Could use some help please we have a fresh build 350 rocket aluminum heads comp cam flat tappet assembled and machine by motor builder in the area I live in the problem I’m having is I can drive around town all day around one 8190 temp wise I get on the interstate and start cruising after about 3 to 5 miles car starts creeping up 200 to 210 to 230 I let off the gas and cruise temp comes back down things I have tried and rulled out head gaskets are good, radiator hoses are not collapsing, brand new champion radiator with 2-14 inch electric fans,valve lash set correctly,no cracks in heads,water pump flowing correct,180 thermostat also tried 160,with all that being said it does not overflow in tank so not boiling over also got 2 different temp gauges just to rule out a bad one compression test leak down test down and check out any ideas would be helpful thanks again

 

Sounds like the electric fan enclosure is blocking air and not letting enough air through the radiator.

 

I agree that it could be an air flow issue at speed.

One thing you didn't mention is the engine RPM when this happens.

During the 100+ summer temps, my car will run at 190 until I take it to 70 MPH+ highway speeds and over 3200 RPM, then the temp will start climbing. Backing down to under 3000 RPM and the temp drops back to 190. My cooling system just can't dissipate the heat generated by the engine turning 3000+ RPM with 100+ ambient temps.

 

It starts climbing around 3000 RPM I have the same champion radiator and fans and shroud on my other cutlass with a 455

 

Make sure all the shrouding and seals around the radiator are in place, especially the “chin spoiler” below the radiator. The little spoiler creates a low pressure area which encourages air thru the radiator.

All the baffles and seals are important, any air that goes around the radiator is air that isn’t absorbing heat.

Is the vacuum advance working? How is the tune? Lean mixture or retarded timing creates heat.

 

12” at idle 36” total spark plugs are a waffle color so I think air fuel is spot on

 

Matt asked about uum (aka vacuum) advance.

It's important for cool running of a street-driven car.

Check timing at idle and 2000 rpm with vacuum advance connected to manifold vacuum and check again with connection to ported vacuum. Let us know.

 

Sorry vacuum adavance is hooked up it’s 24” at 2000 and with vac adv hooked up it 36” at 3000 if I have time today I will recheck those numbers

 

I will second that. Did an engine in a mid 80's Firebird and had the same exact problem. Turned out the spoiler was missing. Put one on and problem solved.

 

Those numbers indicate that the vacuum advance is not working.

 

What is your initial and total advance without vacuum advance connected and what is it with it connected? Total is checked at whatever rpm timing stops advancing. What distributor are you using?

 

Ditch the champion radiator and buy a griiffin. Made a huge difference on my 507 race car.

 

I am using a hei distributor I did not have time today to check timing worked to late I will try and check tomorrow thanks y’all for all the info

 

double check fan rotation, rad cap pressure limit?, air in system

 

I REALLY need to get a new phone case. This one is really scratch up. Despite all the spelling and grammar errors, I’m actually a pretty good speller.

I’ll never understand how I fail to see the errors as I’m typing them, but when I read what I typed the next day they are so obvious Stevie Wonder could probably catch them.

Having said that, thank you for point out my spelling error. I corrected it, I think we can all agree the world is now a better place. 😁

 

Did you change the radiator cap by any chance? I had the same problem recently and installed a new cap and problem solved. OLD CAP WAS FAULTY.

 

The cap will not cause temps to rise or drop. All the cap does is relieve pressure at its designated pressure rating.

 

The crazy thing is I never get coolent in the overflow tank I have tried two different gauges I also used a heat gun and the upper hose reads 193 and lower 180 checked timing with advanced hooked up and it will hit 53” timing at 3500 rpm

 

See post 11

 

Total is 36 without vac adavance with adavance 53 at idle it is 12

 

Your vacuum advance is working perfectly. No problem there!

 

Does anyone else have any ideas on this I took a break and now back on it my next plan is to pull heads and make sure everything is in order.