how to build a 301, Chevy

ok, here is the real scoop. Before there was a 327 with a 4 inch bore there was a 283 with a 3.875 bore. Both had 3 inch stroke. Engines were bored either 30 or 60 thousands. I personally never seen a piston marked .0625 oversize. So if you bored a 283 60 thousands you increased the diameter by 120 thousands. 3.875 + .120 equals 3.995. Calculated out that is 300.8393 or rounded to 301 Cubic Inch. A 327 with a 4 inch bore calculates to 301.5928 or rounded to 302. Now you know the difference in a 301 and a 302.

 

A 301 was a 283 with 3.875 bore bored .060 making it a 3.995 bore. 300.83 cubic inch rounded to a 301.

 

Back in the day a good engine builder could look at your block without even opening it up and tell you if it had a chance of being bored large enough to make it into a 301. I had one done back in the late 60's by a competent machine shop and he simply looked at the freeze plug bosses and how centered they were to the freeze plugs. He told me if they were off center there was too much shift in the cores used, and it wont take a large bore job. If they looked perfectly centered they'd be a good candidate. Old school technology.

 

Val
Found a good article on the subject.

https://mooregoodink.com/what-is-core-shift-and-why-is-it-detrimental/

 

I'm admittedly getting to be considered old, but have not been sleeping in a cave. In my youth built at least six stout 301s using 283s. It's what we had at the time. This is an old resurfaced thread, but when did the terminology about boring change.? Boring 0.060" over was understood to mean increasing the bore diameter by 0.060". We never talked how much the material cut was to get there. We knew that. A 0.060" over 283 was a 292. A 0.120" over 283 was a 301. Pistons were, and are, marked accordingly. So what gives saying you bore a 283 0.060" to make a 301? New math?

 

Yes, that's even better if you have the engine apart to see the block surface.
When I had my last 4 bolt main 350 SBC built for my Austin gasser, the engine shop here has a CNC machine that corrects for core shift by boring off center if it's shifted. This blueprints the engine, and corrects mistakes.
I asked the engine builder what about one wall being thinner than the other after correcting, and he said it's even more important to not correct the core shift if the engine has too much. So they limit those to even less oversized bores.

 

WRONG! I get 3.935 (not 3.995) if I bore a 283 .060. Those were called 292s by the hot rodders back in the day. .030 over 283 and hot rodders put 288 cu in on the side of the car or hood. Bottom line is 301/302 is 4" bore/3" stroke. Whether you destroke a 350/327 or boring a 283 an 1/8".

 

And now MY version (s): You take any block, taken to a 4 inch bore, no matter how it started out (a 283 taken .125 over for a 4 inch bore, or a standard bore 327 with a 4 inch bore, or a 302/327/350 block, using a large journal 3 inch stroke crank)(there were 602 small journal, factory 302 Z-28 Camaro's made). So, we're talking small journal blocks here by the way for the sake of this thread.. The 283 crank is used with a 3 inch stroke to build the 301/302. How do we come up with 301 VS 302? It's a matter of pi; 3.14 will result in a figure closer to 301; 3.14159265 will result in a figure closer to 302. Always round UP in math, unless the decimal is less than .5. Back in the "old days", guys used to say 1/8 over , instead of .125 over; even Jahn's pistons came with over-sizes in FRACTIONS as opposed to DECIMALS. Now my head is starting to hurt, so I'm done. I am Butch/56sedandelivery.

 

Can an engine block be bored over to 0.120? I though 0.060 was the most? Just trying to learn more. To achieve the 301 is a different crank used? I have a 283 in use on my daily and was just wondering?
Thanks in advance,
Mark

 

327 has a 3.25" stroke. Please fact check yourself before posting

Sent from my SM-G965U using The H.A.M.B. mobile app

 

The original recipe for a 301 was a 283 bored 0.120" over. Based on my experience 95%, or more, of the blocks took the 0.120" bore ( 0.060" of material ) without issues. The original forged 283 crank was used. It was my engine of choice in my 55 Chevy. Busted a bunch of driveline parts behind a 301, but the engine was just about bulletproof.

 

Thank you sir for the information, I'm assuming you had a 4 speed behind it correct? Or maybe a powerglide?

 

4 speed and drive it like you stoled it. The 301 is a rev monster. Not so much on torque. One of the few street engines to get a legit 6800 to 7200 RPMs with the right parts. Back then the super built glides were not around. And for a street car, I personally would not put an automatic behind a 301.

 

The 64-67 Chevy II blocks with "721" cast in the side (upside down) were used on both the 283 and 327 assemblies for the 64, 65 and first run 66 cars, these are the blocks with the recessed oil filter pad, these were always popular with racers building 301's, they have gotten extremely rare (and valuable).

 

To clear up confusing readers...try. boring 0.060 over is 292cuin... 0.125 over bore is 301. Pistons are marked by Dia change not radial change. Just FYI

 

Heard that too, was told it was a thick walled block. I have a 283 out of a 65 nova... now 0.040 over flat top.

 

Missed this old post...50lb....then 30lb...

 

Old post. Asking here for an answer to my dumb question
Picked up some old pistons a couple days ago.
Box had 283 written on it by hand. Part number after a search listed em as 265-283-302.
Measurements are 4.030 ish. (Dial calipers)
pistons have .030 on em. Pin height math comes up to 1.80.
Kinda thinking these are for a destroked 327.

 

Yes, they could work with a 3” crank in a 327 block, or else in a .030 over 301/302.

 

Thanks. Pmd a hamber and that’s kinda how we were feeling.
These are nothing fancy, Jahns 2v flat tops.
Nice knowing what they are incase I trade em off.
I do have a 283 rotating assembly in a bad block.
Plus a rebuilt set of 461 heads.
Hmmmm

a long distance way to make a 307

 

I like to tell the Ford guys I have a 5 liter ... the better 5 liter

 

WCFBs

 

USA MADE: DSS makes small bore, short stroke forged Pistons in various dome heights..

My next set of 302 Pistons from there..

 

Don't forget orange paint.

 

I’m surprised that there are so many companies that make small bore Chevy pistons. I’ve got a pair of 283s, and surfing the web, I’ve found 3 or 4 that I’ve got bookmarked now. Anything from stock replacement cast pistons, hyperutectic cast pistons, to forged pistons. And now to make a plan for both…

 

DSS has impressive options.

 

Any engine? A 4.00” bore GMC 6 (stock 302”) is commonly bored to 4.125” for a 320”. So yes there are engines than can be bored .125”.

 

Plenty of 283’s decades ago were bored to 4” and then stroked a 1/2” for 352 cu. in.
Thin wall castings came in as foundry technique got better and that was when .060 began to be the safe limit.

 

Fresh:
1967 0.030 over block on engine stand.
1962 0.060 block and crank as well.

Both need pistons. Figure FTs with Trick Flow DHC heads would work nice mild build.

 

As we approach the Halloween season, zombie threads popping up feels appropriate.