Why eight washers in windage tray install kit P3690939?

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dibbons

dibbons

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I did not find any large washers anywhere when I disassembled the 340 ( 0.40 over) with factory windage tray that I purchased. If they go under the main cap bolts, I don't believe the factory motors had any washers on the bolts and I don't want to limit thread reach by using washers not needed either. ??

Mopar Performance P3690939
 
the factory tray did not use any washers, and there are 10 cap bolts so 8 washers makes no sense
 
318 engines have a shorter, slightly less beefier main caps. Those windage tray bolt kits are for 340/360 engines that have taller and stronger main caps. The washers are there so that the bolts don't bottom out on 318/273 motors.
 
Never compared 318/340 main caps before, interesting. I installed a windage tray on a 273 back in 1975, never looked into before.
 
The washers can be use to avoid twisting or brinnelling the tray by putting them under the bolt heads. I personally would not be to worried about losing 1 thread of engagement but others may opine differently. The stress on the threads in the block at standard torques is well below the pull-out stress; the threads still hold up with a stress increase of 50-70% when lubed ARP studs are installed.
 
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if used without washers the 4 special main cap bolts will not brinnell the tray because the tray sits on top of them. and when I use studs I do not increase the stress by 50-70%
 
Marcohotrod said:
if used without washers the 4 special main cap bolts will not brinnell the tray because the tray sits on top of them. and when I use studs I do not increase the stress by 50-70%
Click to expand...
Yes 'duh' on the tray on top..... I forgot. Tnx.

My statement on the stress relates to using ARP studs (and bolts) with their lube vs dry torqued regular bolts. You don't TORQUE them that much higher, but just using the ARP lube on threads and under the nuts increases the clamping force (and thus thread stress) by about 40-50% even if you used the FSM torque level, and using more torque as per ARP's instructions adds more on top of that.
 
The hardened washers are for 273's and 318's so the bolt engagement stays the same using the longer 340/360 main cap bolts, see post 4. Always torque per instruction, whether dry or with some specific lubrication. It does make a difference.
 
How do we really know the correct answer? Like many things in the aftermarket, no instructions included. This Mopar stuff is much like the Egyptian pyramids in a way, no one currently alive knows for sure how they were constructed. You would think on a forum this popular, we would have at least one bonafide retired Mopar engineer here to answer some of the tough questions.
 
Actually, the washers are for a 360 application. 318s and 340s came from the factory without washers, but the 360 uses the washers because with the longer stroke, the rods tend to clip the tray. The washers move the tray further away from the crank, eliminating the problem. I've only ever seen four washers in the kit, though.
 
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