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Do the 289 heads with the exhaust recirclation holes in the exhaust ports flow less than the older 289 heads without them, after the bump around the hole has been ground flat?
Does somebody have flo figures?
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You can do more than just grind out the thermactor hump. You can actually take out quite a bit of material around the port face and smooth it into the port to help improve flow. It still won't flow all that great, but it'll flow a lot better than a set without a gasket match.
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Tad H.
'67 Fastback
331 stroker
Do the 289 heads with the exhaust recirclation holes in the exhaust ports flow less than the older 289 heads without them, after the bump around the hole has been ground flat?
In a word, the 66-up ports suck, due to provision for smog injection in the casting. They weren't too great before that. You can easily remove the smog bump, and open the port to what was obviously the original design. The upper LH corner is usually filled in, and the opening itself runs from bad to horrible, and must be matched to your exhaust.
Note the amazing anount of iron blocking the edges of this port. The shaded area must go, as well as the nose-shaped injector bump inside.
Here's a head I did. Notice you don't have to go very far in:
If you're worried about the size of the opening, Crane used to sell "Fireball" heads, made from Ford replacements. The hole they cut was so big it required special headers:
The results of this work are very dramatic, increased power at all speeds, and smoother running.
In a word, the 66-up ports suck, due to provision for smog injection in the casting. They weren't too great before that. You can easily remove the smog bump, and open the port to what was obviously the original design. The upper LH corner is usually filled in, and the opening itself runs from bad to horrible, and must be matched to your exhaust.
Note the amazing anount of iron blocking the edges of this port. The shaded area must go, as well as the nose-shaped injector bump inside.
Here's a head I did. Notice you don't have to go very far in:
If you're worried about the size of the opening, Crane used to sell "Fireball" heads, made from Ford replacements. The hole they cut was so big it required special headers:
The results of this work are very dramatic, increased power at all speeds, and smoother running.
What you have done to those heads is pretty well exactly what I'm going to do. The thing is I can get a cheapish pair of smog heads which already have larger valves, inserts, and springs and I have a set of std. 289 heads without the injector bump, our 289's never had them, that need everything done. The smog heads will end up cheaper, because the remaining work I can do myself, but my other heads I thought may end up better.
I'm not interested in aftermarket heads, my heads must look std. on the outside.
The upper LH corner of the port is usually filled in...with more cast iron. You can grind out the ports exactly as mentioned to gain significant port volume and flow.
I port-matched my '68 J code heads that I ran until recently and I was astounded at how much of a difference in port volume there is just from gasket matching.
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Tad H.
'67 Fastback
331 stroker
I've already installed a rebuilt set of no-hump '65 heads couple of years ago. Still have the '66 smog heads, but their gutted. How much of a perf improvement do you really see after the DIY port matching?
I've already installed a rebuilt set of no-hump '65 heads couple of years ago. Still have the '66 smog heads, but their gutted. How much of a perf improvement do you really see after the DIY port matching?
Mine was a stone-stock 65 289HP, so it didn't have provision for smog choking it. It felt like I installed a 10% better cam. I expect the difference with a smog head, removing the "nose" shown above, would be better than that.
Ive fully ported a few sets of both early 289/302 heads and a couple sets of 5.0 heads from roller engines. One thing you REALY dont want to do is mess with the short turn in the port floor. If you want to kill flow and make them run like crap, grind that puppy down so it looks straighter. Smooth it but dont change the shape, the rest you can hog out pretty big.
Still you wont get the same power you will from a decent set of aluminum heads. For a stock looking build you can do ok on power if you are smart about where you remove metal.
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289 smog heads???
