Quote:
Originally Posted by Bob570
Sounds like a badass setup.
I wonder if you could mimic the results of the Hi-ram by shortening the runners in an MSD by an inch or 2, a lot of the C6Z guys have been doing this, although those guy have a much bigger displacement, so maybe it'll push the powerband too far up for an LS3? Just thinking out loud.
I can't wait to find out more, I was interested in your Max Package 1.0, knowing you guys, 2.0 will certainly be even better!
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We run the FAST LS7 LSXR for the "under the hood" option on the Max 2.0. The LS7 version of the LSXR gives us about the same performance the MSD Atomic Air Force does, and it fits better, so it's the winner in our eyes. The LS7 version of the LSXR does not have the variable length runners that the LS3 version has. However, you can modify the LS3 runners to work. So, to your point, it is possible to do a mid or short runner under the hood with a plastic manifold. I don't think the results will be quite as good as a high-ram, but you'll get a similar effect.
Also to your point, it's going to shift the power-band up substantially, and depending on the combination, that may not be desirable. With the standard length runners mine peaks at 7,000rpm, and holds on really good out to 7,800rpm. It's a stick car, so we need to basically rev it as far as we feel comfortable to help with shift recovery. We've got a good valvetrain for that, but to do much more than we do now, we'd really need to go solid roller. A shorter runner like a hi-ram is probably going to see the peak in the 7500-7700rpm range, which would mean 8500rpm shifts in a stick car. Even an automatic would want to turn it to 8000rpm or so. Doable, but depends on what you really want out of it. I wanted to stay hydraulic roller, and have a safety factor over the shift point just in case dumb stuff happens - it inevitably does. So, long runners were the obvious choice for me - and it still turns a bunch of RPM.
You're right on, the bigger cubic inch motors will tame the RPM back down a decent amount, and that makes the short runner stuff more viable for hydraulic roller combinations in that 400+ci range.