350 small block in 55 chevy runs hot...help me

hi, i have a '55 chevy with a small block 350 that runs great, but gets hot (guage reads between 220-250F). it only gets hot at high rpm's. i can cruise around town all day and it will stay right around 190-200F. the antifreze never boils out of the radiator. if my car engine is getting that hot(upwards of 250F) why isnt the radiator boiling over? one time i did take the cap off when it was hot (i thought that the antifreeze level was lower than it was) and it sprayed out a fountain about a foot high. i was nursing my burns for about a week! anyways, here's what i have done to it...

-freshly cleaned/rodded 3 row radiator
-new water pump
-new thermostat(ive tried 160 and 180 temps)
-electric fan mounted on front of radiator
-replaced flex fan with a clutch fan
-new radiator hoses
-60:40 ratio antifreeze:water

another strange thing about this engine is the timing. when timed to the appropriate marks on the timing tab, it runs like crap...hesitates on acceleration, rough ride and even backfires. but when the timing mark is about 1 and 1/2" above the tab, she smooths out purrs like a kitten(other than the knock of course)...any ideas???

A few weeks ago, i replaced the timing chain and sprockets. there seemed to be quite a bit of slack in the chain. on the driver side, there was a good half inch slack and on the passenger side thier was about a 1/4 of an inch. is this normal?? shouldnt the timing chain be tight, with maybe about 1/16" slack?? how can i tighten the chain? also, if the timing gears are off, would the engine be able to run good at all? it does run good with the timing mark about 1 and 1/2" above the timing tab. however, although the engine runs good, the knock is still present at idling rpms and it still overheats at higher rpms(highway speeds). it ONLY knocks at idling rpms and ONLY overheats at high rpms.
another strange thing that happens, is that after the car cools down after being driven, even if it was just around town and the engine did not overheat, the top radiator hose will collapse. I replaced the hose and it still collapses. btw, the bottom hose does have a spring in it and does not appear to be collapsing.

ok, im gonna have to adress this in peices, hope i can be clear.

overheating at high rpms - get a spring for the upper hose that collapses, thats not normal, will restrict flow, and cause the high speed overheating.

timing chain slack - sounds like an old worn out chain, no way to tighten it up, needs to be replaced

timing marks off by 1-1.5inches - could be caused by loose timing chain, but may also be distributor in a few teeth off. i suggest setting the timing by vacume, and seeing how that turns out. the timing chain in my iroc is worn out and thats how i set the timing. well, that and by ear.

coolant mix ratio - remember that antifreeze is not a coolant, water is the best thermal conductor there is, so if you live in a warm weather area, and your engine is overheating, switch to a higher percent water to get more heat out of the system.

opend the radiator while it was hot - im gonna be nice and not go there ;)

engine knocking - is this a detonation knock, or a metallic tapping???? such as a loose rocker arm or connecting rod?

the other thing that i thought of is the nock could be the timing chain if it is too worn out. if you can take off the timing chain cover and look at the inside on the sides and see if it looks like the chain has been hitting it.

i would try what 89 said on all accounts. the only thing that makes me wonder, is did it over heat and thats why you put the fan on the front of the radiator? i would take off the flex fan and put duel elctric fans on the back of the radiator. sence you do have it on the front, are you sure that it is a pushers and not pullers? you cant take a puller and put it on the front cuz it would be fighting itself between the two fans and the air flow when the car is moving.

as far as 89 not going there, i will. NEVER OPEN THE CAP WHEN THE CAR IS EVEN SLIGHTLY WORM. no matter how low the level is it will still shoot out atleast really hot steem. its not like its just an old mith the people say to scare peopel for no reason, your REALLY not saposed to open the cap on the radiator when its worm. the sytem is presurized so it has the same effect as when you open a soda bottle or something.

does your electric fan run all the time?

i put the electric fan on because it was overheating. it can push or pull depending on the way you wire it. i have it pulling air towards the engine. i have tried running the car with the electric fan on and with it off and it overheats regardless. i took the flex fan off and put a new clutch fan on, still overheats.

i have never noticed the top radiator hose collapsing while the engine was running, but maybe it is while i'm at high speeds. i will put a spring in it.

i replaced the timing chain and gears because the chain had what i beleived to be excess slack, but when i put the new chain/gears on, the slack was about the same. (timing chain/gears are interchangeable between all pre-1985 small block chevys arent they?) i dont know the exact year of my engine. i do know that it is pre-85, i bought a timing set for a 1970...this should have been fine right?

i checked the distributor by setting #1 cylinder to TDC and pulling the cap off to see if the point was at #1 plug on the cap and it was, so i assume that the distributor is correct?


as far as the knock goes, i wouldnt describe it as a tapping. it is definately a knocking sound..pretty deep tone. it only knocks at idling rpms and after the engine has warmed up(180F+). it could be a detonation knock. i have had the oil pan off and inspected eveything and nothing felt loose or worn, and there was no metal in the bottom of the pan that would indicate such.

i really appreciate all your help! keep it up
thanks,
shad

not really sure about timing chain interchangeability from the years..... *shrugs*

i mentioned the top cooling hose cuz my brothers 1973 bronco had the same problem.

when setting the number one cylender to TDC, watch the rocker arms. rotate the engine untill the intake valve opens, then shuts, then feel the spark plug hole for air pressure as the piston comes up for its compression stroke. if you rotate it past this point, the exhaust valve should open. if the intake valve opens, then you are 180 degrees out.

if it were a 180 degrees out, would it be possible for the engine to run descent...at all?

shad

if the timing were 180 degrees out it wouldnt run at all... it would just back fire really bad... the timing chain should tightn up when you tightn the cam gear bolts...so if its still loose take it back and try another one... although it should have worked

and if you timing gears are off that would explain y you have to set it above the tab.. first off i would get that timing chain problem fixed.... cause if your timing is outa wack then it will cause the car to heat up