I have a 78 L48 stock engine. Nothing has been done to it. I want as much out of it as I can get. I have new upgraded hi performance distributor and wires to add on as well as plugs. Besides a new cam and headers and exhaust, what else does anyone recommend to do to get more HP out of that stock engine to keep the numbers matching. Or by the time I would add on everything is it not economical to do so and just drop in a larger small block with more HP. Please HELP!

FOOTE

 

Depends on how much wrenching you want to do. Easiest path is to replace the engine with a crate motor, but remember that your engines hp rating is measured differently than the crate engines so you need to check what you are getting or you could end up with an engine with no more power than you started with. Check out the definition of gross v's nett hp if you aren't already aware of it.
A performance ignition will add very little or nothing at all to a std engine compared to a std ignition system in good condition. JMPO but backed by forum gurus experience as well.
A distributor re-curve can make a significant improvement in conjunction with applying non smog timing figures, search the forum there is plenty of info on both.
So, the tried and true formula is get more fuel in squeeze the mixture harder and then get the burnt gas out quicker. These things all have to be done as to work together so just whipping in a cam and putting on some headers isn't likely to give you the result you are hoping for, a true dual exhaust helps though. You are best to seriously look at the compression ratio and better heads as well to make it all work. On the intake side, according to many on this forum the Quadrajet carb can be used successfully for hp if its in good condition. Once you go this far what is left of your numbers matching engine anyway and if you had to deck the block it will be gone completely.

 

If your not putting some heads on, get a crate engine like said.

 

Another vote here for a crate engine.

 

Rebuild the bottom end and buy both a roller cam and afr heads if your budget allows.

 

Rebuilt my stock L-82 into a 355 with roller cam (.525 lift), AFR 180 64 CC aluminum heads, 10:1 compression....killer engine now

If you don't want to do anything, crate engine...

 

Put a set of 64cc chamber heads on it.....this will bump compression one point. (8.5 to 9.5 to 1 roughly).
This will set you up for a nice cam and lifter set.
I like Comps XE274 if you are running a 4 speed...268 if not.
Team this with a nice aluminum intake, Comp roller tip rockers and one piece pushrods.
This will run VERY nice......
For heads...I prefer Dart....but others will pop in....at this level....any of the $1000 heads will do what you want.

Jebby

 

The l48 while rated at 8.5 to 1 was over rated in the compression department and was more like 8 to 1 with the pistons being a 1/4" in the hole. I did almost what you are describing to the op and it ran good, made 260 horse and 290 ft/lbs torque to the rear wheel, went with edelbrock rpm heads, weiand action plus intake and comp xe262h with 1.6 rockers, it ran the best with a 2400 rpm stall converter. If i'd went afr on the heads and a decent roller cam while getting the compression up some with a tighter head gasket I might not have built my 400" that I have now.

 

This sure is the kind of information and knowledge I was looking for. I sure do appreciate you taking the time out of your day to pass this on to me. Thank you Haggisbash.

 

Thanks Bluedawg for taking the time to pass on your knowledge and information to me. By the time I would do any and all upgrades that can be done do you think that this L48 could drop down 300 or more HP or not? Or by the time I would invest in all of the parts would it just be more cost effective to drop in a new engine?

Foote

 

Thanks Bluedawg for taking the time to pass on your knowledge and information to me. By the time I would do any and all upgrades that can be done do you think that this L48 could drop down 300 or more HP or not? Or by the time I would invest in all of the parts would it just be more cost effective to drop in a new engine?

Foote

 

It depends, for me it is the satisfaction of doing it my self. If you do it right there is no reason why you could make an honest 400 horse at the crank, more if you stroke your existing engine. The right combI nation of parts is key. What's your budget and how do you best enjoy your vette?

 

You wouldnt by chance have dyno'd yours since the upgrade have you? I put the same heads(58cc instead) and a little but smaller cam in mine. Air gap intake, side pipes and all pollution crap deleted. Just curious as I have dyno'd her. About 8 years ago prior to heads & cam, it dyno'd at like 230 to the tires...was a little disappointed. I want to get it re-dyno'd but dont wanna be disappointed again...

 

What heads?

 

AFR's...

 

can you list the complete package, something seems wrong.

 

What do you mean something seems wrong?

AFR eliminator heads(58 cc), comp cam(270 dur/470 lift), comp 1.6 roller rockers, edelbrock air gap, k&n breather, smog/egr/etc all deleted, march underdrives, holley 650, dewitts dual electric fans, msd distributor w/ msd wires and hooker headers.

 

I think bluedawg thinks that you should be making more power. I would tend to agree with him.
Could be that cam duration and lift are a bit low, carb or intake (depending on what you got for intake) possibly restricting it.
I'm running Dart SHP 180's with a 270 duration and .549 lift roller cam with side pipes through a TH350 and 3.08 rear, Q-jet carb, dynoed 262HP at the rear tires.
Biggest difference I see is your flat tappet cam. You have better heads than mine.

OP, if you have the mechanical ability, a complete rebuild is really the way to get the power you want. If you put on small chamber heads on the current bottom end you will get more but it might not be as good as you want and it may burn oil due to poor ring seal.
The stock compression on a L48 is 7.66:1. I cc'd the pistons and the heads.
So if you plan on going smaller combustion chamber heads use 18 cc's for the piston volume. Post #31
https://www.corvetteforum.com/forums...er-size-2.html

 

Ok, I gotcha. Yea, the previous dyno #'s were prior to all the work I mentioned earlier. It was pretty much stock. I did have the cam(listed above) at that time and when I did the heads, I just never went up in size. So, yea, I think that its a little small for my setup now...

 

If you want all you can get stuff the biggest stroke crank you possibly can in a roller type block. 3.75 3.875 some go 4"
Youll need a good sized cyl head/intake. Youll be real real happy how much torque it makes and dont have to cam it to the moon to run hard.
Youll forget alllll about a lil 350.