I dissasembled an older Chevy 350 and found the heads do not exactly match.  One is a 3973487 and the other is a 3973487X.  In research I found that the "X" on the end of the casting number means that the intake runners have a little more volume.  The engine appeared to run fine this way but I am wondering if it is an ideal setup to use it this way.  Could the intakes ports be "Gasket Matched" and opened up a little so they would match or would there always be imbalance between the heads?  They both have 1.94 intakes valves and look identical.  

I believe they would be fine for a stock rebuild or low-po overhaul. The chamber volumes should be within whatever the factory tolerance was and the intake volume difference should be negligible unless you have high expectations and expect to "push" the stock ports to make more power than they would want to...

It's far from ideal but it would work depending on how much you're asking of them. Gasket matching is never really intended to improve a port significantly or alter the design of a port rather than to prevent a loss in available flow area from mis-match induced turbulence. It might not be a bad idea to gasket match (especially if you're stepping up to a larger aftermarket intake manifold) but it wouldn't do much in equalizing the volumes of the two heads, I'm sure the volume difference is elsewhere in the port where it can be more beneficial.  

I guess I forgot to add the rest of the equation.  It will be for a half ton truck.  I am more interested in low end torque rather than wide open foot thru the floorboard power.  The rest of the engine will be a stock 350 lower end.  Stock cam or at least one with a smooth idle.  Edelbrock Performer intake, and 600 Edelbrock carb.  Ram horn exhaust manifolds and a true dual exhaust.  I am running a turbo 400 transmission and 3.55 rear end.  

Am I correct that on a dual plane intake it treats the engine as two 4 cylinders, giving one set a little more power at low RPMs and the other 4 a little more at upper RPMs?  Or is this a myth?  

The head with the X in the code is 10CC'S larger.The head without the X in the code was used on 1971-72 LT-1 350 330HP engines but should not be that big of a difference to cause problems on a stock or near stock engine.Both have 76CC chambers but if it was mine I would want a matching set of heads on my engine.  

Your 3973487 heads have 76cc combustion chambers, and were the first factory heads to have hardened valve seats for unleaded gas. They were a lot like the old 441 heads except with a better chamber design and acessory bolt holes on the front. They could have either 1.94/1.50 valves or 2.02/1.60 valves from the factory.

Since the heads were designed for them, I'd say go ahead and have them machined for the larger valves. This will help your bottom end torque, and a three-angle valve job for best flow. Also have them setup the heads for screw-in rocker studs. I'd also have them check the guides and install bronze inserts if necessary so you don't have oil control issues. You can have the machine shop check the intake runners and perform the necessary work to equalize the heads as best as possible.

These are good heads, for your application you'd be hard pressed to find better ones without shelling out some money.  

It is absolutely false that larger valves will help "low-end" torque in his sense of the definition. At part throttle and well below peak torque DECREASING mean port velocity is not a way to GAIN torque, it just doesn't work that way. The velocity is already incredibly slow at these low piston speeds, slowing it down even more worsens the signal to the carburetor booster...

Even though this difference in "low-end" power is probably negligible to someone without a dyno and who isn't extremely picky about their street rides, I just don't want anyone to be mis-informed.

Also, how are these heads "designed" for larger valves?

Overall, If putting in larger valve is going to cost significantly more than stock-sized vcalves then I wouldn't do it.  

It appears the easiest solution is to just grind that pesky little x off the end of the casting number on the one head and then they will match!  The idea of machining the heads for larger valves is out.  I think for my application 1.94s are fine.  I am combing my cousins stock of heads and trying to find a head to match either.  He will just swap with me then they will match.  

The 1.94/1.50 valves will be fine for what you said you are wanting with the right cam you're engine should have plenty of torq.You might want to check out the summit k1102 cam kit.  

hey,just get a cam from lunati, valve lift around 240, be alright, top the valves, and then get roller rockers, 1.5 or 1.6, it'll be fun to drive with even a 2 barrel, this you'll get your torque but with the advantage of better gas economy,    want more power to wheels, take off your fan and put elctric fan in, then some headers, or truck headers,   ugly lil things but they work and they keep your compression up pretty good, keeps blowby from happening when u got load on your truck so u can floor it and get it done,  nice lil puller here.  

Valve lift around 240? Headers keeping compression up? Headers/fan preventing blowby?

Please don't try to give advice if you don't know anything about the subject, and it's clear that you DON'T!  

This post was for a little help on Chevy Heads. I already know what intake and carb I will be using.  Roller Rockers?  No thanks.  Headers? Once again, no thanks, I will be spending my time and money elswhere than changing header gaskets constantly.  Plus, I want to run on pump gas so I don't need the extra compression they will generate.  Wait a minute, how do headers increase compression?  Decreased blowby?  Where do I find a cam with 240 lift?  Top the valves? 2 barrel?  Electric fan? Maybe, but will not help much on low end torque. I think someone has been chewing too many crayons.  

Headers are probably one of the most efficient ways of adding horsepower potential to your build. I understand if you don't want the hassles though...

An intake and carb (4V especially!) is a good start.  

just saying, stop dynoing with a light weight, u guys ever tried putting a load on a truck and then do a dyno with it on it,    what type of results u thonk occur,    mybad u old farts  

If that is how my generation is supposed to express themselves, I would want to be an old fart.  

Hey Guy's,
I need some advice, I took my car to the race track and ran it three times. The first two times I ran it ran smooth. As I turned the car on to go race the third time I knew it was not running on all 8 cyclinders. I still ran it and it did well. I loaded it back on the trailer and called it a night. The following day I took it out for a spin around the block, engine was still running weird. I figured I would replace spark plugs. As I removed #1 plug, a bunch of water came out of cyclinder. What should I do?
By the way, my car is a 67 chevy camaro 350 w/vortec heads.