Hey fellas new to the board I have recently bought a 69 GS 400 that has a 1975 455 in it and it's overheating this is what have done and found in the engine had blown head gasket drivers side I've since replaced both head gaskets had heads done at local machine shop no issues with heads installed 160 degree thermostat new flex fan radiator pulled and rodded new water pump and flushed system nothing has yet changed overheating issue !!!! Also no smoke from exhaust and no water in oil . Any ideas or info would help thanks
How hot is hot exactly? 3 core or 4 core radiator? Is it overheating in traffic or overheating at highway speed? What diameter flex fan do you have? How far in or out of the shroud is it? You do have a shroud right?
Twice I've had overheating problems that were difficult. First, I'd suggest you simply pull the thermostat and run the car without it and see if it still overheats. If that isn't it, then (your car may not have this) beat on the heat valve at the exhaust manifold - it could be stuck. If those two possibilities aren't it, add me to the list of those stumped.
Radiator is 4 core runs up to 220 and I'll kill it I have tried pulling thermostat already didn't factor any change the exhaust valve have been removed also have adjusted timing and it also doesn't factor any change I can look down radiator and see the flow is good I am really stumped I blew all the water jackets out really good when heads were off because previous owner had stop leak in it flex is 18-1/4 and has factory shroud for the record they are way better then a clutch fan any day of the week as long as it is spaced correctly with a shroud
what does, changed the timing, mean. did you put a light on it? and a flex fan isnt better than a clutch fan, they flatten out with rpms. and theyre sharp
At no time have I said this is a race car so Rpms aren't a factor but I'm not gonna argue with u over what I know and I have moved timing from 4-12 degrees and no change except for hard starts
im not talking about racing either. watch it next time your setting the timing. hold the motor at 3k and watch it flatten out. i dont know why your getting so defensive.
Have you verified that the fan blades are about 1/2 in and 1/2 out of the fan shroud and can you feel strong air flow on the motor side of the fan at RPM? Do you know if your motor was bored and, if so, how much? You also mention that there was stop leak used by previous owner and that you cleaned out the heads. What about the block? Could it be clogged too? By the way, I put a flex fan on a 455 motor many years ago. In addition to almost cutting my fingers off, it ran about 10 degrees hotter than the factory clutch fan which I eventually put back on it. Just some rambling thoughts.
Is your car an A/C car and if so, do you have the A/C on? If so, turn it off. With that A/C on it will pull a bunch of heat into the coolant. Also, try not to get too bent out of shape by the suggestions people are giving. I know it's hard to do at times, but taking things in written form is the worst. You just can't get people's moods and sarcasm through words on a screen. So take things with a grain of salt. Pretty much everyone here is here to help. The guys here have butt loads of experience with these cars and overheating issues and remedies are not uncommon on this forum. You would honestly be surprised at the number of guys on this forum, race cars and not, that are running the stock fans, because they have found on their setups that it works better than anything else they have tried. That includes flex fans, electrics, and whatever else you can think of. But every car is different, so it may work for you. Just please keep an open mind when asking for advice. Hope you are able to find your problem. Let us know when you do and what it was.
First, if the radiator is old, it needs to be replaced. At some point, cleaning it doesn't do much. Once they are scaled up, stick a fork in them, they're done. Boiling, rodding, whatever, useless IMHO. Secondly, timing can make a huge difference. If you idle a motor at 4* BTDC, it will heat up. That's retarded timing. Bumping the timing up to 12* should not cause a hard start normally, but it might if the motor is really hot. The engine doesn't run at initial timing. The timing changes once you step on the gas, IF the centrifugal advance and vacuum advance are working. You need to find out what the timing is at cruise speeds. It should be up around 40* or more at light load cruise (highway). You should verify the the centrifugal and vacuum advance is working. Disconnect the vacuum advance and watch the timing as you rev the engine. You should see the mark move if the centrifugal advance is working. As a quick test for the vacuum advance, you can hook the vacuum canister up to manifold vacuum at the carburetor. You should hear the engine speed increase if it is working. You can lower the speed via the idle speed screw, and drive the car. See if that makes a difference.
220[FONT=Times New Roman, serif][/FONT] F is hot, but unless you are puking coolant, it isn't really overheating. How hot can it really get? Have you found that out, or just sidelined it when it got to 220[FONT=Times New Roman, serif][/FONT]? I've had Pontiacs all the way to 240[FONT=Times New Roman, serif][/FONT] idling in traffic, and not damaged them. Maybe Buicks are different? If the PO put sealer in it, it may have a cracked block. A combustion leak is easy to diagnose if you have the equipment, which you can rent from most parts stores.
Just to rule out the gauge, have you tried another (and its components) to see that it too is reading the same?
I would put my money on getting rid of the flex fan and get the stock fan back on and make sure it's spaced in the shroud right. If we are wrong, no money lost and you have about 20 minutes into it. No harm no foul.
I appreciate everything everyone is saying I have tried every single thing that u guys are saying and it hasn't changed one thing it has stayed the same I did a combustion test and it passed I have ran two clutch fans with factory shroud I have moved timing from total timing up to 40 and no change the motor runs very good doesn't miss none of that and it is all stock except an aluminum intake what bothers me more than anything is the low oil pressure it has also at idle it almost shows none then running it will get up to 25 or so I don't know at this point I'm looking for another short block
The oil pressure doesn't sound good that is for sure. Especially on a 455. And that block should already have all the good oil provisions as I believe someone else already mentioned. I think that is the problem I would address first at this point. Slap a different oil pressure gauge on their just to make sure you are getting an accurate reading. Then go from there. I am not as well versed in the 455, but Larry and the bunch most definitely are. The Uncle has run into a similar heating situation as you have. Just can't seem to get the temp down. We put a TA water pump on and that seemed to help quite a bit. We are talking about going a step further and going to an aluminum radiator for additional cooling as well as a trans cooler setup before the radiator.
If it only has low oil pressure when it is overheating, it could just be that the oil is overheated and thin. And it seems since you have tried everything there is no solution to the problem
