I want to build a 383 chevy stroker. I've got an old 3970010 block. I want to be sure I'm starting off with the right kind of block. I understand that 3970010 was the casting number for all 4" blocks made between 69 and 79. This was mostly 350's but also included 327's which were manufactured until 1969, I believe. Am I right in thinking that the 327 and the 350 used exactly the same 4" bore block it's just that the stroke was shorter on the 327 meaning it basically was the same engine just with a crankshaft that had a shorter stroke? If so, am I also right in thinking that the process of turning a 327 into a 383 is identical to the process of turning a 350 into a 383? I.e. overbore of .030 and stuffing it with the right internals. Incidentally, the Engine Suffix Code is K02 24 TYX which tells me it's a 4-bolt main (I can also visually verify that) 350 assembled in St. Catherine's, Ontario on 24th Feb in some year and used in either a 1975 or a 1977 truck or motor home. So I'm confident that this is, in fact a 350 ci engine. I just want to make sure my understanding about the 327 is correct. Also, the casting date stamp is K1. That's it. No third digit. To me that means 'November 1st' but I don't know what year. If anyone can help me identify when this block was cast, I'd be grateful. But no biggie.
Your 3970010 is a 4" 4 bolt large journal block, and as you thought more than likely a 350. This is a fine foundation for your 383.
From what I remember no 327's had 4bolt mains. GM changed to a large journal crank in 68. The Peterson books from back in the day had one called " small block facts and figures". I'll see if I can find my copy.
Threads like this usually just add to the original poster's confusion when people start throwing all kinds of conflicting and/or irrelevant information out there. You have a 1970's 4 bolt main, two piece rear seal, 4 inch bore block, perfect for a street 383. A .030" overbore combined with a 3.750" stroke crank will give you the popular 383" engine. I would suggest buying a kit that will have the pistons, rods, crank, rings, bearings,etc. 327 facts and figures are meaningless to you.
The 010 in the part number indicates that this is a casting designed to be finished with a 4" bore (and nothing else, contrary to popular myth). Both the 327 and the 350 had a 4" bore (and the 302 technically). Without a crank in it, it does not know what displacement it is. It is a block, it doesn't know much. The main bearing caps, and the respective number of bolts, is a finishing process. The block itself is the same casting. It could technically be done, to any SBC block. I have seen 2-bolt codes that were 4-bolt, and vice-versa. The only way to know for certain the number of bolts: count.
Personally, I'd build it, even if it were a 2-bolt main block. Every single bottom end failure, that I have seen, involving a main bearing cap, of a 4-bolt main SBC, showed catastrophic damage, right through the outer cap bolt's threaded hole. Often more than one of them. If you are planning the kind of power that could do that, you are in aftermarket block territory.
The 350 block would still need to be relieved for the 383 crank, the 327 block would REALLY need to be relieved.
I have done four, all 010 blocks. Three started life as 350's, one as a 327. As far as I remember, aside from slight casting variance in the non-machined areas, the difference was not great. The die grinder makes short work of it. It's a labor-of-love.
NO, 307 and 327 cranks are different. 327 FORGED and 327 cast iron cranks had larger (thicker) counter weights. 327 pistons weigh more, hence the more counterweight, and there is no such thing as a forged steel 307 crank. But both had the 3.25" stroke. But lots of machine shops used the cranks interchangeably. A good rebalance was in order to do so. The 010 block was used for, 302 1 year Z28, 327 1 year Corvette, 350 in everything, cars trucks boats busses. The 010 block was 2bolt and 4bolt depending on the horsepower it was destined for. And there is no "code" that tells of 2/4 bolt mains, only of the engine's destiny. If destined for a truck or over 300 (or so) horsepower then it was a 4 bolt. But remember, codes were stamped after the assembled engine was picked for the build order, so things could be, um, "different". 350 2 barrel in a grandma nova "should be" a 2 bolt. And a 3/4 ton 4x4 pickup "should be" a 4 bolt. But.............. Oh yeah, NO 327 had 4 bolt mains, not even the 350 horse '69 Vette version.
To the original poster, perfect block for a 383, I advise buying a balanced kit unless you aleady have a 3.75 stroke crank that needs no machine work. the kits typically come with aftermarket rods that resolve most of the issues with rod end, rod bolt clearance with the block. Making a 383 from stock parts is not impossible, but requires a pricey rebalance, and quite a bit of block clearancing. a stock 5.7" 350 connecting rod is recommended to prevent piston rock and side loading common with shorter "400" rod, that's why all 400's need an overbore when rebuilt. Pistons are available off the shelf for a 383 5.7" 350 rod or a 400 rod.
Karambos,being in the Chevy world for over 45 years I can tell you the advice and comments listed above by the members here are all very true and accurate. You are now asking am I an expert to add this comment...............no,but I have never sent anyone in the wrong direction if I did not know what I was talking about,so I am just giving you some added support about the Info. that has been given to you,and now you can run with it and build that engine ! ( Enjoy)
I would like to say a big THANK YOU! to all the contributors to this thread. All comments are very useful and add to my understanding of the topic. This is exactly why I joined the H.A.M.B. in the first place. Merry Christmas, guys!
i have encountered cap walk on higher output motors, it helps to add main studs, I use ARP if it's a two bolt main, splay steel main caps are installed, I like Milodon. if you use a quality stroker kit it has stroker rods and needs less grinding to do plus more clearance between cam lobes and rod. usually when the block is being machined i have it clearanced at the same time saves on time and does a nicer job at a cost of $100 because the block is already set-up on the cnc.
shopdawg and gimpyshotrods have it right. the '68-'69 327 and 350's used the same (large journal) block and there were no 4 bolt main 327's. So you have a 4 bolt main 350 block, which is the standard block for building a 383 stroker.
There are lots of guys/shops in your area that can assist you in this. All these answers are right...
A friend of mine just bought a .060 over '75 350 short block with custom bearings, a small journal steel crank, and 13.5-1 comp for our Fox body Mustang. 337 cu. in. 7500rpm, here we come.
The 4 bolt mains thing is to keep the caps from moving around, not really any stronger. If you stud a 2 bolt and align hone after, you get a pretty "good to go" block.
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