L46 SBC 350ci/350hp Upgrades?

[AdmiralYoda]

Hello! I'm going to be picking up a 1969 Chevy Caprice soon with the L46 350ci/350hp engine. It has been sitting for some time so I'm going to go through it a bit and was thinking of upgrades that would be a good idea.

The Caprice is a 4000+ pound pig so I don't want to sacrifice low/mid range torque. I'm hoping to get an honest 375 crank hp out of it and 400hp would be even better. It has the 186 heads with 2.02 valves and 11:1 compression and for now I'm going to keep those heads. I'll probably have to use some Octane booster which I'm okay with.

Initially I was thinking of putting a Performer RPM intake on it and an LT-1 or Offroad 140 cam....but I think there are probably more modern options that would improve the overall powerband.

The exhaust manifold is cracked so I'll be putting long tube headers and a good exhaust system on it. I already have some Comp Magnum full roller rockers, a performer RPM intake and a Holley 750 carb ready to go.

Any recommendation on a modern camshaft to bump up the power 25-50hp when used in combination with the above parts and the stock 186 heads? And without killing any midrange torque...or preferably even increasing it? Thanks!

EDIT:
I should also mention that part of the process will be installing a 4l80 for overdrive with a 2600-2800rpm stall converter and probably 4.10's so it will have plenty of stall and rear gear.

[PackardV8]

We all have to be reminded there's no money in arguing with customers.

Recently a potential customer came in with a similar plan; build a 350" SBC, intake, headers, cam, roller rockers, carb, 4L80, converter, rear gears, in a 4000#+ rig.

He went away mad when the DragDynoSim showed for the same money a 454"/TH400 would be quicker/faster.

Build what works for you and have fun doing it.

[AdmiralYoda]

We all have to be reminded there's no money in arguing with customers.

Recently a potential customer came in with a similar plan; build a 350" SBC, intake, headers, cam, roller rockers, carb, 4L80, converter, rear gears, in a 4000#+ rig.

He went away mad when the DragDynoSim showed for the same money a 454"/TH400 would be quicker/faster.

Build what works for you and have fun doing it.

100% true!!!! In the long run I plan to put in a forced induction engine with more cubes.

For now I'm going to run what I've got and since I have most of the parts and I'll already be in there freshening up the L46. I consider a cam/spring upgrade a budget part which brings me back to my question...is there a modern cam that will squeeze out a little more out of the L46 without hurting mid-range or hopefully even improving it?

[mag2555]

How is this motor currently achieving 11 to 1 with 186 heads?

[AdmiralYoda]

How is this motor currently achieving 11 to 1 with 186 heads?

It is a stock 1969 L46. I may be getting my casting numbers wrong... perhaps a they are 492's? Either way the L46 has domed pistons with 2.02" valves and 64cc chambers for 11:1 compression.

[RCJ]

I have a similar motor in a 64 chevy. I liked the performer better than the RPM because of off idle torque. It has a Howard's hydraulic roller 217 @.050 on a 110 l/c

[Tom68]

186 heads, I'd be selling them to a vintage racer and putting on some AFRs, then we can move forward with torque and horsepower.

[bigcam406]

186 heads, I'd be selling them to a vintage racer and putting on some AFRs, then we can move forward with torque and horsepower.

Even a set of 195 cc Profiler's will be a drastic improvement over the 186's. With 11-1 compression, you will need a cam that will bleed off some cylinder pressure while cruising on pump gas.
Stay away from flat tappet cams as they are not worth the aggravation with the reduced costs over a hydraulic roller.

Does the car have AC?

Always liked those early Caprice's, good luck with it.

[AdmiralYoda]

186 heads, I'd be selling them to a vintage racer and putting on some AFRs, then we can move forward with torque and horsepower.

Even a set of 195 cc Profiler's will be a drastic improvement over the 186's. With 11-1 compression, you will need a cam that will bleed off some cylinder pressure while cruising on pump gas.
Stay away from flat tappet cams as they are not worth the aggravation with the reduced costs over a hydraulic roller.

Does the car have AC?

Always liked those early Caprice's, good luck with it.

Hadn't even thought of selling them actually, what are the old 186's, 492's worth in good shape (ballpark)? The car does have AC....

This is a weekend fun car, not necessarily a daily driver although it should be capable of that. It will get 93 octane gas and I'll add some Octane Boost every tank to get it to 96-98 if I need to. I was thinking an XE268H or XE274H for a bump in lift and duration, open to roller cams too....but I'm still a cam newbie.

Eventually this will be a money pit and will run 11's with a different motor For now I just want to throw some the parts I already have lying around at it (roller rockers, Performer RPM intake and carb) and see what it can do. A cam/spring upgrade is about as far as I want to go with this motor....that is IF it is a wise idea and as long as it doesn't hurt midrange.

[barnym17]

You will likely find upon dissassembly flat top 4 valve relief pistons as far as I know the only domed pistons in a 350 were the lt-1 variety starting in 1970 and maybe only lasting one year. You probably have an advertised 10.5 to1 and measured 9.5 to 10 to 1 after tolerances are added up.Which is good for you and your plan The 186 heads will support the power level you want pretty easily with a mild cam.

[Stingr69]

L-46 is a 350/350 Corvette only engine. 11:1 rated forged dome piston and bottom end (same as a solid lifter LT-1). L-46 was a hydraulic cam, cast iron intake and a quadrajet. If you actually have an L-46 in a Caprice, someone put it there well after the car was built. Whatever engine you have, it can be modified.

If you measure the diameter of the harmonic damper you would need the 8" for it to be the L-46. The 350/300 would have the smaller 6-3/4" damper.

"186" heads are pretty cheap these days. I have quite a few rebuilt sets here that I am upside down on. If you get an offer of $700 for your cores, you might want consider it.

[AdmiralYoda]

Thanks for your help guys!!!! After a bit more digging it is the factory L48. That's the 350ci, 300hp variety. Someone put an L46 air cleaner lid (or the sticker) on it a loooooong time ago.

[71vette]

It may be better that you dont have 11:1 compression in that car. For some quick fun with what you have a cheap cam for the heads you have a sum-k00172. A proper tuned 4bbl carb, even the stock intake, good timing curve, and then the rest of the modifications you listed. I might even just do the headers and exhaust system then do the 4l80 and 4.10s before any other engine changes.

[F-BIRD'88]

Check the head casting number under rthe valve cover. A inspection probe will allow you to see inside the chamber to view the piston tops.
Stock heads will need some upgrandes to run a performance cam. The th7004r is a waste of time and money. Stick with a th350 th400 trans.
4:10s just right for the street.

[mt-engines]

Check the head casting number under rthe valve cover. A inspection probe will allow you to see inside the chamber to view the piston tops.
Stock heads will need some upgrandes to run a performance cam. The th7004r is a waste of time and money. Stick with a th350 th400 trans.
4:10s just right for the street.

Where did he mention 700r4? Oh right he didn't.