This site has been great. You guys are a wealth of great information; thank you so much for all of your input!

I have a '76 4x4 with a 390 (comp 268H cam) and I want to make a 410 or a 428 (if my cylinder walls are thick enough - C7ME-A block). I have D2TE heads that I went crazy with a die grinder on - gasket matched intake ports, smoothed short-side radius (intake & exhaust), smoothed and enlarged bowl, polished combustion chambers and exhaust ports. My question is, can I install CJ size valves and have some good-performing heads, or should I start over with some C6AE (poor man's CJ) or something else?

Also, if I do find a crank and 410 pistons (probably .040 over), what would my CR be with those small-chamber heads? The guy I got the long-block from said it was 9.5 as is.

If anyone has any 428 parts (intake, heads, crank, balancer, etc), I'd be interested!

Thank you all again so much for all of your fantastic help and input.

 

You can install the larger valves, but you may have to do some slight notching on the block, or it may shroud the exhaust. You're on the right track. Mock it up with an old gasket and measure the clearance with standard valves, then you'll get an idea of what the clearance would be with the bigger valves. 10,000 words on the FE board here aint worth 1 actual measurement.

 

if you got the clearance and are gonna do it, relieve the chamber wall next to the exhaust valve too, helps flow a ton!!

 

since you have worked the d2's, theres no need to waste time and money on c6ae-r or even c4ae-g. A few things not mentioned, you can rounds the guides so they are not sharp, theres a bump on the exhaust port roof to be removed. Basically any sharp or extreme angles need to be rounded and gradual.

On the valves, I feel a 1.56 is fine. but if you are looking for everything, a 1.65-1.73 valve would be inline.

 

ok i gotta 360 with stock heads- i've never done any of this porting. do you simply just put the gasket up to the head, trace the gasket and then grind out everything to the traced line? if so do you do this on the intake manifold side and the exhaust manifold side? thanbks

 

you wanna blend it back a ways from the edge of the port though....

 

not exactly, you don't need to remove all the floor on the intake side, do not gasket match the exhaust at all.

 

You do want to blend it back a ways. I think about 3/4" back into the port would be appropriate. Make it a nice gradual curve instead of a sharp angle. Dont match the exhaust, the exhaust port is usually a bit smaller than the header flange which creates a reversion dam, which is beneficial. Do polish up the exhaust port so it's nice and smooth.

Do you want the entire speal on head porting, or was that enough? It'd take me a while to type it all out.

 

ya i'd like as much info as you'd like to give me. i'm tryin to learn all that i can so that when i do my 390 build it comes out right the first time. well this will be the second time but i didn't know much about fe's the first time around. thanks guys!

 

Ok here we go...

First, the later heads (later than C6AE I think) have smaller ports than the earlier heads. Intakes like the Performer RPM have bigger ports than these late heads. You need to match them as mentioned above. Use an intake gasket to mark the size of the intake manifold ports. Take it over to the head and mark the size on there. Then proceed to blend the port to the new size. Make a nice smooth curve instead of a straight angle. Again, dont match the exhaust.

Intake porting: You probably dont want to hog it out as much as smooth things out and round things off. The intake ports need to be left somewhat rough to help with fuel atomization. The short side radius should be smoothed up. There is an area below the valve that is smaller than the rest of the port. This is a venturi that helps to speed up the airflow and direct it around the valve. Do not grind it out. Instead, smooth it up and remove any machining marks that may be under there.

Valve guides: Do not remove the valve guide bosses. You can smooth them up and round them out a bit though. If new valve guides were put in, often there will be an uneven piece of original metal sticking out. This can be safely removed.

Exhaust: There is an EGR bump on the top of the port toward the back. This restricts flow. Grind that sucker completely off. After that, smooth everything up. Then polish it to a mirror finish. Make sure the whole there are no sharp corners.

Combustion chamber: This is kind of optional. You can polish the combustion chamber surfaces to a mirror finish. This will help reflect heat back to the chamber, keep carbon from building up, and prevent hot spots that can lead to detonation. If you're going to unshroud the valves, place the cylinder head on the block and mark the extent of the bore on the head. Then you know where to stop when unshrouding the valves. Also be aware that the more you grind the more you decrease compression, so dont go nuts.

Have fun, it takes a while.

 

73F100: I bought the Standard Abrasives head porting kit and video from Summit or PAW. The video and little book they give you is great. It's really not too tough a project and pictures really are worth a thousand words, as rusty's tired fingers could tell you

BTW, fantastic explanation, rusty70!

When I tear the engine apart, I'll try to post pics of the heads and let the experts here critique my work. Thanks again for all the great input!