A few weeks ago we finally put the finishing touches on Project Yukon’s late-model engine swap — a task not nearly as difficult as most sales people will claim, but still not for the faint-of-heart. The good news: The Yukon’s running great with its new heart, and it’s a lot more driveable than it was before the swap.
Read on past the jump for some pictures, sounds, and a final project summary.
After we installed the new Chevy Performance Parts H.O. 350 in our last post, the Yukon was running, but not well. Though we had no major problems, we did have a number of minor problems that added up to some severely annoying crap.
First of all, we had forgotten to move over the knock sensor from the old engine. It’s way down there on the bottom, and even though we saw it there, we just forgot when it came time to pull and install it. This was causing the ECU to do all sorts of crazy stuff to try and reconcile the lack of knock sensor input, causing the timing to go crazy and the engine to utilize a screwball fuel mapping. Removing and installing the old sensor fixed the problem.
The lesson to be learned: Make a checklist as you’re tearing down the other motor. A number of other small problems like this caught us out — things we knew about at the time, but forgot about when it came time to remedy them weeks later. Use your checklist on the reinstall, and you’re good to go.
We had a couple of coolant leaks, most of which cleared up very easily. But one didn’t — a leak from the line running to the heater core. It connects to the manifold with a somewhat complex connector that we’d managed to mangle a little bit. A switch to a good ‘ole standard (and well-sealed) connector did the job just fine.
It’s worth noting that some 350s — like ours — utilize a really annoying combination rubber-and-silicon intake manifold seal that’s a bitch to install. We had to try ours twice, but on the second install it worked fine. Don’t go light on the goop — you’ll end up doing it again.
We also had the timing screwed up a little bit as we forgot to remove the plug to disable the computerized timing adjustment when we were setting static timing. It really wouldn’t have mattered much because the missing knock sensor was driving the computer nuts anyway, but afterward it made a difference. It’s an easy process of removing a wire from the computer, then setting timing like with any other V8.
With leaks stopped, the computer happy, and timing set to stock, it ran quite decently, though we’d also forgotten that the Yukon had been sitting a while before we brought it into the shop. While the gas didn’t smell, it had broken down enough to cause low-octane problems. A full tank of 93 later, and it’s running great.
Read on to page 2 for our end-of-project advice and more photos.
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