enkeivette

How much power can be made with a stock L48 long block? I've got my original engine in my garage. Someday (hopefully in the near future) I'd like to drop it into a boat (like a 17' Tahiti). So being cheap, before I give up on the stock L48 heads, how big of a cam could I shove in there? Sticking with the Q-Jet & HEI, maybe a big single plane manifold and some big upswept headers.

BTW it has 4-bolt main caps, so it should be ok for higher rpm.

mikep3

I did not think any of the L48's had 4 bolt mains. Seed needs horsepower, HP cost $ and how much $ do you want to spend. jm2c

BigBlockTank

Cu.$'s = HP

Jims79

if you talking vette motor I think you have a L48 SB 2 bolt main. You better check again.

Glensgages

I wouldn't think that relatively 'junk' heads would work-well with a large-plenum single-plane intake.....

7T1vette

You could have a 4-bolt main engine. L-48's almost always got 2-bolt mains; but if the line was 'short' of 2-bolts, they would substitute 4-bolts to keep the line running. And I agree with the last poster; you need to change the heads to expect any significant HP improvement with the other changes you make. There are several threads detailing the use of salvaged/refurbished Vortec heads/intake that can make a large HP difference for reasonable $$$.

enkeivette

It's a 4 bolt! it's in my garage right now with the oil pan off, I've seen it with my own eyes. Not to mention I checked the casting number which confirms that it's a 4 bolt, just in case I was on LSD.

I want to spend as little as possible. This does not have the budget that my Vette motor did. I expect to spend less on the boat and parts than I spent on my Vette motor (not including the cost of the supercharger). Just want as much hp as possible for as little as possible.

Glengages, I think you're right... that's what I was thinking when I posted this.

7T1vette, are Vortec heads aluminum? Looks like they come is both iron and aluminum versions on E-Bay, and there are different casting numbers. Any Vortecs better than others? What kind of a cam can be matched to a set of Vortecs?

Glensgages

I believe the aluminum L98/ZZ4 heads, which are aluminum, have a vortec bolt-pattern/combustion-chamber/intake port, yet they have fairly-small combustion-chambers (58cc? ), which will raise your squeeze much-higher than a typical 64cc head, 'specially with those 'upside-down soup-cans' that you probably have for piston-tops in the L-48 short-block:
if it can make 355 HP from that motor, it'll do fine in yours, I'd think?????

Mike Ward

The same casting number was used for both 2 and 4 bolt blocks, can't rely on that as an indicator.

jackson

Mostly correct ... except L98/ZZ4 heads have the conventional intake bolt pattern (not vortec). L48 has dished cast pistons. To raise compression: You can use your big chamber L48 heads along with new pistons w/ small dome ... or ... install small chamber heads w/ OE dish L48 pistons.


if motor has 4bm it's most likely not L48

hogwash

If it was mine& #'s matching I'd store it. Would make your car more valuable.Plenty of motors out there, why reck that one.I've seen this before,4-bolt #'s matching, it's rare.

enkeivette

It's a 78, orig auto, now a 6 speed. 82 bumper molded in and a bunch of stuff thrown away and cut off to save weight. The center console was cut up and modified for the shifter, the dash was cut up for the radio, and the guage bezel was cut up for autometer guages. The power steering has been removed, along with the AC. I had to cut the hood to make room for the supercharger... I could think of more stuff but I think you get the point. If you want to find me a well paying buyer for an orig 78 4 bolt motor, I'll give you a nice cut.

I typed the VIN in some Corvette database before and it told me that I had a 4 bolt L48. Can't believe you guys are so hung up on this. Not to mention that I don't have the L82 air cleaner or the L82 fan shroud. It was for sure the original motor, car only had 82K miles on it when I bought it.

This is kinda getting off topic guys...

comp

if it helps any, my 77p/u came with a L48 4 bolt,,pan has been off

Glensgages

Thanks for the correction..... I had thought that the ZZ4 came with a vortec-compatible intake, and thus the L98 heads were also vortec:
being 'traditional' style heads, the L98/ZZ4 heads wouldn't need a different intake manifold.

I suggested these 58cc heads to the Original Poster because I was under the impression he didn't want to spend any extra money for flat-top/dome pistons.

worship79

Want HP for cheap? Google for 'Goodwrench quest', it's a ChevyHighPerformance article (5 parts) on how to pump up the power on a (cheap) Goodwrench block for little money. Starts with intake and cam, then moves to carb, heads and also discusses vortec heads extensively. Very good read!

With vortecs you need to check of the heads have been modified to allow for more than .450 lift. At least the iron ones need that check. See the Soggin Dickey website for modified Vortec heads and several not too expensive head-cam-intake combo's. Vortecs heads require a different bolt-pattern (and angle) intake.