Thread: I, too, must rebuild my 390, but have ???

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I've read a couple or three different posts on 390 rebuilds here and have gotten very much info but still have a couple of questions.

My 390 is very stock and I'd like to give it some zip. I was thinking 350 to 400 hp, but not sure if this is realistic or attainable. The whole car is stock and I'd like to keep it as stock apprearing as possible, the keyword- appearing.

I think I have the bottom end figured right, correct me if I'm wrong, but stock crank and stock rods, as long as they are not severly damaged, should be good. I shouldn't need to buy a Scat crank or Eagle rods. I would like to use forged pistons.

The heads that are currently on my car are C3AE-C, which I believe are the low cc ones. I would certainly like to use these, but what all should I have done? 2.09/1.66 valves? Roller rockers or adjustable?

I have no idea what cam to use. I don't know if the Edelbrock cam (.460/.480) is too small or the Comp/Crane cams are too big. How do I decide this?

MSD ignition, I figure, is a must.

750 Holley carb, must.

Are the cast shorty headers at a disadvantage over the Tri Y headers, and if so, how much? I'd like to use the cast iron.

Have I missed anything?

Thanks for your help. I appreciate it.

"I have no idea what cam to use. I don't know if the Edelbrock cam (.460/.480) is too small or the Comp/Crane cams are too big. How do I decide this?"

In my opinion, the most important aspect of choosing a cam is matching it to your static compression ratio. If you have a low c.r. and choose a cam with a late intake valve closing, you won't build enough cylinder pressure to pull the hat off your head. On the other hand, if you have a high c.r. and choose a cam with an early intake valve closing, you'll build excessive cylinder pressure and you'll never get it to run on pump gas (severe detonation). Go here and read up on cams. I started writing it a while back and although it's not finished, there is some good info:
http://streetmachinesoftablerock.com...topic.php?t=78

As far as pistons, unless you're really gonna beat on the motor, cast pistons will work. If you want to step up a little, use hypereutectics. Forged pistons are overkill for the street and due to the clearances you have to run to make them work, they're very noisy on cold start-up and much more expensive than cast or hyper pistons.

To figure your compression ratio, see this paper that I wrote:
http://streetmachinesoftablerock.com...opic.php?t=124

By the way, your heads were originally produced for a 1963 406 High Performance motor. The chambers will vary between 64 and 67 cc's.

MSD ignition, I figure, is a must.


A petronix unit in a good stock dist would save a lot of money, opt for their coil also. That's what I'm running in my '73 Ranger.

Those heads are late 406 heads with tiny 56-61 cc chambers. They were also used on 390's with smaller exhaust valves. If they are 406 heads they will have 2.02/1.64 valves. If they are 390 heads the 2.02 and 1.55 were used. Just keep in mind bore notching might be needed if you use the larger CJ size valves. Just match the valve springs to whatever cam you choose. The crank and rods will be fine. You can upgrade to ARP bolts for the rods. Those shorty cast headers are getting expensive. I sold a set for $500 last year and prices seem to be holding around the same money. But they are much more original looking than the Tri-Y's.

G.

G., thanks for the additional head info. We must have different sources.

Tech there are three 406 heads and you were correct on the cc's for the two earlier ones. Some books and guides have the cc's as all the same. The C2SE-B and C both use the 64-67 cc chambers but the C3AE-C smaller cc ones. These were pretty rare to find on the 406 and most used the C2SE versions. BTW some very good write ups you have there and very good reading!!! G.

Thank you all for your help. I appreciate it more than you know.

I hope to have the engine out by this time next week. This all started because it has anti freeze in the #6 cylinder. So I figured, what the hell, pull it out and do a complete rebuild. Too bad. too, because the last time I had the car out it ran beautiful. Best it'd ever run while I've owned it.

So while the engine is out, I was hoping to dress up the engine compartment, rebuild front end, paint everything up nice.

Hopefully my wallet will allow all of this.

Thanks again for the help!

Hi,
Thought I'd post an update. Pulled engine out Mon nite and disassembled tonite. Found that my #6 cylinder is cracked. I thought maybe it cracked over the winter, so I tested the antifreeze that came out of this engine and it was good to 30 below. So i guess it'll be a sleeve job for #6. Must have had two quarts of anti freeze in the pan. Everything elses looked good though. Rods and mains were pretty well worn, clear down to the copper on all of them.

Well, off to the machine shop tomorrow. Can't wait to get it all back and start putting it back together. I love that part.

Any updates on this rebuild?