The car is a '91 RS TTop with an engine swap by the previous owner whe claimed it to be a 350 bored 0.060" over. He did say that he had not been successful with the block ID so I figured I'd give it a try. I've pulled the following numbers from places on the block and heads:

L195 333882 gm27 21
010 020 149
Epc4b 5/8
20
3970010
Also, there was an N and what I think was a D about 160 degrees apart. with an arrow like thing pointing to the D.

I've gathered that 333882 seems to be the casting number for the "best of the really crappy heads" (will this really matter on a street motor?) and that 3970010 seems to be a block that could be anywhere from 305-350 and 2 bolt or 4 bolt main across a twenty year span. I've been told the 010 and 020 are tin and nickel but I have no clue what that means from a practical standpoint. The cam (I have been told Crane) is not original and the intake (Ed. Performer) is also clearly not original nor is the carb (Holley). So, is there anything else that I can determine other than the LARGE range of years and applications that this block could be?

 

On the block and heads, there is a set of numbers usually in the center part of the heads and on the rear of the block between trans mounting and head deck.
They will start with an alpha letter, something like L038.
This translates to December (L) 03, 1978. You might try that.
Most of the 010 blocks are good to build from what I've always heard. I've had 4 and they were luckily all 4 bolt main blocks from trucks.
My condolences on the 882 heads. I've had a couple crack over the years.
Ron

 

I've had an 010 block crack in the lifter valley (it probably was cracked in the lifter valley from lack of antifreeze before the guy who sold it to me got it), and 882 heads crack at the casting line spewing coolant all over the headers.

Nothing I did with the 882 heads improved performance. But, I didn't do things I know how to do now, although not much would improve them.

 

Other than potential cracking problems is there really anything wrong with the 882 heads?

 

Ok, so vanilla 010 block (the absolute most common block ever cast, I have that as well), and equally common 882 heads.
The 882 heads are the worst of the worst of the worst. They keep compression in the chambers, but that's about all they do. (Well, they make mighty fine boat anchors...)

They flow poorly, have big crappy chambers, etc. Want to know what the main difference is between a 160HP 350 chev, and a 350hp 350 chev? Yep, those BS heads.

The block is 010, that means it's a 350. Casting numbers can only tell you that. It's been bored .060" over, casting numbers on the block won't tell you what style of pistons were put in it, and main cap bolts don't really matter.

Remove the heads (throw them out), and see what style of pistons are in there, also measure the deck height. Then pick correct heads and go from there.

 

There are 2 different 882 heads and neither are really good. Take 2 coat hangers and put then into the center exhaust ports. If both coat hangers come out the heat riser passage then the head is junk. That's the thin casting. If only one coat hanger goes through then it's the better of the 2 castings but it's still a poor casting.

The 010 block is a good foundation for a buildup. There are no 305 010 blocks since an 010 block is a 4" bore. The 010 block was used mostly for 350's but was also used for 302 and 327 engines. The 010 and 020 behind the timing chain are suppose to indicate tin and nickel. 1% tin and 2% nickel.

See if there's a suffix number on the block. It will be on a pad in front of the passenger side head. If the block has ever been decked, the numbers will be gone. The suffix number can tell you a lot more about the block.

A .060" overbore is extreme for a 350. Those cylinder walls are getting pretty thin.

 

Is there any way to do that coat hangar test without a lot of dissasembly? I'm mechanically inclined (Almost have my BS in mechanical engineering) but don't know a ton about IC engines other than what I've seen glancing over as my room mate periodically tears down his 405 (after boring, not chevy). I've been told the 0.060" is a bit extreme but given that I haven't had any issues that I know of yet, and that its a street car living happily on 87 octane gas, what are the chances of going through the water jackets if I haven't already? What other downsides are there of this (running hot?).
Back to the heads for a moment, what are the downsides of having the heat risers connected?
I'll check for the other numbers tomorrow if I get a chance.

Thank you for all of the help so far.

 

I wouldn't bother with those 882 heads either way. I'm serious, 160HP, think about that for a bit.

You can port a set of 305 heads that would be light years ahead of those. Those are dirt cheap at the wreckers.

 

It isn't a matter of putting heads I already have on a bare block. This is a matter of whether or not there's a compelling reason to take apart what seems to me to be a reasonably well running engine (and my only car) and throw money into it for a fresh set of heads.

I am curious though. What is the advantage of putting 305 heads on a 350 block rather than 350 heads or are they somehow the same?

 

305 heads = smaller combustion chamber = more compression. I bought a set of "305" 601 casting heads for my 350 rebuild.

 

High compression ratio builds torque but doesn't necessarily make more HP. Power is made from the heads. Bigger engines need more air. A small combustion chamber doesn't mean much if the intake ports can't feed enough air into the cylinders.

Flow numbers can tell how how much power is available from the castings. Many factory SBC castings are lucky to flow 180 cfm. Most are around 160 or less. Some top end aftermarket SBC heads flow 220+. Even buying a set of Edelbrock aluminum heads will be a big improvement from any factory iron casting.

 

Very true. I guess I should have said 305 heads with larger valves. The aftermarket aluminum heads would still probably be a better option.

 

Don't get exited about 882s. They're not the head of choice but thet ain't that bad either. There's millions of them on the road today in those old vans and trucks you pass on the freeway.Corvettes had them on 250hp rated engines in the 70s. If it ain't broke don't fix it.

 

If you're ok with your car running about as fast as an LG4, then sure thing, leave 'er run.
I thought you were interested in the performance of it, and could spare some cash and wanted it faster. If you just need it for transportation then leave it be I suppose.

 

It doesn't make the SLIGHTEST bit of difference what application the block was originally installed in; it will have lost all memory of that by now. All that matters, is what was put inside it when it was rebuilt.

Most often, and keep in mind, this is only what's "most often" done, certainly not "always" or "only" or "has to be" or anything like that; but MOST OFTEN, when you see a motor built out of the parts you've got, it will have stock replacement pistons with the 12cc dish, about .020" extra deck clearance, a 305/350 crank (those being the most common for that block, probably a 442 casting), and just some basic stock rods. But you never know until you open it up and look; people have been known to bolt some off-the-wall stuff into a block.

The tin and nickel stuff is not worth even considering. After some point in about 1969 or 1970, the factory abandoned the idea of using different metallurgy for different blocks, and the casting molds with the different "010 and "020" numbers on them got all mixed up and random ones used for ALL blocks. Pay no attention to that, it's meaningless.

882 heads are about as anti-performance as you can get. They have poor exhaust flow (intentional, sort of "built-in EGR" actually), are prone to crack, and are gas-mileage-hostile, as they were designed to meet the early emissions specs and that was more important at the time than efficiency.

But, whether that setup is "good" or not, depends on what YOU want, and whether it's satisfactory to YOU. I can tell you, it wouldn't be, to me; but that's just me, and my opinion doesn't apply to you. It might be just fine for however you use the car and expect it to work. Are you happy with it? Looking for more? Less? If it's OK as is, then there's no reason to tear into it.

But if you ARE looking to get more out of it, and are willing to swap heads, than there's several paths you can take, depending on your goals and budget, and of course, what the short block ACTUALLY is. Which you really have no way of knowing until you pop the heads off.

 

Sofakingdom, thanks for the information (and everyone else too for that matter). I was wondering if original block application had to do with anything and I'm rather glad to know that it doesn't. It's also interesting that the metal content casting numbers don't actually mean anything. As for internals, I was told flat topped pistons were put in although I've never openned it up myself. Is this something that I could easily determine by pulling a plug and using a mirror and flashlight to see with the piston up? As for the heads, it seems as if those are a good starting place for whenever I do actually have money to sink into this. I don't have a build sheet for the motor but I do know where the shop is that built it.
Would it be poor form to ask theshop that did the build what they put in it or for that matter would they even keep a record of that?
As for gas mileage hostility, how much would a new set of heads change that (as a rough guess)? Right now I'm getting around 20-22 going 70-75 on the freeway. If it matters any the carb is a Holley Street Avenger 670cfm thats a couple years old. Reading the carb section people here don't seem to be thrilled with the carb (and I get the impression that my secondaries open too fast) but it seems to be complaints about price rather than poor function.
To try to re sum up the performance issue, for now I wanted to make sure I wasn't driving around something notorious for failing in street use. At some point I'll probably start changing parts for performance and I'd like to have at least some idea how to go about that. Finally, is there a way through the plug hole to measure compression ratio?

 

No, you can't measure compression ratio without taking off the heads and measuring You can measure cylinder pressure, but there is no way to correlate.

It's hard to optimize the combo without knowing beyond the shadow of a doubt what's in there. I think it's completely allowable to call up the machine shop and see if they remember the engine. Maybe drop the name of the guy you bought it from, and see if they kept a record as to what was done.
I'd ask:

-part number of the pistons
-was the block decked? how much?
-camshaft, part number. (a "268" cam, or "about .460 lift" is not enough information)

Those heads are just inefficient. You can get a bit more MPG with better efficiency heads (better chamber design and swirl). You're doing ok now though, 20mpg is decent. You'd gain HP more than anything with new heads. Same with cam.

The avenger is a vacuum secondary carb right? It's just a bit of a waste of cash to "upgrade" to less flow than a Q-jet, and a similar design.

 

Block applications make no difference at all. They're all the same. The only difference is, in trucks and some other applications, they put 4-bolt main caps on some of them. But even that is a very minor and insignificant thing, not worth worrying about.

Right; there's way too many variables that affect a compression gauge reading, to use that to "calculate" the CR.

You might be able to see into a spark plug hole and tell a little about the pistons. Maybe. It's worth a try, but don't bet the farm on it. The problem is, if they're dished, the part you can see through the plug hole (the center), doesn't usually look any different from flat-tops.

To put the compression issue into perspective, if you plug the way most "rebuilt" 350s are built into a compression calculator, the numbers will be 4.04" bore (.030" over 350 bore), 3.48" stroke, 76cc chambers, .025" stock deck clearance plus the "rebuilder" piston extra .020" for .045" total, .039" head gasket, and 12cc dish, your CR will be about 7.9:1. With the 76cc heads and .039" gaskets, and flat-tops with the usual 6cc valve reliefs, your CR comes all the way up to 8.3:1.

The .045" of deck clearance (the stock .025" plus the usual and customary extra .020" that virtually all cast "rebuilder" pistons, as well as TRW or SpeedPro forged or hypereutectics) REALLY kills the compression. To give you an idea how bad that is, if EVERYTHING ELSE was the same except the pistons come all the way to the top of the bore, the CR would be 9.1:1.

IMO the "ideal" 350 would have .000" deck clearance (pistons come up level with the deck at TDC), .039" head gasket, 64cc chambers, and flat tops; or, 58cc chambers and "reverse domes". "True" flat-tops with about any pistons you can buy that are REALLY 1.56" compression height, will have single-"eyebrow" valve reliefs. 4.04", 3.48", 64cc, .000" deck clearance, .039" gasket, 4cc valve reliefs, is 10.6:1.

You can see, there's a WIDE WIDE range that the CR can be in; but with those gigantic chambers, it's all going to be real low. And then, the deck clearance and the dish, make it that much worse.

What is this car used for? Are you happy with the engine like it is? Wanting to make changes? It's not going to just "fail", so don't worry about that.