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Discussion Starter #1
How can you tell if a 512 block has a 4 bolt main The engine is in the car and the pad has been machined
 

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Check above the oil filter.If there are two pre-drilled holes for an external oil cooler then it has 4-bolt mains.You may also see Hi Perf Pass above these holes if the block isn't that dirty.

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Dean Ciampi(Spring Hill,FL)
Autumn Gold 1970 LS6 Chevelle
Team Chevelle Gold #52 Aces #3094
 

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Discussion Starter #3
Dean what size are the holes suppose to be The middle one has a fiting for the oil preasure sending unit on it and the first hole is tapped with no plug on it.
 

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Rick,
I am not certain that you can tell without pulling the pan. I have seen mid 70's trucks with oil cooleres from the factory and they have been 2 bolt blocks.


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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100
 

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The front hole(toward the front of the engine) has a half inch pipe thread drilled into the oil gallery.Ifthis block is a twobolt the front hole would be 5/16.The second or middle hole is 3/4.the last hole is the same size 2 r 4 bolt.

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Dean Ciampi(Spring Hill,FL)
Autumn Gold 1970 LS6 Chevelle
Team Chevelle Gold #52 Aces #3094
 

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Correct me if I am wrong but 512 blocks were used only up till 71.So its safe to go the oil cooler way.

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Dean Ciampi(Spring Hill,FL)
Autumn Gold 1970 LS6 Chevelle
Team Chevelle Gold #52 Aces #3094
 

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This is a quote from the book How to Hot Rod Big Block Chevys byBill Fisher and Bob Waar (HP Books)

Page 4 paragraph 2 "Note: Hi-Perf cast into a block is not a 100% guarantee that the block has four bolt mains. A resonably positive method of identifying a block with four-bolt mains is as follows: check the threaded openings immediately above the oil filter mount. If there are two plugs--one 1/2-inch pipe and the other 3/4-inch pipe, the block probably has four-bolt mains. Of course, the only foolproof way to check for four-bolt main caps is to pull off the timing chain cover or oil pan and start counting the the main cap bolts."

I can give you some tips on removing the harmonic balancer if you like. You probably could use a timing chain anyway.

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Dale P.
Team Chevelle Member# 423
65 El Camino
72 Monte Carlo
"..you did you take the washer off, right?"
Whiners please point your browser to http://www.nader.org
 

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Rick,
If its a 512 block I will put my money down that you can check the size of the holes and be 99.9% sure its either a 2 bolt of 4 bolt without pulling the pan.512 blocks were passenger car blocks used from 69-71 therefore you don't have to worry about mid 70s truck oil cooler provisions.True what Dale said about the Hi perf stamping it is not a fool proof way,but the oil cooler provisions is with a 512 block.Just check the size of the holes and let us know what you found.Hope you got a 4 bolt!Did you get a chance to look at the casting date?

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Dean Ciampi(Spring Hill,FL)
Autumn Gold 1970 LS6 Chevelle
Team Chevelle Gold #52 Aces #3094
 

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Discussion Starter #10
Thanks Dale P Thanks but the owner of the car I don"t think will have us take the engine apart so we will try the measurement theory
 

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Discussion Starter #11
Dean the casting date is K 17 9 and it is located on the opposite side of the stamping 351 at the top back of the block . Is this in line so far for a LS6 block?
 

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260's pretty much right about this case, if there's two big pipe plugs it's more than likely a four-bolt.
Dated November 17th, it would be an early LS6, that's for sure.
Is the rest of the LS6 stuff there???
 

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Rick,
Yes with that date I would put all my pennys that you got an LS6 block,that is ofcourse if the measurements are correct.Are you looking at an LS6 Chevelle?
 

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Discussion Starter #15
Dave We Managed to take a valve cover off and the head is stamped 291 and has the smaller spark plugs. The intake is aluminim lowrise TSC all gone Headers M22 build sheet cowl tag 04 70 Atlanta Cowl hood CRV rear end 6500 redline tach
 

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Discussion Starter #17
260 Yes we are looking at an LS6 Chevelle But we are talking to the Father of the owner who can not be reached
 

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Rick,
sounds like the real deal.The casting date is a bit early for an april built car but I have seen stranger things.GM was on strike that year.Who knows?I would like to hear more about this car being an LS6 owner myself.Good Luck!
 

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That may be true for earlier 427 blocks like the 439 block,but the 512 blocks had the date cast opposite of the casting number.
 
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