To add a bit, I have a '71 350/270 and it is a 2-bolt main block. What else can you tell us about yours?
engine differences
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Instructor
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From: Eustis fl
engine differences
My 71 cpe. has a 72 350/200. Is it actually the same motor and rating as a 71 350/270? Maybe thats when they changed how they rated HP? Also, is that a two bolt main block? Thank you.
Safety Car
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From: North Royalton, OH
St. Jude Donor '06-'07
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From: Eustis fl
I checked the letter code on the block, I forget what they were, but I looked it up in an old motors manual, and it said a 72, 200HP. Now, if thats correct that 72 was the yr. they changsd the ratings, I'm wondering if its actually the same 270 hp eng. from 71. ALLSO, I forgot to ask this in the original post, but it has those skinnier spark plugs. They didn't come uot till aroind 1980, right? Its got an edlebrock 600cfm perf carb, and an edlebrock perf. manifold also, don't know if cam was changed.
Former Vendor
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From: walpole ma
I checked the letter code on the block, I forget what they were, but I looked it up in an old motors manual, and it said a 72, 200HP. Now, if thats correct that 72 was the yr. they changsd the ratings, I'm wondering if its actually the same 270 hp eng. from 71. ALLSO, I forgot to ask this in the original post, but it has those skinnier spark plugs. They didn't come uot till aroind 1980, right? Its got an edlebrock 600cfm perf carb, and an edlebrock perf. manifold also, don't know if cam was changed.
Instructor
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From: Memphis TN
A 2-bolt main block refers to the number of bolts that secure the main (crank) caps to the block. There is a bolt on each side of the cap. A 4-bolt main block has 2 bolts on each side of the cap to secure it. In high-output engines, there is a risk of crank bearings "spinning" between the crank and cap surface, so the extra bolt adds strength. A 2-bolt can be converted to a 4-bolt by buying 4-bolt main caps and drilling/tapping 2 more bolt holes in the block.
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From: Eustis fl
Yes, I know about 2 and 4 bolt blocks, though I never new you could just add the extra hole to make it a 4 bolt, never really looked into it, I just assumed there wouldn't be enuogh meat on the journals for another bolt. How about those heads with the skinny plugs, you think thewre newer heads?
Drifting
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From: Upstate South Carolina
Chevrolet rated the 71 base engine at 270hp gross and 210hp net. 72 was the year that rating changed from gross to net, but there was actual hp loss in all engines, although very small.
Le Mans Master
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From: Lebanon Township New Jersey
Yes, I know about 2 and 4 bolt blocks, though I never new you could just add the extra hole to make it a 4 bolt, never really looked into it, I just assumed there wouldn't be enuogh meat on the journals for another bolt. How about those heads with the skinny plugs, you think thewre newer heads?
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From: Peekskill NY
Team Owner
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From: Springfield MO
St. Jude Donor '07
4-bolt blocks were used long after 71. All L-82s should have 4-bolt mains, for instance.
Pro
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From: Holtwood PA
ditto...if the casting is the same>>.WOO HOO!!! I got 3 4 bolt blocks that aren't done yet!!