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Nuts & Bolts
4-Wheel & Off-Road
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515
fax 323.782.2704
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Big-Block In Blue
Question: I am building a 4x4 drag truck to race at a local mud bog. We race on dirt in the first half of the night and in mud in the second. Both tracks are 200 feet long. Can you recommend a Ford engine configuration to run in my truck? We are limited to cast-iron production blocks; however, we can do any mods we want to them. We can put whatever fuel, heads, carb, crank, and so on. We are not allowed to run nitrous. Basically we can go all-out except for the block. I want all the horsepower I can get, but I want it to be bulletproof (I don't want to tear down a muddy motor once a month). My budget is $10,000.
Joe Wright
via 4wheeloffroad.com
Answer: I'm not going to lie to you. Ford motors are not my forte. Though I like them, I've yet to purchase my first Blue Oval. However, my amigo Grande Stephano is a Ford man to the core. He's got more Ford projects than he'll ever get done, and he's not afraid to start more. I gave him your letter and got the following answer.
There is no replacement for displacement. Assuming that you are building a fullsize truck I would recommend going with the Ford 429-460 base engines. You can buy some nice stroker kits for that engine making the engine up to 514 ci. A company called Scat (310.370.5501) has just released a line of forged-steel (not cast steel or iron, be careful) crankshafts. Get a midweight connecting rod like a Scat I-beam (be sure the power rating of the rods you buy is at least 750) and a lightweight forged piston (flat top preferred, use small chamber head)
Cylinder heads make all the power. I recommend a set of small-chambered Blue Thunder heads with Chevy exhaust ports if you can find a set (low-production runs). Keep the intake work to a minimum. You don't want a large intake port; it will hurt the low end and acceleration.
Each point of compression will give approximately 15 percent more power. The small chambers and flat-top pistons will give you about 12 to 12.5:1 compression, so you will need good gas. You can go higher but large-dome pistons will hurt the flame travel of the engine. I would rather run lower compression with more timing; it's more forgiving and easier on parts. Can you run alcohol?
As far as the camshaft, Comp Cams (800.999.0853) has some pro mud-drag camshafts. You will have to call them and speak to a tech. If those camshafts are not available any more, ask for a short circle-track cam. I like single-plane manifolds and single carburetors that are annular discharge, around 950 to 1,050 cfm.
Don't forget the trans. I'd recommend a C6 with low planetary and a 10-inch converter that matches the cam's operation level.
Additionally, you can find Alan Huber's big-block Ford buildup on our Web site at www.4wheeloffroad/tech/huberbigblock1 and part two at www.4wheel offroad/tech/huberbigblock2.
B.O.M. Bummer
Question: I pulled a rear axle out of an '81 Ford F-350 pickup. The numbers I found on the tag on the cover are
3 73 ET2A ANA
605040 5
I also found these numbers on the passenger-side axletube
MR61U1741C4023B
605040 5
I was wondering if you might be able to tell me what I have, and if it's worth restoring and using. Any help would be greatly appreciated.
Brad Panzer
via 4wheeloffroad.com
Answer: To find the secret of your axle I called a couple of drivetrain specialists such as Parts Mike (530.885.0673) and my friend Big Steavie at 4-Wheel Parts (800.548.6454), where many Dana axle parts are sold every day. By referencing the bill of material (B.O.M.) numbers "605040-5" they both agreed that you have a Dana 61 full-floating rear axle with 3.73 gears. Not exactly the perfect axle, but not total garbage either. Dana 61s were built with a greater pinion-to-ring gear offset to allow for very high (low numerically) gearing as can be seen by your first three numbers on the tag, "3 73"; this represents the 3.73 ring-and-pinion ratio.
The digits "ET2A ANA" are some Ford number as is the "MR61U1741C4023B," though the MR61 is likely a reference to Model 61. Your axle also houses a "tall" Dana 61 carrier, which should allow you to go as low as 4.10 gears by using Dana 60 ring-and-pinions. Randy's Ring & Pinion (800.209.2881) also offers thick Dana 61 gears that can be used in conjunction with a Dana 60 carrier, but again the lowest available gearset is 4.10.
In order to go lower than 4.10 you will need a Dana 61 tall carrier (a Dana 61 Detroit Locker will also work) and one or two ring-gear spacers. I have not used ring-gear spacers personally, but have been told they are not the most recommended method. Most all of the drivetrain specialists I spoke with recommended you look for another axle to start with.