steverw

Any chance of combustion gases getting into the coolant causing this? Bad head gasket seal?

rustyroger

A bad head gasket would make your engine overheat fast.. Any signs of oil in the coolant?.
Even if the original radiator isn't up to coping with a 455 on the road it should deal with keeping it cool while idling.
Have you checked for a collapsing bottom hose?, might be worth checking none of the hoses are plugged with a wad of paper, you do have a custom build, and I came across just this with a friends Model B Ford replica with a Chevy V8. The bottom hose connection had been plugged to stop water dripping out while the engine was out of the car.

Roger.

Sampson

Seems to me I remember a similar issue on CO recently that turned out to be an incorrect water pump gasket. Gasket looked correct but actually blocked one of the water passages. Anybody else remember this? Again you should be able to tell if it is a flow issue by squeezing the top hose or looking in the radiator to see how much water is moving.

MDchanic

Also, how is the radiator connected to the engine?

The original radiator has two inlets on top, one from each head.

This is why PICTURES would help.

- Eric

willyhuaz

Thanks for all the info! The 195 degree thermostat slowed the heating down a lot, the water stayed in the radiator at idle for 15 minutes, so we are on the right track. One thing, the crank pulley is 5" diameter, the water pump pulley is 5 1/2" in diameter. I can see water flowing through the radiator with the cap off. The original 38 Cad engine was a huge346 CID flathead. The radiator was recored with a new 4 core unit. The reason I kept the radiator is all the brackets to hold the front fender on are on the radiator suport.
I don't know how to include pictures, I do have a lot of them to show you.
Thanks again!

MDchanic

To get back to this, you said earlier that the original crank pulley was 7½", while the new one is 5½". You also said that the water pump pulley is currently 5". Presumably, if the diameter of the water pump pulley had changed as well, you would have told us, so based on this information, we can see that the original ratio was 1.5:1 (the water pump turned 1½ times faster than the crank did), and that the current ratio is 1.1:1, which means that with your new setup you are turning the water pump ⅔ as fast as you were before.
That might well be the cause of your problem.

Why did you go with aftermarket pulleys?
Why did you use that ratio? and
Is it possible to try this again using the original pulleys, to see whether that helps solve your problem?

Oh, and Chris, do you have your list handy, with the specs for all the pulleys?
It would be good to know what the normal range of ratios was for these engines (I presume about 1.5:1, but I know there was variation, for instance on a 260 I had, it was about 1:1).

- Eric

willyhuaz

I went with after market billet pulleys because the original pulleys were very rusted. I assumed the billet pulleys were the correct ratio. I will check to see if I can find a lower radiator hose that will be out of the way of a 15" steel fan.
Thanks for the help, If I can figure out how to post some pictures I will do so.

MDchanic

Be sure that your lower radiator hose has an internal spring, or a very strong rubber structure - if not, it'll collapse as you rev the motor and stop all flow.



To post photos, click on the button at the bottom of the page, and then, on the next page, click on the button.

This will open a window that will let you upload five photos, but only of certain formats and sizes (listed in the window).

Once you have uploaded the photos, close the little window, and links to them will be visible in the widow you were just in, right above the button.

Now, if you want to, you can Control-Click or Right-Click on each link, select "Copy Link Address," click on the little postcard button above the text box you're typing in, and paste the link into the box that opens - Now your picture will show up right in the body of your message.

- Eric

dave1226

My experience with 455's is slowing down the flow to the rad. Using a a/c water pump, 195 degree thermostat. The smaller impeller on the water pump slows the flow, and the higher thermostat keeps the water in the rad longer.

MDchanic

This is incorrect.

See information in this thread.

Welcome to ClassicOlds.

- Eric

65dynamic

Your pulleys are definetely the culprit. When I rebuilt my 425, I could only find a long neck water pump which forced me to use a 3 row 5.5" pulley. I had the same problem, engine would overheat quickly. I finally found a oe size water pump neck and switched back to the stock water pump pulley and now I can barely get the temp up to 180 deg.

Throw your stock rusty pulleys back on and give em a try. My pulleys were a bit rusty too, after a good sand blast and powder coat they look fine.

CutlassDad

MDchanic-lots of good info in the "this thread" thread. It nails the lid on the coffin of the "low flow cools better" train of thought.

MDchanic

Thanks.

Yeah, it's all pretty simple, but it's amazing the power of the human mind to concoct wrong explanations for simple things [see: All of human history].

- Eric

dave1226

Eric, thanks for "this thread". Must be something else caused "my experience".

MDchanic

When something happens, we often attribute it to one thing when it was actually caused by a different thing, especially when all of the aforementioned things are things that we really can't see (like flow and pressure differences inside the cooling system).

- Eric

Sampson

Eric, X2 on thanks for posting "this thread". Very well written and informative read.

willyhuaz

willyhuaz

You were correct! Along with some other suggestions I used, I found the original crank pulley, cleaned it up in my blast cabinet and installed it yesterday. The enginedid not heat up like before, the water going into the rdaitor was 190 degrees, coming out at the botom was 120 degrees. The water pump was not spinning fast enough with the 5.5" billet crank pulley. I was elated, not looking forward to a complete teardwon. The last Oldsmobiles I had was a 1950 and a 1957 88 hardtop.
Thanks to everyone who helped, this is a great group of members!
*****

MDchanic

You're welcome! Sounds like a great project!

- Eric

Octania

I have.
Jeep with brand new straight 6. I was called in to finish it. Some idiot put the wrong WP on it- a reverse rotation unit. First test drive, get in, go down country road, less than 1/2 mile to the paved road... overheated. WTH?

Finally I found the WP box, inside was the HUGE BRIGHT ORANGE SHEET stating NOT to use this WP on a std v-belt engine, it must be used with serpentine belt system.

So, you say that a larger crank pulley, which turns the WP faster, resulted in BETTER cooling?
Like described in the infamous "this" thread?
Huh.

By extrapolation, if slower circulation cools better, then no circulation is best... :-)

MDchanic

Thank you.

- Eric

Sampson

So if we really want to fix the problem, take this one step further. Drain the water. Now the gauge will register cool and there is no steam. Problem solved!