Gary Lewis Posted December 4, 2019 Share Posted December 4, 2019 This is to document an unusual reason why the backing plate is needed on 460's with the poly-groove belts. (The backing plate is a necessity for proper cooling as well.) When I got Huck, the 1990 half-truck, I noticed that the AC/PS bracket was broken at the bottom. Bill quickly suggested that there might not be a backing plate behind the water pump, and sure enough there wasn't one. So, why does a missing backing plate cause the bracket to break? In the pic below, circled in red you can see the four 7/16" bolts that very securely bolt the bracket to the block and the head. But circled in yellow you can see the one little 3/8" bolt that secures the bottom tab of the bracket to the water pump. In this pic you can see how that tab on the bracket is supposed to hit the water pump. The top four bolts are snug and the bracket hits the water pump perfectly. But without the backing plate there is a 3/16" gap between the bracket and the water pump. And the pic below shows what happens if you don't put the backing plate in and tighten the bolts down. The bracket on the left has been broken but fixed while the bracket on the right, which is the one off Huck, is still broken. Why do the brackets break? Because the bracket is pretty solid up top, and when those four bolts are tightened down it is going nowhere. And that little tab isn't nearly strong enough to flex that cast aluminum. So it breaks instead of bends. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 4, 2019 Share Posted December 4, 2019 So wait... You had TWO broken accessory brackets? I was pretty darn sure it was intact. 🤨 Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 4, 2019 Author Share Posted December 4, 2019 So wait... You had TWO broken accessory brackets? I was pretty darn sure it was intact. 🤨 I have three AC/PS brackets: The one you sent from the F450 and it has not been broken; The one from Huck and it is broken; and one from I don't know where and it has been broken but is repaired. Bill - Did you send me one? Was I supposed to send it back after PC'ing it? Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 4, 2019 Share Posted December 4, 2019 I have three AC/PS brackets: The one you sent from the F450 and it has not been broken; The one from Huck and it is broken; and one from I don't know where and it has been broken but is repaired. Bill - Did you send me one? Was I supposed to send it back after PC'ing it? No you I didn't, I was going to offer the good one from the new engine in return for a PC'd set, even the repaired one if you needed it. BTW, what water pump are you using? I have never had a fit problem on mine. Link to comment Share on other sites More sharing options...
CountryBumkin Posted December 4, 2019 Share Posted December 4, 2019 No you I didn't, I was going to offer the good one from the new engine in return for a PC'd set, even the repaired one if you needed it. BTW, what water pump are you using? I have never had a fit problem on mine. That's a good point about the backing plate adding the additional thickness needed for that bottom bracket bolt. But I'm not so sure that bottom bolt is even needed. The water pump sure doesn't need it and the bracket itself is very well secured to the cyl head by the four 7/16 bolts. Â Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 4, 2019 Share Posted December 4, 2019 BTW, what water pump are you using? I have never had a fit problem on mine. Y'all EFI guys are using the later pump, with the different inlet??? Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 4, 2019 Author Share Posted December 4, 2019 BTW, what water pump are you using? I have never had a fit problem on mine. Y'all EFI guys are using the later pump, with the different inlet??? I'd agree that the bracket probably doesn't need the lower bolt. But I want it there as Ford designed it that way. As for water pump, it is the later EFI pump, although I don't know the brand. Came from Scotty, so I'm sure I have the brand in the paperwork. But it does have the larger shaft and flange as Huck's pulley won't fit. Only the one Jim sent from the F450. Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 4, 2019 Share Posted December 4, 2019 That's a good point about the backing plate adding the additional thickness needed for that bottom bracket bolt. But I'm not so sure that bottom bolt is even needed. The water pump sure doesn't need it and the bracket itself is very well secured to the cyl head by the four 7/16 bolts. It is probably more of an anti-vibration stabilizer. Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 4, 2019 Share Posted December 4, 2019 BTW, what water pump are you using? I have never had a fit problem on mine. Y'all EFI guys are using the later pump, with the different inlet??? I have an early pump on Darth, but the new engine has the later pump. on neither one is there any interference with the alternator tensioning bracket. I am using AutoZone new Duralast pumps. Link to comment Share on other sites More sharing options...
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