Which heads to use on my 383?

[fastback383]

I am going to be taking the 400 out of my Barracuda and sticking a freshened up 1969 383 in. Just a quick ring and bearing on it, cast pistons and all. Now , which heads should I use, I have the set of 906's off of it and I have a set of 452's. I know the 452's have the hardened seats in it. But, I also have a set of Mopar Performance valves to put in them. The 2.14 intake and 1.81 exhaust. If I put them in the 452's do I lose the advantage of the hardened seats. I have been told as soon as they open up the exhaust seat to accept the bigger valve the hardening is gone. Is this true. I also plan on using the MP porting kit on the heads. I have also been told using the bigger valves on a relatively stock 383 without alot of compression ( its around 10-1 I am guessing ) may slow it down. It will lose some bottom end torque ? Am I going to be wasting these valves and some cash here ? Should I just port the 452's and forget about the bigger valves ? Has anyone here had any experience with this particular setup ? Any and all replies appreciated. Thanks, Dave aka fastback383.

 

[dave571]

If you measure the deck clearance when the heads are off(how far the piston is down the hole) you can use a compression calculator to figure out the actual compression. If it is an hp motor it may be as high as 9 to one. If it a dished piston 2 bbl motor, it's closer to 8 to one.

With open heads (906 and 452) the piston needs to have a dome that comes out of the block to get 10 to one, on a 383. The chambers of the open head are really big for the smaller B engine.

even .040 quench with a closed 915 ect will be shy of 10:1 if the piston has valve reliefs in it.

In my opinion, the bigger valves are a waste. Save them for another motor. Port the heads as you have planned, and go with some good bolt on stuff. 500 horse crate motors from brand X use a 2.08 intake, and a 1.60 exhaust. The stock valves in those heads are plenty, even for a fairly radical 383. Then you don't need to worry about the seats being cut away either.

 

[chad72duster]

well you can always mill the heads down and lower the CCs on the chambers. i have a set of 906 heads that are cut down to 75 cc and cut for bigger valves. the valve seats just have to be replaced to enlarge the valves it not that big of a deal. check Indy they have a set of valves $150 for both the intake and the exhaust. If you are going to run these on a 383 you can build them now and have them for a later build on a bigger and better motor.

 

[fastback383]

The 383 I am doing now is for next summers fun, it is already freshened up and just sitting on a engine stand. I figured I may as well use it 1 summer anyways. The long term plan is a decent build on a 400 block. I picked up a nice set of brand new KB hypereutectic .020 over pistons 10 -1 new in the box REAL cheap. That will be assembled next summer hopefully . So anything I do now will be used on the 400 later. I may just put the valves in the 906's and sell them and stick with the 452's. I have a buddy with a 73 Sattellite with a very mild 440 , cast crank 9 1/2 -1 comp , 3:91's , MP 509 cam, 452's ported with the MP kit, stock valves ,
.It is very sedate looking and I have seen this car go 13.06 @ 114 mph through exhaust on street tires , It apparently has hit the 12.80 's before . So the big valves may not be required as you said ? Thanks guys , Dave.

 

[AdamR]

Either head will run about the same if the same work is odne. You can mill them down alot. My last BB had the 346 heads milled down so much they were almost closed chambers.

The only problem with that is the quench is bad and you could have detanation problems even with compression in the 9.5:1 range or lower. Mine needed some 110 mixed in when it was hot out or it wouldne be happy.