When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello Corvette Family, I have a 79 L-48 stock numbers matching car the only thing that was charged was the intake to an Edelbrock by the first owner. I would like to keep the original motor and Rochester quadrajet Carburetor to remain original, but upgrade it to about 330hp. cam, valves, springs, guides push rods and rockers ect I already upgraded the timing chain to a double roller. I would like to start buying parts and putting them away until I have it all the problem is I don't know what to buy, what cam, what rockers and push rods to combo with the cam to achieve my goal. I am going to purchase the SUM-G-9003 headers and true duals from Corvette Central but after that I'm lost please help guide me in the right direction.
Thanks in advance
Aaron
I have updated to an electric choke after this photo
It's going to be hard to get 330 hp out of that L48 with bolt ons, but you're going in the right direction. I had a '75 L48. Replaced the cam with a "mild" upgrade, added headers and exhaust, put a 650 Holley and aluminum manifold. I also played with advance.
I have know idea what the final HP was, but it felt and sounded great to me. Fun little motor.
I'm not sure I'd spend the money to replace the valve train without pulling the heads for valve job and maybe a shave.
Keep us posted
Summit headers PN-SUM-G-9003 are probably the worst headers you could buy. They are painted and Summit even says the paint is just there for looks as it will burn off. I guess you could have these coated, but in reality you should buy quality coated headers to begin with.
I'd toss the heads too & swap on some chinesium ones off of ebay (don't buy their valves or rockers though). Then your cam will be able to perform. Lars can rebuild your Q-jet and have it easily perform at that level.
Not trying to sound like a jerk, but I also have a '79 L48. Ripped that engine out and sold it to someone that just had to have a 'Corvette' engine. Built a SB396 as a replacement & never looked back.
The 79 L48 has dished pistons, For low compression. along with really crappy heads with large combustion chambers. For extra low compression.
If you're looking for over 300 HP., I would lose those pistons for some flat tops. And get some decent heads. then we can talk about cams.
The 79 L48 has dished pistons, For low compression. along with really crappy heads with large combustion chambers. For extra low compression.
If you're looking for over 300 HP., I would lose those pistons for some flat tops. And get some decent heads. then we can talk about cams.
Thats a full rebuild and a massive can ov worms. Thousands. You can bump that compression almost as high as you like, with a plethora ov aftermaket aluminum heads available for good prices (even after your head guy checks them out). I've seen them as little as 59cc chambers... which would certainly add some squeeze to that old truck engine. Lots in the 64cc range. Get a matching cam, a good intake, and some GOOD exhaust, and that 330HP goal will be a joke...
I respectfully disagree Mr. Roadster. with those dished pistons, stock undecked block, 64 cc chambers and shim type gaskets you will be pushing **** uphill to get it to 9-1. And at that compression ratio your not going to run a very aggressive cam.
Old Man in a c, I read that the Rochester quadrajet is 750 cfm so I thought why change it.
Ratflinger, SUM-G-9003 headers I did read that the paint burns off I thought I'd have them sand blasted and coated but after that I probably would be at the price of already coated headers so your right.
4-vettes and Pale Roader thanks you all for your input.
we all know the 79 L-48 is slower than a wounded turtle I just wanted to keep it a numbers matching car, upgrading to that degree all i see is dollar signs maybe around $4-$5k when I'm done. but it makes more sense to me to just buy a new deluxe create engine for just over $5k. Do you agree?
Problem with the L-48 and engine upgrades is ultimately the pistons. They are dish 4 valve relief tops. So no squish band. That is going to limit the CR you are able to achieve. The limited CR is limiting for your cam selection.
you can bolt on new heads with small chambers and improve flow due to new tech on aluminum heads, but if the cylinder pressure gets to high you’re flirting with detonation all the time due to lack of quench.
The L-48 is the same as the Goodwrench 350 replacement engine. If you Google "The Goodwrench Quest" you'll find a series of articles on how it was modified at different steps. I also agree with others and get ceramic coated headers just for longevity of the under hood components.
Fly skids up and Eddnflow this new engine seems to be the way to go instead of an engine rebuild I just have to make the right engine choice.
Eddnflow, engine #1 or #2 would you recommend using the Edelbrock intake and Rochester quadrajet carb etc. I already have to complete the engine.
Aaron
Your intake won't fit on any those engines. The first one is not drilled for a fuel pump push rod and probably the camshaft doesn't have a lobe for it nether.
Thanks 4 the link Ratflinger you guy's are giving me options I didn't know I had, at this point I have narrowed it down to a deluxe create engine but still haven't chosen one. I need to make sure it fits the engine bay with heads so I have to do some homework you guy's are AMAZING.
Your intake won't fit on any those engines. The first one is not drilled for a fuel pump push rod and probably the camshaft doesn't have a lobe for it nether.
Correct on count one; all Vortec (aka L31) heads require Vortec intake.
Incorrect on count two; there's been a change at GM in that all New replacement L31 motors are now built in USA (eg first one) and now have a completely finished fuel pump mount including finished hole for fuel pump push rod.
Correct on count three; first one's roller cam does not have eccentric aka lobe for mechanical fuel pump. Go electric pump or R&R cam. For < $250 will get one of these four USA-made billet steel roller cams: https://www.summitracing.com/search/...rder=Ascending
OP 413C379
Nowadays, virtually all crate motors have a one-piece rear main seal (GM changed from two-piece to one-piece '86-'87); their flexplates & flywheels have different bolt patterns and are not interchangeable. You'll need a New flexplate but your TH350 trans will fit-work the same as now. New flexplate can be had for < $40. All three GM crates I suggested above have Forged Steel crankshafts and are the newer One-piece RMS design which have a smaller bolt circle than your Two-piece RMS motor has.
Be advised. All the above GM crates are completely brand new top to bottom. And have the best warranty in the business with No Restriction on where you Must file any claim (sue) if you can't resolve a warranty issue.
Be advised. Crates from either ATK (aka Vege) and BPE have a warranty which Restricts user to file (sue) in Company's State of choice; ATK/Vege = Illinois while BPE = Nebraska. Suggest read the fine print and/or consult Your counselor Before writing the check; because, sadly, sometimes stuff happens.
The BPE motor referenced above has a New block but many (if not most) BPE crates use a remanufactured block which has been bored out to (or beyond) blocks' intended/practical limit.
ATK/Vege crates are similar; some have new blocks while some use a remanufactured block which has been bored out to (or beyond) blocks' intended/practical limit.
Cast Steel is Not Forged Steel. Cast is Cast. Forged is Forged; and is more robust than Cast.
FWIW, GM sells a True 383" with standard 4 inch bore & 3.800" stroke forged crank. The above BPE 383 is in reality a 377" with standard 4 inch bore and 3.750" stroke cast crank.
In a moment of levity, I ask & answer; does six inches really matter? Ask her.
79 L-48 engine upgrades
