Lightweight

I have an 85 Iroc with a 305TPI. I'm used to finding small block Chevy numbers on the Identification plate on the passenger side front of the block. On mine there is nothing there. It hasn't been ground off or anything, just no numbers. It is a 305 though, only 2 freeze per side. Anybody got any other info for block id spots?? I ran the VIN and the car is an Iroc so that part is at least right. Thanks

92RSFivePointSlow

there's a pad on the block behind the driver side cylinder head.

AlkyIROC

That will give you a casting number. Casting numbers don't tell you a lot since many different vehicles or models can use the same block casting. It will tell you if it's a 305 block or not.

The suffix number is stamped on a small pad in front of the passenger side head behind the alternator. It's usually covered in dirt, oil or paint and very hard to read. The suffix number will tell you exactly what the block came out of.

Lightweight

That's what I'm saying, the pad on the passenger side is blank, and yes its clean, spotless even. I thought maybe somebody ground them off for some reason. It is perfectly smooth, like there has never been anything there. I'm used to getting the numbers there so i know what to look for there but there isn't anything on that pad. Really weird

RB83L69

Sounds like your block has been decked at some point in its life. Therefore, you have a rebuilt motor, which might or might not be the one that actually came in the car (probably not).

What is it you would like to find out from that number?

Lightweight

It wouldn't bother me that the motor is rebuilt. I kind of figured it was. I changed the oil pan a couple months ago and you could still see the cross-hatch marks on the cylinder walls. Car has 145,000 miles on it. The valve seals were trashed though. I'm guessing they put a short block in it and slapped the heads back on without doing anything to them. Still has GM pistons in it though. It ran 9:41 in the eighth the other night, and its bone stock except for a cat-back and a regulator. That's why I'm trying to find out what's in it.

RB83L69

Well if it's been rebuilt, the numbers on the front of the block wouldn't tell you anything about it anyway, because whatever used to be in that block, isn't there any more. There's something else in there now.

The casting number on the back of the block will at least tell you the bore size, and maybe a little about what year vehicle it came from. As far as details about it, like whether it was a high-perf or low-perf or whatever, all that is irrelevant now, it has rebuilder pistons in it. Or, it's a "crate" motor from GM, which didn't come in a vehicle to begin with.

What was the crank casting number? Any numbers on the pistons?

Lightweight

Yeah, I had the numbers written down. But then i moved from Neb to SC and they got lost. They were GM though. Am I right about the 2 versus 3 freeze plug call. I've never seen a 350 with 2 and I've never seen a 305 with more than 2. Just curious, guess I need to get the numbers off the back.

AlkyIROC

That's the trouble with SBC blocks. Once the block has been decked, the suffix code is machined off. All you'll have to go by now is the casting number.

RB83L69

No, that is not correct about the freeze plugs.

All SBCs have 2 freeze plugs in each side of the block, except for the early 400 blocks, which had 3 - and also mostly had 4-bolt main caps installed. No blocks with 3 freeze plugs have been made since about 73.

Lightweight

Well, I pulled the alternator and tried one-last time on the front pad just to make sure. Nothing there at all. Found some numbers on the back pad though. 14010201, that specs out to an 80 to 85 305. I found my piston numbers but I'm not having any luck finding a match. 14081252. I have some numbers written down off the main caps but I think they are nothing. Maybe somebody put a small cam in it. It doesn't act like it at all but it runs better than it should.