Need some help,

I have a 454 that keeps over heating. I have replaced the water pump, fan clutch, and thermostat. All from oreilly, nothing special. I have had the radiator flushed and checked at a radiator shop. My initial timing is at about 15-17 degrees with about 32-35 total with vacuum advance hooked up to manifold. It takes awhile to heat up. I let the car idle in my garage for about about 40 mins and the temp was just above 210 degrees according to the stock gauge. I took the car for a short drive where the temp slowly creeps up to 225. I then get it home and dont let it get any hotter so i dont damage the motor. I was running a 50/50 mix and i am now running mostly water which seemed to help a little but my temp keeps creeping higher and doest stop. Any advice would be great.

Thanks
Nick

 

Nick.... I just went through this with my new 427..... Timing... Advance the timing... I went to 28* initial, all in at 2000 @ 37* and cruise @ 46*. ...... This fixed my heating problem

 

Advance the timing Abit, 40 minutes idle is plenty. Do you have the add on AC ring for the shroud? That would help, Fresh Aluminum radiator might help. Good Luck man! Post results.
Mine woulnt cool down no matter what i added this under the air dam

 

pauldana, are you running vacuum advance at idle also? How is your starter holding up with that much timing? Im not sure when ill get a chance to work on it this week but ill defiantly give it a try. Im getting desperate.

 

illemema, im not sure about the ac ring, does that go between the core support and radiator?

 

does it stay cool at highway speeds ?
or only overheat in city traffic ? or both ?
Do you have the correct shroud? factory setup ? radiator/ pump/fan / Thermostat?
radiator insulators ? front air dam in place.
It is very difficult getting all air out of corvette cooling system,
and this is a symptom, of this typical problem.
a proper operating stock system can handle the 454 heat load, I am running a 454,
OEM radiator, 180 degrees rock solid, after finally getting the air out of system.

 

Where did you hook up the hoses to your mini radiator? I like the idea actually... Mine is working without it with my advanced curve .... But you can never have enough cooling when it's 100*+ and you wand the A/C


I run an ezefi 2.0 and can control the timing via computer 100%... Thus how I have it set up.... I run a light weight high tq mini starter with 11:1 compression and have no problem

 

Do you have a 4 core radiator? Are you sure there's no air pockets causing hot spots in the heads? Many things can cause this from a cracked distributor cap, bad rad cap, clutch fan or a leaky head gasket.

 

Get a new radiator.... Odds are, the stock radiator is shot.... Even boiling/rodding them out doesn't always work...(didn't for me)... I tried all the tricks and I still couldn't keep it under 205* on the highway.... Then I slapped a Dewitts radiator in it and it dropped to 170* on a 90* day...

Highest I ever see on the highway is 180-185* and that is with the AC on, 95* ambient temps... Around town/idling its about the same....Fan is cycling with the AC so....it holds right around 180* all the time..

I agree some more initial advance may help you some, plus make it a little more "peppy"....but ultimately, your radiator is just not efficient any more..

 

I am pretty sure I have a stock cooling system setup. The water pump and fan clutch are brand new stock replacement parts from oreilly. When I took the radiator to a radiator shop they were pretty sure that my radiator wasnt the problem. I am not sure if its a 4 core or not but it is the original 454 so it would have came with the bigger radiator unless someone changed it in its life time. It does have the stock shroud. I am not sure if I am missing the air dam or not. Ill have to check for that. I have been scared to get it on the highway so its been around town but not bumper to bumper traffic. I tried running the car at different rpms with the front of the car jacked up to try and get the radiator as high as I can to get the air pockets out. Is there a better way?

thanks
Nick

 

Also, I did think about the head gaskets. I think the previous owner told me he changed them. But i did check the oil and the coolant that came out of the car and i didnt notice any signs that they were mixing.

 

anyone have a pic of what the air dam looks like?

 

so you have had the system apart,... my bet is air in system,
took me about 4 attempts to get ALL air removed.
you will know when the temp gauge stops at your thermostat temperature.
(you do know your Thermostat temp. right ?)
use the radiator hose like a fill hose, holding it up above engine,
let water run out of top radiator hose connection.
you also must verify Every part they gave you is correct.
they can do stupid stuff like give you incorrect parts.
(like incorrect water flow direction in the water pump)

 

Before you modify anything, check the ignition timing! Timing that's too advanced will cause overheating problems. Factory spec for a 73 454 is 10 deg BTC at idle with the vacuum advance disconnected. Yours is 5-7 degrees too advanced.

Also, make sure your vacuum advance has a proper vacuum source. Your car has a "transmission controlled spark system" which allows vacuum advance only in the top gear. These are often improperly bypassed, allowing full manifold vacuum at all times- which will cause too much advance at idle and lower rpms. The shop manual devotes a lot of ink and photos to how this works. If you do choose to bypass TCS, make sure to reroute the vacuum source so it is ported (using the vacuum port on the Q-jet above the throttle plates). Bypassed properly, there's no vacuum advance at idle. If you go this route you may want to also change to a vacuum advance unit designed for use without TCS. A variable vacuum advance unit is a good choice.

 

Thanks for all the help. I have been working alot of hours latley so I have not been in the garage yet. I will defiantly look at the timeing and try retarding it some and re hooking up the vacuum advance. I am not familiar with the Transmission Controlled Spark. When I bought the car the original distributor had already been replaced with a hei unit and hooked up to Ported vacuum. I hooked it up to manifold trying to battle the temp increasing. I will post when i can finally get out there and try some of the advice.

Thanks

 

This reply is well written, and gives the impression that the author knows what he is talking about. However, it goes against the conventional wisdom that advancing timing helps solve overheating issues. Now, I understand that "conventional wisdom" can very often be completely wrong, and so, MarkEdmondson, I wonder if you might offer an opinion on this.

Not trying to challenge your views or argue with you at all, just curious about it, as it seems to go against the prevailing current, so to speak.

Scott

 

make sure all these seals are in place. the pix may not be exactly correct for your year. all the vendors have the sets. cheap, easy thing to check. took my big block 20 mins to overheat at idle before i installed these, and only a few were missing or shot. afterwards i couldnt get it to overheat.

of course all the tuning, radiator condition etc stuff needs to be addressed as well, but, if ur old radiator is good the seals may do the trick

hth

 

Excellent point! The fan creates a low pressure area inside the shroud. Any air that is coming in to equalize that low pressure area must be coming through the radiator for it to do any good. Air coming through between the shroud and the radiator is that much less air coming through the radiator. And engine cooling boils down to just two things: coolant moving through the cooling system, and air moving through the radiator.

Scott

 

There is a lot unique parts and stuff period that is on a stock 73 -74 454 that keeps one cool.

I have all the original bits on my car including radiator and shroud and the foam filler pieces still intact. Those foam seals ARE important .

Mine rarely runs past 195 ...it's got to be hooter than the throw of hell for it to run 200....like 100+ with 90 % humidity. Once it's on the highway the temp pretty much hangs at 185 to 190.

Over the years a lot of parts are removed, change ,replaced wrong, junk parts installed etc. Study the AIM Manuel.

Take a AIM Manuel and go though the parts sections dealing with cooling .

One thing often missing is the front air dam extension / extension....454 and latter AC equipped L82 in the late seveties used a five inch or so deep rubberish extension that riveted on to the black plastic nose spoiler or air dam ......simple , but effective. ..in shoveling air in.

This makes a HUge difference in air pickup , as it close to double s the air thrown up to the radiator as the car is MOVING.

Original extensions are rare as hens teeth .you can try and make one up......it's i the AiM. Or rob one from. 1979 AC L82 car , still most were knocked off or thrown away as the owners didn't understand .

My car has the HD fan clutch and it's original seven blade fan . My clutch fan went south 20 years ago"..but I found a NOS one

I do run a few degrees more timing on my stock engine.

 

My experience is that improper timing, either too advanced or retarded, can cause the engine to run hot. Timing that's too advanced can cause pre-ignition (pinging if severe, but can be inaudible), which in turn can cause higher combustion chamber temperatures.

Over advanced timing can be caused by improper initial timing, a mechanical advance that's too aggressive, or vacuum advance that's too aggressive. These are often caused by improper adjustment, improper mods (like by-passing TCS using full manifold vacuum), or component wear.

Lars has a great post about distributor wear, which can lead to erratic timing- and overheating:

http://forums.corvetteforum.com/c3-t...e-them-in.html

I'm not a professional mechanic, but I was in my teens and twenties in the 70s-80s when muscle cars were affordable. I didn't have much money for mods, so I focused on the basics: a super tuned ignition and carburetor. I found a few $ spent on fresh plugs, good secondary wiring, coil, cap, rotor, points, condenser, and a properly working distributer not only made a good car run better but often cured other symptoms (over heating, poor gas mileage, starting issues, hesitation, etc.) Once the ignition (and car) is working properly, then spending time on fine tuning the advance curve is one of the most effective yet cheap ways for more power.

This involves a lot of time and experimentation, but it's fun. It's also an example of "wits beats wallet": I would end up with a "stock" engine (stock intake, exhaust, tuned Q-jet) that ran faster, cooler, quieter and more reliably than many of my buddies' cars with a bunch of aftermarket "performannce" mods.

So bottom line: Spend time to find the cause of over heating. This means make sure everything GM installed is working properly (ignition, fuel, radiator seals, fan clutch, radiator, thermostat, air dams, etc.) before adding stuff on your own (like extra coolers or fans). Unless you're racing or have a modified engine, extra stuff isn't needed and may only be compensating for the root cause of the problem.