Flye

what should a set of rebuildable 394548 sell for?

Or in reverse, what should i expect to reasonably pay for a pair?

I assume whatever I get has to be rebuilt anyway, so just good, useable heads with the rocker arms/stands still attached. some of the postings say the castings are same whether big valve or not, and you can just have bigger valves cut in when you redo them anyway. assuming that is case.

Thanks.

joe_padavano

Well, I just got a pair of bare C heads for $50, but they are majorly rusted and need to be hot tanked. Yes the castings started out the same. If you are having them cut for big valves, be sure the machine shop properly undercuts behind the valve, otherwise there won't be much improvement. Oh, and you MIGHTASWELL grind down the A.I.R. bumps in the exhaust ports at the same time.

hotrodpc

Dumb question here, but I do not know. Do all C heads have the AIR bumps in the exhaust port? Is that maybe dependant on the year of the heads. I was certain that all C heads had the same cast #, but will some have the bumps and some not or do thay all have it? Sorry, somewhat new to the old Olds parts.

J-(Chicago)

An iron is an iron. They will all require a considerable amount of massaging to get them flowing decent. If you find any A, B, G, or Ga heads cheaper, I'd just get them. Depending on your application, you might even just need a J head.

I just sold a running pair of B's for 100 bucks.

For some reason, C heads and #5 heads are a big deal with the internet crowd. I don't get it.

hotrodpc

Same here Chicago. I have both a set of C and a set of G. I am not seeing big differance. I seen a flow chart once, not sure where, I wish I would have kept it, but although their is a hair of a differance in the C, but not worth all the hype put into it., Also not a huge differance in the small and big valve heads as you'd expect but everyone seems to spend to much for big valves. I'll be running my small valves C and or G heads, whichever ones will need the least bit of work. I'd stay away from J heads though.

gmrocket

in my opinion the small valve C's are the best to start with if you staying with the stock 2.00" or 2.07" valve. the big valve C has some goofy bowl work done by the factory that actually hurts flow. ten minutes with a die grinder on the small valve C's and you'll have a better performing head

hotrodpc

I did not hear that part gm, but maybe that does have to do with a part that I did read on Olds442 for whatever thats worth, but there is something else negative said about the big valves hurting performance. If I go with my C heads and I think they are small valves, not positive, I am leaving the valves as is. Just going with hardened seats cut at a triple angle. Some people have also said that is BS about the hardened seats being necessary. I am doing it anyway. I have not had alot of experience with Olds, but I have with SBC, and I have seen the damage that unleaded fuel has done to SBC heads. I'd think if it can happen to SBC, it can happen to Olds too. Unless for reason in 67 Olds was already using hardened seats but I have never seen such a claim. I have just seen that unleaded gas does not damage exhaust seats and I know for a fact it can. I have some pics of what it can do and I still have the heads too.

hotrodpc

Here is one of the sections quoted on O442 that mentions the negative of big valve heads, if this is true, I do agree with it for the reason, if Olds don't like high RPM, then I want to run a bit a taller gear in the rear and compenstate that with alot more bottem end and mid range power, not top end. :::


This brings up a good point regarding the difference in actual valve size, \ and any performance advantage. I realize that the bigger the valves, the more airflow typically you can get in the cylinder (disregarding any MAJOR differences, and looking at the basic type of intake tract). But how much is it really worth to have the larger valves? Is it worth extra HP, or is it not a valid need until higher RPM. My contention would be this. With a normal street motor, running typically at 3000 RPM, and occasionally up to say.... 5500-6000 range, I'd bet there isn't much of a difference in the basic overall view of things. It may be down a bit on HP when buzzing the redline a bit (with the big valves), but face it, how many people here spend any considerable amount of time at that RPM? In fact, I'd say that for people that really like the "grunt" of the bottom end of these motors, you may be better off with the smaller valved heads (yep, you heard right...). Typically you will make better low end power with the smaller valves than with the bigger ones (the same thing can be said for carburetion also, in that a smaller size carb will give better low-end power, and a bigger carb tends to lose bottom power, but gain top end).

hotrodpc

Here is the other remark quoted with negative comment about the big valve head.

Best Flowing BB Head

The '67-69 C (#394548) heads are reputed to flow the best. Pretty much goes without saying that big-valve heads ought to flow better than comparable units with smaller valves. Bigger valves may diminish low-rpm performance and throttle response

hotrodpc

I guess I have found the answer to my own dumb question above. As quoted on O442. So, I will be sure to grind that away as suggested. Thanks for that tip.


Good point, however I must think that this is strictly an unintended function in the "it's not a bug, it's a feature" vein, as the bump existed as early as 1966, long before EGR was even conceived. Clearly the actual intent of the bump is to provide a location into which the attach feature for the A.I.R. tubes could be machined. Since it was easier to maintain one casting design instead of two, the bump was used on all heads, whether or not A.I.R. was used.

Warhead

That was written by someone who owns a Chevy.
Everyone drives on the street at part throttle, but the 455 is NOT in danger of losing any part throttle torque when going to a 2.072 intake.
The heads on a 455 are the bottle neck, and they need all the help they can get.
Small valves on a 455 (even if it has 10.5 compression) will only SLOW IT DOWN.
Go big on a 455.
A nice, cleaned set of C heads should net you around $150.
Jim

hotrodpc

Thanks for the info War. Although I think O442 is a great site, I have found many many inconsitancies in info and suggestions. So although I find the info there, I am also conferring with others or looking for more info to verify which is correct and not. I myself just wonder for the expense if its really worth the gain. We are talking a differance of .07, can it possibly make that much of a differance? Maybe it can when multiplied by the lift and duration of your cam. Just not so sure myself as of yet.

kaz442

How many sets do you need? I have several $100 a set. Will need to be gone through. I could probably get them delivered to you reasonable as well. LMK Jkaz