1958 Corvette Cam Specifications

[Alden M.]

I am having problems locating the correct cam specifications for a 1958 Corvette 283ci x 270hp. Can anyone help?

[Joe C.]

Re: 1958 Corvette Cam Specifications

I am having problems locating the correct cam specifications for a 1958 Corvette 283ci x 270hp. Can anyone help?

part number: 3736097

228/230 @ 0.050"; .395/.401 valve lift; 108/110/112 (intake c/l, LSA, exh c/l)

[Alden M.]

Re: 1958 Corvette Cam Specifications

part number: 3736097

228/230 @ 0.050"; .395/.401 valve lift; 108/110/112 (intake c/l, LSA, exh c/l)

"Joe is this what is called the Duntov cam that was used in the fuelie engines? Is it the same came used in the 270hp with 2-4's?"

[Steven B.]

Re: 1958 Corvette Cam Specifications

"Joe is this what is called the Duntov cam that was used in the fuelie engines? Is it the same came used in the 270hp with 2-4's?"

Alden, the "097" cam is also known as the "Duntov" cam. It was used in all solid lifter engines from '57-'63, the 270 dual 4BBL, the FI's, and the solid lifter '62-3 single 4BBL engines. Steve

[Richard M.]

Re: 1958 Corvette Cam Specifications

If you're looking to purchase, the Sealed Power CS113R cam and a set of AT992 solid lifters are equivalents from your local NAPA store.

Comp Cams can also supply the cam as a custom grind at a greater cost. But their lash spec will be different from the stock spec of 0.012" I & 0.018" E.

Rich

[Timothy B.]

Re: 1958 Corvette Cam Specifications

Richard,

Can you explain why the comp cam lash spec is different than the original GM specs, is the clearance ramp different.

[John D.]

Re: 1958 Corvette Cam Specifications

Alden,So the parts man at NAPA doesn't turn you down tell him to plug in Federal Mogul for the CS113R.
It's a great cam and very affordable. I had no problems ordering one from Car Quest also.
This cam puts out great vacuum. 16" at 900RPM.
Probably a 100 or more posts on this cam here. Started off life as a TRW cam. Then Sealed Power Cam. And Now a Federal Mogul cam. Wonder who will be next. JD

[Richard M.]

Re: 1958 Corvette Cam Specifications

Richard,

Can you explain why the comp cam lash spec is different than the original GM specs, is the clearance ramp different.

Tim, When I went to set the lash on this cam the first time I checked the specs and didn't understand why a difference. I called their Tech line and they explained the reason was "due to our manufacturing process". I was certainly confused that if they did a grind on a cam to original spec, then it should have original lash specs. As you can see the specs are 0.010" I and 0.012" E. I was given this built within a short block rebuilt engine so I had to stay with it. I truly don't have a degree in camshaft technology so I couldn't argue with the data or the lash spec. THis could get confusing for future owners & technicans so I'm going to paste the Spec Card in the glovebox somewhere.

P1080023.jpg P1080024.jpg

Alden,So the parts man at NAPA doesn't turn you down tell him to plug in Federal Mogul for the CS113R.
It's a great cam and very affordable. I had no problems ordering one from Car Quest also.
This cam puts out great vacuum. 16" at 900RPM.
Probably a 100 or more posts on this cam here. Started off life as a TRW cam. Then Sealed Power Cam. And Now a Federal Mogul cam. Wonder who will be next. JD

John, I believe Federal Mogul is the parent company of Sealed Power products........Here is some info.

http://aftermarket.federalmogul.com/en-US/Brands/Sealed-Power/Pages/home.aspx

[Alden M.]

Re: 1958 Corvette Cam Specifications

Tim, When I went to set the lash on this cam the first time I checked the specs and didn't understand why a difference. I called their Tech line and they explained the reason was "due to our manufacturing process". I was certainly confused that if they did a grind on a cam to original spec, then it should have original lash specs. As you can see the specs are 0.010" I and 0.012" E. I was given this built within a short block rebuilt engine so I had to stay with it. I truly don't have a degree in camshaft technology so I couldn't argue with the data or the lash spec. THis could get confusing for future owners & technicans so I'm going to paste the Spec Card in the glovebox somewhere.

[ATTACH=CONFIG]50087[/ATTACH] [ATTACH=CONFIG]50088[/ATTACH]



John, I believe Federal Mogul is the parent company of Sealed Power products........Here is some info.
http://aftermarket.federalmogul.com/...ages/home.aspx

"Does anyone make a hydraulic equivalent cam that is simular to the "Duntov" specification"

[Timothy B.]

Re: 1958 Corvette Cam Specifications

Rich,

I am glad you posted that information, I know enough about this to get in trouble but it's got to be a different clearance ramp to change the lash specs.

Alden,

To answer your question it's the L-79 hydraulic camshaft and IMO it's a nice camshaft for a street driven car. Keep in mind you will get many opinions about camshaft selection so be careful.

[Joe C.]

Re: 1958 Corvette Cam Specifications

Rich,

I am glad you posted that information, I know enough about this to get in trouble but it's got to be a different clearance ramp to change the lash specs.

Alden,

To answer your question it's the L-79 hydraulic camshaft and IMO it's a nice camshaft for a street driven car. Keep in mind you will get many opinions about camshaft selection so be careful.

Timothy,
Although lash will reflect clearance ramp height and should "take up" all of it, as you probably know many solid tappet cams have more than one lash spec. For instance, the 097 (Duntov), as installed in 283 engines used .012/.018 lash, while in 1962-63, as installed in the 327 used .008/.018 lash.

The 151 cam is very different from the 097. It has 114 degree lobe separation v 110 of the 097, has 221/221 0.050" durations v 228/230 on the 097, and has .447/.447 gross valve lift versus .395/.401 of the Duntov.

[Timothy B.]

Re: 1958 Corvette Cam Specifications

Hi Joe,

Thanks for setting me straight on the camshafts. So if I understand this right the L79's 114* lobe separation would give more vacuum because of less valve overlap and a little less duration would not rev like the 097 camshaft.

[Joe C.]

Re: 1958 Corvette Cam Specifications

Hi Joe,

Thanks for setting me straight on the camshafts. So if I understand this right the L79's 114* lobe separation would give more vacuum because of less valve overlap and a little less duration would not rev like the 097 camshaft.

Timothy,

The advertised durations, or durations @ .006" valve lift of the 097 vs 151 cams are 270/270 vs 290/290, so despite the 151s wider lobe centers, it has more valve overlap. This means that it will produce less idle vacuum than an engine of equal displacement equipped with the 097 cam, and will have the ability to produce more power at higher RPMs by virtue of exhaust pulse tuning and intake pulse tuning because of its greater overlap. The 097 will have the ability to rev higher because it's a solid lifter cam, although the 151, with its longer duration and larger overlap should maintain higher torque until valve float sets in.

[Duke W.]

Re: 1958 Corvette Cam Specifications

Hi Joe,

Thanks for setting me straight on the camshafts. So if I understand this right the L79's 114* lobe separation would give more vacuum because of less valve overlap and a little less duration would not rev like the 097 camshaft.

A couple of points.

1. You cannot directly compare .050" lifter rise duration of mechanical lifter and hydraulic lifter cams because part of the first .050" lifter rise of a mechanical lifter cam is clearance ramp where the valve is not yet moving. In the case of a hydraulic cam, at least theoretically, all of the lifter rise above the base circle is converted to lift at the valve. In the case of the Duntov cam the tops of the constant velocity clearance ramps above the base circles are .008/.012". The comparable duration data for the Duntov cam would be at .058/.062" lifter rise. At these lifts the Duntov duration is about 220 degrees, which is very close to the L-79's 222. This information I derived independently from the lift data (specified to five decimal places every cam degree) in the GM drawings and my dynamic analysis, which computed the velocity, acceleration, and jerk profiles for most OE Chevrolet lobes.

The Duntov cam has very harsh dynamics just above the tops of the clearance ramps compared to the L-79 cam, so the SAE J604 duration (measured at .006" valve lift) is considerably less than the L-79 cam. Chevrolet learned in the early to mid-sixties with the Optron machine that dynamics needed to be softened to avoid false valve motion and valve bounce off the seat upon closing at high revs. These lessons are reflected in the L-79 lobe dynamics.

By the same analysis the .050" duration (above the tops of the clearance ramps) of the 30-30 cam is 239/239 and the LT-1 cam is 231/239 compared to the specified 254/254 and 242/254. The L-72 cam specified at 242/242 is really 231/231. The reason some of these numbers are the same is that the LT-1 uses the 30-30 lobe on the exhaust side, phased four degrees earlier, and the L-72 lobe on the inlet side on a slightly smaller base circle.

2. Given the wider LSA of the L-79 cam, which has nearly the same effective duration as the Duntov, it has less effective overlap than the Duntov, which is why the L-79 cam has a tamer idle (750 @ 14-15") versus the Duntov's 900 @ 12-13".

LSA can only be used to compare effective overlap if durations are the same or very nearly so. If duration increases at the same LSA, effective overlap will increase.

The Engine Analyzer simulation program computes effective overlap in square-inch-degrees. The L-79 is 4.2 and the Duntov is 7.5; LT-1 is 8.1 and the 30-30 is 10.8. Since effective overlap is partial function of valve size, these values will vary slightly depending on installed valve size. BTW the 300 HP cam is 0.9.

Modern Corvette engine camshafts compared to vintage SHP cams are generally shorter duration and have less than half the effective overlap of the L-79 cam, but valve events are phased 6-10 degrees later, and this also defines the McCagh Special camshaft that I designed specifically for base engines with massaged vintage OE heads. It makes up to 20 percent more top end power and another 1000 useable revs without affecting low end torque or idle behavior.

When you have high head flow, you don't need a lot of low-end-torque killing duration and overlap to achieve high specific power output, and short duration/low overlap yields a smooth idle, stump-pulling off-idle torque, and good fuel economy.

High overlap is only effective with a racing exhaust system - properly designed headers and open exhaust that can harness wave dynamics to increase volumetric efficiency. You can't harness wave dynamics with manifolds and mufflers and increasing exhaust back pressure increasingly negates the effect of headers, which is why modern Corvettes have high flow manifolds and exhaust systems in conjunction with relatively short duration, low overlap cams that are phased very late compared to vintage cams.

The "Tale of Two Camshafts" article in the fall 2010 Corvette Restorer has a chart of basic specs that illustrate the different design philosophy of then versus now.

Duke

[Joe C.]

Re: 1958 Corvette Cam Specifications

A couple of points.

1. You cannot directly compare .050" lifter rise duration of mechanical lifter and hydraulic lifter cams because part of the first .050" lifter rise of a mechanical lifter cam is clearance ramp where the valve is not yet moving. In the case of a hydraulic cam, at least theoretically, all of the lifter rise above the base circle is converted to lift at the valve. In the case of the Duntov cam the tops of the constant velocity clearance ramps above the base circles are .008/.012". The comparable duration data for the Duntov cam would be at .058/.062" lifter rise. At these lifts the Duntov duration is about 220 degrees, which is very close to the L-79's 222. This information I derived independently from the lift data (specified to five decimal places every cam degree) in the GM drawings and my dynamic analysis, which computed the velocity, acceleration, and jerk profiles for most OE Chevrolet lobes.

The Duntov cam has very harsh dynamics just above the tops of the clearance ramps compared to the L-79 cam, so the SAE J604 duration (measured at .006" valve lift) is considerably less than the L-79 cam. Chevrolet learned in the early to mid-sixties with the Optron machine that dynamics needed to be softened to avoid false valve motion and valve bounce off the seat upon closing at high revs. These lessons are reflected in the L-79 lobe dynamics.

By the same analysis the .050" duration (above the tops of the clearance ramps) of the 30-30 cam is 239/239 and the LT-1 cam is 231/239 compared to the specified 254/254 and 242/254. The L-72 cam specified at 242/242 is really 231/231. The reason some of these numbers are the same is that the LT-1 uses the 30-30 lobe on the exhaust side, phased four degrees earlier, and the L-72 lobe on the inlet side on a slightly smaller base circle.

2. Given the wider LSA of the L-79 cam, which has nearly the same effective duration as the Duntov, it has less effective overlap than the Duntov, which is why the L-79 cam has a tamer idle (750 @ 14-15") versus the Duntov's 900 @ 12-13".

LSA can only be used to compare effective overlap if durations are the same or very nearly so. If duration increases at the same LSA, effective overlap will increase.

The Engine Analyzer simulation program computes effective overlap in square-inch-degrees. The L-79 is 4.2 and the Duntov is 7.5; LT-1 is 8.1 and the 30-30 is 10.8. Since effective overlap is partial function of valve size, these values will vary slightly depending on installed valve size. BTW the 300 HP cam is 0.9.

Modern Corvette engine camshafts compared to vintage SHP cams are generally shorter duration and have less than half the effective overlap of the L-79 cam, but valve events are phased 6-10 degrees later, and this also defines the McCagh Special camshaft that I designed specifically for base engines with massaged vintage OE heads. It makes up to 20 percent more top end power and another 1000 useable revs without affecting low end torque or idle behavior.

When you have high head flow, you don't need a lot of low-end-torque killing duration and overlap to achieve high specific power output, and short duration/low overlap yields a smooth idle, stump-pulling off-idle torque, and good fuel economy.

High overlap is only effective with a racing exhaust system - properly designed headers and open exhaust that can harness wave dynamics to increase volumetric efficiency. You can't harness wave dynamics with manifolds and mufflers and increasing exhaust back pressure increasingly negates the effect of headers, which is why modern Corvettes have high flow manifolds and exhaust systems in conjunction with relatively short duration, low overlap cams that are phased very late compared to vintage cams.

The "Tale of Two Camshafts" article in the fall 2010 Corvette Restorer has a chart of basic specs that illustrate the different design philosophy of then versus now.

Duke

The underlined is very true.

I was not talking about 0.050" durations; I was talking about "effective" seat to seat durations which are what is specified in SAE J604d. Although some cam manufacturers, like Federal Mogul use J604d for advertised durations, others use values like 0.010", or another which is very close to SAE J604d, in order to approximate "seat-to-seat" durations. The advertised durations are more important than 0.050" durations when matching SCR to camshaft because the valve effectively passes no more air/fuel mixture once closed further than (about .006"). Valve timing at .006" valve lift is what's needed to determine the intake valve closing point ABDC. The durations quoted in post #13 are from Speed Pro's cam cards for their reproduction 151 and 097 cams.

Engine idle vacuum can not be established by using a single duration such as "seat-to-seat" or 0.050" lifter rise alone. Two or more durations at different valve lift must be employed together, and then both curves plotted on a cam degree versus rise graph, preferably using rise as the abscissa. Each camshaft's area under the curve during the overlap phase, must be compared in order to quantify differences in idle vacuum. It's easy to see that a cam whose lift/degree is rapid, like a roller cam, will have less vacuum at idle compared to a flat tappet camshaft whose seat to seat OR 0.050" lifter rise durations are equal. The difference, in degrees, between J604d and 0.050" durations, which I call "delta" determines the aggressiveness of the cam. The smaller the "delta" the faster the cam's flanks and the more efficient it is in filling the cylinders. It goes without saying that the comparison engines MUST have the same displacement!

Because the validity of camshaft comparison is based on at least two separate durations, the accuracy of Engine Analyzer cannot be relied on. This program only uses an approximation of camshaft dynamics with a drop down menu listing "mild", "aggressive" and "inverted" cam lobe profiles. Engine Analyzer Pro must be used since it defines a cam by, among other things, quantified durations at at least two different points (J604d, 0.050" lobe lift, 0.200" valve lift).