Can I swap non-roller cams and rockers into a roller head without messing with the valves, springs, or shims? I have a complete roller engine, and I want to put it in my '94 G20t, but I don't want to replace the springs ($600) just to keep my 7500 RPM redline. I also don't want to spend $500 rebuilding my low port head, nor do I really want to put a low port head on my roller block if I don't have to separate them.

the problem is the roller rocker valves and valves springs aren't designed to rev that high. I've heard of one or two people who were able to rev to 7500 on a stock roller rocker head using a B14ecu, but I wouldn't rev that high on a daily basis.

this has been discussed at length over on b15sentra.net...check out this thread:

SR20DE Valvetrain swap? - b15sentra.net forums (http://www.b15sentra.net/forums/showthread.php?t=64125)

"Also, to clear some stuff up, you can't mix and match roller engine parts (JDM and b15 stuff). The roller rocker has valves that are 3mm shorter (37mm versus 40mm) but the same head so changing the valve length, rockers, springs, and cams you can go from roller to non roller rocker. Head stays the same, but you can't use springs from a roller motor in a non roller or vice versa. You also can't mix the cams and rocker arms types and most JDM roller engines have different cams than the b15 (and higher revlims). This is a function of cam and spring..."

could always get a t25 and just shift at 6500 :)

If you have the time and space to work from an engine stand, a head swap is not hard. It's just a little time-consuming to label everything you disassemble, scrape old gaskets off, then seal and reassemble everything to specification. I did this over the winter in my carport when I put together a bastard engine with a rebuilt highport head and a low-miles lowport bottom end, proving any sap can do it.

Jon, what happened to your G20's lowport head? I have a lowport head (minus cams) from a '99 G20 with 45k on the clock that you could have for cheap if you wanted to go that direction.

the problem is the roller rocker valves and valves springs aren't designed to rev that high. I've heard of one or two people who were able to rev to 7500 on a stock roller rocker head using a B14ecu, but I wouldn't rev that high on a daily basis.

As I previously understood it, the springs are okay as long as you're not using a roller cam. The ramp speed on a roller cam is massively faster than that of a conventional cam, and running a stock spring with a high-lift roller cam is a recipe for disaster. I didn't catch the part where the valve was shorter.

Jim, you're getting an email.