390 heads

[R.Smith]

I've got an extra pair of stock 390 heads and was thinking about rebuilding them now in preparation for installing them later. Anybody have suggestions on modifications to the stock units that would give better performance?

Thanks.

[fordman]

i have heard larger valves and porting and polishing the ports. plus new springs for the valves.

[390F100]

It all depends on what you want the future FE to be, are you gonna look for big power gains or try to keep it stock, heads are where the power is at, and can cost a pretty penny to make them right. I know my brother is spending 2000 on the head work alone for his 429SCJ heads. In Mesa there is a retired GM engineer that designed heads for GM for many years and is now running a machine shop business from his garage. This guy does some amazing work but it all depends on what you want for the engine itself and what you are looking for. just my

390

[rabbithunter2005]

I spent 2200 dollars getting my heads done with all new valves, valve guides, seats, seals, and all the surfaces ground flat. Personally i wish that i woulda bought alumnium heads they cost about 1500 bucks and they flow better.

[R.Smith]

What am I looking for? Why, more power and better mpg, of course!

Seriously, I just have the heads and was thinking it might be fun to experiment with them. They would go on a daily driver so I don't want anything radical. I sure a shell don't want to spend 2 grand.

I have access to a machine shop but have little experience modifying cylinder heads. I know flow is good, compression is good (but can be too good.)

I'm just looking for ideas.

[dustman_stx]

I can tell you what I've discovered in my limited experience. I had two sets of heads. I couldn't find any info, so I sacrificed one. I discovered that you CANNOT take all of the bump out of the exit area on the exhaust side, but you can take a little off and smooth it out. There are all kinds of bumps and knots down inside the exhaust port that I ground out, with no apparent ill effects. I also smoothed out the corners flowing from the ports where they turn down to meet the valve. After talking to various people, the best consensus I came to is this: 1. The straighter the path the better. 2. You want to maintain velocity, so bigger isn't always better. Once you get to a certain point, you can get your ports and valves too large for your application, hindering velocity and flow. 3. Get the exhuast ports as smooth as possible, but leave a rough finish to the intake to aid in fuel atomization. Keep in mind I'm new to this, and am learning as I go. Also, I found some 2.09/1.65 stainless steel valves for $120 shipped on ebay. Had the heads completely cleaned at a machine shop for $20 each. I think I can get the larger valves installed and hardened seats with a 3 angle valve job for around $500 for the pair. So, best I can tell I will have less than $700 in them, and will hopefully get flow equivalent to a pair of ported and polished CJ heads. We'll see. Oh, I'm installing a pretty beefy cam and had to get new springs, retainers, etc., so figure another $200 for that.

[R.Smith]

That sounds like what I'm looking for. I want to do the work myself and this sounds like something I could do without totally screwing the heads up.

knock on wood.