I need some advise here. I have a professionally built street driven 327 with an Isky hyd. roller cam and kit. Engine is 4 years old with 8K miles on it. Upon tear down I find cam wear on most of the lobes including the oil pump concentric. The engine builder has gone out of business, a machine shop here in town says the wear is because the cam blank is cast iron, should have been hardened steel. Spring pressures are 120 on the seat and 325 psi on the nose. What do you guys think? Should this cam be shot under these conditions? Thanks, Bill

 

Alot of cams are made of cast iron. Cast iron can easily be hardened . It has a high carbon content. White cast iron used for example in drain covers is extremely hard.
I teach an engineering class and for the lab I cut up a GM 3800 roller cam with a normal band saw and cut between the lobes with ease. The lobes are induction hardened so the cam is basically soft with case hardened lobes.
It certainly is not normal for all lobes to wear down but cast iron is normal for a cam. How did the mechanic know it was cast iron????


[Modified by norvalwilhelm, 7:42 PM 3/23/2004]

 

Some thing to look into is if the springs used by the builder are the ones required for the cam. Excess spring pressure would wipe the lobes or the lifters. I have done hardness tests on the lobes of roller cams and you would be suprised at how soft they are. I could do a hardness test tomorrow and post the results. If you think the cam lobes are too soft have a hardness test done on them. You need someone with a rockwell hardness test, Rockwell C to be exact and the reads could be checked against the company producing the cam.

 

Camshafts can be made of "chilled iron" which involves placing steel heat sinks around the lobes in the mold. The rapid chilling yields a very hard lobe surface, but it must be close to final contour to avoid excessive grinding. OE blanks typically are unique to each cam, so little grinding is required to achieve the final contour. With high volume production, this is the lowest cost process.

Aftermarket cams can be ground from cast iron or steel blanks. Grey iron blanks can be induction hardended after grinding, and steel blanks always require hardening after grinding.

Your spring pressures are high compared to OE, but not excessive. You might want to consider another cam vendor. Isky has fallen somewhat behind the times.

Duke

 

have a hardness test(rockwell) done on the cam lobes and compare them to a know good cam. a lot of roller cams were made from cast iron rather than hardened steel because of the lack of steel billits cam blanks when the manufacture went out of business. i think crane make all the steel billit cam blanks now

 

Duke/Norval,
Thanks for the reply. At this point there are more questions than answers. The builder (who has gone out of business) MAY have substituted an el cheapo cam and told me it was an Isky. All manufactures data has been ground off the back of this cam. I talked to an Isky tech rep yesterday, they would like to see the cam, it is headed West now.
One thing I did not mention in my original post, the fuel pump concintric has about 1/4" worn off of it. What does that tell you about the hardness (or lack of) of the camshaft? I am running a standard GM fuel pump.
When I get a definitive answer (10 days- 14 days) I'll post what has been learned, thanks again! Bill

 

If the manufacturer's ID is ground off, it is definitely suspicious, and the wear indicates some kind of problem - lowsy blank, not properly hardened after grinding, or reground beyond the useable limit - could be any number of issues.

I don't mean to knock Isky. Ed's sons run the business now, and Ed has stuff stashed throughout the buildings in Gardena, CA. The place isn't impressive to see and the equipment is old, but they are good people and will treat you right. However, if they determine it is not one of their cams or has been altered they would not be obligated to make an adjustment. You may have been screwed by an unscrupulous shop.

Let us know what Isky has to say.

BTW, to expand on Clem's post, I believe that all roller cams, hydraulic or mechanical lifter, OE or aftermarket are (or SHOULD be) ground from steel blanks, and then hardened. Chilled iron lobes are fine for flat tappet cams, especially for the mild acceleration of OE cams, but are generally not satisfactory for the more aggressive acceleration characteristics of roller cams or very aggressive flat tappet cams.

A true "racing cam" is generally considered a replaceable item and should not be expected to last the life of the engine like typical OE cams.

Duke




[Modified by SWCDuke, 12:06 PM 3/24/2004]