More valve spring or rev kit?

[clutchdust]

The springs in the used AFR heads I have are barely rated at what my cam is spec'd. So for a while I've been thinking of just putting in a different set of springs. But I'm really wondering now if I would be better off buying a rev kit and just running the old spring (provided I don't have coil bind). I really see an advantage to running the rev kit and the cost would not be significantly different than the valve springs my lift would require. Besides, I'm concerned with the additional weight/inertia effect of the roller lifters vs. the flat tappet lifters I believe most springs are rated for.

 

[Carb Doc]

If your springs are at all marginal to what your cam requires. I believe that you have NO CHOICE but to upgrade to spec or better, the rev kit other than being a pain to install is a good idea anyway but they will not make up for the lack of valve spring pressure, the old rule of thumb used to be that you could get 250 to 500 more RPM out of a given set up but that was 30-40 years ago, cam profiles have changed a lot and the big issue is flying the lifter off the cam nose at full lift at higher RPM, the ovbvious result of this loss of contact over the nose is wrecked lifters, then the cam in very short order, the other alternative is to limit the operational RPM of the engine so thet the lifter is not moving fast enough to build up the momentum it needs to over come the Valve spring pressure, I know that this is a bummer but is a basic law of physics, there is a point somewhere above 5500 rpm that the spring can not keep things in contact as they should.. There is some VERY INTERESTING stuff on this , look on youtube spintron valve spring tests, some (good) springs are completely out of control well below 5500.

 

[clutchdust]

No, that's pretty much what I wanted to hear. I've been planning on buying new springs anyway. I don't think the springs that are in there are particularly marginal, it's just that they seem to be rated for a hydraulic cam with less lift than I'm going to run.
However, I really do like the idea of the rev kit. Anytime you can spred some of that spring pressure around. It would be nice to just use the valve spring to close the valve and a lifter spring to hold the lifter against the cam.
Right now I don't have any indication that the lifters, or valves, are floating. But I'm only running about .510" lift now. That will go up to about .540" when I put the AFR heads and 1.6 rockers on. I know it's still pretty mild, but it's more than what the springs that came with the heads are rated for, but just barely, hence the thought of using the rev kit.

 

[Carb Doc]

I don't know if you know about them or have ever delt with them, "COMPETITION PRODUCTS" in Ohkosh Wi, is a GREAT source of HD parts, they are a sub of Howards I think , we have delt with them for years and find that they give excellent service and advise, most important is that they are less expensive on a lot of things as they buy in bulk and there is no fancy packaging to pay for, they are on line at competitionproducts.com or 800-233-0199 or 920-233-2023, they have a great web site , and an excellent selection, you will have no problems coming up with valve springs to meet or surpass your appplication there.

 

[clutchdust]

Thanks for the suggestion. I will give them a shout once I get done with all my prep work. I'm smoothing the bowls and will lightly port the runners. "Clean up" is probably more accurate. I hope to get the heads mounted by summer, kind of a long shot though since I plan to install a whole new exhaust at the same time.