Can anybody tell me if a set of 13 heads from a 70 400 will work on my 69 350? Will there be any benifits with the larger valves? can these be milled to increase the CR? My current heads are bad and need to be replaced and I found a set of these that I can pick up for about $200, are these worth $200?
Thanks for any input Wes

Taking a few liberty's here but...
We've run some flow simulations on the 350, the 2.11 and 1.77 valves seem to be a little big on the 350, we found a 2.07 and 1.66 actually gives better velocity while the flow is about the same.

#13 heads should have 2.11 and 1.77 valves and 72cc chambers like the 350 HO heads did, but I've heard they can be more or less cc when stock, have them cc'd and a .010 clean up cut done at least.
The 1.77 exhaust valve is iffy in a 350 clearing the bore, but a 69 350 should have the bore already chamfered to clear. As long as you don't run a very high lift cam and or 1.65 rockers they should clear fine.
Also, if the pistons are about .020 down in the bore (close common #) 7cc of valve reliefs in the pistons, a head gasket of .040 and a true 72 cc chamber you should have a compression of around 9:1, pretty good # for pump gas.
Worth $200? Depends on how much work they need. New guides, valves, springs, etc... and machine work will run around $800 min, add in the $200 and you have $1000 in #13 heads. Are #13 heads worth $1000 to you?
Matched with a good cam, intake and headers and you will get some benefit from them.
A lot depends on the total package and what you want out of it though.

Personally I think the older 350 stock Pistons are junk for a performance engine, very heavy and deep valve reliefs. Clevite makes a inexpensive decent replacement though, after that you get into customs, around $500+ a set. Not a lot of 350 Piston options out there.
Overall, just doing this head swap won't gain you much, but together with a careful build the little 350 runs pretty good.

ho428 thanks for the info I dont know if I want to sink 1000 into a set of 400 heads, I have already done a lot of work on this engine bored and aftermarket pistons, cam, converter, intake, headers ect., lost 2 sets of valve guides in stock 350(small valve #47) heads (just the inner exhaust valves) within 100 miles and figured my machine shop botched the guide job.
aftermarket alum heads run about 2k, not sure I want to spend that amount either but it sounds as if I might be better off.

I have a set of 13's.
Thier the same as the other hp d-ports.
But with 75 cc's(avg).

As long as the cylinders are chamfered, they'l work fine.
The 068 cam with 1.5 rockers works good in a 350 with big valves.
Rec 3.23 or higher gears.
3.55's are ideal.

Didn't mean to scare you off the 13's, just throwing out the good and bad points. If they don't need new valves, guides, springs and such just mill them, machine the guides and install sure seals if they don't have them, the heads will fit and run, just don't expect much of a power gain unless you change a few other things like the cam Ponch says.

I'm having some Aluminum heads built for my 350, custom chamber, ported to 290 cfm, milled to 60 cc and using the valve sizes I mentioned, yeah they do get pricey but sinking another grand or so into 40 year old lo-po Iron heads like the #17's I'd been running on a 350 isn't a good option either, IMO.
And KRE's are about your only option unless you plan on a RA-IV exhaust.
Just one more reason people install 400-455's, just so much easier to mix parts on. But 350's will run like the devil when built.

ho428, what do you think about these? I believe a machine shop is doing these asking $800
PONTIAC CASTING 1968 # 15 HAVE BEEN PORTED AND FLOW TESTED ON "SUPERFLOW 600 " FLOW BENCH BY WARDEN PORTING SERVICE . CHAMBER SIZE IS 72cc WHICH IS PERFECT FOR A 400 0R 350 OR EVEN HIGH COMPRESSION 455 ! THE HEAT CROSSOVER HAS BEEN FILLED WITH ALUM. THEY HAVE MULTI ANGLE SEATS CUT BY "SERDI" VALVE SEAT MACHINE .THEY HAVE BEEN MACHINED FOR SCREW IN STUDS. THEY COME WITH A FULL SET OF FERREA STAINLESS VALVES 2.11 INTAKE AND 1.77 EXHAUST , 5.O9 LENGTH SO YOU CAN USE TALLER VALVE SPRINGS, FLOW NUMBERS FOR INTAKE SIDE ARE .300LIFT=205cfm,.400LIFT=240cfm,.500LIFT=250cfm,.600LIFT=255cfm. THE EXHAUST SIDE IS .300LIFT =145cfm,.400LIFT=195cfm,.500LIFT=210cfm,.600LIFT=215cfm.THEY ALSO MACHINED FOR P.C. OIL SEALS . HEADS DO NOT INCLUDE SPRINGS/RETAINERS/LOCKS/OIL SEALS, THESE PARTS CAN BE INSTALLED FOR 150.00 FOR HYD. CAM

Not bad specs but the price is kinda high, more of a race prepped 400+ head. You really don't need the taller valves, can't run a high lift without checking some piston-bore to valve clearences. I'd also ask about hardened valve seats as well if this is strickly a street engine.
You'll still have about a grand in them with the springs, retainers, etc...
Also says machined for screw in studs but doesn't mention having them, guide plates or the lock nuts, and you'll need poly locks for them if you get roller rockers.
SD performace offers fully prepped and built Iron heads for a little more than what you'd have in these when done. I think Butler and KRE does as well.

I don't have an easy answer for you, but personally I wouldn't sink a bunch of money into a set of heads on a stock or tired bottom end 350.
If the goal is to just get it running, fix your heads or check the 13's out real good. I found some 62's at a swap meet for $100, but they need everything so $200 for heads that just need a rebuild isn't bad, but until you get them opened up and cleaned you won't know.

Tough decisions and none are cheap.

You should listen to him. Don't waste money. Save a little longer and do it right. I would pull it and go with a 400. Much more potential for fun. You keep the original block (If thats what it is) put it in the corner of the garage. I love pontiac as much as the next guy but 400 and up is really the only way. I know I'm not going to make any friends saying that either. Am I wrong?

thanks for the feedback guys, Im going to have to think about this a little more before I make this investment, I would like to keep the 350. ran great with the stock iron heads, but as I stated I cant keep the guides in these heads, I dont know if the machine shop botched them or somthing else is going on. when I first rebuilt the engine I had put about 500 miles on it and then developed a tap which turned out to be bad guides. took heads back to machine shop and had new guides put in again these only lasted about 100 miles and started to tap again. I cant afford to keep pulling the heads and putting new guides in every couple hundred miles so I thought I try another set of heads and see if this corrects the problem

Guides don't just go out, something else is going on. Hell, I've run knurled guides in race engines, sleeved guides, you name it, sloppy as you know what and still kept running.
What else have you done or checked? Cam? lifters?
Running guide plates? Rockers ok? Any flat spots on the rocker tips? How are you adjusting the valves?
What kind of clearence did the shop put on the guide to stem?

ho428 thats what I thought too but everything seems to check out.