robertfrank

iTrader: (27)

Also Cosmick you'd do well with a ZZ4 cam and mildly worked L31 heads. I know my L03 with ZZ4 heads and cam was a fun little motor. Didn't take me much to tune in as well.

robertfrank

iTrader: (27)

So my last thing to say is the LT1 cam is a total waste of time. I personally wouldn't run anything less than a ZZ4 cam using 1.6 rockers on the intake and 1.5 rockers on the exhaust. It's a great combo with the right set of heads and a tune.

cosmick

I've driven a ZZ4-cammed L31, it's an excellent match. The L31 heads have a lot better intake flow than exhaust, the ZZ4 cam uses a bunch more exhaust lift and duration that helps compensate. The RPM ranges are fairly well matched, both are good through 5500 but are nosing over before 6000, and the lift is an excellent match, the ZZ4 intake lift is 0.474", the L31 intake port flow stalls above 0.475" lift. If you lift the intake valves any higher, flow falls off dramatically, and doesn't recover when the valve closes past the 0.475" point. The ZZ4 cam is great for low-end torque, as is the Vortecs being only 170 cc, which is best matched to 340 ci. Plus the ZZ4 cam is good for emissions, as are the fast-burn chambers of the L31 heads.

cosmick

I would. My '94 Z28 was a heavy convertible with an automatic and the lame 2.73:1 axle, a 2.5" cat welded into the 2.75" intermediate pipe, and a Hypertech tune, but the cat was little restriction at our high elevation, where we only get 85% of advertised power anyway.
But that LT1 cam idled dead smooth, gave good idle, emissions, and mileage, plus it pulled through 6200 RPM.
Sure, you could do slightly better with a hair more lift, but I don't want it from higher-ratio rockers that are counter-productive for power in a high-RPM HR application.
If I wanted more power from an LT1, I'd just turbo it, and I'd love to find one for my S-10, since the LS swap doesn't fit as well as advertised, even when you do the Cherokee steering shaft and the tubular upper control arms. But having already done one S-10 350 swap, I wouldn't turbo an LT1 in an S-10. And an L31 is a cheaper, more-common version of the LT1, without the Opti-spark problems, so I might try a '94 Z28 cam in an L31 yet.

Fast355

iTrader: (2)

I have run a LT1 cam in a 1999 Suburban and it was a QUICK truck. I had a LT4 cam with 1.6s in an otherwise stock L31 in my Express and it pulled strong until the intake choked it about 5,500 rpm. As far as higher ratios not working at higher RPMs all I can say is BS on that. Factory LS rockers are 1.7 and the LS7 even has 1.8s. My Express currently has a '395 marine cam and 1.7 rockers on top of a set of ported 2.02/1.60 valve 906 vortecs. I pull my travel trailer with it and it pulls very strongly up to 5,500 rpm despite the baby cam. I run tri-y headers and a marine intake with a coil per cylinder 24x ignition and 0411 PCM on the Express. Puts down 290 rwhp @ 5,000 rpm and 330 rwtq @ 3,400 through a 4L80E/9.5" 14-bolt despite turning a Duramax mechanical fan. Better than the Stock 8.1 Suburban with the same driveline that ran right after my dyno that day. Also only 10 HP less than an intake/exhaust/tune LQ9/4L60E that ran right before but 40 ft/lbs more.