Top end upgrade vs crate engine
Thread Starter
Intermediate
Joined: Dec 2013
Posts: 30
Likes: 1
From: Greenville, SC
Top end upgrade vs crate engine
Greetings, I have a survivor L48 79 with just over 60,000 miles. I want to get more horsepower for my ride. I was looking at crate engines but I'm worried about receiving an inferior engine. I was also looking at upgrading the top end with new heads, intake and cam. My goal is a 350+ hp engine. Any thoughts and/or opinions on which direction to go? Any comments greatly appreciated. Thanks
Phil
Phil
Burning Brakes
Joined: Jul 2013
Posts: 963
Likes: 57
From: Vancouver, BC
I ended up having the top end rebuilt on the 350 that's in my 68. Its not the factory correct motor, when it was taken apart it appeared to be an early 70s truck motor. So we built on that, new aluminum heads, cam, intake, carb and torque stall converter. Our goal was to achieve 400-425hp at the crank.
NCM Grand Opening Veteran
Joined: Sep 2005
Posts: 20,979
Likes: 384
From: South of giving a damn
St. Jude Donor '11, '17
At only 60k miles that block should be in reasonable shape. I'd jerk the engine, take it apart and decide then. I don't know if the L48 were dished or flat, my 79 had a replacement engine when I got it. There may not even be much cylinder wear, might get by with a quick hone to tidy up. Since you are looking for modest hp, if the pistons are flat topped & the bores are good, and none of the bearings show signs of damage then: hone the cylinders, install new bearings & seals, new oil pump, choose cam, heads, intake, carb, ignition to achieve your goal and put it back together. This gives you lots of experience in how things go together and work. If this is intimidating, that's okay - go the replacement engine route. If you go with a reputable source then the chances of getting a bad engine are low. Because of economy of scale, you might get an engine package cheaper than doing it yourself.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Greetings, I have a survivor L48 79 with just over 60,000 miles. I want to get more horsepower for my ride. I was looking at crate engines but I'm worried about receiving an inferior engine. I was also looking at upgrading the top end with new heads, intake and cam. My goal is a 350+ hp engine. Any thoughts and/or opinions on which direction to go? Any comments greatly appreciated. Thanks
Phil
Phil
At only 60k miles that block should be in reasonable shape. I'd jerk the engine, take it apart and decide then. I don't know if the L48 were dished or flat, my 79 had a replacement engine when I got it. There may not even be much cylinder wear, might get by with a quick hone to tidy up. Since you are looking for modest hp, if the pistons are flat topped & the bores are good, and none of the bearings show signs of damage then: hone the cylinders, install new bearings & seals, new oil pump, choose cam, heads, intake, carb, ignition to achieve your goal and put it back together. This gives you lots of experience in how things go together and work. If this is intimidating, that's okay - go the replacement engine route. If you go with a reputable source then the chances of getting a bad engine are low. Because of economy of scale, you might get an engine package cheaper than doing it yourself.
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
Original SBC from the 60s and the 70s have a usefull life span of about 90k to 100k depending on maintenance. Yes there are some that get a lot more mileage out of them So your engine is approximately 2/3 worn out. By replacing cam and heads you will increase your compression causing some compression to push past your rings causing blow-by. Note to all who want to argue: this doesn't happen to all engines. Just wanted to advise OP that this could happen. Remember that this engine is in a Corvette and previous owners might of driven it like a Corvette should be driven and that does take a toll on engine longevity. T
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Original SBC from the 60s and the 70s have a usefull life span of about 90k to 100k depending on maintenance. Yes there are some that get a lot more mileage out of them So your engine is approximately 2/3 worn out. By replacing cam and heads you will increase your compression causing some compression to push past your rings causing blow-by. Note to all who want to argue: this doesn't happen to all engines. Just wanted to advise OP that this could happen. Remember that this engine is in a Corvette and previous owners might of driven it like a Corvette should be driven and that does take a toll on engine longevity. T
I have done it though......put a whole top end on a pathetic 350 truck engine (That had .050 in the hole stock pistons in it) and ran Dart 180's, Comp 292h Magnum, and a tunnel ram (yes, tunnel ram) with two Holley 450's through a 350 turbo with 3000 stall in a 3300lb. 37' Ford Business coupe.....damn thing would make you giggle......but I even told the owner that about ten hard 1/4 mile passes and this engine is done.
Jebby
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
Le Mans Master
Joined: Oct 2007
Posts: 7,454
Likes: 977
From: RI, Now Franklin/Nashville TN
9:1 pistons, decent flat tappet cam/moderate roller cam, aftermarket 64 CC iron heads (10:1 compression)...easy <400 gross HP with a cast crank L-48 rods......Heck a bone stock non emissions stock L-82 made 310 Gross HP back in the 70's......
Last edited by jb78L-82; Jan 16, 2019 at 12:44 PM.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
https://www.ebay.com/itm/GM-OEM-NEW-...nA85:rk:6:pf:0
Summit-Jegs get over $2K for same motor
Again, I checked to update price on above crate last night ...and did a "what if" at checkout...advertised price $1746...checkout showed $100 discount....so $1646...then the dealer gives $50 spend anywhere giftcard ...so delivered price is $1596. For a Brand New L31 Vortec head roller cam 4 bolt main 350ci motor. $1596 NEW
Take that … pay a local machine shop $100 to finish the fuel pump mount pad... spend another $500 on valve springs & bigger cam...For under $2500 you'll have an all new motor easily making 350-400 hp at crank.
BTW, BluePrint 350, 383, 396 motors have used blocks that're already bored +0.040" over … look it up it's on BP website.
Summit-Jegs get over $2K for same motor
Again, I checked to update price on above crate last night ...and did a "what if" at checkout...advertised price $1746...checkout showed $100 discount....so $1646...then the dealer gives $50 spend anywhere giftcard ...so delivered price is $1596. For a Brand New L31 Vortec head roller cam 4 bolt main 350ci motor. $1596 NEW
Take that … pay a local machine shop $100 to finish the fuel pump mount pad... spend another $500 on valve springs & bigger cam...For under $2500 you'll have an all new motor easily making 350-400 hp at crank.
BTW, BluePrint 350, 383, 396 motors have used blocks that're already bored +0.040" over … look it up it's on BP website.
Racer
Joined: Aug 2018
Posts: 252
Likes: 48
From: Cincinnati, Ohio
I disagree on that 310 hp. In 79 that motor L-48 only produced 190 HP. with all the smog crap and small valves 8:5 to 1 compression.. With it being a stock bore and crank with dished pistons he could get 300 +, But not 400 gross HP.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
The 79' L-48 is a bad engine to compare as the cam barely lifted the valves off the seats.
The 350/200 that came in my Vette would make an easy 275 hp with a pair of headers on the dyno at 8.5 to 1 compression......this is on par with the GM Goodwrench crate engine with a Q-jet setup......
The only thing in an L-48 that stinks is the no-quench pistons....but if the timing curve is right....no issues there either.......you may lose 15 horsepower with crappy quench...or about 2 horsepower per cylinder.
A Goodwrench crate engine with Dart 180 heads, Air Gap, and a Comp 280H Magnum cam would make 400 horsepower no problem......all day.
Jebby
Le Mans Master
Joined: Oct 2007
Posts: 7,454
Likes: 977
From: RI, Now Franklin/Nashville TN
Super chevy magazine as well:
"Loyal readers will remember that the low-compression L82 was equipped with 882 heads, L46 hydraulic cam (0.450/0.460 lift, 222 duration) and an induction system consisting of a cast-iron intake and Q-Jet carb. The Q-Jet was actually less of a hindrance than you might suspect as the 750 cfm rating was more than adequate for the needs of the 250hp L82. In stock trim on our dyno, the 9.0:1 L82 produced 313 flywheel (gross) horsepower at 5,500 rpm and 355 lb-ft of torque at 3,800 rpm. The engine produced adequate torque relative to the horsepower rating, but it wasn't exactly what you'd describe as earth-shattering."
All horsepower discussed is GROSS NOT Net (much more real word), including carte motors which are almost all, GROSS HP, NOT Net. There is a big difference in the outputs..despite most who want to deny this variation as not significant.
Last edited by jb78L-82; Jan 16, 2019 at 02:17 PM.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
A 100K on a 70's sbc? If pampered, maybe. I got 65K out of my L-82 which has all the good internals. Anyway, I would put that L-48 in a bag if it's number's matching. Otherwise, toss and get a crate.
Le Mans Master
Joined: Oct 2006
Posts: 6,842
Likes: 285
From: Palmdale CA
Voodoo Hydraulic Flat Tappet Cam - Chevrolet Small Block 262/268
Product Description
Lunati's Voodoo series of Hydraulic camshafts deliver more area under the curve than any other series of Hydraulic camshafts. This means more throttle response, quicker acceleration, more vacuum, better efficiency, combined with maximum horsepower and torque! Hydraulic Flat Tappet. Mid-level performance street cam with excellent drivability. Exceptional replacement for muscle car type cams with automatic transmissions. Works well with stock type exhaust manifolds and dual plane intake with mild 4 bbl carb. This is an Awesome 4X4 and performance marine cam.- Advertised Duration (Int/Exh): 262/268
- Duration @ .050 (Int/Exh): 219/227
- Gross Valve Lift (Int/Exh): .468/.489
- LSA/ICL: 112/108
- Valve Lash (Int/Exh): Hyd/Hyd
- RPM Range: 1400-5800
- Includes: Cam Only
Part Number: 10120702
Last edited by F22; Jan 16, 2019 at 02:42 PM.
Le Mans Master
Joined: Oct 2006
Posts: 6,842
Likes: 285
From: Palmdale CA
The L98 heads, because they have small 58cc combustion chambers, work really well with a stock, dished piston L48. Add the cam, an Edelbrock Performer (regular, not the RPM), headers and a Holley 650 Carb and you will be good to go, without touching the bottom end. Don't forget new lifters, if you get a new cam. My L48 motor, really woke up, with this combo. It was plenty fast, pulled hard all the way through the 1/4 mile at the drag strip (low 14's) and had 175-180 pounds of compression on the cylinders. I picked an RV-Marine-4x4 cam, because for a mild build, torque is more important than absolute horsepower, especially at the bottom end of the RPM range, where you want it to kick you in the butt when it takes off.
Racer
Joined: Aug 2018
Posts: 252
Likes: 48
From: Cincinnati, Ohio
This is what im getting at is – People get disappointed when they dyno their car and it dynos at 320 HP when people are telling them that you should be 400+ HP with that motor because it’s what he said. Gross vs RWHP is a lot different. I’ll leave it at that
If you want it to run better and cannot pull the motor – Then do as they are telling you . 60,000 miles aint bad – people do it all the time with no issues. Gotta remember it’s a small block Chevy, one of the best proven motors of all time. That thing would run on paint fumes if it had too.
If you want it to run better and cannot pull the motor – Then do as they are telling you . 60,000 miles aint bad – people do it all the time with no issues. Gotta remember it’s a small block Chevy, one of the best proven motors of all time. That thing would run on paint fumes if it had too.