2 bolt main into 4 bolt main
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
You don't say which platform SB or BB??
If you're talking BB I can show you a short cut to have 4 bolt caps with any new caps, any align boring, or any align honing! Over 50 years we've done hundreds using this method, have one here today we're wrapping up! (Modified cap photo below)
When doing the machine work for the (outer row) of fasteners you need to pay close attention to the depth of these particular holes, if not very careful you can intersect the oil passage from the pan rails to the cam tunnel?? I've seen many shops ruin good blocks from not be familiar with this area of the casting!
Thanks, Gary in N.Y.
P.S. Here's the finished cap, on very high HP builds I would definitely use aftermarket caps though, once above the 700+ HP range! The 2 outer holes are in the identical location as the OEM 4 bolt holes, if anyone wanted to put the OEM style 4 bolt ones back on the existing holes are positioned correctly. We set them up for some 7/16" fasteners and supply the ARP main stud kits.
If you're talking BB I can show you a short cut to have 4 bolt caps with any new caps, any align boring, or any align honing! Over 50 years we've done hundreds using this method, have one here today we're wrapping up! (Modified cap photo below)
When doing the machine work for the (outer row) of fasteners you need to pay close attention to the depth of these particular holes, if not very careful you can intersect the oil passage from the pan rails to the cam tunnel?? I've seen many shops ruin good blocks from not be familiar with this area of the casting!
Thanks, Gary in N.Y.
P.S. Here's the finished cap, on very high HP builds I would definitely use aftermarket caps though, once above the 700+ HP range! The 2 outer holes are in the identical location as the OEM 4 bolt holes, if anyone wanted to put the OEM style 4 bolt ones back on the existing holes are positioned correctly. We set them up for some 7/16" fasteners and supply the ARP main stud kits.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,398
From: SW Florida.
At first glance I thought you couldn't do the rear main the same way, but then I looked at a 4 bolt rear, and the outer 2 are offset forward a bit. This is a gen 5 rear, but I believe they are bolted in the same locations as a Mk4 and here are 2 and 4 bolt caps side by side.
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
If you are line boring it anyway, why not go for the 4 bolt mains and have it done all at once. If you aren't line boring it until you stroke it later why not run some 2 bolt ARP main studs until the time you stroke it so you only have to pay once for a line bore. If it can be done cheaply 4 bolt mains are a nice thing have holding your crank in place.
For what it's worth, my block is only a 2 bolt block with ARP main studs and it saw 7000RPM shifts on the regular at the track and even saw a missed power shift that went past 9000RPM and never had any problems.
For what it's worth, my block is only a 2 bolt block with ARP main studs and it saw 7000RPM shifts on the regular at the track and even saw a missed power shift that went past 9000RPM and never had any problems.
Last edited by bence13_33; Dec 16, 2017 at 11:15 AM.
Thread Starter
Instructor
Joined: Dec 2017
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I can’t as my dad is the one that got the engine for me from his friend so that would be kinda rude on my part lol.... I appreciate the offer though. I’ll arp stud it.
Racer
Joined: Aug 2011
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I'am just wondering if you guys understand what installing studs on a 2 bolt block entails to do the job right, anyone care to tell me what must be done? Will the average machine shop "do the work" to make it right? Factory BBC main bolts are not grade 8 bolts.
Last edited by Vortecpro; Dec 16, 2017 at 09:13 PM.
Thread Starter
Instructor
Joined: Dec 2017
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Obviously from the questions I’m asking no I do not know��. Hopefully the machine shop I’m going to use here locally does. They’ve been around for 40 years or ss, so I’m hoping they do. I’m looking at the splayed main caps and no way I could do that and feel comfortable by myself and yes if I used stock caps I would of just put on the mill and drilled and tapped holes but maybe that’s wrong, I heard there’s an oil galley to watch for. Anyhow there is too much at stake for something to go wrong so of course I want it done right.
This is very simple....all I’m trying to find out is what is the best way to put 4 bolt main caps on a 2 bolt main block without buying a new 4 bolt main block. That’s it....
Last edited by vettebuyer6369; Dec 18, 2017 at 01:37 PM. Reason: Combine repeated posts
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From: Lincoln, CA
Race Director
Joined: Jul 2015
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From: SW Florida.
ARP's instructions say the clamping force is much higher so the holes should be checked for size-roundness and possibly honed. they are fine thread nuts so they pull down a lot harder than the coarse thread bottom threads.
Last edited by derekderek; Dec 17, 2017 at 07:25 AM.
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From: Napa Valley California
I've considered buying a seasoned 4 bolt block $400-$800 or new GM 4 bolt block $1300. New GM blocks have the 4 bolt mains and come clearanced for the longer stroke and H beam rods so I would save some $$$ on machining. Then I could sell my OEM motor and TH 400 as a unit. Right now the only part on my OEM motor I might be using is the block anyways.
Last edited by OldCarBum; Dec 17, 2017 at 03:14 PM.
Race Director
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From: Napa Valley California
Thanks, I would consider that as an option for anyone, when the time comes. Right now I'm at least a year from pulling the body and starting my project.
Race Director
Joined: Apr 2007
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From: South Western Ontario
Post proof of the stock bolt being grade 6?
Post proof from a reputable source recommending the use of off the shelf grade 8 bolts for the mains?
I'd bet that the stock main bolts are much closer to the grade 8 120,000psi proof load rating then the 74,000psi grade 5 proof load rating.
Thread Starter
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Race Director
Joined: Jul 2015
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From: SW Florida.
I just sold four 350 and a couple extra sets of heads and a steel 20 under 350 crankshaft. I was lucky to get 350 bucks for the whole pile. But would have happily traded in for some aluminum big block heads. It's amazing how hard it is to sell 350 stuff anymore. The guy was so old school, he didn't even want my one piece 350 4 bolt block with rollers. So I still have one small block left if I have to have it.
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Close for review
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Completed.
Just a reminder, everyone who participates in the conflict will get sanctions, not just one guy.
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Completed.
Just a reminder, everyone who participates in the conflict will get sanctions, not just one guy.
Last edited by vettebuyer6369; Dec 18, 2017 at 01:43 PM. Reason: Completed review
