Camshaft for 270 hp 283

[Steve H.]

I am looking for recommendations for a camshaft for the 1961 270 hp solid lifter engine that will yield the general characteristics of the original "097" cam while taking advantage of design and machining advances that have taken place since 1961. The Speed Pro CS-113R has shown up on this discussion board as being a good representation of the "097" but I wonder if the design includes enhancements that provide better power over broader RPM bands. Are there cams form Crane, Lunati, Comp Cams, or others that would be appropriate?

It would also be great to hear the opinions of 270 hp 283 owners about their experience with different camshafts.

Thanks for the help.

[John D.]

Re: Camshaft for 270 hp 283

Steve, You will be happy with the CS113 R cam. Good idle and great response. JD

[Duke W.]

Re: Camshaft for 270 hp 283

I am looking for recommendations for a camshaft for the 1961 270 hp solid lifter engine that will yield the general characteristics of the original "097" cam while taking advantage of design and machining advances that have taken place since 1961. The Speed Pro CS-113R has shown up on this discussion board as being a good representation of the "097" but I wonder if the design includes enhancements that provide better power over broader RPM bands. Are there cams form Crane, Lunati, Comp Cams, or others that would be appropriate?

It would also be great to hear the opinions of 270 hp 283 owners about their experience with different camshafts.

Thanks for the help.

The laws of classical physics haven't changed for over 400 years that I'm aware of. One could design a lobe with equal duration but more aggressive dynamics and more lift, but you'd need more valvespring, which increases lifter-lobe interface loading and increases the possiblity of wiping a lobe.

There is no free lunch. You're reading too many hot rod forums. The LS-series engines have "roller everything" and a much stiffer valvetrain. You would have to spend a zillion dollars to "upgrade" a vintage small block valvetrain to this level.

As with any vintage engine, the first "performance modification" to make is head massaging to increase flow.

The Duntov cam has a couple of "problems", one of which can be "fixed" and the other can't without redesigning the lobes.

The first issue is excessive overlap with the 108.5/112.5 POMLs and 110 LSA. I've recommended several times in the past to have the lobes ground on 110/118 POMLs, which is a LSA of 114, so it effectively becomes the L-79 cam with a little less total lift. The idle will be tammer and it will have more low end torque. If you want to trade some of the new low end torque for more top end power install it with 2-4 degrees retard. Crane has Duntov lobe masters and they can grind to the above specs for about a hundred bucks more than their off the shelf Duntov replica.

The second issue is the harsh dynanmics just above the tops of the clearance ramps. Though overall the cam has relative mild dynamics peak jerk occurs just above the tops of the clearance ramps, so it's important to maintain the tight lash specs that I recommend.

The above is the reason why the Duntov cam is a little noisier than other solid lifter cams when all are lashed to the specs I recommend.

If you install some aftermarket hot rod cam that someone convinces you is an "improved Duntov" you're likely to be disappointed.

Duke

[Bill B.]

Re: Camshaft for 270 hp 283

Just 7 months ago I installed the comp cam updated version L-79 cam into a 1962 327/340 engine. The owner is ecstatic, I'm impressed with the specs and talked him into it. I drove the car before and was a very good runner, he wanted more performance, he got it, there is a definite low mid and impressive top end power.

Comp Cams (new) Nostalgia Plus+ series of camshafts offers a unique combination of vintage muscle car sound with contemporary performance. While these cams have the distinctive idle of the originals, they will produce as much as 30 more horsepower, thanks to the latest design technology that delivers that old nostalgic sound.

Part Number 12-671-4
Grind Number N+L79H
1800 t0 6200 RPM range
Valve Timing .006
LCA 112
Intake Centerline 108
Valve Lash .0
Duration Int/Exh 276/283
Duration @ .050 Lift Int/Exh 229/236
Valve lift Int/Exh .468/.462
Lobe Lift Int/Exh .312/.308

I am seriously considering installing this puppy in my 1961 283/315 fuelie,
Bill

[Duke W.]

Re: Camshaft for 270 hp 283

Nothwithstanding the fact that it is a hydraulic lifter cam, which will have a lower valvetrain limiting speed than a mechanical lifter cam, the basic specs are a hell of a lot closer to the LT-1 cam than the L-79 cam, however, as is typical of aftermarket cams it has too much overlap. The LT-1 cam would be a much better choice.

It's going to be gutless down low on a 283, and the low manifold vacuum is probably going to cause idle problems with the FI system. Unless you are building a dedicated racing engine you have to consider the entire operating spectrum. A road engine spends 99.999 percent of its time below 4000 revs and less than WOT.

Road engines are not one-dimensional, but that's how most hot rodders and cam companies think - all they talk about is "horsepower".

As I have said time and time again, horsepower is a function of head flow, torque bandwidth is a function of valve timing.

Duke

[Joe C.]

Re: Camshaft for 270 hp 283

Just 7 months ago I installed the comp cam updated version L-79 cam into a 1962 327/340 engine. The owner is ecstatic, I'm impressed with the specs and talked him into it. I drove the car before and was a very good runner, he wanted more performance, he got it, there is a definite low mid and impressive top end power.

Comp Cams (new) Nostalgia Plus+ series of camshafts offers a unique combination of vintage muscle car sound with contemporary performance. While these cams have the distinctive idle of the originals, they will produce as much as 30 more horsepower, thanks to the latest design technology that delivers that old nostalgic sound.

Part Number 12-671-4
Grind Number N+L79H
1800 t0 6200 RPM range
Valve Timing .006
LCA 112
Intake Centerline 108
Valve Lash .0
Duration Int/Exh 276/283
Duration @ .050 Lift Int/Exh 229/236
Valve lift Int/Exh .468/.462
Lobe Lift Int/Exh .312/.308

I am seriously considering installing this puppy in my 1961 283/315 fuelie,
Bill

The original, and any true "blueprint" 097 cam has durations of 228/230 @ .05" valve lift, with "advertised" (AKA: "seat-to-seat", or sometimes .015" valve lift or SAE J604D which is .006" valve lift...........depending on whose specs you are looking at) durations on the order of greater than 300 crankshaft degrees! What this means, is that the ramp rates are extremely gentle, which is great for durability, but terrible for power production. The excessive effective overlap causes pressure bleed-off on the compression stroke, as well as excessive exhaust gas dilution during the overlap phase (which occurs in a band surrounding BDC).

As an example, Comp Cams apparently makes a faithful reproduction of the 30-30 camshaft (Comp 12-107-3), which lists the .050" durations as 254/254, and the durations at .016" lift as 346/346. This correlates EXACTLY with Duke's measured lobe lift data, and yields (for a symmetrical lobe) about 85 degrees @ .016" times four (1/2 lobe times 2 times 2 to convert to crankshaft degrees) which is about 340 degrees!!

For lack of actual lobe lift data for the 097 cam, using its .050" lift data of 228/230 and extrapolating the results from the 30-30 to the 097, @ .016" lift durations yields the following proportionality:

346/254 = X/228
and
346/254 = Y/230

solving for X and Y yields: 310/313
respectively, as extrapolated "seat to seat" (.016" lift) durations for the 097 camshaft.

The lengthy analysis serves to point out that the difference in how long the valves are off the seat between a conservative "advertised" duration of .016" and the rather standard .050" lift is more than 90 degrees for the 30-30, and more than 80 degrees for the 097!

Now look at a modern cam with more aggressive ramp rates and you'll note that the differences are more in the range of 35 - 40 degrees.
The ramp rates are more aggressive, true, and the springs that they require, although with higher rates, will not develop excessive forces because the lobe lifts are relatively low. With the recommended Comp spring for the example cam, the on the seat forces are about 115 (@ 1.70" installed height) and over the nose forces are about 205 @ 1.49". These forces are about 45% greater on the seat (where you want it) and about 23% higher over the nose. Substantially more than the 3911068 spring, which was used for many years as original equipment on 327/350 SBC, and as replacements for some 283 engines. The 068 developed 80 pounds force on the seat, and about 168 pounds @ 1.49". Net difference of about 35 pounds on the seat (which is most important in order to minimize valve bounce), and 37 pounds force over the nose.

I would retain your original stamped steel rocker arms, and your pushrods, but I recommend installing screw in valve spring studs.

Two notes of caution:

With any "modern" flat tappet camshaft, I would supplement the ZDDP contained in the CJ-4 oils with a can of ZDDPlus or equivalent.
I would think twice about increasing spring rates with any flat tappet camshaft (N/A for a roller) if you plan on using your Corvette as a daily driver and/or you plan on idling the engine for extended periods.

[Duke W.]

Re: Camshaft for 270 hp 283

The original, and any true "blueprint" 097 cam has durations of 228/230 @ .05" valve lift,



With any "modern" flat tappet camshaft, I would supplement the ZDDP contained in the CJ-4 oils with a can of ZDDPlus or equivalent.
I would think twice about increasing spring rates with any flat tappet camshaft (N/A for a roller) if you plan on using your Corvette as a daily driver and/or you plan on idling the engine for extended periods.

You CANNOT directly compare mechanical lifter "cam specs" to hydraulic lifter cams. It's apples and oranges! In the case of the Duntov, the valve doesn't even move in the first .008/.012" of lobe rise ! The .050" lifter rise durations, ABOVE THE TOPS OF THE CLEARANCE RAMPS, of the Duntov, or .058/.062" above the base circle are 220 deg. on both sides. This is the ".050" lifter rise duration" to compare to a hydraulic lifter cams.

There is ABSOLUTELY NO NEED for any kind of oil supplement for normal oil change use with OE valvetrains as long as C-category oil is used.

All these so-called "modern" camshafts do is increase the dynamic loading on the valvetrain, (the recommended valve springs are likely higher rate than OE), and they would probably not pass the GM durability tests of the day, which is why I recommend avoiding them if you want to put together an engine that you will never need to open up again.

Duke

[Bill B.]

Re: Camshaft for 270 hp 283

What we have here are two really good comments of two different views. I believe there are no complete right or wrong answers, its a matter of preference. Some of us are original at heart and thats what NCRS stands for. The second side is striving for a slight edge over stock, its in our blood to go faster. Isn't that what the foundation of the Corvette is based upon? Yes, its taboo! (You decide).
If its stock you are safe and correct!
If no one can tell........Priceless!

Stock #461 Camel Hump "Fuelie Heads" 1.94 Int/1.5 Exh @ 28'' of water max flow is:

64.35% at .400 lift = 407.3 hp
67.68% at .500 lift = 443.3 hp
Note: Had to use #462 data because #461's only listed 2.02/1.60 totals.

But as previously stated it puts a strain on the valve train, very true.
Then you would probably need a rebuild around 75,000 miles.

I vote for whatever the correct answer is. Bill

[Duke W.]

Re: Camshaft for 270 hp 283

64.35% at .400 lift = 407.3 hp
67.68% at .500 lift = 443.3 hp

What.............?

[Joe C.]

Re: Camshaft for 270 hp 283

What we have here are two really good comments of two different views. I believe there are no complete right or wrong answers, its a matter of preference. Some of us are original at heart and thats what NCRS stands for. The second side is striving for a slight edge over stock, its in our blood to go faster. Isn't that what the foundation of the Corvette is based upon? Yes, its taboo! (You decide).
If its stock you are safe and correct!
If no one can tell........Priceless!

Stock #461 Camel Hump "Fuelie Heads" 1.94 Int/1.5 Exh @ 28'' of water max flow is:

64.35% at .400 lift = 407.3 hp
67.68% at .500 lift = 443.3 hp
Note: Had to use #462 data because #461's only listed 2.02/1.60 totals.

But as previously stated it puts a strain on the valve train, very true.
Then you would probably need a rebuild around 75,000 miles.

I vote for whatever the correct answer is. Bill

Bill,

I assume that those are intake flow coefficients @ 28" water column, at differing valve lifts.
If so, then they are somewhat optimistic. What I have, is tweaked to be somewhat better than a known set of 462 heads with 2.02/1.6 valves. I am not certain (yet) whether or not these intake flow coefficients are achievable without pro-stock modifications involving expensive braze-up, which goes well beyond simple porting techniques:

LIFT.................FLOW.................COEFFICI ENT
.10 .................. 070..................... .721
.20 .................. 154..................... .793
.30 .................. 190..................... .652
.40 .................. 231..................... .595
.50 .................. 250..................... .515

Using EA, and plugging those flow numbers in, along with COMP's N+30-30S, using stock 1.44 ratio rockers, LT1 intake manifold, 780 CFM Holley, and 1 5/8" x 26" ; 3" x 16" collectors, into free flowing exhaust, yields the following @ SAE:

224 ft-lbs torque @ 1500 RPM

409 ft-lbs peak torque @ 4500 RPM
343 ft-lbs average torque between 1500-7000 RPM
435 peak HP @ 6000 RPM
288 average HP between 1500-7000 RPM

410 horsepower @ 7000 RPM

[Duke W.]

Re: Camshaft for 270 hp 283

Bill,

yields the following @ SAE:

SAE what... gross? Net? This thread has turned into some kind of unintelligable riddle.

Duke

[Joe C.]

Re: Camshaft for 270 hp 283

SAE what... gross? Net? This thread has turned into some kind of unintelligable riddle.

Duke

Unintelligable?

[Steve H.]

Re: Camshaft for 270 hp 283

I want to thank all of you guys for the information and opinions you have posted here to help me make my cam decision. I appreciate the specific cam manufacturer part numbers some have suggested because my knowledge and understanding of many of the details of cam design is quite basic. Thanks for your comments on actual experience.

On the other hand I have found that some of the more technical numbers that I don't entirely understand have made me search for answers and I have really enjoyed learning more about camshaft design.

By April, when it warms up enough up here in Northern Maine to work in our unheated garages, I am confident that I will be able to make a good decision that will produce a great 270 hp 283 for my "61 Vette.

Thanks