My 86 Camaro came with a 305 but had the engine swapped at some point. The only details I can get on the block are that it’s an 010 block so therefore has a 4 inch bore. The blocks been decked at some point so the stamping on the front passenger side of the block is gone and I can’t ID any block details other than bore size. Is there any way other way to identify details of the block without doing a tear down? Second question has to do with heads. Drivers side head is a 416 and passenger side is a 601. Has anybody every had success, issues just any experience at all with running non matching heads?

 

Neither can anybody else. Thing is, that number, or ANY OTHER "number" on the block for that matter, won't tell you a damn thing, once somebody has had their d***-skinners in it.

It's a small block Chevy. That means ALL blocks of a given casting number (010 in your case) are EQUAL, as far as any "numbers" go. I haven't got any actual "data" as proof, but I'd be willing to bet that no more than .001% of all 010 blocks that might be found in cars they didn't come in, haven't been "rebuilt". Which means that the crank, rods, pistons, cam, etc. etc. etc. have all been taken out and randomized with random others in the giant pile of cores (except that if there were any particularly "good" cores in the pile, the shop employees would have ganked them for their own motors and left the customers all the crap), reworked, reground, replaced, or otherwise altered from what any "numbers" you might find on the block, would tell you.

Meaning, any inquiry as to "numbers", is UTTERLY FUTILE as far as determining what you ACTUALLY have.

That said, you already know it's 99.99% likely to be a 350 in whatever overbore (probably .040" or .060"), and that you have 1 416 head and 1 601. Both are 305 heads from the early - mid 80s, let's say, 82 or so, to 86; therefore foreign to a block casting made from 69 - 80. You know thereby that your motor is NOT "factory" in any manner way shape form or fashion, rendering any "numbers" on the block null and void.

What matters about a 70s block is the quality of the original factory machine work. I can't tell you how many of those common 70s blocks I scrapped back in the day. Most were junked for The Starter Bolt Hole Problem, wherein the entire starter bolt pattern is drilled too far from the crank, which means it's impossible to get a starter to ever align to it properly, and it EATS starters, flex plates, etc., while being almost impossible to start and making that loud grinding gnashing noise when it tries. Next greatest number I've thrown away had The Lifter Bore Problem, wherein some of the lifter bores don't point properly at the cam centerline (most often pass side toward the rear, so #6 and/or #8), which makes them EAT cam lobes and lifters. Others were for The Bell Housing Dowel Pin Problem, wherein the bell housing dowel pins weren't centered on the crank, which makes them EAT torque converter bushings. Another common issue was The Cylinder Bore Problem, wherein the cyls weren't perpendicular to the crank from front to rear, which made them EAT the sides of rods. Doesn't matter whether they were a "LT-1" out of a "Z/28"; doesn't matter whether they were small or big blocks (I have a 74 454 sitting in a car in my driveway to this day that has both The Starter Bolt Hole Problem AND The BH Dowel Pin Problem); doesn't matter doesn't matter doesn't matter doesn't matter doesn't matter. 6-cyl, truck, hi-perf, small block, big block, sedans, taxicabs, ALL of them had these issues, statistically. They ALL had to do with the automatic machining processes, and the machines themselves, at the factory where the blocks were produced. In the 70s, "quality control" at GM evidently meant, making sure the quality NEVER exceeded some bare minimum, which at the time, the warranty on new cars was 3 months or 3000 miles.

Notice how many of these things involve EAT? I can assure you, it takes all the joy and fun out of this hobby, to go out and score some "deal" on some block, then spend untold cubic $$$$ on machine work and parts and effort, and then for it to somehow EAT itself to shrapnel within the first couple hundred miles in some way you can't diagnose. Gets even worse when you conclude that you must have done something wrong, and go spend another wheelbarrow full of $$$ on it, and it does THE EXACT SAME THING all over again. Very discouraging. THAT'S what you should be concerned about and paying attention to, NOT "numbers".

Yes lots of people have had mismatched heads on their engines at one time or another. "Success" with such things is largely in the eye of the beholder. In the case of your motor, does it run? Then it's successful to that extent. Did it make it through whatever warranty period it had when installed? Check. Are the dissimilar head castings causing you any problems? Check again. And so forth. So, I can't be sure what you're wanting to know, when you ask about "success", therefore I can't be more definitive.

Those 2 head castings are fairly similar though not identical. The 416 is nominally about 58cc, the 601 about 56cc, although there's LOTS of variation in both, and even more as they have aged and had valve jobs, been decked, etc. etc. etc. Both came with (who knows if that's what they still have) the typical 305 valves (1.84" / 1.50"). The 601 has a marginally better chamber shape; kinda more a kidney shape, where the 416 is more a bathtub. Both mostly suck in stock form but can be made somewhat OKish, for performance, if you spend enough time or money on optimizing them. I seriously doubt any such thing has been done to yours butt who knows, I can't see them, so I'm just going off of what I've seen time and again, and what I would therefore expect in your situation.

The reason people put 305 heads on 350s in the first place is to raise the compression while using the cheeeeeepest possible "rebuilder" pistons, the cheeeeeepest and most commonly available heads, and the cheeeeeeepest possible processing (which is to say, none whatsoever); or maybe only, that's just what they just happened to pick up at the moment when they reached into the giant pile of junk parts, and there was no conscious thought or intent at all. They can work pretty well if they're not the weakest link in the induction system as a whole, which if the motor still has exhaust manifolds on it, they're not. I seriously doubt that you'd be able to notice any difference whatsoever if you went back to the same place that those heads came from (so that you'd get the same valve job etc., if any ... apples to apples) and "matched" them to either casting #.

If you can get any numbers off of the cam we can maybe tell you more about what that is. It certainly won't be "factory" although it might be a "replica" of a factory cam, most likely the 929 grind (.390"/410", 194°/204° @ .050" or thereabouts) since that's the most common one there is BY FAR and that's what people building the cheeeeeepest possible "rebuilt" motors would tend to use, although there's no guarantees.

Basically I'm telling you, it sounds like you have the cheeeeeepest possible "rebuilt" motor, from the cheeeeepest possible source in your town (or whatever town it came from). Not something that is worth any further "research". If it's not what you're wanting in some way, best to direct your attention toward turning it into what you DO want, if that's even possible (for example if it's already .060" over and the bores are no good, the block is scrap) without worrying about what it is now, since practically every single piece is likely to go straight into the trash ANYWAY in the process of "improving" it.

 

More than anything was just wanting to know what exactly I was dealing with not that it matters that much anyway. Believe it or not even as hodgepodged together as my engine is it’s still a pretty good runner all things considered.

As far as the heads go I knew they were off a HO 305 just wasn’t sure on different port sizes, chamber size, valves, etc. Have no plans at the moment for making any crazy power numbers but if any problems pop up though I’ll have to refer back up to all the manufacturing defects you listed, thanks!

 

I have seen mass rebuilder stuff at 0.080" over even. Even cranks with a single journal turned 0.020" or welded up and turned. Most are total garbage.

The 601s are actually 53cc nominal. That is 1/2 point compression bank to bank as well as different burn rates between chambers. The engine will never run smoothly, unlike factory L31s and LS based Vortecs that the GM factory mix matched practically identical castings with different casting numbers. My aunts 2010 5.3L Tahoe had 1 799 and 1 243 head on it, but they are the same heads. The mass rebuilders also buy pistons 0.020" reduced compression height and often do not deck the blocks as intended. They make a piston that has a ~22cc dish for 350s to run the commonly available 305 heads, so putting good 350 heads will put that engine around 7:1 static compression and that is even worse with those 0.043" thick rebuilder style Felpro garbage head gaskets.

 

Both the HO motor like mine (L69) and the LG4 usually got the 416 castings. 601 more usually appeared in trucks for some reason. The rest of the measurements, as detailed in my earlier post, are ... as detailed in my earlier post. Ports are largely the same. With the small valves, and even more so if you still have exhaust manifolds, the ports aren't the bottleneck, in any case. Only difference between the 2 castings is the 2cc or so of chamber volume, which can EASILY be swamped by things that have happened to them since they were cast; like the valves getting sunk into the seats by wear and valve jobs, the deck surfaces needing sliced off, and so on. "Nominal" specs often have little meaning in the real world.

But in the end, if it RUNS good, it IS good, at least as far as that's concerned.

My whole point is, since your motor has obviously had somebody's bishop-buffers in it, ANY "numbers" that might have been stamped on the block, have lost their meaning. Wrong avenue of research. Other things DO have meaning, and that's where you should devote your concern, if the engine in your car is even the main concern with it to begin with. After all, maybe brakes, tires, steering, suspension, air conditioning, interior, paint job, and so on, are more important, if the engine works well enough to push the car around reliably. I have no way of knowing any of that.