Author Topic: Billet main cap replacement  (Read 7948 times)

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Offline gusszgs

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Billet main cap replacement
« on: October 12 2018, 07:41:52 PM »
Guys TA offers 2 bolt billet main cap kits, either all four or the front 3


My question is, can this or would this be a wise upgrade on a USED stock block in good shape if your going to "push"it shall we say. Not crazy, but say with ported irons and a nice 206 or 212 roller cam with something like a 6262 turbo.
What would be involved in installing these caps? Simply pull the factory caps and insert your bearings into the new billet cap and retorque? (new ARP hardware would be added)


Forgive my ignorance as I've never dug into the little 6 before and I'm far from a machinist. TIA
Jim   
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Offline Steve Wood

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Re: Billet main cap replacement
« Reply #1 on: October 12 2018, 08:20:57 PM »
You cannot simply bolt them on.  Different shops will probably do things differently, but, at a minimum, they will need to be align honed.

Yes, I think it is worth it if you are going to push it.

check with Joe Buick...that should be a good starting point and don't tell him what the internet said....LOL
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Offline gusszgs

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Re: Billet main cap replacement
« Reply #2 on: October 12 2018, 09:03:56 PM »
Lol ok thanks Steve, I kinda suspected this but wasn't too sure. Cheers
Jim
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Offline good2win22

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Re: Billet main cap replacement
« Reply #3 on: October 12 2018, 11:54:17 PM »
For what you're looking to do, just the two centers would be plenty.  The corners will need the edges chamfered and the bores align honed.
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Offline daveismissing

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Re: Billet main cap replacement
« Reply #4 on: October 13 2018, 12:13:35 AM »
Is it that costly to go them all?
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Offline Scoobum

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Re: Billet main cap replacement
« Reply #5 on: October 13 2018, 12:27:37 AM »
Is it that costly to go them all?

Machining is where the cost is. The caps may have to be chamfered to fit the block. An elongated dial indicator is used to the check bores. Too loose and the caps have to be cut. The align bore is best...as you can take most of the meat from the caps...and not the block...which keeps the crank from moving further up in the block.

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Offline wmsonta

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Re: Billet main cap replacement
« Reply #6 on: October 13 2018, 12:56:59 AM »
I wasn't going to get involved in this, new here and all. Seemed well covered.
No experience w/gn's, but some with chevys, fords, mopars, etc.
All the billet replacement main caps in my experience, needed align bore and honed.The last one was a mopar, which required a special order timing chain. Probably half will. Easy to get, not cheap + the hassle of trial/error, shipping, etc. I prefer the IWIS chain, especially w/mopars.

Few main caps actually break. Fitted billet caps are the modern answer to cap 'walk'. Previously there were 'strapped' caps, 'wedding bands', various girdles, etc.
HTH
« Last Edit: October 13 2018, 01:03:37 AM by wmsonta »

Offline earlbrown

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Re: Billet main cap replacement
« Reply #7 on: October 13 2018, 01:14:38 AM »
Another thing to consider is the machinist has to make DAMN sure the thrust bearing is square and true before line boring. Since the Buick V6 uses a narrow cap for thrust, it's pretty easy to get it crooked and clamp it down.

 If it's off, only 1/2 the bearing area will be available to do the job.  With our power levels and converter pressure, that's pretty much a death sentence.
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Offline Steve Wood

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Re: Billet main cap replacement
« Reply #8 on: October 13 2018, 10:37:59 AM »
Line boring, or align boring, is another kettle of fish as it brings its own problems because it moves the crank closer to the cam which means we need a shorter timing chain.

Hopefully your block is not "warped" enuf to need that, but, only the machinist knows. :D

Another problem that may be encountered is the fit of the aftermarket caps to the block. I recall quite a few that failed because the the caps did not index properly to the block saddles and they "walked" under power and  there went the bearings.

The most important factor in installing new caps is the machinist...Lo tsa of people running steel caps so there should be some comfort there :D
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Offline earlbrown

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Re: Billet main cap replacement
« Reply #9 on: October 13 2018, 12:08:30 PM »
Definitely all about the machinist. And to a lesser effect, the tooling.


Line honing takes material all the way around the bores and moves the centerline up towards the cam tunnel.
Line boring, when done right, will leave an ever so slight dirty spot on that very top of the main bores.  That way all the material removed will be off the caps.  Then a couple of quick strokes with a honing mandrel for a better finish.
 Needless to say, doing it right, takes a lot of time.    It really depends on if the machinist is in it for the money per clock hour, or anal (giggidy) enough to do all the steps to do it right.

The bad part is, both ways cost the same.

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Offline Grumpy

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Re: Billet main cap replacement
« Reply #10 on: October 13 2018, 01:04:59 PM »
Might be easier to just run a RJC girdle ??  :chin: Good machinist are out there BUT ya have to find em. :rock:

Offline TexasT

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Offline ss/gn

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Re: Billet main cap replacement
« Reply #12 on: October 13 2018, 07:24:48 PM »
Might be easier to just run a RJC girdle ??  :chin: Good machinist are out there BUT ya have to find em. :rock:





This or just replace stock bolts with studs. You will be surprised how much a stud will change things, and no machining involved.
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Offline earlbrown

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Re: Billet main cap replacement
« Reply #13 on: October 13 2018, 08:15:55 PM »
Studs are easy. Based on what I've seen with my own two eyes (and a bore gauge) there is not change in the bore size when changing over.

A girdle does require machining the caps, but pretty much any monkey with a mill and a quality vice can make that happen.
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Offline wmsonta

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Re: Billet main cap replacement
« Reply #14 on: October 13 2018, 09:01:58 PM »
This thread has evolved all the way to girdles?Did I miss what the goal is somehow? How fast does the original poster intend to go?

I spent my formative years during the evolution of Modified Production racing. I have seen some girdles. JMHO, girdles should be a forced alternative, not a choice.

No aftermarket blocks available?

What happened to stock motored gn's knocking on the 10's w/just bolt on components?


 

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