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November 2005 4x4 Tech Questions - Techline

Posted in How To: Tech Qa on November 1, 2005
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Address your correspondence to:
Four Wheeler
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515.

All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Question: I have been spending the last couple years slowly restoring my '78 Ford F-150 Custom 4x4. It has a 351M engine and a C6 transmission. My 351M runs, but sounds like there's a bag of marbles in it. I recently came across a two-wheel-drive F-150 for $500 (on eBay) with a 302 and a C4. I bought the truck for the bed, which is in cherry condition. Since I have an extra 302 now, will it bolt up to the C6 replacing my shot 351M? Also, are there any books available that tell you what Ford parts interchange on these late-'70s trucks?
Joey C.
Strong Island, NY

Answer: Well, here's the bad news, Joey: The 351M is similar in design to your acquired 302, but there are several differences. For one, the block height is 1 inch taller, they take different motor mounts, and-the really bad news-your version of the C6 will not bolt up to the 302's rear block pattern. The 351M and the 400 use the same block pattern as the 429/460 engines. Now the good news is that there were a few C6s built for the 302. These are usually found in vans and Rancheros, but you're going to have to do some searching to locate one.

As to books on interchangeable parts, Ford's Motorsports Performance Equipment book may be a bit of help as to engine parts. I am sure there are specific books available, but all I have ever seen are books that deal with popular Ford cars such as the Mustang. However, one book that does come to mind is something that wrecking yards use and it's called a Hollander Manual. I believe these can be ordered through (800/761-9266).

Question: I love your magazine, and I've got to say I'd never have gotten my Jeep this far without it. I've hit a brick wall, though, on my Jeep and need some advice. I recently decided to paint my Jeep (rattle-can, of course). When I start a project, I like to get it right the first time, so I stripped all the diamond-plate off my rig to sand the whole tub down. Well, the previous owner installed the diamond-plate over 1/4 inch of Bondo body filler! How do I get this stuff off my Jeep? I spent all day with a chisel, a hammer, a grinder, and about every scraping tool I could muster, and this stuff just won't come off!

Anyone who uses body filler should be taken out and have every orifice packed with the stuff!
Jason Rowley
Grand Canyon, AZ

Answer: Two questions: if you're going to all the trouble to prep the body, why not buy a $29.95 spray gun, rent a compressor for the day, and do the job right? Why are you worried about getting the Bondo off? It must be "bonded" on pretty darn good to be that hard to get off. And if it's under the diamond plate, who's going to see it anyway?

If you want it off, you're going to have to spend another day or two with the chisel, grinder, and such. Be sure to wear safety goggles and a face mask. Oh, and by the way, my Jeep has lots of Bondo on it.

Question: I have stroked my '94 Cherokee XJ's engine, and installed new stock pistons and cam (I'm the original owner.) It now has a severe loss of power at highway speeds, detonates and/or pings under load, and overheats. I have a high-flow pump and thermostat and a three-row radiator. I cannot find anything wrong. Do you have any ideas what's causing my power loss? I suspect if I cure the power loss and pinging, the overheating will stop.
Martin Goetsch

Answer: Did you do the work, or did you have some shop do the rebuild? If it was the latter, then you and the shop wrenches better have a long talk before the engine self-destructs. As to the problem: As I see it, there could be three different problems. Lean fuel mixture, due to inadequate fuel flow; over-advanced ignition timing, most likely because the distributor was installed one tooth off; or improper cam timing due to the marks on the timing gears not being in alignment.

And while it's a total long shot, have you double-checked the spark-plug wiring? I have seen all sorts of weird things that indicated the above problems, but it turned out that spark-plug wires were just improperly routed.

Other things that could contribute to the problem: the computer, wrong spark plugs, and even some type of restriction in the exhaust system. Have you looked for a smashed tailpipe or a damaged muffler or catalytic converter?

In the Aug. '05 issue, a reader wanted to know what was the best limited-slip for his Dana 35 rear axle, and my advice was to forget about limited-slips as they were not worth the trouble or expense to put in. Well, did I ever get jumped on-not only by readers but by some folks at Tractech. Yep, you got it-the makers of the Truetrac limited-slip. I guess my mind was out four-wheeling with my Detroit Lockers when I answered that letter.

I keep forgetting that Tractech calls its very capable Truetrac a limited slip. I always think of it as a geardriven torque-biasing differential. When someone mentions the term "limited-slip," I mentally think of clutch-pack-type differentials like GM's Positraction or Spicer's Trac-Lok. From personal experience, I don't have a lot of love for clutch-pack differentials. Yes I know the Truetrac is a great unit. I had one up front in our Scout ("Project Tonto"), I had one in my high-horsepower CJ-5, and in fact I just talked a buddy into putting one in the front of his TJ. So I apologize to all for my error.

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