Looking for a block to build. I want the block that has the rear block vent (road draft, PCV system, etc).

I see a lot of 870 blocks for sale, And I just wonder about that block, in comparison to a 2657 block.

I am not an in a hurry, but I haven’t seen a 2657 for sale in months…


I plan a stroker crank, new rods, Trick Flow double-hump heads…. So really just looking for a 327 block that has the rear vent hole.

my current block is a 2657 casting, but I’d rather find another to build, simply to avoid my car being down for an extended period. Mine runs okay, but it’s burning oil so I am just preparing.

Mine also has a casting date of J 12 7, which I think is October 1967. My car was built in June 1967. My block has been decked.


I found a guy selling a 2657, but a complete engine. It has an MS suffix, do I think this is actually a 67 Camaro 350 block…. Would this be a large journal? I think that’s what I was reading. Maybe get this and not need to turn-down the mains on a stroker crank?

no need to try and sell me on a Blueprint engine or an LS swap, not looking to go those ways at this time…

 

The 2657 block was used in 1967 Corvettes, Camaro SS and Z28s and have value as such.

Is the engine currently in your car the original? You said it has been deck so I am assuming the numbers are gone?

Depending on how important numbers matching are to YOU or if you plan to sell the car down the line then now would be the time to do it right. If that is the case I would check with Engines Limited as the usually would have a correct date coded block, can broach it and stamp it with the correct numbers.

 

I have this really nice std bore 512 CE block available. It has the bearing grooves for both small.and large journal, currently a small journal. I was saving it for a stroker build which I'll never get around too. It has the rear draft hole on block.

https://www.corvetteforum.com/forums...g-grooves.html

 

last I looked J comes after F so it can't be an orignal block to his 67. maybe for a 68 car

 

That was my understanding…

my block was decked, so no numbers. Heads and distributor dates are “ correct” for my car.

I have the tank sticker, so I know it’s an L79. Trans had matching VIN number…. I was told there was a theft early in the cars history, but perhaps it’s a CE warrantee motor? I don’t know.

100% correct not required, but of course, I would pay a little more for a date correct block, just because…

No plans to waste money on broaching/restamping, or buying/shipping from a “resto” business (with a likely up charge just for “Corvette” parts). Just looking locally ( Craigslist, etc).


If this was highly modified car/engine, I’d just go with a 350, etc….

But it looks relatively “correct” looking, and I like that…. Correct valve covers, and intake, vent tube to the air cleaner…

I really like the stock valve covers with no holes …. Looked at the PML (?) repros with the side PCV holes, but just don’t look right.

Therefore I want to keep the rear vent fitting in the block…


I like building my own stuff, and I am confident I can be satisfied at a lower cost than a BluePrint engine, etc…. I like performance but don’t need the maximum hp…

 

I bought a 1967 2657 short block 25 or so years ago that had "327" written on it. Has just sat in my shop with the idea I would look for a 283 crank and then build an old school 301. I finally got a crank, and was going to pull apart the 327 a couple years ago. Come to find out the crank was a large journal. Blank pad on it, but definitely a 350. Kind of messed up my original plan, but I do think if I do anything with it, I would go the stroker route. I'm not married to it, but Cali is a long ways from Michigan, lol.

Rich

 

I have a spare 657 block, I’d be willing to sell, but it’s in Washington state. Standard bore, crank still in block. Blank pad, with factory broach marks. Dated late June, I’d have to look again for exact date. Be perfect for someone wanting to stamp it to their car, with a build date of July or Aug 67.

 

Okay, there are some details that may or may not be important for your goals. First, the production small blocks had the rear vent through the 1967 production year. For Corvettes, the '63-'65 block was the '870, 1966 was '174, and 1967 was '657. All of these are functionally identical if you just want the rear vent.

The 1967 '657 block was the first Chevy small block that was designed to support large-journal mains. For the 327, it used small-journal mains, but for the Camaro 350 it used large-journal mains. All '657 blocks were machined with the bearing notches for both small-journal mains and large-journal mains. So, a small-journal '657 can be converted to a large-journal '657 by simply line boring the mains to the large-journal size (the rear main oil deflector on the large-journal crank has to be reduced in diameter for use in a small-journal block).

The '657 also had cast-in notches at the base of each cylinder for added rod clearance for the 350 stroke. This is nice, but not essential if you are building a stroker motor.

After 1967, GM had a service replacement block that ended in '512 that was essentially identical to the '657. Like the '657, it had the rear crankcase vent and bearing notches for both small-journal and large-journal mains, and was machined for either small journal or large-journal mains depending on the application.

If your stroker engine will be using small-journal mains, any of these blocks will work fine. If you want to use large-journal mains, you should use either the '657 or the '512. These two blocks were designed to be machined for large-journal mains, and they have more "meat" on the front main journal.

The attached article describes how I built a large-journal 383 from a small-journal '657 block. In hindsight, I think that grinding the 383 crank journals down to the small-journal size would have been fine, and would have cost less to do.

 

L78,
I have a 870 block freshly machined and ready to assemble. I have all necessary pieces to build. The cylinder heads are fresh with all new valves/springs etc. it’s .040 over with forged flat top pistons. Speed pro bearings and lifters. Several cams to chose from. Let me know if you’re interested in any or all. I live up the hill from you in Jackson. Was going to build this for the 63 I had before I bought my 67’.
Chris

 

Thanks for the offer Chris, but I’ll pass. I really only need a block, as my plans are a stroker crank and aftermarket rods and heads…

I have thought of swapping a used, running motor and rebuilding my 2657 block, but I know my projects take a long time…. Trying to keep the car drivable.

I just found a guy with a running “Corvette 327”, 2657 casting, Dec 66 dates, but “MS” suffix (I found that’s Camaro 350 suffix). So I am considering this, but all I really want is the block.


Joe,
thanks. Yes, I have read your article many times, but since I am usually on my phone, I don’t have it saved anywhere for reference. I kind of figured I’d be having the stroker crank ground for small journals ( not much research, but I didn’t find any small journal stroker cranks). But when I saw this engine I was like “ hmm, large journal with the vent…

as mentioned, no hurry. My 327 runs “okay”, and I should be focusing on my Chevelle resto…. But I keep thinking about the Corvette too…. So I always have my eyes open for pieces ( like a block).

 

Those factory large-journal '657 blocks are pretty rare. They were only used for the 1967 Camaro 350, which was a rather rare option. Most 1967 Camaro small blocks were either 327 or 302 CID.

Having a large-journal '657 block would allow you to use an off-the-shelf stroker crank, since standard stroker cranks appear to always have large-journal mains. However, for under $200 you can have a large-journal crank ground to the small journal size and have the oil diverter diameter reduced slightly, and drop it into any small journal block, not just the '657. If the engine will be naturally aspirated with no power adders, I think small journal mains are fine.

It is also possible to line bore a '657 block to the large-journal size, simply doing what GM did when they machined a '657 block for the Camaro 350. However I think that costs a lot more than having the crank journals turned down. If your plan is to do that, it makes the large-journal '657 an attractive alternative to consider.

 

I have s 657 block that I bought to build a 383, but then I sold the car it was to go in. I have no use for it, so PM me if you get desparate.😊
Mike