RSFreak

I'm buying an L31 from a 2000 Chevy truck (don't know the model). From what I've read, the minimum specs are 250hp and 330lbs/ft. That would already be quite an upgrade from my '85 LG4. I'm going to use a carb and probably dual plane intake manifold. My question is, should I upgrade the cam or keep the stocker? This isn't my daily driver so a somewhat rowdy cam would be ok but I still want to keep it mild enough for the street.

cosmick

Stock was 255 net HP @ 4600, 330 net TQ @ 2800, "best" is a nice idea in theory, best for you depends on what you're trying to accomplish. Best emissions-legal cam that matches the flow of the heads is the Lunati 20080543. It's enough for 425 gross HP at 5600 RPM, peak TQ at 4200, how much depends on which headers, Best match is Hedman 1.625" long-tubes, but then fitting cats is a PITA, and so is clearing speed bumps in parking lots. You'll want a 2400 stall and 3.73:1 gears if 700R-4.
Try it with the stock cam first.

RSFreak

My car is emissions exempt here in Washington and has long since shed all emissions equipment. I already have 1 5/8" headers and true duals with no cats. As I said, this is not my daily driver. I just want a healthy street car. I don't want to machine the block for higher lift springs either. I'm not trying to break any records with this build.

cosmick

You may not currently have emissions-testing locally, but rememver, federal law hasn't changed, and they can cut off all highway funding to any state at any time if the state doesn't enforce federal law. It doesn't cost anything extra, nor power, to keep it legal, so why risk it?

skinny z

The problem with the L31 head (Vortec) is it's limited valve lift capability. That said, with it's weak(ish) springs and pressed-in studs, you're limited in cam choice anyway.
For what it's worth, I ran an old school flat tappet cam when I swapped Vortecs onto my 350. Max lift was .454". Duration of 218 @ .050". Combining that with 10:1 static compression and a RPM Air Gap intake made a fun driver. RPMs were limited to about 5500 with the combination probably making peak power around 5000. HP estimate would be about 350 based on 1/4 mile speed and vehicle weight.
If you want to keep the engine long block intact, as in not taking apart for now, then a roller cam with lifts in or around .450" with duration similar to the cam noted above will produce a decent ride. Or should anyway. It'll work with the stock heads without any mods. You can always upgrade from there.
No comment on removing emissions equipment.

RSFreak

In my state any vehicle older than 25 years is exempt from testing and we've never had visual inspections. Regardless, I haven't had emissions equipment on either car for years. ;-)

cardo0

Hyd roller if u can. Something in the 270* full duration range - maybe even 275* - on a 108-110 LSA. U need to keep lift under 0.46" unless u change spring retainers and better springs is good idea here too. If u really do have good exh sys then a single pattern cam will save u some overlap and vacuum.

So many cams like this shopping will make your head ache. Take slow and make it fun. Look for the best package deal. One more thing 280* full duration will not be fun to drive in traffic.

Good luck.

zraffz

We have an L31 with shims to bump the compression up a hair, rpm air gap manifold and an xr276hr (with springs, roller rockers)... the car scoots for a budget car. I'd say it's bolt on LS1 territory.

dmccain

iTrader: (2)

Herbert Cams has a few nice roller cams with under the 475 max lift you can run on those heads. I think they have one 215 220 @ 465 lift maybe.CCH216 in think. Should be great cam for 5500-5700RPM which should be about what you want to run on that stock Vortec engine and it should get you 300+HP with full exhaust and headers. 2400 stall, good shift kit.. youre in business!

Damon

The stock Vortec motor is pretty potent, even with the factory pickup truck cam in it. As was pointed out, above, the limiting factor is the max lift limit of the stock heads, which is around .470", depending on your particular heads (and who you ask).

If you want a cam that could make a bit more power but without having to machine the heads for more lift clearance and without having to change out the valve springs, a factory L98 TPI cam or a factory cam out of a later LT1 engine would be what you're looking for. About 10* more duration, a smidge more lift, but nothing that the stock Vortec heads couldn't handle.

86LG4Bird

iTrader: (1)

Yes, but just be careful and don't get an LT1 cam from a B/D body (ImpalaSS, Caprice, Roadmaster, Fleetwood). Those have the same cam specs as the L31 truck cam except the installed ICL is 111 in the cars and 106 in the trucks.

zraffz

Why would you bother wasting money on a cam that doesn't even require springs?
I can assure you the xr276hr we put in the L31 had no machine work, just different springs.

skinny z

I ran the xr276hr with my Vortec headed 353 and it was an overachiever for sure. With 10:1 compression via flat top pistons (.030" down) and an .026" gasket, it pushed my 3700 lb all street heap into the 12's. Decent highway mileage too at 22 mpg (Imp). It idled great and I was always complimented on the sound. Now my Vortecs visited the machine shop for screw-in studs and an opening up of the push rod holes to accommodate 1.6 ratio rockers but I could have put my Comp 26918 springs (or 26915) in with no machine work (as per zraffz's comment). Lift with the 1.6 rockers was .530/.540 and that is arguably where the Vortec intake stops producing more flow and stall (more like .500") so keep that in mind when making your selection. 1.5 ratio rockers might have actually made more power but I never went there.