1973 L48 engine rebuild
 

Hi everyone,

I just became the proud of owner of my first Corvette - a 1973 coupe with 79k and all the originals, born 4 years before I was :yesnod:

The L48 engine is in relatively decent shape, probably what's expected for the original after 79k miles. It puts out a hint of blue smoke every once in a while (mostly on warm restarts), and the 190 hp just won't do, so I've decided to give it a go at rebuilding the engine with a little more juice.

I've never done anything under a hood more sophisticated than attaching jumper cables (which scares me) so I want to keep this project modest. I have some pretty experienced helpers available, but I'm looking for opinions on how to proceed with the rebuild. It seems like there are tons of options.

I don't want to remove the engine block, and I would prefer not to mess with the exhaust system (it's new). So I was thinking of changing the cylinder heads and replacing some of the other components. Does anyone have ideas about some relatively basic modifications that could keep the engine healthy and give it more muscle?

I'd like to get around 300 hp, I'd prefer not to go too high compression, and I don't have to pass emissions. I'm hoping to shoot under $1500 for the whole rebuild.

Thanks in advance! Can't wait to get started.

Re: 1973 L48 engine rebuild (humiliategravity)
 

Dart Iron Eagle Heads,
Cam Swap,
Intake.

This should get you going.

Re: 1973 L48 engine rebuild (humiliategravity)
 

Thanks... which size Dart Eagles would you recommend?

Re: 1973 L48 engine rebuild (humiliategravity)
 

You might look into the vortec head conversion kit that scoggin-dickie sells $800 includes heads, intake manifold, rocker arms, bolts and gaskets. All you need is a pair of valve covers. Add a new cam and lifters and you have a total personality change for about a grand. Joe

Re: 1973 L48 engine rebuild (humiliategravity)
 

That depends on your choice of Cam shaft. Smallest heads for a cam with a <206 intake duration (measured at 50/1000" ) and the higher the duration, the bigger you want the heads to be. Remember though, at about 215-220 you loose a "factory idle" and the car will lope when sitting still.

Obviously these are basic guidlines. People may argue about the exact numbers, but these are pretty good numbers to do basic planning with.


And yea, the Vortec conversion is something you want to look into.


[Modified by Fozzy_Bear, 9:08 PM 5/27/2004]

Re: 1973 L48 engine rebuild (humiliategravity)
 

SOrry, but I'm gonna be the spoiler. There is NO point bolting a bunch of performance parts to a tired, 80K engine (especially the L48). Kinda like putting lipstick on a pig. Find someone you can trust to pull the engine and do it right!!! :yesnod:

Re: 1973 L48 engine rebuild (Fozzy_Bear)
 

I had the same intention with mine and this is what I came up with this winter; Edelbrock 750cfm carb, performance allu intake, a set of 291 heads, .270,.470 comp cam, and headers all this for under a grand thanks to ebay...........your best bet is to find someone who knows this art inside and out and ask a lot of questions. The combinations are endless. :steering:

Re: 1973 L48 engine rebuild (Michel B)
 

I have a 79 L48 app 110 thousand miles I have Trick Flow Twisted wedge G2 Heads,Edelbrock Rpm air gap intake and cam,Holley 670 Street Avenger,1.6 roller rockers,Dynomax headers 2 1/2 dual exhaust with x pipe into Flowmaster 50`s all on the stock block with no problems so it is possible to beaf up the L48.Before starting any work I would suggest doing a compression ck on all cylinders first. Congradulations on your new vette :thumbs:

Re: 1973 L48 engine rebuild (79 vette)
 

Do a leak-down test :thumbs:

Re: 1973 L48 engine rebuild (humiliategravity)
 

Congrates! :party: Excellent choice!

I don't agree with this decision. It's nearly impossible to keep the engine bay, fenders, hood, etc. all in one piece and un blemished if you are leaning over it with wrenches and dripping grease & oil & solvent and other stuff (beer, french fries, etc.) on the paint. It's also impossible to remove the camshaft without removing the radiator and A/C condenser, and even then you can not remove the cam bearings (replacing cam and not the bearings is bad :nono: ), and at nearly 100K you definitely will need to remove crankshaft and check it for wear...I guarantee that if it's still the original engine then there is enough wear to warrant new bearings and possibly a regrind...my engine had been babied for 50K miles and it had .001" wear everywhere...that is the limit on the specs...oh, for fords they may say .010" is the limit, but you didn't buy a ford. Also, unless the exhaust is a at least 2.5" high flow non-restrictive exhaust then if you don't change the exhaust to allow for increased flow then anything you do to the engine will be severely limited.

Follow these steps:
1. Pull hood, have a friend help, or I use the rafters in the garage to hang the hood by looping rope around the hood so I can raise and lower it...that way I can return it to the exact same position as it was originally...mark where the hinges bolt up so you can line it up...use something that you can wash off afterwards.

2. Pull tranny...this is not that difficult, easier with a manual since the body can be removed from the bell housing; but, ebrake cable needs to be disconnected at the Y loop near differential, shift lever and linkage needs to be removed, forward U-Joint needs to be removed and drive shaft moved out of the way, speedo cable, clutch lever (for manual), kickdown lever, vacuum line, and cross member (for auto), then remove tranny using a floor jack or custom tranny jack to lower it.

3. Drain engine coolant, remove fan shroud extension (shroud can stay), fan and extension piece and remove studs if possible (otherwise they may scrape or break the fan shroud), fuel line must be plugged and removed, throttle linkage, clutch idle shaft (manual), vacuum lines, accessories (A/C, alternator, power steering, etc.), unbolt exhaust from the exhaust manifolds, remove distributor (helps to clear the firewall), remove lower bolt on motor mounts & use cherry picker to remove the engine and place on engine stand.

4. Now not only can you rebuild the engine without any worry about messing up the car, you can get into the engine compartment and clean it up and paint it...tie up the wires and hoses properly, etc.

5. If you got this far, then clean everything up, measure everything for wear, replace worn parts with upgrades, and put everything back in the opposite order.

Also, I find video taping the disassembly greatly increases the chance of getting it put back together properly.

Re: 1973 L48 engine rebuild (Rockn-Roll)
 

6. Buy a bunch of ziplock bags and a permanent marker. Each time you pull bolts, etc off keep them all in bags and mark them accordingly (oil pan, timing chain cover, etc.)
7. Don't throw a single thing away until you have the rebuilt engine in the car running.

Re: 1973 L48 engine rebuild (humiliategravity)
 

Thanks all. Does anyone else vote to replace the entire engine in this thing? Is there any reasonable (affordable) way to test the quality of the block?

Re: 1973 L48 engine rebuild (humiliategravity)
 

Crate engines are everywhere, and are affordable (relatively). GM crate's are a little high, but they're new and they have a warranty. Sallee Chevrolet makes a 325 hp crate engine, with aluminum heads, for pretty cheap. OOHHH MAN! I think you just got bit by the "while I'm at it bug".....don't worry it's not lethal! I try to get bit at least once a month.

Re: 1973 L48 engine rebuild (Rockn-Roll)
 

This is very common and I would guess everyone on this forum who changed the cam without pulling the engine has done it with no long term ill effects. On a well cared for engine, those bearings should last a long time. Of all the people that have "blown" engines, I have never heard a complaint of a bad cam bearing.
If you have the thing out and are doing a rebuild anyway, change 'em. If you are doing it in the car, do it and don't be worried.

Re: 1973 L48 engine rebuild (humiliategravity)
 

My vote is: Drive it as is for the summer, then this winter, get some heated shop space, pull the engine, and do it right. That's my plan. Prior to buying my vette last fall I had never done anything more than change brake pads and oil...since then I've completely re-done suspension and brakes, swapped in a Hurst shifter, pulled the entire interior and cleaned/painted/re-installed, re-built my speedometer/odometer, installed a new starter, rebuilt my emergency brakes, and then when a valve broke a month back pulled the manifold and passenger cylinder head to get the valve replaced, then got it all back together (myself) AND IT RUNS!!! :D

"While I was at it" :rolleyes: I changed the steering box , the oil pan gasket, popped on new valve covers and gaskets and a new rear main seal, and now I have NO MORE LEAKS! :party:


I've done a hundred other little things along the way, learned a lot, and had a very enjoyable and satisfying time doing it. I have a good friend who knows lots and helps me when I need it. You will have fun, buy tools, and gain an amazing new confidence that you can do it yourself. This forum is also an ultimate resource, use it often.

Just my .02

-Roy

I rebuilt my first engine last year an I agree with Rockn-roll
Pull the engine not a big deal to do, clean, tear it down, measure (take to machine possibly), clean again, rebuild, clean again paint, set her back in and enjoy!!!! Get a book buy David Vizard - how to rebuild a Small block Chevy, take tons of pix and ask tons of questions. You will be proud of the accomplishment, know exactly what you have. And did I say be really proud of what you accomplished?
Good luck!

This thread has been dead for nine years. How/why do you guys keep digging this stuff up?

Apparrotly........because I just joined the forum recently and needed to read all this good advice......

(By the way.....I'm usually the one who replies to ancient threads without checking the posted date....LOL)

Thanks Men!


:thumbs:

Hahaha apperantly I didn't read the date either!!!

It's the thread that came back from the grave! WOOoooOOOOooooOOOOoooOOOOooo! Scary stuff, eh, kids?

Scott