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So this weekend while changing out some gaskets to fix an oil leak I discovered my 302 has 289 heads. I got the head code and date codes of tof them and they date back to dec 15 1963, the head code was C3AE. Searched for the specs and came up wth 1.67int 1.45exh, and 54.5cc combustion cambers. Oh and they have stud mount rockers as well. But this kinda rasies the question of if my 302 is not a 302, it's a 289 that someone rebuilt and swaped in. Back on point here, my question is should I take the heads I have now and cut them for bigger valves (was thinkng 1.94I/1.6E), to take cost out all I need are the stones I have access to a the thing you cut valves with,my mind went blank on the actual name it's called. That and do a good port/polish with the help of my shop teacher. Or should I go get a set of GT40 heads and use them while only doing mild port work on them. (I would also like to add that the junkyard I go to charges a flat rate for stuff, heads are 35.00 buck each includng a core charge added in, only thing is that it can be a hit or miss)
Are the studs pressed in or screwed in (have a hex head at the base)? If your whole engine is 63 vintage 289 it will use a 5 bolt bellhousing instead of the 65 and up 6 bolt one.
-Johnboy
Are the studs pressed in or screwed in (have a hex head at the base)? If your whole engine is 63 vintage 289 it will use a 5 bolt bellhousing instead of the 65 and up 6 bolt one.
-Johnboy
The studs are pressed in, that was one of the first thing I looked for. Where is the date code for the block located, and how can find out if it's a 289 block? I haven't checked the bell housing, I'll do that later when I get home from school. Can anyone give a rough est. on my compression ratio, I know it's just a basic rebuild. I know it's not much to go on but you never know.
Putting 289 heads on a 302 was an old school trick people used to up the compression ratio. I have done it and the seatofthepantsometer says it worked. You have to remember though this was done a long time ago...like in the eighties. Check your block before you do anything else to make sure what you have before you buy any parts. Good luck. Tom
Putting 289 heads on a 302 was an old school trick people used to up the compression ratio. I have done it and the seatofthepantsometer says it worked. You have to remember though this was done a long time ago...like in the eighties. Check your block before you do anything else to make sure what you have before you buy any parts. Good luck. Tom
Yes you're right- it was even done in the 70's! The heads made befor 1966 are best with larger runners because in 66 that's when the sog laws kinda got started so the runners/ports were smaller- made for better emmissions and mileage but perf went down!
As for compression, 2bbl 289s were 9.2 or 9.5, 4bbl were 10.1 or 10.5 or so. Your compression depends on your piston type, gasket thickness and compression height of those pistons. Flat top or dish, zero deck, etc.
With pressed in studs they aren't going to be HiPo head or any thing special just decent small chambered heads, I think the GT40s would be better.
-Johnboy
With pressed in studs they aren't going to be HiPo head or any thing special just decent small chambered heads, I think the GT40s would be better.
-Johnboy
What's the combustion camber size on the GT40 heads? Also do they had the pedestal mount rockers?
I think they came in 64cc and 58cc but I am not positive but you will gain more from the increased flow than you will from the little bit of extra compression. I am pretty sure they are pedestal mount. There is also what they call a GT40P head off the explorers and mountaineers that you might be able to get cheaper but they have a different spark plug angle than can give you trouble with some headers.
-Johnboy
I think they came in 64cc and 58cc but I am not positive but you will gain more from the increased flow than you will from the little bit of extra compression. I am pretty sure they are pedestal mount. There is also what they call a GT40P head off the explorers and mountaineers that you might be able to get cheaper but they have a different spark plug angle than can give you trouble with some headers.
-Johnboy
Whats the difference them other than the spark plug angle? I know I'll get increased flow but I don't want to lose much compresion, pretty the 64cc will lose a couple points. The 58cc sound good, plus I can get them milled for a little extra if needed.
It will only be about a 1/2 a point difference between 58 and 64 not going to make a huge difference.
-Johnboy
Oh ok I thought it would be more than that for some reason. Well I figured out stock 76 302 heads were 58.5cc's. I'm gonna go check to see if I can find the casting number off the block here in a minute.
Just from experience, you'll spend more trying to put bigger valves with hardened seats for unleaded fuel in those iron heads than they're worth, with a good valve job. IMO, not worth the effort. They're worth more to someone that's doing restoration work than you'll spend rebuilding them. E-bay them and go with a newer head. JMHO. There are easier ways to build effective compression that will run on pump gas, like the right cam, etc.