New heads?

S-Car-Go said:

289s had 54cc chambers. It probably has 9.2 compression. I wouldn't go to a bigger chamber. Port the stock heads, upgrade to an RPM intake (or stealth), a holley and maybe a gear change. Make sure the distributor has a quick curve to it. At the end of the day, it's still just a 289 with a mild cam, low compression and hipo exhaust manifolds.

If you need more later on down the road, go with a roller block, heads and stroke it.

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You're assuming it has the factory small chamber heads. The majority of the time this just isn't the case on motors in these old cars by the time you end up with it.

Then I'm odd man out. I've owned 10 or 11, 65/6 mustangs with 289s. All of them had original heads. Maybe it's a bay area thing. BUT if he has 289 heads on a 289, they are 54 ccs.

btw, I bought Canfield aluminum heads for my last 289. When I pooched the 289 crank, I decided to stroke the new motor but my heads were too small to go on a 347. I built a 331 instead but would have preffered a 347. This was Jay Allen and John Fenton's recommendation.

I think everyone will agree the parts have to be sized right and work together for best results.

I have the e-street edelbrock heads on my 68 302 in fact i have the whole 321/347 package from edelbrock and my car is performing beautifully. The heads were about $900 for both. Highly recommend it. As an old retired engineer i can tell you it's always better to match your parts.

mhjo said:

Thanks for good and healthy ($) advice!!



Hmmmmm....(thinking)......

I will ask my mechanic about porting my heads. He knows how to do that.

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It's not rocket science. A guy near here wanted to re-use his original 67 smog heads, but the ports were really bad. I port matched one port, and he borrowed a grinder and did the other seven to match at home. The engine later pulled 323.5 hp @ 5300 on the dyno, with a hydraulic C9OZ-C cam. Not including R&R, exhaust port matching can easily be done in under 2 hours.

For the money, it is hard to pay for labor anymore VS the cost of new heads with springs, etc. already installed.
Do you drive a lot of highway miles, at 60+ MPH? Are you concerned with keeping the car original? A new rear end gear is always the cheapest boost in the seat-o-meter, but is hard on top end fuel economy. If it is a pure fun around town car, then a 3.50 rear end gear will be a trememdous boost in fun. Unless you have an OD transmission, then you can go for an even more performance ring gear, and still get some good gas mileage..

+1 on porting and port matching the stock heads. I'd start out by removing the thermactor bump, and blending the exhaust back smoothly from the port. The intake side really doesn't need anything other than a port match with your intake manifold. You'll see a big improvement. If you want to go further, like the article 2+2GT posted you can remove some material around your valve guides and blend the bowls but many first-timers feel more comfortable with the former.

mhjo said:

I already have 3:55 rear + AOD. Someone mentioned MSD ignition box (6) as a further step beyond installing new heads.

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Unless you're having some issue with a misfire under high cylinder pressures or need to incorporate a spark controller to retard spark at specific rpms, I wouldn't bother as any gain wouldn't be cost-effective. If anything, try a 1" or 2" carburetor spacer if you have the hood clearance. Also, if you do end up changing the heads or porting the existing heads, consider a move up in carburetor to supply the needed airflow. A 1.12 Autolite 4100 or a 600 cfm aftermarket carb would be better.

Another thing would be to install the piston/rod assembly backwards. It will reduce rod angularity and make the engine run like it's got a .030" longer rod. The downside is that you'll have a little bit more noise when cold from skirt slap. Ford built the rod offset into the SBF for this reason. This is worth 15-30 additional horses.