I've been thinking about putting new heads on my stock L48
and I was wondering if the bottom half of engine can handle the
added horse power. The motor has 80k miles and I know I have cast internals and not forged.
If anyone has any advice on this it'd be helpful

 

A lot of people go real fast with "junk". With that said, the only aspect of your motor that might make someone scratch their head as to throwing big money parts at it would be the mileage. If it were me, I wouldnt sweat it too much, but maybe just do a compression test on the motor to get an idea of what kind of shape its presently in.

Outside of that, I say go bananas. If you buy good heads and the bottom end lets go, well you can always put those heads on a fancy new shortblock. Me personally, Id go cheap...set of 305 sbc heads and a cam swap, intake, headers, and viola...youve got a satisfying driving experience

 

That's what I was thinkin. Thanks man. My buddy tells me that with a set of decent heads and some cams I can get up around 300 horses. Sound about right?

 

I say you friend is right if he's talking at the flywheel. I would have no worries putting heads and a cam in a well taken care of 80K L48

 

May I ask the question about the 305 heads? What makes them special? What years are you talking about? If they make that much of a difference, I'll go to the local junk yard and look for some. Thanks.....

 

I've got a 77 and the main reason for the low hp in these years was because of smaller heads and cam

 

58cc combustion chambers...probably not the best overall flowing head, but in a budget oriented situation they can certainly bump the compression and flow well enough to get the job done.

 

Thanks, any years I should look for in the yard? If I come across a GM 305 non-vette, what year would fit on my 77?

 

Those heads might raise the compression ratio a bit...but the small valves would negate any gains from the C.R. increase. You could put some money into them and have the valves enlarged.

Better to buy a decent set of aluminum heads.

 

The only positive about the 305 heads is the compression icrease. They do not flow any better than you stock heads. If it were me, I would go with a set of DART or equivalent set of 180cc intake runner heads with 2.02/1.60 valves; either 64cc or 72cc chambers They are generation ahead of your stock or the 305 heads and they will be a better foundation for more power.

Add a performance recurve of your distributor and performance adjustments to your carb (q-jet?), and you will never look back!

As a footnote, my '80 L48 was generating 224rwhp/288rwtq way back in 2002. That was after cam, headers, heads, distributor recurve, intake, carb,... I baselined at 160rwhp.

So, yes, the engine is capable. Keep the combination balanced.

 

That's gross HP at the flywheel, pretty tame.

 

I dont disagree with the opinions of others, as I did acknowledge that its not the best flowing of all heads, but were talking about a motor that probably isnt seeing the better side of 4500 rpms as it is.

An aluminum 64 cc head would see benefits, and the freshest L69 heads are probably not growing on trees these days, but if I found a good set I'd use them over anything else just for the novelty of bang for the buck.


About 15 years ago, a buddy of mine took his old L69 heads and put them on a fresh 355 short block that had domed pistons..estimated compression was about 10:1. Dont remember what cam, but It wasnt too radical. This car was a daily driver 79 regal that was a hodgepodge throw together of all sorts of left over crap, and threw down a 14.0 in August heat on its first time out. Would a set of aluminum heads with a larger valve worked better? Undoubtedly, but he had those heads kickin around, and the combination didnt suffer from it.

I would be inclined to think that a flat top doggy L48 would wake up nicely with the 58 cc head and a cam. Im not saying that these heads are magic, but if the right parts were found at the right price, respectable results can be yielded that would probably make someone think twice about spending money on the brand new aluminum head.

Again, I also agree [even in my original post] that the money spent on aluminum heads could always find their way onto a new motor and leave room to grow.

 

I got 11,000 miles on a 59,000 mile bottom end @ 257 rwhp & 296 on rwtq. The rings wore out. But at 80,000 miles I'd probably atleast see we're your at with a compression test. If you decide to buy decent heads as you'll be more likely to reuse them.

 

Summit sells some nice cast iron large valve heads, #152123 for $630 shipped to your door. The have 72cc fast burn chambers, .525 springs, screw in rocker studs, 170 intake runners, angle plugs, and are ready to bolt on. They are made by Dart. I got rid of my 624 boat anchor heads on my 84 carbed C4, added a mild Isky solid lifter cam and I am very happy with the increased performance.

 

I have similar set up to Ted's, (stock short block, rest updated) all this was done 2 owners ago, I would say about 15 years not sure how many miles. I don't rev over 5k, however hard launching is an every day thing with rews going to 5k through every gear. Not sure about the condition of the engine since I did not take it apart, it has some issues due to age but doesn't smoke, doesn't leak, don't have to add oil, con rods didint fly out or anything so since this setup had been running for at least 15 years I would say it is capable. not sure what the CR is -the heads are obsolete Elelbrocks 64CC's seen in my avatar-any guestimates are welcome!

 

I had my carb redone, pulled off the cat and installed a test pipe, put in a new distributor (mine was very sloppy) used the light springs, advanced timing to 12 degrees and tuned it up.

It is a different car!!

 

Ditto on the aftermarkets
As said those 305 heads dont move beans for air they are bad..lol
Some of the TPI/Fbody guys glom over them have no idea why

 

Don't feel the 305 heads would be a good idea. They obviously would bolt on, but there wouldn't be much if any boost on power. If I'm not mistaken when I was looking at modding a 305, 350 heads were not an option short of grinding some relief into the top of the block so the valves would clear. The 350 combustion chamber is physically a larger diameter than the 305 bore (3.75")... the flip side is that the 305 combustion chamber is a smaller diameter than the 4" bore on the 350.

Beyond that, 300hp is not too high for an L48. It's more an RPM limit on the bottom end. I wouldn't want to spin one more than 6500 and that would only be short bursts. I'm looking to make my L48 into a torque monster with about a 5500 rpm upper limit. Not too worried about making max hp.

 

Just completed a roller cam swap on my L48.Already had Edelbrock heads but didn't know what head gasket was used.Decided to change the head gaskets to 1094 Felpro's for better quench and compression.If changing heads those Trick Flow 56cc heads look pretty good for an L48.
The write up on the roller cam install..
http://forums.corvetteforum.com/c3-t...-cam-swap.html

 

I'm installing a set of L98 aluminum heads with the 58cc chambers. The iron heads aren't 58cc, they're 64, if I'm not mistaken. The L98's came in two flavors of castings, with the 113 having D-ports on the exhaust and better flow than the 128's. They both take the regular SBC intake bolt pattern, unlike the Vortecs.

The compression will be bumped up as a result, from about 8.0 or 8.5 (depending on who you believe) to at least 9.2 or 9.5. Of course, the heads should be gone through and a recommendation by the Cylinder Head Exchange guys here in Los Angeles, was that they would cut down the guides so that more lift can be added. Add the fact that they're aluminum and are thermally efficient, you can add another point of compression. Also, you should use the thinnest factory gasket possible, and I'm going with a 0.023 Victor Reinz gasket to minimize any CC losses to a thick gasket.

It's a proven combination and the tech at Cylinder Head Exchange was enthusiastic about it and knew it well. The L98 was RPM limited to begin with, so I'm going with a cam that will top out by 5K RPM, with strong low and mid range torque and horsepower.