CHEVY SBC 400 ID

[ssn696]

The one on the right looks like the 400 I already have. '509' cast into the cylinder wall and the missing middle freeze plugs. What's the one on the left? Sorry, I didn't take a second photo. The mystery motor has three oil plugs above the cam shaft, while the familar one has two.

Thanks for your advice.

 

[lilbowtie]

Check the block casting numbers located on the driver's side, top rear of the engine block to identify them. The number stamped on the front passenger side of the engine block will let you decode it. Nice blocks possible bowtie.

 

[druggles85]

What lilbowtie said.

I usually start with the suffix code on the front pad, sometimes they get reused so it's good to verify with the back casting number.

Bare block should be pretty easy to id. Check the bore, and look for the steam holes in the deck...

I thought middle freeze plugs were supposed to indicate a 4 bolt 400 block. I know none of my 350's have had them. But both of those engines In the picture appear to have splayed caps, thought you needed to start with a 2 bolt block for those? I've got lots to learn. Lol

 

[ssn696]

Of all places, YouTube provided the answer.

The one on the left is a 511 block, 70-73.

Other places suggest that the later castings have more material on the main webs, so the 511 may not be the better of the two.

I haven't committed. If they get bought, then the decision was made for me.

 

[mccormack944]

Of all places, YouTube provided the answer.
View attachment 155788
View attachment 155787

The one on the left is a 511 block, 70-73.
View attachment 155789
Other places suggest that the later castings have more material on the main webs, so the 511 may not be the better of the two.

I haven't committed. If they get bought, then the decision was made for me.

I don’t know what kind of motor you’re trying to build as far as power level is concerned and I do realize this is probably a lot more $ than those 2 used blocks but personal experience here only way I would build a 400 based engine for anything is with an aftermarket block, little m is preferable for all out power but an shp block is pretty dang good too. I’ve seen a lot of gm 400 blocks fail, crack, etc but I’ve never seen those issues with a dart. Heck I’ve seen engines drop valves crack pistons throw rods out of the bottom and the block just need some minor clean up maybe a sleeve but never unrepairable damage

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[Ribbedroof]

Years ago I pulled the 400-2 barrel out of my father's 71 Impala. It was a 3 core-plug, 2 bolt block.

 

[druggles85]

Pretty sure my boss scrapped a 400 a couple years ago. I wish I would have known something about Chevy small blocks at the time.

Was a 3 freeze plug block. He had been saving it for years, but checked the suffix code and decided it was a 305...

There's at least 3 suffix codes for 400's that got reused on 305's

 

[bracketchev1221]

Yes 3 core plug blocks were the early 400’s. That’s how all the street guys knew how to identify a 400. That and the balancer were pretty big giveaways for people trying to pass them off as little motors. I had a 406 in my 79 Malibu in the early 90’s and none of the young guys knew what it was.

 

[gnvair]

I have a late 72 400 block that has 3 freeze plugs per side and is a 2 bolt block. Most casual observers do not realize that the 2 bolt 400's have the 3 center main caps that are as wide as the 4 bolt caps. As such, the registers in the block are already the correct width. The smaller 2 bolt small blocks have narrow main caps on the center 3 mains which requires machining to fit 4 bolt caps.

 

[ssn696]

I have a ‘509’ block 400 in the coupe. I found a spare uncut 509 few years ago for $50, but one of these could be an upgrade with the spiffy main caps. I’ll use the stock modular crank but upgrade to a 5.7 or 6.0 rod and hyper-eutectic piston combo. I have Dart S/R Torquer heads with the big valves that cc’d at 68. I was surprised - I thought I ordered the 76 cc chambers back in the day. I have a pretty gnarly hydraulic cam to try out. We’ll see how this plays out.