Hey guys, heres my question. Assuming everything is in new and working condition (radiator, water pump, thermostat etc...) would 302 heads on a 289 block cause overheating because of the water passage differences? Thank you.
What water passage differences? The only differences I'm aware of are sometimes called "steam holes" between the block and heads, small holes about 1/8" with 4 on each bank, older heads have them, newer heads don't. Some people say that a mismatch will cause overheating. Other than that, I don't know of any reason 302 heads won't work perfectly on a 289.
We used to just bolt them on in the late '60s and never had a problem. of course we didn't know any better and maybe that is why.
Thats what im talking about. I have new everything on my 63 fairlane, but the temperature still creeps no matter if i drive it hard or easy. Running a 3 row radiator, and new pump thermostat etc... its down to that.
Are you using a stat off the rack or did you buy a good one. Those Stant stats are not what they used to be, try a fast acting performance stat. Moroso or Mr Gasket sells a good one and they are only about 11 bucks.
Ive run no thermostat 195s 160s NOS ford, and even just spacers. Problem is the same. Replaced head gaskets and the old ones were good.
Use the gasket as a template to drill the steam holes into your early block. You only need to do cylinders 1 & 5 (the front ones) 1/8" holes. this will alleviate the steam pockets that can cause overheating
Thank you, I wanted to pretty much confirm if they steam pockets did cause overheating. I have a set of 289 heads but i need to drill them for pedestal mount roller rockers. I wanted to make sure I was doing the right thing before going through all the trouble.
it boils over. I get about 25 minutes of driving, either stop and go in traffic or doing 40-45 the whole way.
This is obvious, but are you sure you have the head gaskets installed right? They'll install either way, but backwards will cause overheating. They should be marked 'front', that has to go to the front....
Its obvious, but we still miss details like that once in a while right? LOL Yes the gaskets are on right and both FRONT are facing the front. Also I can see the square tabs protruding from each head
I hate to burst your bubble but the steam holes in the heads are not the reason you are boiling over. Unless there is a mid alignment on the normal water passages and it is not letting the water flow into the head you have another problem aside from the different heads. The reason that the 289 didn't have steam holes in the block is because they don't run as hot and don't need the steam to escape the block to cool them. I would think about things like too much over bore, timing off, spark advance not working. Water pump not pumping enough water. Air not moving properly through radiator. Make sure that you have good airflow through your radiator and that your pump is pumping and not just stirring the water first then go from there.
How's your ignition timing? Could be a source of overheating. I wouldn't swap to pedestal rockers. Better to swap to stud mounts for their adjustability. Pedestal mounts have to be pretty precisely measured for pushrods, and your only adjustability will be with shims which are a pain.
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