68hemi

I have looked at a lot of cam choices for my 1957 383 stealth engine that I am going to run original type dual quads on with factory manifolds and 2 1/2" exhaust. I am pretty much following suggestions from two other similar builds on this site, one F.I and one 2x4 that are running 450-500 h.p. I want to run a hydraulic cam that will be all in at 5800-6000 RPMs.

Is there really any better choice that the factory L79 cam? If so what?

Scott Marzahl

Its a great cam but the L82 350hp cam is designed for the longer stroke 350 with similar durations and a tad more lift.

jdk971

engine compression would also determine the cam, i believe. jim

68hemi

It will be 10.5 compression and will have aluminum heads.

SWCDuke

Definitely! Like Scott said the L-46/82 cam is the best high-performance hydraulic cam Chevrolet ever made. It's got two degrees more .050" duration (224) than the L-79 cam with the same 114 deg. LSA, better lobe dynamics, and the inlet POML is a late 114 deg. ATC.

Idle behavior is about 14-15" @ 750.

For 327s I recommend installing it four degrees advanced to bring the inlet POML back to equal the L-79 cam of 110 deg. ATC, but install it as ground on longer stroke configurations.

There is a recent L-46 dyno test posted on the NCRS TDB, and it made 90 percent of peak torque at 2000, which is better than I expected. Power was average, but the heads weren't massaged.

Like I always say, select a cam for good low end torque and work the heads to maximize power.

The Federal Mogul part number for the L-46/82 cam is CS1095R.

Duke

AZDoug

+1 on the L-82 350/350 cam.

It would work well with your slightly larger cubes. You can also zero lash it as well, and it will run to 7000 RPM without valve float with the matched OEM springs.

I ran that cam for decades and was very pleased with it, good idle vacuum, and it really turned on at about 3000 RPM in a 327, yet behaved very well from just above idle.

Doug

65tripleblack

Why not 2 or more degrees retarded with a longer stroke engine like the OPs 3.75" stroke 383.

SWCDuke

That's up to the user. More retard will shift the torque curve slightly up the rev scale, but since most road engines spend 99+ percent of their time below 4000 it may not be worth it and 2 degrees is pretty close to noise level.

When you get down to this level of detail a simulation program is best to work out the final number from some baseline.

SWCDuke

Depending on head flow, I doubt if the L-46/82 cam would make 450 GHP on a lab dyno, but those numbers don't mean much. What counts is installed in-the-vehicle performance, and that's highly dependent on exhaust back pressure. You should have at least 2.5" exhaust pipes all the way through and low restriction mufflers.

It's not uncommon to see an engine that makes 500 GHP on a lab dyno with headers and open exhaust not even break 350 SAE corrected RWHP with OE manifolds a reasonably street legal exhaust system.

Another issue is the small ports of the OE 283 2X4 manifold. They will be the limiting factor on inlet flow. Fortunately they are only about 3" long, but you should open up them up as much as possible to match the head ports while not punching through to the adjacent port and leaving enough surface area at the head to get proper gasket sealing.

Also, if you plan to rev over 6000 you'll need the highest quality crank and rods that are available.

You would be well advised to buy the Engine Analyzer simulation program, which allows you to simulate SAE net in-the-vehicle performance including inputing exhaust flow at 1.5" Hg depression. One of the outputs is exhaust back pressure that you want to keep at no more than about 3 psi. For the C2 under-the-car exhaust I use 500 CFM total flow at 1.5" Hg depression, and this yields at little over 3 psi exhaust backpressure for a massaged-head/LT-1 cam 327 making close to 300 SAE corrected RWHP, which correlates well with expected RWHP,

Don't get hung up on top end power. Unless the config makes at least 80 percent peak torque at 2000 it's going to feel soggy in normal around town driving. If you keep adding "more cam" (assuming you have very good flowing heads) you keep reducing low end torque, driveability, idle quality, and fuel economy.

Engines are not one dimensional - top end power. The best road engines have broad torque bandwidth, which means a lot of power in the low to mid-range where you spend most of you time.

Duke

68hemi

Looking for the best cam to accomplish 450-500 gross h.p. with my combo of 383 C.I.D., 10.5 comp., aluminum heads, factory dual quads, and likely 3.08 gears.

2 1/2" exhaust pipes with 2 1/2" low restriction muffler inlet and 2" outlet and tail pipe just as a factory 2 1/2" system.

Intake will be opened up and port matched as will be the heads and rams horn 2 1/2" manifolds.

Looking for a cam that red lines at 5800 RPMs.

Not real interested in top end. I will drive at 80-85 mph on freeway occasionally. More interested in low to mid-range.

AZDoug

I can only estimate gross HP my 427 SB makes, on a chassis dyno, through full 2.5" exh, it peaks at about 440 ft-lb and 440HP, but we dialed that back a bit to 410/410 RW HP/RWTQ both at around 4500 RPM via ignition timing as dyno tune timing is too advanced for street use.

The cam I use is high lift Hyd roller, with .540I/.536E, 230/236 duration at .050, with Dart Pro-1 CNC heads which have 2.08" intake valves.

Power is limited by the 1.62" headers and the low height Vic Jr manifold (to fit under the hood), both which are taking away top end power.

On Engine analyzer, my combo says 505 HP gross power, with its 9.5:1 CR. 10.5:1 CR in theory would give another ~8-10% power and Tq.

You will need more cam and tuned headers to get the 500 HP gross, IMO. I do think the 350/350 L82 cam is great street cam for your size motor, but that 2x4 manilfold and air cleaners and rams horns are going to limit your power at the RPMs you need to make that power.

Doug

68hemi

In the link below is what I am trying to duplicate however I now I will give up some h.p. with a lower red line hydraulic cam and higher gears than I have run in cars in the past. I just don't want to adjust lifers and want to give longer life to the engine with lower red line and the easier gears at highway speeds.

https://www.corvetteforum.com/forums...ll-almost.html

AZDoug

That is why i have a hydraulic roller.

The area under the valve lift graph, is what makes roller perform better than flat tappet, as your VE is increased considerable on either side of maximum lift vs flat tappet. They don't necessarily make more peak power at equal maximum valve lift, but they let you get higher maximum lift as well as giving you greater lift between start of open and peak than you can get with a flat tappet on the same base circle.

I don't like adjusting valves either, any more than i like dorking with points.

There is nothing wrong with rollers, Harleys have used them for decades,and OEM car makers for some years also. They got bad rap when some aftermarket cam makers started making them as they didn't use proper materials and they failed early, but those days are long past.

Edit: My very street-able 427 SB makes more average power between 2000 and 5500 RPM than an L-88 ever did. If I put 1.75 or 1.87" headers on (If I can find them, and if they would fit the frame and angle plug heads), and added a 1.5" spacer between the Vic jr and throttle body, my RPM power range would be 2000-ish to 6500 RPM. I don't think a flat tappet cam can produce as wide of a power band.

Doug

68hemi

I am planning on using stamped steel rockers with roller tips.

AZDoug

You still need a roller cam if you want a wide power band, and to be able to utilize those heads to their fullest.

I don't see that roller tip rockers are gaining you anything in a low lift cam like the L-82 cam. IMO.

And to clarify by street-able, I mean with my 3.08 gears, i can cruise around in 5th gear (1:1) at 1200 RPM if I am careful with the throttle, and I have 400 ft-lb of rear wheel Tq at 2000 RPM.... The car isn't un-drivable under 3000 RPM, like many who claim their motor is *streetable*.

Doug

68hemi

May have to re-think this, can you elaborate?

AZDoug

Those Dart heads flow better than any Head Chev ever made in the 1960s or 1970s. You can find flow lift data for both on the web.

Or, here is link i saved: http://www.users.interport.net/s/r/s...ehdc.htm#Chevy

If the dart heads are capable of flowing more CFM, why not select a cam that opens the valves higher, across the cam duration, to allow more air TO the heads.

more air=more VE=more power.

Of course you need to consult the cam supplier to assure there is no valve to piston contact. They can tell you that over the phone, though they also will tell you to turn the motor over by hand with some clay on the piston top to make sure there is no issue. i doubt you would have any issues under .520 lift, though.

I would google "cam lobe profiles roller cams vs flat tappet cams", or "air flow roller cam vs flat tappet cams" for more info.

Doug

SWCDuke

First you say:

"Looking for the best cam to accomplish 450-500 gross h.p. with my combo of 383 C.I.D., 10.5 comp., aluminum heads, factory dual quads, and likely 3.08 gears."

Then you say:

"Not real interested in top end. I will drive at 80-85 mph on freeway occasionally. More interested in low to mid-range."

Which is it?

What's the point of demanding 450-500 GHP on a lab dyno with headers and open exhaust and then putting it in the car with manifolds and mufflers.

You may be able to get 450-500 GHP out of a 383 as above on a lab dyno, but it will require a pretty big roller cam and massaged aftermarket heads that flow at least 250-260 CFM at 0.5" valve lift, which are going to cost a bunch, and then the OE manifolds and mufflers will kill off at least 25-30 percent in the car!

You say "aluminum heads", but haven't provided any details like manufacturer, model, and FLOW NUMBERS.

Picking a number like 500 out of the air is setting yourself up for disappointment, and achieving it will require some decent system engineering and a lot more budget than sticking with the best vintage OE parts. Cost increases exponentially with increasing peak power requirement.

If you go with the L-46 cam you will have a nice broad torque bandwidth engine that might provide a useable power bandwidth to about 6000 depending on head flow, but without head flow data and a simulation program you won't be able to guess even a ballpark number.

BTW, roller tip rockers are a total waste of money. Even all the LS engines don't have them. Roller trunnions, yes, roller tips, no. They're worthless! Stick with the OE rockers arms, but they might not work with a high lift roller cam. Aftermarket OE design rockers might, but you may have to go with roller trunnion rockers (expensive), and then the OE valve covers won't fit.

I don't recall that you mentioned the block you are using, but a 283 or 327 (other than the '67 ...657) block is not a good basis for a 3.75" stroke engine and I highly advise against it. A 350 block is best, but will require "stroker rods" and some clearancing work with a die grinder.

On that thread you referenced, did he ever test it on a chassis dyno to compare SAE net at the rear wheels with SAE gross on the lab dyno?

I don't have the time to wade through all 11 pages of posts.

Duke

AZDoug

And,

do what Duke said earlier, buy Engine Analyzer.

http://performancetrends.com/Engine-Analyzer.htm

Its about $100 or so, you don't need the Pro version which is several hundred $$.

You can play with CR, and cams, and heads and exhausts until your heart is content, and it will give you pretty good idea of what works and what doesn't, and will alert you if something you are trying is not recommended, or a possible problem.

The HP and Tq graphs are "fairly" close to what you actually get, but of course, real life will be a bit different in places in the RPM range than what their graphs show.

Doug

65tripleblack

Valve lift on my 327 is .608/.605 with more than .060" clearance at both valves.

Some valuable and true statements here, and the OP would be wise to install a roller cam with full roller trunnion rocker arms. There is no advantage and actually a disadvantage with roller TIPPED rockers with their higher inertial weight they will limit max safe engine speed.

AZDoug: Can you post a graph of your Dynorun. I'd like to compare it to mine. More food for thought for the OP. My engine uses a solid roller cam. Wise choice using 2.08 intakes with the larger bore. Hopefully you relieved the decks adjacent to the intakes.