2 or 4 Bolt Main
Dr. Detroit
Joined: Mar 2012
Posts: 10,090
Likes: 4,015
From: New Braunfels Texas
There have been a few GM foundry workers who claimed that the 010 020 under the timing cover is BS. Wives tale is that these blocks contained .1% more tin and .2% more nickel. Tin makes 'em easier to machine and nickel makes 'em harder.
There's not a factory block that will hold a candle to an aftermarket block, including Bowties, when it comes to hardness. Ask any machinist - particularly the ones that bore and hone blocks. It's a completely different cast iron recipe and the ingredients are a small part of why these blocks are more expensive.
There's not a factory block that will hold a candle to an aftermarket block, including Bowties, when it comes to hardness. Ask any machinist - particularly the ones that bore and hone blocks. It's a completely different cast iron recipe and the ingredients are a small part of why these blocks are more expensive.
The “high nickel” block is total BS created by the same guys who worship 4 bolt blocks.....What cracks me up is after 30 years of building Chevrolet engines...it wasn’t until 2016 that I even had heard of anyone calling a factory block “high nickel”.....now the ******** here call all of them that....to sell them to the uneducated....it is like a damn counterculture of sheisters who pose as idiots.....
The misinformation and BS stories kill this hobby for me and others.....it is waaaaaay too expensive to be cheating people and I for one will not put up with it.
The people who know, know....and those who do not, tell stories.....
Jebby
Last edited by Jebbysan; Aug 1, 2019 at 10:21 PM.
Le Mans Master
Joined: May 2007
Posts: 5,007
Likes: 1,114
From: North tonawanda NY
This is the exact Mark's on the block I found for my build.. out of a 76 3/4 ton truck which is in my car now. my original 2 bolt main block is awaiting a future rebuild but I have no reservations about using it vs my current 4 bolt for a replacement.
Le Mans Master
Joined: May 2007
Posts: 5,007
Likes: 1,114
From: North tonawanda NY
There have been a few GM foundry workers who claimed that the 010 020 under the timing cover is BS. Wives tale is that these blocks contained .1% more tin and .2% more nickel. Tin makes 'em easier to machine and nickel makes 'em harder.
There's not a factory block that will hold a candle to an aftermarket block, including Bowties, when it comes to hardness. Ask any machinist - particularly the ones that bore and hone blocks. It's a completely different cast iron recipe and the ingredients are a small part of why these blocks are more expensive.
There's not a factory block that will hold a candle to an aftermarket block, including Bowties, when it comes to hardness. Ask any machinist - particularly the ones that bore and hone blocks. It's a completely different cast iron recipe and the ingredients are a small part of why these blocks are more expensive.
Race Director
Joined: Mar 2018
Posts: 10,497
Likes: 1,993
From: Golden Colorado
Just to add my .02
I ran 400 2 bolt sbc in bracket car with cast GM crank ARP studs and phase 2 bow tie heads with 12.7:1 compression and shifted at 7000 and went through the traps at 7200. Never had a problem but the engine had a very good balance job. 
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
I never actually checked my 010 020 block for nickel content. I put a set of 462624 2.02 heads on it. Dropped a valve and broke cyl number 1. So then it was a nickel a pound. https://www.jalopyjournal.com/forum/...e-odd.1054133/
Last edited by derekderek; Aug 2, 2019 at 07:07 AM.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
400 blocks have mains a lot more like a big block, much wider registers on 2-bolt blocks than 4" bore blocks. This provides a much larger clamping area, similar to a 2-bolt big block. If GM had done this with 4" bore blocks, there wouldn't ever have been an issue with 2-bolt main cap blocks. It's not the 2 or 4 fasteners that are the issue, it's the register areas.
Most of us aren't going to beat hell out of our daily drivers, at least not hard enough to actually test the limits of any block, 2 or 4 bolts. I build my own engines and treat them according to what they're built for. Daily drivers don't get revved past about 4500 - 5000. Those with aftermarket blocks, cranks, rods, pistons and heads....those I beat the snot out of since they were built for it.
Most of us aren't going to beat hell out of our daily drivers, at least not hard enough to actually test the limits of any block, 2 or 4 bolts. I build my own engines and treat them according to what they're built for. Daily drivers don't get revved past about 4500 - 5000. Those with aftermarket blocks, cranks, rods, pistons and heads....those I beat the snot out of since they were built for it.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
On 350 blocks that is the case. But 400 blocks with wider main journals were weakened by adding the outer 2 bolts on the 3 center journals. It is established that if one is shopping for a 400 block to beat said snot out of, 4 bolts are to be avoided.
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Burning Brakes
Joined: Jul 2018
Posts: 979
Likes: 258
From: Maryland
generally a high performance option for other cars. If I'm not mistaken the L48 350 was the top 350 for the Camaro for that year. Back to the point, why did GM engineers specify a 4 bolt main for a 300 HP engine when a
2 bolt would probably have sufficed? Perhaps the GM folks thought the average Corvette owner was going to hop up their engines?
Dr. Detroit
Joined: Mar 2012
Posts: 10,090
Likes: 4,015
From: New Braunfels Texas
I often wondered about this as well. For instance, I know the 69 L46 350 was a 4 bolt main, but I was surprised to find the base 350 that year was 4 bolt as well. Perhaps one reason is that the base Corvette engine was
generally a high performance option for other cars. If I'm not mistaken the L48 350 was the top 350 for the Camaro for that year. Back to the point, why did GM engineers specify a 4 bolt main for a 300 HP engine when a
2 bolt would probably have sufficed? Perhaps the GM folks thought the average Corvette owner was going to hop up their engines?
generally a high performance option for other cars. If I'm not mistaken the L48 350 was the top 350 for the Camaro for that year. Back to the point, why did GM engineers specify a 4 bolt main for a 300 HP engine when a
2 bolt would probably have sufficed? Perhaps the GM folks thought the average Corvette owner was going to hop up their engines?
Remember...GM built solid lifter 327's with 2 bolt mains and Jenkins used these exact blocks in his early pro Stock efforts........
Jebby
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
I've had two '71 base auto trans cars ... both CJK code 350 ... both 2 bolt w/ cast cranks ... both kinda puny but good motors.
IIRC, '70 base 350 had same cam but much higher compression and 30 more hp.
IIRC, '70 base 350 had same cam but much higher compression and 30 more hp.
Drifting
Joined: Jun 2015
Posts: 1,325
Likes: 743
From: Doctors Inlet Florida
Parts Sherpa
Joined: Feb 2017
Posts: 520
Likes: 98
From: ICE boneyard, Pa
