My First post! GM Performance Cam 3863151 Question.
Thread Starter
3rd Gear
Joined: Oct 2019
Posts: 3
Likes: 1
From: New Brunswick, Canada
My First post! GM Performance Cam 3863151 Question.
Hey Guys,
I just picked up a 76 L48, Auto. The guy i bought it from had the engine rebuilt 5 years ago. According to him its a stock freshen up. I just got a great deal on a "New in Box GM performance, Cam Lifter kit part # 12364050" its 15 years old but never taken out of the box. According to the cam card it has the same duration and lift as a GM 3863151. I have a set of summit 1.6 roller rockers from another project id like to put on. According to my calculations that will bring it from .447 lift to .477 is that exceptable for new stock valve springs?
I just picked up a 76 L48, Auto. The guy i bought it from had the engine rebuilt 5 years ago. According to him its a stock freshen up. I just got a great deal on a "New in Box GM performance, Cam Lifter kit part # 12364050" its 15 years old but never taken out of the box. According to the cam card it has the same duration and lift as a GM 3863151. I have a set of summit 1.6 roller rockers from another project id like to put on. According to my calculations that will bring it from .447 lift to .477 is that exceptable for new stock valve springs?
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
No.
Buy a set of "Z28" 1.250 springs from Elgin on E-bay or other sites......much better spring overall to handle .480 lift and they are a drop in......in fact.....get the whole spring, lock, retainer kit and some umbrella seals......
https://www.ebay.com/itm/Elgin-Z28-S...oAAOSwAGhdoOAX
The other issue is that with stock GM heads....it is a crap shoot if the 1.6 rockers do not move the pushrods in so far as to rub on the head.....you HAVE to check this....some do, some do not.
The car in my Avatar was my 66' L-79 Vette......it had a .447 lift stock L-79 cam in it with 1.6 rockers but it had guideplates......it ran VERY well for a 331 inch engine through manifolds......
Jebby
Buy a set of "Z28" 1.250 springs from Elgin on E-bay or other sites......much better spring overall to handle .480 lift and they are a drop in......in fact.....get the whole spring, lock, retainer kit and some umbrella seals......
https://www.ebay.com/itm/Elgin-Z28-S...oAAOSwAGhdoOAX
The other issue is that with stock GM heads....it is a crap shoot if the 1.6 rockers do not move the pushrods in so far as to rub on the head.....you HAVE to check this....some do, some do not.
The car in my Avatar was my 66' L-79 Vette......it had a .447 lift stock L-79 cam in it with 1.6 rockers but it had guideplates......it ran VERY well for a 331 inch engine through manifolds......
Jebby
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
Not sure if your 350 still has the stock low compression pistons but if they are then you are probably at 8.0 c r. I had a 76 L82 Auto with a 3.36 rear and it was a little doggy off the line. I later went with a Isky 264 Mega cam with 216 216@ 050 .450 .450 lift 108 lsa and it made a huge difference in low and mid range compared to the L82 cam. If you had a 4 speed you could get by with the L79 cam. If you find the L79 is doggy for you then maybe a 3.73 gear would help.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
First of all you need to understand that NONE of those old GM cams are performance enhancement. NONE, ZERO compared to modern lobes and springs.
Also the expense of installing a cam with minimal lift and duration changes without other engine enhancements will result in minimal gains
You also stated that it was some sort of newer version rebuilt engine. Your score on the GM cam could feasibly be a step backwards
50 year old GM stuff is really just junky. Even my new 79 l82 was not a performance car
Also the expense of installing a cam with minimal lift and duration changes without other engine enhancements will result in minimal gains
You also stated that it was some sort of newer version rebuilt engine. Your score on the GM cam could feasibly be a step backwards
50 year old GM stuff is really just junky. Even my new 79 l82 was not a performance car
Last edited by gkull; Dec 6, 2019 at 12:21 PM.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
x2 use a better cam. Some are in love with that old stuff its not worth the labor. Absolutely dont use old/stock springs when changing cams.
Even an old tech Isky 270 which is close in spec will outperform the GM all day.
Even an old tech Isky 270 which is close in spec will outperform the GM all day.
Last edited by cv67; Dec 6, 2019 at 12:42 PM.
Thread Starter
3rd Gear
Joined: Oct 2019
Posts: 3
Likes: 1
From: New Brunswick, Canada
First of all you need to understand that NONE of those old GM cams are performance enhancement. NONE, ZERO compared to modern lobes and springs.
Also the expense of installing a cam with minimal lift and duration changes without other engine enhancements will result in minimal gains
You also stated that it was some sort of newer crate engine. Your score on the GM cam could feasibly be a step backwards
50 year old GM stuff is really just junky. Even my new 79 l82 was not a performance car
Also the expense of installing a cam with minimal lift and duration changes without other engine enhancements will result in minimal gains
You also stated that it was some sort of newer crate engine. Your score on the GM cam could feasibly be a step backwards
50 year old GM stuff is really just junky. Even my new 79 l82 was not a performance car
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Hey Guys,
I just picked up a 76 L48, Auto. The guy i bought it from had the engine rebuilt 5 years ago. According to him its a stock freshen up. I just got a great deal on a "New in Box GM performance, Cam Lifter kit part # 12364050" its 15 years old but never taken out of the box. According to the cam card it has the same duration and lift as a GM 3863151. I have a set of summit 1.6 roller rockers from another project id like to put on. According to my calculations that will bring it from .447 lift to .477 is that exceptable for new stock valve springs?
I just picked up a 76 L48, Auto. The guy i bought it from had the engine rebuilt 5 years ago. According to him its a stock freshen up. I just got a great deal on a "New in Box GM performance, Cam Lifter kit part # 12364050" its 15 years old but never taken out of the box. According to the cam card it has the same duration and lift as a GM 3863151. I have a set of summit 1.6 roller rockers from another project id like to put on. According to my calculations that will bring it from .447 lift to .477 is that exceptable for new stock valve springs?
Summit has more than a dozen house brand HFT sbc cams ... all under $100 ... several would be better than 151 for a 350 w/auto.
As others said, install new springs with new cam; as said Z28 springs are good for most HFT up to about .480" lift.
Suggest first pay attention to assuring both carb & ignition are properly set up, optimized & tuned. If admissible in your locale, true dual exhausts will help a lot.
-addendum-
Remember, a '76 L48 has relatively LOW compression ... if it was just a "freshen up" it still has Low compression; remember that going forward w/ hi-po plans.
Last edited by jackson; Dec 6, 2019 at 03:54 PM.
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,502
From: Little Rock AR
The problem you have is lack of static compression. The stock 76 L48 engine is a typical smog era type with low compression from the factory. The "151" cam requires more static compression to work right. If you put that "151" cam in a low compression engine you will end up with a soggy bottom end and no real performance increase. Swap the heads for something with smaller combustion chambers would increase compression. That would help make that cam work better but it might not be in your budget at this time. I actually do like that cam and its younger brother the 350/350 cam if the rest of the engine is built right for it.
In my opinion - The right way to move forward is to run the Comp 268H cam. It was originally designed specifically to work in your stock smog era L48 and give you a performance increase while still working well without a lot of additional mods and expense. You can do additional mods to add to it later as your time and money allow.
In my opinion - The right way to move forward is to run the Comp 268H cam. It was originally designed specifically to work in your stock smog era L48 and give you a performance increase while still working well without a lot of additional mods and expense. You can do additional mods to add to it later as your time and money allow.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
The problem you have is lack of static compression. The stock 76 L48 engine is a typical smog era type with low compression from the factory. The "151" cam requires more static compression to work right. If you put that "151" cam in a low compression engine you will end up with a soggy bottom end and no real performance increase. Swap the heads for something with smaller combustion chambers would increase compression. That would help make that cam work better but it might not be in your budget at this time. I actually do like that cam and its younger brother the 350/350 cam if the rest of the engine is built right for it.
In my opinion - The right way to move forward is to run the Comp 268H cam. It was originally designed specifically to work in your stock smog era L48 and give you a performance increase while still working well without a lot of additional mods and expense. You can do additional mods to add to it later as your time and money allow.
In my opinion - The right way to move forward is to run the Comp 268H cam. It was originally designed specifically to work in your stock smog era L48 and give you a performance increase while still working well without a lot of additional mods and expense. You can do additional mods to add to it later as your time and money allow.
Jebby