wonl2

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

gjohnson

Retire the L48. Check out Blue Print Engines. Getting ready to order mine # BP3503CT1

titanle

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.

ratflinger

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.

jackson

what is your budget?

OE L48 has dished pistons

cv67

ID be tempted to toss in a BP 400...maybe even sneak a B and M blower on it. Talk about endless tq..

terrys6t8roadster

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

Jebbysan

This is a good point.....unless that engine is pristine, it could cause piston blow by. Stock L-48 had crap cast iron rings that are eggshell brittle........
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

DAD111

You will never get 350+ HP out of that motor unless you redo the bottom end too. Maybe 2 turbo chargers or nitrous shot with the top end work you will get close.

jb78L-82

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......

jackson

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.

DAD111

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.

Jebbysan

Heads, cam, intake and carb.....it would make 400 very easily, even with crap dished pistons.....just use a 64cc head for 9.2 to 1.
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

jb78L-82

What I said was that a non-emissions L-82 made 310 Gross HP...Here is the source if you doubt it:

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.

resdoggie

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.

F22

Voodoo Hydraulic Flat Tappet Cam - Chevrolet Small Block 262/268

cv67

GM Hotcam kit is less than $500 I bet and will wake things up. Add a set of nice 180cc heads should be a good reliable runner wiht manners. May even crack a 13

F22

DAD111

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.

cv67

x2 350hp perhaps but 400 wont be made with low compression, a 200-215cfm cfm head , baby cam and headers no way