Lt1 block Q's 2 bolt vs 4 bolt
TECH Regular
Joined: Feb 2008
Posts: 458
Likes: 1
From: Keller, Texas
A factory four bolt main block is stronger than a factory two bolt block. Corvettes came with four bolt main blocks. There have been reports that some F-body cars had four bolt main blocks towards the end of production, probably because they had more Corvette engines made than they needed.
A block with splayed four bolt mains is stronger than a factory four bolt main block. You can only have a splayed main block by tacking a two bolt block and having a machine shop do the conversion.
Other than these differences, the blocks are identical.
The strongest blocks are two bolt blocks that are converted to four bolt splayed mains with steel caps and studs.
A block with splayed four bolt mains is stronger than a factory four bolt main block. You can only have a splayed main block by tacking a two bolt block and having a machine shop do the conversion.
Other than these differences, the blocks are identical.
The strongest blocks are two bolt blocks that are converted to four bolt splayed mains with steel caps and studs.
"A 2 bolt big block will take a lot more than that. There's a lot of people running ~700hp on 2 bolt mains with stock bolts"
I'm sure that's so however, a performance machine shop will advise to go to a four bolt main block above 500 HP. If they say you can go 600-700 HP on a 2 bolt main block, find a new machine shop.
I'm sure that's so however, a performance machine shop will advise to go to a four bolt main block above 500 HP. If they say you can go 600-700 HP on a 2 bolt main block, find a new machine shop.
I'm sure that's so however, a performance machine shop will advise to go to a four bolt main block above 500 HP. If they say you can go 600-700 HP on a 2 bolt main block, find a new machine shop.
Way back then the power ratings system was different, when they went to the current rating system numbers came down. Point being 400hp in 1970 is not comparable to 400hp today. That was also a different block, different metalurgy. About as comparable as the BBC comments above.
Fact of the matter is 400+SAE is readily achievable on a truely stock shortblock and the guys who do wound the motor at that level almost always hurt a rod bearing not a main. A 400rwhp A4 car is going to be 470ish SAE. These failures seem to be rpm related not power though, guys who keep the rpms lower and spray WAY beyond 400rwhp do so with pretty good reliability till they get greedy and spray too big and take out a piston, often closed ring gap from the heat not that the piston or anything else is weak.
rpms are a bigger deal in engine reliability than power, at least in an NA motor.
If you are talking boosting the stock engine, something else will likely give before the mains, if looking to build an engine discuss studded 2-bolt or 4-bolt conversion with your builder. Would not be a bad idea to spend the extra $500 if already building an engine then there is no worry.
Fact of the matter is 400+SAE is readily achievable on a truely stock shortblock and the guys who do wound the motor at that level almost always hurt a rod bearing not a main. A 400rwhp A4 car is going to be 470ish SAE. These failures seem to be rpm related not power though, guys who keep the rpms lower and spray WAY beyond 400rwhp do so with pretty good reliability till they get greedy and spray too big and take out a piston, often closed ring gap from the heat not that the piston or anything else is weak.
rpms are a bigger deal in engine reliability than power, at least in an NA motor.
If you are talking boosting the stock engine, something else will likely give before the mains, if looking to build an engine discuss studded 2-bolt or 4-bolt conversion with your builder. Would not be a bad idea to spend the extra $500 if already building an engine then there is no worry.
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Brett Foote
Teching In
Joined: Jan 2009
Posts: 29
Likes: 0
From: MI
lt1 block 4 bolt ratings I have the non factory 4 bolt warranty replacement bock, which is probably the old corvette block. How much hp, torque, and rpms can this block handle? I've done some maybe not needed mods like high volume oil pump, canton race pan. I was thinking of spraying 125 shot with my LE2 package. Had the nitrous kit but never used it because of high rpm miss. Hopefully the MSD will cure that. Thanks 
TECH Regular
Joined: Jul 2006
Posts: 440
Likes: 0
From: Ohio
Staging Lane
Joined: Jun 2008
Posts: 80
Likes: 0
Well i ran my 2 bolt main with arp main studs 383 for 2years running mid to low 10.s with a 200-275shot, in 3600lbs camaro,but when i pulled the engine a few months ago i found i had some really bad main cap walk, so i now had to go with splayed mains, i would say you will be fine with under 500h.p at the flywheel but i would put splayed mains on it if it was mine.
I have the non factory 4 bolt warranty replacement bock, which is probably the old corvette block. How much hp, torque, and rpms can this block handle? I've done some maybe not needed mods like high volume oil pump, canton race pan. I was thinking of spraying 125 shot with my LE2 package. Had the nitrous kit but never used it because of high rpm miss. Hopefully the MSD will cure that. Thanks
Fact of the matter is 400+SAE is readily achievable on a truely stock shortblock and the guys who do wound the motor at that level almost always hurt a rod bearing not a main. A 400rwhp A4 car is going to be 470ish SAE. These failures seem to be rpm related not power though, guys who keep the rpms lower and spray WAY beyond 400rwhp do so with pretty good reliability till they get greedy and spray too big and take out a piston, often closed ring gap from the heat not that the piston or anything else is weak.
rpms are a bigger deal in engine reliability than power, at least in an NA motor.
If you are talking boosting the stock engine, something else will likely give before the mains, if looking to build an engine discuss studded 2-bolt or 4-bolt conversion with your builder. Would not be a bad idea to spend the extra $500 if already building an engine then there is no worry.
George B made well over 1000 on the factory 4 bolt setup with good caps, so I don't think most people need a splayed vs 4 bolt for more strength. The cost of picking up a 4 bolt block isn't much cheaper than doing splayed mains usually though.
I also put well over 500lbs of nitrous down that thing, and with a stock crank. 
Teching In
Joined: Jan 2009
Posts: 29
Likes: 0
From: MI
This is the guy I'm referring to, if you haven't been around for awhile I'm sure that is why you don't know who I was talking about, as you can see, it's back from 2001 when he made these passes.
http://www.f-bodyhideout.com/videos/baxter_9_04.wmv
George Baxter's 1997 Camaro SS convertible goes 9.04 at 155.33 mph (2001). Make no mistake that this video was shot by Fred Forsythe "Injuneer".
http://www.f-bodyhideout.com/videos/baxter_9_04.wmv
Sorry, any of you saying a splayed 4-bolt LT1 block is better than a 4-bolt straight converted or stock 4-bolt block absoloutly DO NOT know what you are talking about...
The LT1 blocks have less material in the webbing, thus a 4-bolt splayed LT1 block is weak by lack of material.
A factory 4-bolt block, or even better yet, a shop converted 2-bolt to straight 4-bolt block is the best you will have on a LT1.
For other blocks a 4-bolt splayed may be the best, but FOR SURE not on a LT1...
It is just amazing how stupid the responses get when a few people in the know stop posting... This was a known fact about LT1 blocks FOR YEARS! I mean WOW, a bunch of guys here just read an article and think they have a clue, or hang around some old-school guys and think they can just repeat what they heard without having any idea about what they are 'experts' in...
Hell, most of us knew this back in 1998-1999... It is pretty damn easy to even compare the amount of material in the webbing vs some of the older style blocks... It is quite visible that the LT1 blocks are light in that area.
It is just amazing that no-one else even mentioned this well-known 'FACT' of LT1s...
Then again, most of those with a clue just refuse to post, or don't care about the boards anymore due to all the stupidity going around... Hmm, maybe it IS time to move onto the LSx motors???
The LT1 blocks have less material in the webbing, thus a 4-bolt splayed LT1 block is weak by lack of material.
A factory 4-bolt block, or even better yet, a shop converted 2-bolt to straight 4-bolt block is the best you will have on a LT1.
For other blocks a 4-bolt splayed may be the best, but FOR SURE not on a LT1...
It is just amazing how stupid the responses get when a few people in the know stop posting... This was a known fact about LT1 blocks FOR YEARS! I mean WOW, a bunch of guys here just read an article and think they have a clue, or hang around some old-school guys and think they can just repeat what they heard without having any idea about what they are 'experts' in...
Hell, most of us knew this back in 1998-1999... It is pretty damn easy to even compare the amount of material in the webbing vs some of the older style blocks... It is quite visible that the LT1 blocks are light in that area.
It is just amazing that no-one else even mentioned this well-known 'FACT' of LT1s...
Then again, most of those with a clue just refuse to post, or don't care about the boards anymore due to all the stupidity going around... Hmm, maybe it IS time to move onto the LSx motors???
I have heard that on some blocks it is weaker to go 4 bold as you say due to the lack of material, I just left mine up to my engine builder, He says its ok then I will let him be the judge, If you judge him, just to let you know he ONLY builds very high end Pro Motors,Like I said at 648 RWHP my caps danced around so I am hoping going 4 bolt will give me a little more stability....