Technical Differences In SBC's

I just posted in the 3/27 thread that all sbc's look pretty much the same, but what are some of the differences between them that guys can look for to tell what engine they have? Off the top of my head, newer blocks have a smaller second hole for the water pump and 400's have three frost plugs. but what are some other things to look for like road draft tubes, oil filler tubes in the manifold, etc.

 

Manifolds can be interchanged so that is not a reliable indicator of which engine it is.

 

Glad you asked..... You see.... there IS no difference.... they're all Corvette engines!! Guys just change some of the external ginger bread to throw people off track. That's right.... ALL Corvettes.....

 

Are you trying to stick with differences of the 2-pc RMS small blocks?
And if the engine is out, the flywheel/flex plate flange can ID size (I’ve seen the chart posted before).

 

After nearly 70 years of them, and all of the mixing and matching of parts that has gone on in that amount of time, casting numbers and stamping codes are the best way to tell what they are. Of course, '55-'57 blocks don't have provisions for side mounts.

 

I only go by the casting number on the driver's side, behind the head, on top of the bellhousing
mount to confirm what the motor is.

As far as I know, the 400sbc is the only one with three freeze plugs on the sides, versus two on other sbc. Last count, there are about 150 sbc different casting numbers;

Chevy Casting Number identification - Block casting numbers (outintheshop.com)

 

You have to look for the bellybutton to see whether it's an innie or an outie.

 

some time in the late 70s they made the pad that the numbers are stamped on at the front of the block shorter and wider. 1980 they changed to pass side dipstick. But there are differences in the block such as the change in crankcase breathing made in the late 60s, when they eliminated the vent hole at the back of the block and got rid of the fill tube in the intake manifold. Also the heads changed over the years, the valve covers changed bolt pattern mid 59, and the heads got accessory bolt holes in the ends in the late 60s. The casting pattern like the triangle for PP heads and the double humps for the "fuelie" heads gave way to all kinds of odd shapes beginning in the late 60s. The harmonic damper went from being a crank pulley in early engines to a stamped metal ring on a cast hub on earlier 283s, to a smallish cast ring on later 283s, and the size of the ring grew larger as the stroke grew longer on the 327, 350, and 400. Water pumps changed in 69 on most engines, as the long pump and pass side alternator mount were introduced. Intake manifolds changed as the carburetor and choke design changed from heat tube to manifold heat stove in the early 60s, then again to a heat tube at the intake in the 70s. Distributors changed design in 57, and then from iron to aluminum in the later 60s, and again to HEI in 75. Exhaust manifolds changed from log type in 55-56 to rams horns, then to the style that went below the plugs in the late 60s, then to logs again in the late 70s on some engines. The 55 engine has it's own unique crankcase ventilation system, and no oil filter boss.

But yeah, they're all the same.

 

The older engines have the oil dip stick on the drivers side, early early engines bolt the starter to the trans not the block, I believe very early ones also have no spin on oil filter. The rest you gotta just run numbers because you can mix and match until Your heart is content

 

58-67 blocks have the hole for the breather/vent tube out the back of the block. 68 and later removed those as they went to a PCV system. The spin on oil filter came in 1968 as well. The accessory holes in the heads came in 1969. Also the swap from short water pump to long was 69/70

 

this helps when looking at an original engine as 302/327(large journal)/350 all use the same block casting number.

 

NONE...

It's too easy to mix and match parts, and many do.
Swapping cylinder heads is WAY too easy to do, and this is one of the key designators what engine you MANY have.

Putting late model Vortec heads on an old 327...yeah, been done.

Mike

 

On the 67 and older 327 s and 283 s we could tell the difference between the two by feeling on the drivers side there is a slight casting defect on early 327 s but the 283 s did not have it. It was on the front of the block between the timing cover and water pump. We could barely feel a slight casting defect there. Hope i helped more than confused.

 

i have had 400's with 2 and 3 freeze plugs.

 

And then there are the newer 1987 and up SBC engines! After decades of only playing with pre 1987 SBC engines I bought a 1990 to build back in 2019, and immediately felt like I'd stepped into the Twilight Zone! Every time I went to buy another part for it, or use an existing part I had, I discovered it was different.
The change to a one piece rear main seal required all the parts and pieces for that, but also changed to a different oil pan. And the timing chain, cam, etc. were also different. Dipstick tubes were different, and the only thing that was common to earlier SBC engines was the heads still interchanged if I wanted to use older heads on the newer engine.

 

There are a few that I can think of that have already been mentioned;
-The road draft tube provision on the 67 and earlier engines
-The no side mounts on the 57 and earlier engines
-the no oil filter on the very early engines
-The early engines with the small balancers
-The 59 and earlier valve covers with the staggered bolt pattern
-Obviously the later 87 and up center bolt valve covers
-Arguably the 69 and up long water pump

But...

When push comes to shove, these minor changes are splitting hairs, and the engines are largely the same. I consider any Gen 1 SBC to be a traditional choice of engine, because it is.

 

You forgot the steam holes in the 400 block.

But the middle one was undrilled right?

 

The 64-67 Chevy II 283/327 blocks are (at a glance) the most distinguishable of all the SBC's.

 

Forgot this one

 

Those Nova blocks are rare anymore, there was 66 327 Nova block somewhere in Portland for sale online not to long ago, first one Ive seen in a long time.

Then 92-97 LT1s, those are the dreaded "opti spark" blocks and easy to spot and avoid. They will lack the traditional hole in the back for the distributor as they had it in the front of the block running off that end of the cam.

 

The 1955 Chevy 265 Is Unique In That The Block Does Not Have Provisions For A Oil Filter And Is Optional And Mounted On The Intake Manifold...Which Is Also Unique..

 

They're hard to see when you're just looking at an engine.

Neat how I listed a lot of things that changed from the 50s to the early 80s, and still missed about half of them.

Meaning that if you can't glance at an SBC and get a good idea of what era it's from, you need some more edumacating.

 

Theirs a good thread on early 265's on here, if I can find it and the pictures aren't all gone.

 

Don't forget the Studebaker and Checker versions

 

I'll never forget the Checker version. I remember being puzzled years ago when I saw a small block Chevy bolted to a Ford automatic transmission lying on the ground in a junkyard.

 

my 66 stude 283 was no different than any other 283, except the valve covers had no script, just Studebaker stickers,and the weird transmission it was bolted to. I believe they were just commercial engines. I saved the valve covers, 2 jet, and scrapped the rest, I was more interested in the flanged dana 44 posi and disc brakes.

 

Don’t forget about the late 60s 4 bolt main (iirc) 327s in Massey Ferguson 510 combines. There something different about the heads, large chambers, small valves?

 

McKinnon plant supplied the Studes IIRC, I imagine they were just continuation of replacement engines. I mentioned Checkers, but probably over 90% of their Chevies were inline sixes