Quote:
Originally Posted by FUNFER2
Hey Fred, those look like good numbers for the hyd. cams.
I know quite a bit about motors and cams so, it's just deciding on the type. I like rollers and Keith said the one's he uses, with oil holes drilled in the bottoms, have lasted around 20,000 miles, which is a lot for our cobras.
We lash the valves on the sprint car every week but, having to lash the cobra all the time,....I don't know. I guess I'll ask you guys and Keith apx,...how often, if driven weekly.
I check my solid flat tappet twice per season. |
Hi Kevin,
It was nice talking with you today! For the benefit of others on the forum, let me share some of what we talked about on the issue of a hydraulic roller vs a solid roller cam. The big difference between a hydraulic roller vs a solid roller CAM setup has to do with valve train strength, weight, and therefore how agressive you can get with the lobe profile (ie how fast the CAM can open an close the valves). The lighter valve train weight of a solid roller (the lifters are lighter) also allows the engine using one to rev to higher RPMs. There are lots of good reasons to run a solid roller CAM in a race applications (sprint cars, drags, etc) where high RPM HP is very important. On the street where lower end torque is usually more important the advatages are less. Consider this. To get the lifter to stay on a very radical lobe that most solid roller CAMs use to gain their performance advantage, you need to use VERY stiff springs and make all of the other valvetrain components as light as possible. Its not uncommon to see springs that increase seat pressure substainly and the use of exotic components like titanium valves and retainers in such engines for example. All of this works great in a race motor but you would have a hard time making such a setup last on the street. What did the CAM manufactures do to address the street guys who want to say they've running a "solid roller" cam? They created a less radical set of lobe profiles that don't require all of the exotic valvetrain components. These CAMs do produce some more lift and may rev a little higher than the hydraulic roller alternatives but the gains are much less pronounced than a race solid roller setup. In a street appplication that is operated below 3000 RPM and maybe buzzed to 5500 RPM once in awhile, I'm not sure that the performance gains would be great enough to justify the added expense and maintenance. I would build the motor with an aluminum flywheel instead and spend the difference somewhere else. This will get you a good bit of the fast reving performance that you are looking for and should be OK in a lightweight car like a cobra. Hope this helps.
- Fred