i was wondering if there was any difference in camshaft manufacteurs. Like crane and melling for example. I would like to go with the melling because it only cost about 80 dollars but the crane costs close to 300. Also will i be able to tell any difference in between a stock hei distrubitor and a msd unit. Thanks for the help

 

Melling tends to be older designs. Newer cams push the envelope as far as quicker lift action. A good bang for the buck cam line is the Energizer from Crane, used to be made by Cam Dynamics. I've liked these since I saw a mag test where an Energizer with 228* duration beat out a Comp Cams High Energy cam with 230*. I run the 222* version in my 71.

Summit used to sell these for 100 bucks, cam & lifter set. Up to 122 a set now, still a good buy:

http://store.summitracing.com/egnsea...=KeywordSearch

As far as the HEI, if the engine is the typical street/strip sbc making 300-400 hp and the stock unit is in good shape, probably not. Spin it over 6k, or apply nitrous, then you need a better ignition.

 

You can have different cams with the same lift and duration and they're perform differently. The ramp profile is what makes the difference. Changing the profile can make a cam more aggressive by having the valve open more at lower lifts. It's all what's under the curve. Other factors not thought of when buying a cam is the Lobe Separation Angle, overlap and even the valve timing. The same duration but advancing valve timing a few degrees will make a cam perform differently.

The Comp Cams Xtreme Energy cams have very aggressive ramps.

If you take a program like DeskTop Dyno 2000 and input the different cams, you can see how much each changes the power curve. Sometimes the subtle changes don't look like much on the graphs but can be a big difference in the way the engine runs.

 

The $80 cams I have seen are mild flat tappet grinds and the $300 cams are likely billet rollers. Sounds like an apples to oranges comparison here. In any case, the published cam specs are vital to consider when comparing cams but they do not tell the whole story. Starting with "area under the curve', which has already been mentioned. You have to keep in mind you can have too much of a good thing. Some of Comps XE grinds work very poorly unless the supporting components are chosen carefully. The ramps are so aggresive that when combined with typical springs/retainers/valves, etc. they will not rev. Valve control is lost earlier than the cams peak power range and the results are often very disapointing. A simple sim like DD2000 does NOT take into account the ability of the rest of the valve train to work harmoniously with the cam.

Going a little further, there is the issue of valve train longevity. Two cams can be nearly identical except for subtle differences in the opening and closing ramps. One design may really slam the valve down on the seat and lead to accelerated wear or even parts breakage in addition to valve float. Another may be much easier on parts. The, of course, there are differences in the quality of materials and manufacturing process. Comp has really gone downhill lately. There is the debacle of the 918 springs documented on this site. Their cams have also been going downhill. We have had a number of defective gronds in the shop recently. One SBF cam had a couple of the lobes 1/8" out of the proper position - the lobe was not centered under the lifter bore. This caused the loss of a very expensive motor and gave me another thing to check when assembling a motor. Just the worst example.

Rich

 

I think im going to go with the melling and save a couple of bucks and maybe go with the high dollar setup later on if i decide to rebuild this engine.
Thanks for all the help.