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Has any one ever put dowel pins in the main caps to stop cap walk, I was at the machine shop today and we were looking at my block which has had some cap walk and thought of doing hollow dowel pins on each bolt, looks like it should help a good bit, what do you guys think :confused:
 

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Has any one ever put dowel pins in the main caps to stop cap walk, I was at the machine shop today and we were looking at my block which has had some cap walk and thought of doing hollow dowel pins on each bolt, looks like it should help a good bit, what do you guys think :confused:
Great idea.
 

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Ford does that on the A 460 blocks' caps front and rear. It might help a little but I think that most all of the metal transfer from cap "walk" really comes from the cap simply flexing around under the load and I think you'll always see a small amount. I can think of a few instances where the engine showed a very small amount of metal transfer after a season or so of use and it looked the same the next time the engine was freshened too, it never got any worse.
 

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Has any one ever put dowel pins in the main caps to stop cap walk, I was at the machine shop today and we were looking at my block which has had some cap walk and thought of doing hollow dowel pins on each bolt, looks like it should help a good bit, what do you guys think :confused:
I dont know that there is enough room for dowel pins on the 2-bolt blocks but dowels around the main bolts (like those used on the cylinder head bolts) could help in some cases and there's plenty of room. I've evaluated this and would fab dowels from seamless chromoly tubing.

Although I have no personal experience, I suspect that, A) it may help minimize cap walk in some (but not all) cases, and that, B) there is likely a "hp window" where this is beneficial BUT once you exceed that hp window you might be better off leaving the dowels out and letting things move around rather than pinning the caps in place and thereby diverting those extreme forces somewhere less strong in the block such as the center of the main caps or something like that.

Paul
 

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It has been done for 30+ years. It does a good job at stopping cap walk, but as Paul speculated it just moves the failure point. The following pictures are from a 408W circle track engine that was dowel ringed. After about 20 nights in a 1/4 mile paved oval outlaw late model we broke 3, 4, and 5 main cap. The engine was still running, but oil was pouring out the bellhousing from the rear main cap. The rear cap was broken in 3 pieces, only being held together by the oil pan and main studs.







Craig
 

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FWIW Pontiacs came from the factory with solid doweled(1/4" iirc) caps since 55. The dowels are located outboard of the centerbolts on both 2 and 4 bolt versions. If the fit is loose they fit a 5/16 pin.
Two things, 1 they do position the caps in the same place. That usually translates to seldom ever needing align bore/hone.
2 They have to fit correctly. Too loose they dont serve their purpose, too tight and you create a stress point in a area where you want to minimize stress. If you used aftermarket steel caps on an iron block the expansion rates are different, and this could add to stress at those points so you only need a bit tighter than slip fit.

Using a factory production block tied at 4 corners or solid in the middle, puts twisting forces thru the block which wreaks havoc on main cap/bulkhead alignment. They were never designed to be part of your frame.

If you use a mid-plate and soft mounts you are putting twist primarily to bell... a very strong area and with rubber mounts its not going to put as much twist force thru the block. Of course if you've been using the entire block to control chassis twist you'll need to find another way.
 
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