The 4 bolt main LIE !!! Or is it???

[HotRodPC]

So I tripped over this video this evening. I'm sure I've said it on here several times over the years. I DO believe this. I know you've seen some of my comments about my Street/Strip rides in the past. I ALWAYS did 2 bolt mains and spun them as high as 7000rpm with a stock OE cast crank. I was a budget racer and KNEW that BALANCING is most important than anything. Not Factory OE balanaced either. I mean TRUELY BALANCED, like by a professional with the equipment to do it. Have the whole rotating assembly matched, trued and balanced. I had guys GIVE ME 2 bolt blocks. They didn't want a thing to do with them. I've also said, if you really think you need a 4 bolt main, cuz some might depending on how hard they're going to beat on it, like maybe a high boost launch etc, then start with a 2 bolt main. Buy Splayed main caps, and have them and the block line bored. Then you have added strength. 2 more holes straight down into the main webbing is just weakening the block in that area IMO. The splayed mains will be angled bolts, also the holes are drilled further away from the main web in the block. All the splayed main is going to do, is add strength to the main cap, not the block webbing. I ended up selling all my 4 bolt blocks cuz people offered me to much for them and I'd just use a 2 bolt block GIVEN to me and spank their 4 bolt block they bought from me when they got it together.

But yeah, it's all up to you. I know there's different opinions, but I'll stick to my 2 bolt blocks. Of course, I'm not racing or have anything of any significant horsepower or torque these days.

Mind you, we are talking Small Block Chevy engines here, NOT LS engines. LS 4 bolts DO MAKE SENSE and they all are 4 bolt. Some even 6 IIRC. Ford Mod Motors, also are 4 bolt mains that make sense, like the 4.6 and 5.4 common truck engines.

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[Ricko1966]

I have no preference 2 bolt over 4 bolt they both have their weak points.In the majority of street small block builds a studded 2 bolt is just fine.

 

[Rustisbest]

I like an engine that runs, preferably in a car/truck that I can drive. Everybody knows 3 bolt mains are the ticket

 

[TotalyHucked]

Interesting take. I've heard all my life that what ya want is a 4-bolt main block but never looked into it more than that. I never even knew if the bolts were splayed or not. Splaying a 2-bolt block definitely makes more sense.

Just FYI, all LS engines are 6-bolt mains cuz of the deep skirted block. 4 straight down and 2 cross bolted through the skirt

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[Jrgunn5150]

Sometimes a thing can be true, and not matter in a given application.

It's why I cringe when anyone asks what the "best" thing is, for literally any aspect of life. I have a colleague who paid 13k for his dog, my Peanut was free. He's the best dog for me, 14 years now. He won't win a race, has no idea what a fight is, can't catch a duck. He's still the best dog for me.

Machining 2 bolts into splayed 4 bolts was the hottest ticket 15 years ago, for guys to drive down to the Sonic on Saturday nite and tell everyone they have it.

99% of hot rodding has always been, just bragging about how much you spend, gotta pay to play, know what I'm saying, hurr hurr hurr

 

[TotalyHucked]

You're not wrong. So many people hyper focus on one detail that they've been told is the best and they have to have that particular thing without considering everything else.

Like the guys that come around asking "What's the best place to get the biggest cam I can put in my 5.3 so it chops hard??". Go ahead and put that .660/.670 .248/.250 106 MF'r in there and that POS is gonna chop harder than a lumberjack on cocaine. But the minute you put it in gear with a stock converter it's gonna surge through the brakes so hard you can't stop it. Not to mention the power band is now up around 9500 so those 3.23 gears aren't gonna do you any good. And even if you manage to get the thing up there, the stock driveshaft isn't rated for more than 98mph so good luck when that exits the chat.

They don't consider all the ancillary stuff it takes to make a certain mod work or even worthwhile. Gotta think through the whole build stem to stern and pick realistic goals. Most people won't make use of the benefit of splayed caps just like alot of people won't push an LS hard enough to actually need 6-bolt mains. Although it is nice peace of mind to have if you have the budget for such things.

 

[Jrgunn5150]

Yeah, I mean, whether they're better or not, 99% of use cases will never test it.

 

[dragstews]

I started to build a 2-bolt 454 cid big block ..
Got pretty far into the build before I decided to do a 4-bolt ..

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This motor was mostly stock, rods, crank and pistons were Oem, never been apart since leaving the factory ..
Came from a motorhome with low mileage on the clock .. Was intending to low ball the build and roll the dice ..

Then I got to thinking about horse-power ..
I'm sure the 2-bolt could handle 400 or 500 ponies and stay together doing so ..
But not so sure about 600+ and taching to 7,000 rpm's ..

Okay ... For peace of mind I choose to go with a seasoned 4-bolt block with hi-po parts .. Goodbye Oem ..

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Forged steel 4340 stroker crank, H-beam rods and forged .080" over pistons took the 454 BBC to 500 cubies ..

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A 4-bolt main block is better for high-performance applications that involve extreme horsepower, high RPMs, or forced induction (like nitrous or a blower). For a standard street engine, however, a 2-bolt main block is often more than sufficient.
In the future the motor just might see a blower ??

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Got room for it and still be able to close the hood ..

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Keeping it a sleeper ..

 

[idahovette]

@dragstews Ya got a lot of toys don'tcha. In that vein, have you ever repaired a bbc front timing gear face where the torrington bearing went bad and dug into the block surface?

 

[dragstews]

Years ago I did a repair on one ...
In a mill did a counter bore to get under the damage .. Made a shim to sit in the bore ..
I been drilling .040" holes in the two oil galley plugs for additional lubrication to the cam chain and gears ..

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Plus bumping up the oil pump relief spring for a few more pounds of oil pressure ..
If running a deep pan a high volume pump works well ..

As far as the toys go ... Yeah, too many ..

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Dang turbo made this bike feel like riding 'Flipper'

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[xm20k]

I don't think it matters if 2 or 4 bolt for most SBC builds most are under 500 the majority of those probably actually under 400.

If built Correctly 600 is about all you'd want to try and squeeze from a SBC using a stock block. Yes a SBC could make more but then you're looking at Dart blocks with cam tunnels moved around oversized for rollers etc. not stuff the average guy is going to consider even looking at. At that point it's cheaper to go Big Block.

 

[dragstews]

At that point it's cheaper to go Big Block.

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[xm20k]

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Yes my next big power project will be putting a belt driven manifold on one of these, or similar if I build it myself.

Pardon Our Interruption

 

[dragstews]

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Damn shame to hide all that goodness under a oil pan !

 

[Goldie Driver]

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Damn shame to hide all that goodness under a oil pan !

Do they make a clear one ?