Valve Question

65 Mustang

Well-known member
Hello Everyone,

Currently have a 200 inline cylinder head with C6 casting. It has the stock 1.649 intake and 1.38 exhaust valves. Is there enough room to have a machinist bore out the openings to accept both a 1.75 intake and 1.50 exhaust? If not room for both, which would be more beneficial? The intake manifold has been bored out from 1.5 to 1.75 to accept larger carb. I am not running headers. Thanks in advance.
 
Given the starting point ('66 head), just do a larger intake valve and clean up both ports.
Exhaust gasses are forced out, but intake is 100% vacuum (except for turbo/supercharged engines of course). A bigger intake valve is the better ROI. Ford thought so, too.

Be aware that the early head chamber wall -significantly- shrouds larger valves, so that would also need to be addressed, or the increase in flow potential from the greater curtain wall area will be largely strangled. You'll need to have the chamber wall relieved around the larger intake

I'd try a longer duration cam first, though.

Rick(wrench)
 
Two options would be a better one would be a better camshaft. I would call Jerry at Schneider Cams & they have several up grades over a stock cam.
Second is up grade your ignition system. A DS11 recurved for your combo would be a real plus.
 
Ok. Thanks for the info guys. I'm leaning towards sticking with the stock size valves during the rebuild. While I'm not planning on installing a new cam at the moment, I am interested in hearing your opinions on the type of valve springs I should use on the rebuild. I understand that the springs should be matched with the cam. When I do get around to installing a new cam, I will pick one that favors a low end torque and smooth idle. Any thoughts on best valve springs for this application? Thanks
 
Howdy Back 65 Mustang:

I don't have enough information to offer you a rational suggestion. Are you replacing the valves because they are worn and unusable? Are you doing any other upgrades to this engine? Are you limited to this head? What exhaust are you running? What carb?

To answer your question, Yes. But not without accommodations to deal with shrouding. If your question was hypothetical; Will adding bigger valves to an otherwise mostly stock engine improve performance? The answer is- marginally. And probably not worth the expense.

FYI- you can increase valve flow by- back-cutting which means adding another 30 degree angle cut above the 45 degree valve-to-seat cut. And/or milling the head surface which drops the open valve out of the combustion chamber and deeper into the cylinder. Both of these are less expensive options than buying new valves. Either way, you should consider milling to attain your desired compression ratio and back-cutting the valves to increase flow.

I'd sure like to know more about your project before I can offer meaningful suggestions or opinions. Sorry.

Adios, David
 
Howdy back:

Stock springs shimmed .030". should be adequate for your intended use cam.

Adios, David
 
Thanks so much for response David. The real drive behind this is for me to have the head shaved to increase compression. I feel, though, while it's in the shop why not try to make some other improvements. My original plan was to take the cylinder head that is currently on my car in, but now I'm going to bring a spare cylinder head in that I have. I removed it from the spare engine yesterday. Since I do not know the history of this particular head, I thought it prudent to just replace everything (valves, springs, retainers, etc..). Also, I plan to have head milled by .05". I'll have the machinist make all the cuts on the valves and seats that you suggested. You mentioned in another post recently that if the head is milled this much you need to reestablish groove in oil passage by bolt #11. Since I don't trust myself with a dremel grinder on the head, is this something a machine shop would typically know about doing? Also, is there any way to tell if a cylinder head has been previously milled? Is there a thickness measurement I could check for using vernier calipers? Thanks so much for your valued information.
 
I haven't run it yet, but I have had 1.75 and 1.5 valves installed on a '65 head. It can be done. There is some shrouding of the valves to the outside of the combustion chamber.

I may be wrong but I believe the recesses around the push rod passages and the oil passage around #11 are indicators for maximum safe milling.

Best bet would be to CC the combustion chambers to figure out where it's at.
 
Howdy back all:

If you are only milling the head .050" and installing with a thicker head gasket you are ok. No need to do any grinding to restore oil transfer groove.

If you have money to throw away on replacing stock parts that are in good condition and reusable go ahead. I'm not that rich.

Frozen rabbit got your other question. Measuring the cc volume is most accurate.

Adios, David
 
Haha! I'm not that rich either! I'm going to bring the cylinder head in tomorrow and have the machinist make the call on all the parts. I'll definitely get the head milled .050". Thanks so much to everyone for all of your input. I'll let you know how it turns out.
 
CC the head 1st so U can tell the shop what U want done…
:nod:
Also:
go in w/as much info & a plan or that dog's tail will wag this whole dog.
 
Just thought I would mention that a late model head, 77 and up, could be a good component to have in place if you think you might go the cam route later. I just referred to my copy of the Falcon Performance Handbook and it states that the 66 / 200 head has 1100 cc intake manifold volume while the 77 head has 1345 cc. Some 77 and up heads have 1420 cc. They have the 1.75" intake valve and 1.75" carb bore.
Not as easy to find now but still around. If you can find one at a reasonable price then pretty much a stock rebuild could give as much or more performance than a 66 head with a lot of money in it.
 
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