I bought a set of 289 heads on this forum and I just noticed one is a 65 and one is a 66... They look the same, if I throw these on my old 302 will it matter that there two different years ? They have screw in studs guide plates and matching after market springs and roller tip rockers...
The combustion chambers should be measured on each head to determine if thy are the same. If they're not the same then you will have a different compression ratio on each side of the engine which will cause the engine to be imbalanced.
While I certainly agree that it's always pertinant to measure chamber sizes to be sure they are close to similar(although it's best to remember that these heads can be off by more than 3 cc's from one end to the other on the same head).. those heads will be the same if they have cast in guides. If that's the case.. they are called "early 66".. or "pre-rail" style. It wasn't until 67 or 68 that they enlarged the chambers well after the switch to rail style rockers(no cast in guides) in mid 66. I'll give you an easy "po' man's blueprinting" trick to easily check them. 1. Playdoh pushed into a valved chamber and shaved flat along the heads deck. WD40 or similar helps to avoid sticking. Before I invested in a buret setup.. I used to use a 4" wallpaper scraper but a 5 or 6" drywall taping blade works well too. 2. Large 4 cup measuring cup to fill with exactly 3 cups water for baseline. You don't have to use a measuring cup and can also just mark any clear container to establish a baseline volume to work from as well. 3. Fully submerge Play doh into cup. Doesn't even matter if it holds shape since you're just measuring volume differential anyways. Just make sure there's no air trapped inside if you fold it to fit the container, is all. 4. Suck extra water out with a CC based syringe(meat injector or med syringe works fine) to get back down to the 3 cup baseline measurement(or whatever you baseline mark was set at). 5. Read volume drawn. A lot less messy and quicker than cc'ing if you aren't already set up to do it. And you can also just rough measure variance by starting at one end of the head and working with the same wad of Play doh(after it's finish molded to the first chamber).. pressed into each chamber as you work your way down to the other end. Or in your case.. from one head to the other. If one head is slightly larger than the other.. most likely from milling through the years.. just shave it down the appropriate amount. IIRC.. .010 mill should equate to about 2 cc's on those little chambers. Even if you don't do them all.. I'd highly recommend doing the end chambers on each head at the very least. Many times they are already off from nominal factory specs due to core shift.. and milling them unevenly(happens a lot more than most realize) only compounds the problem even more sometimes. Are the smog bumps already removed? Stock sized valves?
65 and 66 heads are the same.... I once worked on a low mile untouched 66 Mustang that had one 65 and one 66 date coded head from the factory.....
lol.. if one head has even 3cc's differnece than the one on the other side?.. that's almost a half point of compression variance in that little motor. Better have a true dual plane with staggered jets ready to go on that baby.
Actually.. a higher compression motor would be less affected by the percentage differences than a lower compression version. It's all about the percentage of variation.. and 1/2 point CR differences are more than enough to warrant attention to the details. My mentality is this. If it's really worth doing?.. it's usually worth doing right. Not to mention that if 1 head is slightly different CC than the other?.. it's a cheap and easy fix to remedy it before assembly.
Thanks for the advice, These heads where on streamliners (the gulf car) 289 before he updated to aluminum heads... It is just something I wanted to do until I buy my new motor... The original heads are so noisy because of worn rockers and likely some of the push in studs got pulled up a little from the larger cam...(I have been driving it with the clattering heads since 2006) Its a 74 block and I also have a good set of e5 heads but I was told they will drop my compression to much...
I know how your opinions are by now, Frank. And I would rarely take offense to them either. When you eventually see my buildup(the degree of head work alone will be spectacular).. you'll understand that I overthink just about everything related to engine building. Racy parts are certianly good sometimes.. but the greatest power, efficiency, and longevity is ALWAYS found in the little details. That's how lessor hardware often trumps the higher dollar stuff. And trust me here.. the immediate respect and satisfaction gained when it happens is absolutely priceless. Junk to jewl.. is always kewl.
Has anything been done to those heads to warm them up? If so.. they'll easily smoke those E5's. Otherwise.. the compression increase alone will even things out for slightly noticable improvements. Compression alone makes these little short stroke motors feel bigger throughout the range. And if you have a taller deck block.. which I beleive that 74 casting is.. thinner head gaskets will improve quench enough to add that much more to the mix. There are others to be had as well.. but this one.. http://www.summitracing.com/parts/sce-036062.. would help immensily if you have those slugs down in the holes of that block. Quench is good. Plus.. you'll be able to take some timing lead out of that setup(a very good measure of combustion efficiency) and chance of pinging will be greatly reduced(another good measure).
put the heads on your motor. you will be happy......do check pushrod length. Enjoy grass roots hot rodding. that should boost your compression about 1 point maybe 1 1/2 points. I have done this swap on an 74k mi motor I ran on the street and it was cheap and easy and worked great. Ford heads varied in stock form so minor chamber volume differences 2-3 cc's wont be noticed in a stock street motor.
If someone took the time and effort to do those mods, they probably took the time to match the chambers too, not that they'd need it.
