Thread: Blocks and Heads

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Let's try this again. I have a block, Casting numbers 14093638. My research says it is a 350, 86-94. On it are heads, Casting numbers 354434, which my research says are off of a 262/305, 60cc. 75-80. There is a stamping on the rear drivers side 8633. I am trying to determine if these heads are Corvette, and if this is a good match. I want to put this in something along with a 350 tranny I have. I am not a gear head but not a novice around engines either. I just want to be sure of what I have before I go further.Any help would be really appreciated. Thanks

Nope, not a Vette head, they never had a 305 in them. Some folks like to put the small CC 305 heads on the 350's for "performance". Unfortunately, without a ton of porting work and bigger valves, etc you end up with a wheeze box top end that is done making power at about 4,000 RPM...... Another lesson that cheaper isn't always better!!!

GM cylinder head casting #354434
4.3l 262 cid vin code G 75-76
5.0 307 68-73
5.0l 305cid vin codes 7, g, h, q,u years 68----88

Dave is correct. I see this all the time, fellows bolting 305 heads to a 350 block to raise static compression ratio. In my opinion, they're shooting themselves in the foot, because raising static compression ratio is only one piece of the puzzle in building a performance motor. Each full point of SCR has the ability of raising hp and torque by about 3 1/2 percentage points, so for instance, raising the static compression ratio of a motor from 8.0:1 to 12.0:1 might raise horsepower by ~13%. Raise a 250 hp motor by 13%, with all other things being equal, and you have theoretically achieved a 32 1/2 horsepower increase, to 282.5 hp, theoretically. But hold on a second there Sparky, you forgot about a far more important aspect of engine building, cylinder head flow. If the heads you use to achieve the static compression ratio increase, have flow characteristics less than the heads you removed from the motor, even at the original head's lower static compression ratio, then you have achieved nothing. Matter of fact, you have gone the wrong way and the motor will likely make less power than it did originally. Plus, with the higher SCR, the motor has a much improved tendency to detonate, depending on the fuel you use.

So, you're thinkin' to yourself......what if I get out the Dumore and grind some material from the port walls and make the heads flow better? Great idea Bunky. Get yourself a flow bench and a respirator and start grindin'. Every youngun out there thinks he can make a set of cylinder heads flow better than they did from the factory, but it ain't as easy as you think. Cylinder head ports are not necessarily all about size, they are more about shape and if you don't know where to cut as a result of having done heads successfully in the past and relying on your flow bench to tell you if you're going in the right direction, you may end up with 80 lbs of junk cast iron. I speak from experience here, been there, done that. My youngest son and I built him a '72 Chevy Luv pickup truck (built for Chevrolet by Isuzu) to drive in high school. We bought it as a roller from a drag racer friend who had installed a narrowed 10 1/4" Olds rear. We installed a bone-stock 455 Olds/Turbo 400, took it to the dragstrip and ran 102 mph at low 13's. I removed the heads and spent 28 hours cutting and grinding in the ports, doing what I thought was right, but having zero experience in porting heads and no flow bench to check my work. Well, we went back to the dragstrip and went 103 at low 13's. So, we picked up 1 mile per hour for 28 hours of grinding. So, now I pretty much advise these younguns to begin with the right parts from the git-go and that does not include grinding on ports with an unknown result.....or a disappointing result.

Another thing about cylinder heads, while I'm up on the tire, is that in order to back up what I said about PORT SHAPE, research different heads, their port volume and flow rates and you'll find out pretty quickly that port volume is not the whole answer. Not all heads are created equal. I have seen over and over that some heads with smaller intake runner volume will outflow and outhorsepower heads with larger volume ports due to mixture velocity and packing the cylinders better with a faster mixture speed. Do not choose heads based on volume of the ports, choose heads based on the verifiable CFM that the heads have shown to flow on a good flow bench. It's like when my ex-wife used to ask me if her caboose was too big.....I would tell her "no honey, it's about the shape, not the size. And while you are doing your research, pay attention to the intake pipe diameter the flow bench operator used for testing (did they use a 4.00" pipe or a 4.030" pipe or a 4.060" pipe or a 4.200" pipe?), whether or not the valves were backcut on the stems, what valve job was on the valves and heads (were they 1-angle, 3-angle or 167 angle seats?), what size valves were used, whether the ports were "as-cast" or CNC profiled, etc., etc, etc.

Best bottom line: Do a lot of research. Read replies from a number of hot rod forums such as this one. Look on websites posted by cylinder head manufacturers. Read technical articles or complete books written by those who know or knew what they were doing, David Vizard, Smokey Yunick and John Lingenfelter for starters. Hotrodders are a pretty good lot of guys, generally speaking, and they will tend to lead you in the proper direction. A cylinder head guru named Chad Speier is responsible for the current crop of heads that I support, Pro-Filer heads. Their 195cc aluminum offering will support 500 hp on a 383 and the price is less than $1100 for the pair, ready to bolt on with hydraulic roller cam springs.
http://www.profilerperformance.com/r.../sbc-23-degree
Their 180/185cc intake runner volume heads would be just right for a 350/355/360 motor in my opinion.
For a little more dough, you can own what I consider to be the best heads on the planet, Airflow Research. Or you can go the less expensive route and try Assault heads. They will do a pretty good job for the price.

You fellows who may never have $1100 in your fist for a set of heads will just have to continue farting around with production stuff or offshore aftermarket heads of an unknown quantity and doing the best you can, which will put you into "also ran" status in my opinion. Not trying to be mean-spirited here, just being real.

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Thanks Dave...Wanna buy a wheez box...cheap!

Thanks Tech. I'll make you the same offer I made to Dave: Wanna buy a wheeze box cheap! I really appreciate the tutorial. I know a lot more now for when I reconfigure this boat anchor...if I do. The last time I ported and relieved an engine was in 1954 and it was a 1929 model A 4 banger It's amazing what a 14 year old will attempt to make his $15 car into a street racer! (Wish I still had it!)