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cap walk

Post  Darrin Gorham on December 12th 2015, 1:36 am

Pulled my 466 apart after a broken oil pump and spun bearing. I used studs on #1.3.5 main caps and bolts with stud on 2,4. Engine is a 14 to 1 with eagle rods arias pistons dove heads 710 lift roller . The caps with the studs had half the metal transfer than the bolts.I know its been said the bolts are better than studs but this is my experience fyi.

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Re: cap walk

Post  Paul Kane on December 12th 2015, 3:26 pm

2-bolt passenger car block?
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Re: cap walk

Post  Darrin Gorham on December 12th 2015, 5:46 pm

yes

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Re: cap walk

Post  Paul Kane on December 12th 2015, 6:00 pm

I think you misunderstand the idea behind sticking with the OEM main bolts.  

Darrin Gorham wrote:Pulled my 466 apart...I used studs on #1.3.5 main caps, and bolts...with 2,4. The caps with the studs had half the metal transfer than the bolts. I know its been said the bolts are better than studs  but this is my experience.
The idea behind main bolts vs studs in a stock block is not to diminish cap walk, it's to allow the cap walk (as a matter of speaking).

OEM main bolts in exceedingly high horsepower builds allow the passenger car block to "breathe" or move around.  By upgrading to a stronger fastener, the standard bolts no longer work as dampening devices and instead the shock forces are transmitted directly through the stiffer fastener and straight to the main webbing (read: casting) which now must endure a far greater shock load than were OEM bolts utilized.

Therefore the main webbing is far more likely to fail with aftermarket fasteners than with OEM bolts. So when it comes to exceedingly high power builds that use passenger car blocks, let the main caps walk; that's the whole idea. Smile  Stronger fasteners belong in stronger blocks, and cap walk should be an accepted part of your ultra-high horsepower stock-block engine program.  If you simply cannot get over the idea of cap walk, you can get yourself a stronger block.

So it's not that "bolts are better than studs," it's that in this particular situation the OEM bolts are the better choice than an aftermarket stud upgrade.
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Incidentally as far as comparing cap walk between aftermarket studs and OEM bolts, your research is only half done.  In order to measure how much of a difference the bolts vs studs makes on your particular engine combo, you now need to assemble your engine in reverse with the main studs on 2 & 4 and put the OEM main bolts in 1, 3, & 5.  That way, you can document how each main cap's walk compares relative to the type of fastener in that specific main cap. Why? Because the crankshaft flexes in a "whipping" effect like that of a cowboy whipping his lasso around and so each main cap/fastener receives differing shock loads, and caps 2 & 4 inherently endure more loads than 1, 3, & 5 in the first place.  It might have been best to have done your comparo with all studs, then all bolts (or visa versa).
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Re: cap walk

Post  DaveMcLain on December 12th 2015, 8:50 pm

What I've always found interesting in the blown alcohol monster truck builds I've done using the SVO and production blocks is that whatever metal transfer has happened seemed to have done so on the first build of the engine. I've had those apart many times over the last 15 years or so and it seems like it has never changed or increased in any way.

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Re: cap walk

Post  gt350hr on December 14th 2015, 5:23 pm

Darrin Gorham wrote:Pulled my 466 apart after  a broken oil pump and spun bearing. I used studs on #1.3.5 main caps and bolts  with stud  on 2,4. Engine is a 14 to 1  with eagle rods  arias pistons dove heads  710 lift roller . The caps with the studs had  half the metal transfer than the bolts.I know its been said  the bolts are better than studs  but this is my experience fyi.

The broken oil pump and spun bearing are a sign of a balance/harmonic/detonation issue beyond the cap walk problem. A Kaase pump will solve the pump breakage but not what causes it. that's up to you.

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Re: cap walk

Post  Lem Evans on December 14th 2015, 8:07 pm

gt350hr wrote:
Darrin Gorham wrote:Pulled my 466 apart after  a broken oil pump and spun bearing. I used studs on #1.3.5 main caps and bolts  with stud  on 2,4. Engine is a 14 to 1  with eagle rods  arias pistons dove heads  710 lift roller . The caps with the studs had  half the metal transfer than the bolts.I know its been said  the bolts are better than studs  but this is my experience fyi.

   The broken oil pump and spun bearing are a sign of a balance/harmonic/detonation issue beyond the cap walk problem. A Kaase pump will solve the pump breakage but not what causes it. that's up to you.

Agreed and it's not clear if the oil pump issue and the bearing issue happened at the same time....if it did it's a clear case of the broken oil pump killing the bearing.

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Re: cap walk

Post  Lem Evans on December 14th 2015, 8:18 pm

"caps 2 & 4 inherently endure more loads than 1, 3, & 5"......quoting P. Kane
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That's been my observation.....regardless of bolts or studs....2 bolt or 4 bolt caps. If/when the tune up gets fussy the bearings at 2 & 4 are always the ones that look a bit pissed off.

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Re: cap walk

Post  rmcomprandy on December 14th 2015, 9:19 pm

Darrin Gorham wrote:Pulled my 466 apart after  a broken oil pump and spun bearing. I used studs on #1.3.5 main caps and bolts  with stud  on 2,4. Engine is a 14 to 1  with eagle rods  arias pistons dove heads  710 lift roller . The caps with the studs had  half the metal transfer than the bolts.I know its been said  the bolts are better than studs  but this is my experience fyi.

Stop the unheard detonation and/or the probable inherent imbalance and the main caps won't walk around.  I doubt you have enough cylinder pressure with any 466 NA engine to otherwise fret those cap surfaces.

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