With a 289, you need to be mindfull of chamber size. With a 55 CC chamber and flat top pistons, you'll be about 10:1 CR. Most heads have much larger chambers and could result in an easy full point drop in CR. Offsetting somewhat the improved flow of the heads and also effecting cam selection.
When you go hotter in cam timing, cam manufacturers will also recomend higher compression. So you see that it is a vicious circle on a 289.
A mildly prepped set of heads should provide excellent service. You may want to also consider a set of GT40P heads. You can pick up a fully assembled pair, brand new for about $500.00. They can be surfaced down to 55 CC's from 60 CC's, maintaining that all important compression. They also have a modern, efficient chamger too. There are several people using these heads on this forum on 289's and love them.
The down side, you'll need specific headers or a pair of MAC long tubes.
I've heard that 351 W heads are the best vintage Ford heads for a 289 (I've also heard they should be milled to keep the compression up). I picked up a clean set for $150 and will be putting them together as my next project (which will proceed when the Federal funding comes through...).
IMO, for most applications, the early W heads, properly prepped, even in uported condition (except for smog knorbs being removed) can give the best bang for the buck spent, especially if you have access to low or no cost machine work for the valve job. The ones I used on the race car were essentially free, other than the cost of the parts (think I had about 300.00 in good valves, rocker studs, guide plates, guides, seals, springs, keepers and retainers...but that was in the early 80's *G*).
Personally, given today's gas, I think they'd be fine on a 289 (and even better, a 302 *G*) if one was running flat-top pistons, not dished....
Aftermarket heads definitely are better in stock form but I guess it depends on how fast you want to go and how much money you have...*G*
Another thing to think about though...Although it is true that if you go with the 351 heads that you have machining costs and what not, you may have some of those costs on an aftermarket set as well. You really should not just bolt on a set of heads unless you want to throw away some of their potential. If you go aftermarket you should still go through them and make sure everything is in order.
Let me just throw this in to confuse you more. If you go aftermarket "bolt on" doesn't necessarily mean "bolt on an old 289". I bought the AFR heads and love them dearly...but I couldn't just put them on my engine and drive off. Checking piston to valve clearance showed the AFR's larger valves were going to hit my old slightly dished c-code pistons.
Also, as has been mentioned...you really need other changes to make your heads shine, like a cam for instance. Also, "complete" heads like the AFR's don't come with rocker arms or polylocks, so you'll need those. It just goes on and on. It's really hard to do an engine one piece at a time...especially when you're dealing with cylinder heads.
Thanks Phil, I was gonna e-mail you direct but your's isn't
listed. Therefore, THANKS for the added input. I truly appreciate it. I know what you mean about AFR heads I put a WONDERFUL set of them on my 86 Indy Pace Car Corvette and loved them. LOTS of HP! But as you say, they needed rockers and etc but that's all part of the deal. Right!
Thanks for your input.
What were the specs on your heads from AFR if you don't mind sharing that info. I loved the one set I got from them.
ALmost too beautiful to put on an engine. Ha
You need to visit my More Power Page if you're really interested in learning about putting AFR heads on a 289. It's my "webdiary" of all the fun I had with mine. "Fun" is a good word too. You've got to enjoy this stuff or it would drive you crazy.
AFR has 3 types of Ford heads available. They have 165s, 185s, and a bigger "race only" set. For street, they reccommend the smaller (165s) for 289/302s and the 185's for strokers and 351Ws. I've got the 165s. I've seen dyno testing in Muscle Mustangs and Fast Fords that shows that the 165s have a slight advantage in low end power and torque on a 302, but not that much. The 185s have a significant advantage on power at the top end. Both types make great power for a street car.
Specifically I got the set with 58 cc combustion chambers for stud mounted rockers. My original plan was to just bolt them on and take a bit of a hit on my compression ratio. However, as you'll see if you read my page, I ended up with new pistons anyway, and this gave me the opportunity to get exactly 10.0 to 1 CR, which is a great CR for good performance on pump gas.
The page takes a few minutes to load, as it has many pictures.
I had a set of heads done by powerheads and they were junk.They lost my roller springs and sent them back with generic flat tappet springs,and the valve job was sloppy,had to do it over again.When I called powerheads,they said"that couldn't have happened here",and my only option was to spend more money on shipping to get this rectified.I'll never do machine work by mail order again at any price or circumstance.If the work is done locally,I can take it down the street and settle the issue in person.The above mentioned heads will make good door stops...