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I have an engine block. 3970010 . The front right pad is smooth so either its a replacement block or its milled. Rear date code is E205 so i am guessing a 75. Good news is there is a plug above the cam. I was reading all 4 bolt main engines have this. Did crate motors have blank pads and if its been decked will a stock intake fit?
 

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No the plug above the cam is just the end of an oil passage two and 4 bolt blocks have this.

No it’s not a crate engine all engines leave the factory with a stamping on the pad. This is a good indication that the block has been decked.

The only way to tell if its a 4 bolt block if there is no stamping on the id pad is to pull the pan and see what’s there.

The good new is the 010 casting is a heavy duty casting that is they feature thicker walls, they were used as a basis for truck engines and high performance car engines. If used in a light duty truck or up to about a 300 horse car engine it likely was built with two bolt mains, if it went into a 3/4 ton or up or a high performance car it is likely to be a 4 bolt main. A lot of 4 bolt engines also got a forged crank, not all but it is a frequent find.

Youre going to have to open it up to see.

Bogie
 

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Will stock manifolds fit if the block is decked. The pistons have 4 valve reliefs in the top, does that make it a L82 engine?
Not from the factory....original L82 pistons have a single long valve relief trough and not individual relief eyebrows.

Sounds like it is probably just a generic flat top rebuild.
 

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Not a factory L82 this is more likely than not a rebuild. Everything leaving the factory has a code stamped on that front pad. The code is essentially a part number, part numbers not casting numbers are what either ends up on the factory production floor, is sent to secondary prime builders which can be other car builders like Checker for cabs as an example, industrial builders which are making anything from fork lifts to industrial pumps to marine boat builders. Some are built as over the counter replacements as in crate engines. The stamped code dates when and where the engine was assembled there is a suffix code that id’s its end use. Here you see in books and on line usually the inside GM suffix code. Engines assembled as second tier car builder, crate, industrial, and marine are often much harder codes to crack as for the most part they escape the popular reading material.

As for manifold fit that is an open question as milling the head’s and or decking the block lowers the head’s with respect to the crankshaft centerline which is the reference point for these other dimensions. Lowering the head’s brings them closer together which then makes the intake act as if it is too wide resulting in it sitting high relative to the inlet ports and attachment fasteners. This will be complicated by using aftermarket intakes as everybody has their idea of what the width dimension is and of course is holding their own tolerances around that dimension. So you have to go through some trial and error proto-assembly to check this stuff out for fit. To some extent you can fiddle gasket thicknesses to correct this if alignments are so poor you can’t get the bolts threaded. But here you hit other constraints such as the squish/quench clearance of piston at TDC to the chamber step which you want to get as close to .035 to .045 inch as possible. Some rough measures of things is the factory piston crown edge to the head deck is .025 inch +/- .005 inch so your looking at a band width from the deck to the crown of .020 to .030 inch. Generally less indicates the deck has been cut, this indicates either a mass builder that cuts everything going through the shop or a home town shop that found the necessary qualities of the deck were out of spec so it was milled some amount to clean it up or it was being built as a high compression engine and this was a means as is milling the deck mating surface to the head as a means of gaining compression. A danger hiding in all these numbers is if the deck was zero milled those builders will often use what is referred to as a rebuilder piston which has a .020 to .025 lower compression height (distance from pin center to crown) which restores the original factory crown to deck clearance thus factory compression ratio; or they may be used to fiddle compression ratio on a performance engine. So there are lots of things can can happen here that without disassembly and measuring are not easy to detect.

Now it’s a pretty fair guess that your looking at a performance build with flat top pistons where from the top you can’t tell if they are cast or forged nor what alloy was used. The pistons are probably an oversize and the amount is often stamped on the crown which if not carboned up you should be able to see that. Getting the head casting number will lead to chamber size which will let you get a rough idea of it’s compression ratio.

Cams are often a mystery if you can’t find a number that leads anywhere, that is a likely outcome, then you have to use a degree wheel and dial indicator to devine the event timing and lift. Keep in mind that lifters and lobes are married couples they muse go back together the way you found them or they will wipe out and you’ll be doing cam and lifter replacement surgery. There are inexpensive plastic valve train organizers these are a most worthwhile investment.

Bogie
 

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Cutting a block/heads flat doesn’t change the intake face angle. The math don’t work like that.
Only angle milling the heads/block changes the intake to head interface angle.
If flat cut enough, the intake WILL sit higher, meaning the ports don’t line up exactly anymore but…the big butt, I’ve cut blocks to 8.900 and heads to .060 without too much trouble getting a intake to seal up. Lining up the bolt holes is the bigger issue. Its largely a non issue on a street performance deal as
there’s plenty of material there for your standard 9.000-9.025 deck height and .060 head flat mill. These days it’s way easier to buy the head with the chamber size and shape than get crazy with a flycutter like we did 20 years ago or more.

010/020, to the best of my research and discussions with guys who have worked the GM casting factories report those numbers are casting mold identifiers for GM internal documentation. There’s never been any documentation from GM ever, over the last 60
years about extra nickle ever being used.
 

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I really don’t know if the identifier 010 and or 020 inside the timing case signify an alloying additive or not.

Tin is routinely added to cast iron to aid in flow. Given in terms of adding it to molten iron it has a much lower melting temperature than iron so it is evaporating out at the molten temps of iron so it is something that has to be constantly replaced to the melt in order to be an effective percentage. I expect this is common to all thin wall castings at least since the mid 1970’s. Tin added to iron was the trick the English figured out back in the 16th or 17 th century which produced a more uniform thus stronger cannon casting. It gave the Royal Navy and Army a longer reach with a heavier ball than other nations artillery which served them well for a long time before other nations foundries figured that out.

Small amounts of nickel add a lot of strength, it’s starting down the path to stainless steel but in cast iron, the difference in iron to steel is the greatly reduced amount of carbon in steel. Nickel melts at a much higher temp than iron let alone tin so to alloy it takes a lot more heat so now not only is the tin boiling away but so is the iron. This adds a lot of cost not only in the raw material but in maintaining the needed heat. A scratch test on the casting is a fair indicator if you have sharp eyes. Cast iron when scratched is rather gray in color where if nickel is present even in small amounts it lends a faintly yellowish silver tone.

Bogie
 
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