes: 76
I would ....
invest in 2.5 inch dual exhaust drop cats if you can..this modification will be needed whether you go crate, headers , heads etc..i would keep manifolds for now and remove the heat flapper valve.
time the engine 36 total and re curve the distributor....
consider rehabbing carb and tuned..
look up Lars timing papers and carb advice for last 2.
then assess how it feels and go from there with minimal wallet damage or waste.
other options i like
180f thermostat
cap egr
i bet you will be where you need to be
invest in 2.5 inch dual exhaust drop cats if you can..this modification will be needed whether you go crate, headers , heads etc..i would keep manifolds for now and remove the heat flapper valve.
time the engine 36 total and re curve the distributor....
consider rehabbing carb and tuned..
look up Lars timing papers and carb advice for last 2.
then assess how it feels and go from there with minimal wallet damage or waste.
other options i like
180f thermostat
cap egr
i bet you will be where you need to be
Thanks
Thread Starter
Racer
Joined: Nov 2020
Posts: 265
Likes: 76
Thanks for the replies. I did get rid of the cats and went to dual exhaust a couple of months ago and it did make a difference. As suggested I'm also planning on adding headers as well since thats a good upgrade no matter what i'm doing with the motor. I went to lars site and will replace the springs to see what kind of difference that makes but based on responses and the fact that I'm not looking to get 400+HP I'm just looking to add some pop maybe 300HP range to make the afternoon drive with the wife more enjoyable I think I'll look at heads, manifold and possibly cam. The cam would require pulling out the engine so would you guys say that it's worth the trouble based on how much the cam change will impact performance?
Also I live in Miami and drive to the keys every weekend and going down the highway at 75mph @3000rpm is not optimum. Any recommendation on an auto OD 5 or 6 speed transmission? I've seen some nice drop in options online but very expensive. I don't know if anyone has recommendation that may have worked for them that isn't as costly. Maybe from another newer Chevy that would work?
Thanks agaon.
Also I live in Miami and drive to the keys every weekend and going down the highway at 75mph @3000rpm is not optimum. Any recommendation on an auto OD 5 or 6 speed transmission? I've seen some nice drop in options online but very expensive. I don't know if anyone has recommendation that may have worked for them that isn't as costly. Maybe from another newer Chevy that would work?
Thanks agaon.
Race Director
Joined: Nov 2006
Posts: 13,177
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
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Cruise-In VIII Veteran
Absolutely no need to pull the engine to swap out a cam. Not certain where you got the idea that the engine had to come out.
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Thread Starter
Racer
Joined: Nov 2020
Posts: 265
Likes: 76
Race Director
Joined: Nov 2006
Posts: 13,177
Likes: 7,781
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
You need to pull the Radiator, lossen and shift the air-con condenser forward a 1/4 inch. and out it comes.
With heads and headers, perhaps a performer intake. a nice cam will defiantly help. Lots of choices, recommendations will depend on which heads and intake you may choose. flat tappet hydrologic will be very cost effective, roller conversion more costly, but more power and less worries about the type of oil you run.
Make your decision on heads. then start a new thread asking about cams. which headers? which heads? what intake? low RPM Torque? High RPM Power? Flat tappet or roller? 300 HP is not at all hard to hit with good heads, A moderate streetable cam and a decent flowing intake with factory carb.
With heads and headers, perhaps a performer intake. a nice cam will defiantly help. Lots of choices, recommendations will depend on which heads and intake you may choose. flat tappet hydrologic will be very cost effective, roller conversion more costly, but more power and less worries about the type of oil you run.
Make your decision on heads. then start a new thread asking about cams. which headers? which heads? what intake? low RPM Torque? High RPM Power? Flat tappet or roller? 300 HP is not at all hard to hit with good heads, A moderate streetable cam and a decent flowing intake with factory carb.
Race Director
Joined: Mar 2017
Posts: 11,923
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From: Virginia
Start with headers, and the Lars-style ignition tune. My 80 L48 with side pipes is about a million times more fun to drive than my 79 L48 with true duals but stock exhaust logs. Both have the Lars tune, which helps, but the 4-speed in the 80 makes a huge difference.
Le Mans Master
Joined: Jun 2019
Posts: 7,649
Likes: 2,466
From: Indiana
Factory mine does 3400 rpm at 75...so no sympathy.. 😆 drive it...
you stated it runs great! Just more power..
i am no expert but would wait on headers until you decide heads, cam etc..and imo i would watch heat especially miami..
Other than that your other options get expensive...
i would suggest clarity for great advice others will give...
budget?
where why do you want the extra power?
Current transmission ?
other mods you have done? Said stock but cats and duals on..
other emissions? Thermostat temp?
AC?
Taking a great running car and an arbitrary # of horsepower may not get you where you want to be or over shoot it and lose the great running aspect you may like...
basically trying to meet the quality expectations, not exceed them unless $$$ no object..
Edit...also pictures of your ride!!!!! Engine etc...always cool
you stated it runs great! Just more power..
i am no expert but would wait on headers until you decide heads, cam etc..and imo i would watch heat especially miami..
Other than that your other options get expensive...
i would suggest clarity for great advice others will give...
budget?
where why do you want the extra power?
Current transmission ?
other mods you have done? Said stock but cats and duals on..
other emissions? Thermostat temp?
AC?
Taking a great running car and an arbitrary # of horsepower may not get you where you want to be or over shoot it and lose the great running aspect you may like...
basically trying to meet the quality expectations, not exceed them unless $$$ no object..
Edit...also pictures of your ride!!!!! Engine etc...always cool
Last edited by interpon; Apr 11, 2021 at 09:18 AM.
Race Director
Joined: Mar 2017
Posts: 11,923
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From: Virginia
As @interpon said, please let us know what you have (with pictures). My two cars have nearly identical engines, and have picked most of the low-hanging fruit for easy HP. The auto vs manual difference is huge. The biggest improvement I could make on my 79 auto would be a higher stall speed torque converter.
Here's a thread where a member did a head and cam swap without pulling the engine. Not that I'm suggesting that.
https://www.corvetteforum.com/forums/c3-general/4045083-my-79-hotrod-project-build-thread.html
Here's a thread where a member did a head and cam swap without pulling the engine. Not that I'm suggesting that.
https://www.corvetteforum.com/forums/c3-general/4045083-my-79-hotrod-project-build-thread.html
Last edited by Bikespace; Apr 11, 2021 at 07:42 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
Headers most absolutely do improve power and especially torque down low......
Leave the stock heads for now....go with a 2101 Performer, 262 Comp cam, long tube headers and a good distributor curve......you will see 75 horsepower right off the top......see if this is enough for you. Also use a 1204 Fel Pro gasket on the intake and convert to electric choke.
Do the heads later on.......that will pick up another 50-60.......
The stock heads will support about 330 horsepower.....that's 260 to the tire.....or about what a 93' Z/28 LT1 throws down......
Jebby
Leave the stock heads for now....go with a 2101 Performer, 262 Comp cam, long tube headers and a good distributor curve......you will see 75 horsepower right off the top......see if this is enough for you. Also use a 1204 Fel Pro gasket on the intake and convert to electric choke.
Do the heads later on.......that will pick up another 50-60.......
The stock heads will support about 330 horsepower.....that's 260 to the tire.....or about what a 93' Z/28 LT1 throws down......
Jebby
Safety Car
Joined: Nov 2008
Posts: 3,716
Likes: 551
From: Seattle Washington
Putting in a more modern Trans in be it automatic or manual with a lower 1st gear and a higher top gear will wake it up as well. With out doubt putting a 700r4 in my 1980 L48 back in 1985 or so was a big transformation. Probably the next biggest thing was replacing the 700r4 with a TKO 600.