Engine Play
I followed the Jp 350 build and have a couple of questions. I have a '98 K1500 Z71 with the 5.7L Vortec engine in it. Can I do the same build to my current engine and expect the same power numbers? I shouldn't need the new heads as I already have Vortec heads, but the rest I would need, correct?
Dustin Hall
Marysville, WA
The short answer is yes and no. Yes you can work with your existing parts. No, you shouldn't use the same combo as I did.
For starters, you've got a roller cam block, so I wouldn't really recommend going with the flat-tappet cam and lifters that I used. A roller cam is much better and has the same or better power potential with more torque. You should be able to reuse your factory lifters and save a lot of money as long as they're in good shape. The GMPP LT-4 "hot cam" would be a good choice, but I wouldn't run the recommended 1.6:1 ratio rockers unless you're going to pull the heads because they require the pushrod slots to be clearanced.
On the cam specs, shoot for a hydraulic roller with an intake duration of around 210-214 degrees @ 0.050 and a max lift in the 0.470-0.480-inch range. That'll save you the hassle and expense of swapping springs. Or, if you're gonna swap springs, keep the max lift around 0.525-inch. The best thing to do would be to call a cam manufacturer's tech line and tell them your combo. They can recommend a good camshaft profile. It'll probably have 112-114 degrees of lobe separation angle for good idle quality with your injection. The cam I used has a rather choppy 110-degree LSA and would give your factory injection a more-difficult time down low and at idle.
The stock Vortec intake and poppet-style injectors are going to be your biggest limiting factors. With the right cam and upping the fuel pressure you can probably eke out 375hp/400lb-ft from your factory-injected Vortec. Or, if you're gonna go carb, pull the heads and clearance the pushrod holes for 1.6:1 ratio rockers and install the LT-4 camshaft, Comp 918 beehive valve springs, and keep your stock roller lifters and pushrods for cost savings. You'll be right near 400hp/400lb-ft with that combo.
Vintage Wheeler
I'm a retired old guy who just got into four-wheeling. I can't climb mountains anymore or even walk too far. But I can still drive, so I bought a new '09 Sahara and have a 2.5-inch TeraFlex lift scheduled which will allow me to put on 35-inch Goodyear MT/Rs. My next project, when finances permit, will be lockers, one at a time. I've read where rear lockers should precede front lockers, but since the Sahara came with a limited-slip rear end, I thought maybe a front locker would do me the most good. All of my trips will probably be here in Arizona, and I have no extreme rock crawling in mind. I have a few old-guy neighbors who have rigs and we just like to get back into the desert where few other folks tread. Your advice will be appreciated.
Ron Pinkowski
Gold Canyon, AZ
That sounds like a pretty good build plan. You'll like the TeraFlex lift and those Goodyears are great tires. But I do think you'll be less than impressed with the performance of the stock rear Trac-Lok limited slip once the larger tires are installed. The Trac-Lok works well with stock-sized tires, but it's relatively low-bias friction packs are geared more towards remaining invisible on-road than delivering off-road performance.
To that end, I'd still recommend the rear locker first. For starters, the Jeep will be more predictable when scaling obstacles. It will also put less stress on the weaker front axleshafts. If the rear isn't locked and the front is, you could find yourself in a situation where the front axle shafts may be more likely to break. It helps to have the rear axle pushing the vehicle along in conjunction with the front.
I'd also consider waiting and doing both front and rear lockers along with a gear swap. You'll see why when you get the 35s under your Jeep. Unless your Jeep has the optional 4.10 axle gearing, chances are you'll have a miserable time driving on the road with those bigger tires. I'd recommend 4.88 or even 5.13 gears to regain your on-road performance with the 35s.