I would love to upgrade the heads on my 1976 L-48. However, my car is a very low mileage original with ALL matching numbers. Is there a way to have the stock heads improved, and still maintain the orignal heads?

I was thinking about having them machined and larger valves installed. MAybe polishing the ports.

If this can be done, what size valves should I upgarde to. (intake & exhaust)? The only other modifcation that I would be doing right away would be a slightly larger cam and true dual exhaust.

 

For the money you would spend having larger valves and having them ported you could buy a set of good heads. Put on a set of newer heads tha tflow better and have better ports and a smaller chamber to increase the compression a little. You will be far better in the long run going this route. Put the numbers matching heads in a bag and put them under the bench. A numbers matching L48 is no big deal and the heads are very common heads. Small ports and large chambers do not make a good performance head.

 

Get yourself some Vortec heads, as stated above they flow better and will bump your L48 compression up almost a full point.

Add to it a Summit cam and lifter combo, an Edelbrock Vortec manifold, and have your carb tuned or rebuilt.

Follow that with a complete tun up, plugs, wires, fluids, filters...blah blah.

When you can afford it after all of that, have some headers and true duals installed.

That'll get you some pep.

Then if you're still looking to spend more, drop some coin on an overdrive transmission of some kind and rear gears better suited for the engine and transmission combo.

 

Back in an 1996 issue of Corvette Fever Mag they took a L48 and built it to add 150hp just by doing what you want. They rebuilt the whole motor and detailed everything including where they got the parts. When they were done the motor would have passed any judging because everything done was internal. I have a copy if you would like to see it, send me an email to: bmclau5079@aol.com

 

If not too much trouble, I'd like to see a copy also.

 

ID love to se that write up... My 77 L48 runs strong but in the morning its blowing smoke so i think its a valve issue. So heads and a cam down the line seem to be in the picture.

 

Kindly send me a copy too if its not much trouble.
stewarth@samsungsoa.com

Thanks!

 

When i 1st got mine over 10+ years ago It was bone stock I put on a $100 wieand Stealth Manifold, Custom True 2 1/4 dual exhaust $150 $25 each dynomax mufflers. $75 Summit Headers a $190 Carter 625cfm carb, $175 msd distributor and $30 coil and boy did it wake up something fierce.

I was a kid and was on a cheap cheap budget. A little each week kicked some major butt after I Popped the Rear racing a Mustang and replaced with 3:90 gears

Good Luck

 

I would also like to see a copy of that article/write up if you would....?

TIA!

Bri

<brio71@comcast.net>

 

If I could, I'd love to see a copy of that article too.
<bud2@dodo.com.au>

Thanks.

Bud.

 

The copies I had scanned are no longer readable so I will try to re-scan the article and send it to those of you that gave me your Email address. There are 10 pages so expect a large file.

 

I would love to have a copy as well!
badman@free.net.nz

Cheers Glenn

 

I *think* the stock heads for the L48 are the (in)famous 333882 - not a desireable head by any stretch. The "D" chamber is lousy, as are the ports. Valve size is 1.94/1.50. They top out around 200 CFM @.400 lift in stock form.

You could have these ported including a bowl and chamber sweep, have 2.02/1.6 valves installed and upgrade the springs...but you'd still be well short of the power in virtually any aftermarket cast iron head and have more money (figure $1K+ by the time all is done) in them. And, you'd have mucked about with your original heads.

There are aftermarket heads that you could paint orange that have accessory holes and are perimeter bolt for the stock valve covers. You'd need to stay under .450 lift or so with the stock valve covers. I've used 1" spacers to get the stock valve covers up high enough to cover roller tip rockers...but it's pretty visible.

IMHO, you'd get more "grunt" from a mild cam upgrade than investing in new heads - and it's less impact on your original engine. I *think* the stock cam is .390/.410 lift; investing in something like the CompCams 12-205-2 or the 12-230-2 would provide a nice SOTP increase in low-end torque with a bit of sacrifice on the top end. The additional lift wouldn't buy all that much, but the duration would help a bit. You'd need to very carefully check the valvetrain geometry for coil bind, etc.

I did some mucking about with Desktop Dyno Advanced including modeling the 3663152 cam and saw 40+ TQ (flywheel) gain through about 4500 RPM with the 12-230-2 cam. I also tried the stock cam with a set of Dart Iron Eagle heads and picked up about 6HP and 8TQ. Note that DD is NOT definitive by any means - and it all depends on the quality of the models - but it's pretty decent at these type of comparisons for engines making < about 1.4 HP/CID.

Power is all about matching components - improving the heads doesn't buy much without a corresponding cam upgrade...and it goes on from there IMHO it wouldn't be easy to push past about 300 HP (flywheel) if you're sticking with the stock manifolds.

 

I have just sent the article to those of you who asked for it.
tyler77@kc.rr.com,
NHRalph@aol.com,
Dltalfa@aol.com,
stewarth@samsungsoa.com,
brio71@comcast.net,
bud2@dodo.com.au,
glassbowtie77@netscape.net,
badman@free.net.nz,
jgrigg0903@yahoo.com,
bizdata@ix.netcom.com,
ptroxx@sbcglobal.net
Please let me know if you don't get it or if I missed anyone.

 

i half to go with billa on every thing exsept the stock exhaust mannafolds i have stock on my 350 center dumps an put some time into them getting rid of casting scag an port matching an smoothing an used my dremmel with greate results my understanding is that they flow allmost as good as a set of headders without the heat an keeping the stock look an just abought any one can do this not to start a bad thread its just annother option and annother way to save money an i think every one should have all the info that they can get myself have found a lott of great info here and im very greatfull sorry so long so keep the good things comming thanks bert.

 

Good catch and I agree - the "rams horns" with a bit of work are pretty close to a set of "budget" headers. Vizard has proven this many times over.

 

hi guys, I have this link to a website where they built the L-48 step by step to over 400 hp from the wheasie 195hp

http://www.corvettefaq.com/c3/goodwr...20part%201.htm


hope it works for you.

 

It's a good article...but in the end it's not "building the L-48" but rather building a whole new engine from scratch - new block, new heads, new cam, new intake.

 

Get aluminum heads. Period, end of story... and save the OEM ones if you want for posterity.

Heads were the only place I scrimped on my engine when I built for my 76. Details in my profile...she's got 6" aluminum H-Beam rods, all forged lower end and yada yada yada ...

But I did not buy myself aluminum heads I got the 4-bolt main block and a boatload of goodies, but the end result: I missed my horsepower goal and have an engine prone to ping when the weather is hot.

It runs great and I am quite satisfied but I know it would have come out better if I had not spent all the money I did, on OE heads and bought aluminum ones instead. I did the porting, polishing, and even had the heads and intake port-matched.

I wound up with 275HP at the wheels. Only average as far as I'm concerned especially when I know I built the bottom end like a tank. I know I can always put better heads on it ... but that's spending good money after bad.

So I know from first-hand experience: Don't waste a lot of money on stock, cast heads. Spend the money on aluminum ones and don't regret where those dollars were spent - because the cost is the same.

 

rayluka50@yahoo.com