Thread: Help with 390 heads

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i need some help with rebuilding a 390. I have stock heads (i have no idea what the serial number is) and i have these to put on it: C6AE-R..thats all i know about them....

my question is: how much better are the these than the stock ones ?

any help will be greately appreciated.

Depends on what the stock ones are

From the numbers he's giving those are 1966 heads and about the best head compression wise, for a factory head. Should be about 10.5 to 1 and over 300hp.
I'll check my book later, left it in the shop and it pouring rain out right now.
Kurt

thanks for your help. i want to say that the ones that are mounted on the block already are a D2-AA and something else.....not sure because to be honest with you, this is my bro-in-laws engine and he's providing me with the info....he doesnt know for sure what's on there....he just removed his 428 cobrajet and is rebuilding a 390 for his 73 F100 to make it a daily driver.

i had him check....he has a set of D2TE-AA.

anything to be proud of ?

another question:

regarding gas…..octane numbers…….

What would be the difference if he installs the C6EA-R entirely ported with CJ valves………..and……..unmodified D2TEE……..remember, it’s a daily driver and he doesn’t want high octane fuel

thanks

The C6-R heads have 72-74 cc chambers. The D2-AA heads have 68-71 cc chambers. The range of the numbers is given for casting differences between batches. Most heads I've cc'd have been to the larger side spec wise. Also add in if the heads have been milled etc.... You can get thick or thin head gaskets to help dial things in. But you really need to know what your working with. Performance wise the C6 heads are better. Economy wise the D2's get the nod. What's the plan for the rest of the engine? No sense porting C6's and using bigger valves if the intake and exhaust are going to remain stock and be a cork. It's kind of a waste really. JMO.

he wants a mix of economy and performance......he just doesnt want to have to run his engine on avgas or vp or fnl like he did his 428. but he does want a bit of torque when he needs it. lots of sand out here, but he's planning on making that his daily driver. i'm sure he will follow my advice once i become informed by you as to what would be better for him. the C6's he has are already worked on. the D2's are not they are stock. he ordered a complete rebuild kit for it, upgrading most of the components (pistons, cam etc.) i'm sure it will be a great 390 once he's done with it, but he doesnt want lots of compression to save on (pump) gas.

If he's sticking with the stock exhaust manifolds have him take a look at the D2's in relation to the ex port location on the C6's. D2's have a raised exhaust port which might not match up very well on the C6's depending.Does he have headers? Or if not what exhaust manifolds doe he have to use? If that's all a non issue and the R heads have the right ex bolt pattern for his exhaust they can't hurt and are a good start. He can cc the head chambers (easy to do) and compare the two. And adjust the head gasket thickness to get the deisred CR. There are online calculators you/he can use to figure this out. Along with knowing piston height and dish size. This also leaves room to upgrade the intake, exhaust, carb etc.... later if he likes. He pretty much has everything he just needs to do some figuring to see where his CR will be at exactly. Google "engine math" and you should get some site sits to calculate everything. Email me if you can't and I'll send you a few. This way there are no surprises. You can get shim head gaskets that are .015 thick. Fel-Pro Vic Reinz are .042-045? and Cometic makes head gaskets up to .125 thickness. But Cometic gaskets are somewhat expensive (almost $200 a set) but reuseable. But he should be able to get the CR he's after doing a little homework.


Edit to add....if he had a 428CJ in there have him doublecheck the ex manifolds to the C6's if he's using the same ones. Port match will be good between the 2 just double check the bolt pattern. FE heads have 8, 14 and 16 bolt exhaust bolt patterns. The vertical 8 pattern is common to early lowriser heads and all pickups. 14 bolt was the GT and CJ pattern. 16 bolt heads can use both exhaust patterns thus the 16 bolt holes. Those normally are later service heads.