I've been watching a set of heads for sale, but I don't know enough about choosing a head to drop the $ on these. They are NIB, AFR 185 #1420 72cc combustion chamber, w/mild exhaust porting done. 185s is what was recommended to me when I asked TMOSS on the Mustang forum about porting a 351 GT40 manifold.

I don't need to buy heads, but would if there was a significant savings.

My real concern is the large combustion chamber, can these heads be milled to make the cc smaller if that was what I needed. I don't want to buy the wrong set & end up selling them later. Am I putting the cart before the horse, should I be choosing pistons & cam before the heads?

I've sent an email to the vendor selling them, asking the same questions, but wanted some independent opinions on the matter.

Thx

Need to determine all your internals first. Compute compression ratio etc etc. Then figure out which cc chamber you want and adjust your compression ratio accordingly.

FYI....even the head gasket you choose will affect compression.

I just spent some time on the phone with the vendor (Brian @ Mid American Racing Products - Independance, MO). He was straight forward and took a lot of time educating me. Since I'm not planning on changing much (rods, crank, etc), he was able to give me a good idea of how the heads would affect my compression ratio.

With a good head gasket (.035-.040 thick), and stock pistons, he expected my compression ratio with the 72cc heads to end up around 9.0:1. Roughly .6-.8 higher than stock.

With flat top pistons, bored .030 w/valve reliefs the compression ratio will end up around 9.25-9.50. This number was based on Diamond pistons, overkill for my application. He said I could safely go with a less expensive piston, Diamond would run 600-700hp, something I'll obviously never see.

A 66cc head with .030 over, flat top/valve relief pistons would end up around 10:1.

Since these heads can be safely milled to a 67cc combustion chamber, I felt it gave me enough flexibility to make the commitment. Since you can't add cc to a head, the 58cc heads would start me off at too high a compression ratio, and be difficult to get the ratio down to a streetable ratio.

He has gasket matched the intake runners to the Fel Pro 1250 gasket, and done mild porting to match the exhaust runners. He does this to all his AFR heads to even out the flow between cylinders. He does not recommend porting the AFR intake runners or playing with the bowels, he said he's seen AFRs turn out worse than they start when you do that.

I'm broke now.

Here is the flow sheet for the heads:

You will love those heads....I'm very jealous! I'm going with the 205s for the 427w but those 185s will flow just fine for a 351. Where are you with this build? Do you have the block and rotating assembly all ready to go?

Which springs did you go with? They need to be chosen based on cam.....hydraulic roller, flat tappet etc.

I'm stoked to have gotten these, my impulsiveness struck last night. I've been watching for heads for a while, and couldn't help myself. My "build" is in the parts accumulation phase. I have my GT40 lower, and now my heads. I have the motor on a stand, but haven't even torn it down. The motor is in ok shape, but had a cracked exhaust manifold, so its going to get stripped & everything checked. Hoping to not change much, new pistons/mill the heads to achieve my a desirable compression ratio, somewhere below 10:1 I suppose. Replace the normal parts & rebuild it. Thinking of trying to use the truck serpentine system, but also considering using my existing v-belt system. I need to figure if the truck's a/c pump can be used or modded for OBA. Or if I can find a cool way to mount a York to the serp system. I may have to move my core support forward to accomodate the truck serp, but since my front clip is way out of whack (truck was put on its side before I bought it) it needs some work anyways to straighten up my hood opening and right hand door gaps.

I'd love to get the motor in this winter or early spring. Next I need a good garage heater like you installed. Years ago, I learned that trying to work in a garage at 10* sucks to say the least.

I'll sell off my E7 heads from the 96 351, and eventually my EFI 302.

I received the heads yesterday. I've been trying to read up on storing them. I won't be installing them till winter, at least.

Should they be stored on end? I've read conflicting posts.