Circle track cooling tips

[tracyracin]

I have a 406ci circle track engine running upwards of 8000 rpm on dirt. I seem to have an over heating issue which happens inconsistently. Last week the air temp was 85 and the engine didn't over heat. Last night it was 60 degrees and I got 6 laps in before I shut it down. 240ish degrees and blowing water. We have changed the cap.. running a gutted thermostat. Radiator seems to be good.. no rust no restrictions good air flow. Is there any tips to help solve this problem?

[dfitz16]

4 Blade Steel Fan
26” Aluminum Radiator
Run a restrictor in lower hose
Good formed hoses, the ones with wire so they don’ t colaspe.
Open nose no air box or ducting
Add 6” piece of plastic from bottom of rad towards ground.
Make sure your pulleys aren’t slipping
Check temperature gauge

[pamotorman]

maybe water pump cavitation. if running a stock production pump remove every other fin from the water pump impeller. install a pressure gauge in the intake manifold water passage next to the thermostat housing to see if you are building pressure and if not you have cavitation.

[Kevin Johnson]

From just the one event to the next? Good suggestions but also check the coolant for combustion gases; bubbles might only appear under load when the block/gaskets/heads are stressed.

[user-23911]

Headgasket is probably leaking under load.


Tests for combustion gas don't work.

A pressure gauge on the cooling system DOES.

[F-BIRD'88]

You have lifted a head gasket. Check for detonation issues and causes. Did you change fuels... Or... What did you change?

[Tuner]

What else about the weather? From 85 with a low barometer and high humidity to 60 with high barometer and low humidity can swing the A/F about two jet sizes. If you were close to too lean to begin with the weather change could move it into A/F more likely to result in detonation.

What cylinder heads, compression ratio, cam timing? Many recently designed cylinder heads have 'fast burn' combustion chambers and do not need or want as much timing advance as traditional 23 deg. Chevy heads, some are good with 28 or even less with higher compression ratios, 13/1 + . Nearly all new heads need less timing than old-school stuff, in fact are allergic to too much timing. Advance you can get away with on a drag strip will burn a motor down on an oval.

4 Blade Steel Fan
26” Aluminum Radiator
Run a restrictor in lower hose
Good formed hoses, the ones with wire so they don’ t colaspe.
Open nose no air box or ducting
Add 6” piece of plastic from bottom of rad towards ground.
Make sure your pulleys aren’t slipping
Check temperature gauge

Are you nuts? Why would you put a restriction in the lower hose, you want the pump to cavitate?

[user-23911]

You don't actually need a fan.
Nobody does unless you're not moving.


If you work it out, a fan will give the equivalent airflow to about 15 mph if it's a good one. If you're moving faster than that then it's a cooling hindrance not a help.

Nor do you want something inside a hose to make it flow less.

[Tuner]

You don't actually need a fan.
Nobody does unless you're not moving.


If you work it out, a fan will give the equivalent airflow to about 15 mph if it's a good one. If you're moving faster than that then it's a cooling hindrance not a help.

Nor do you want something inside a hose to make it flow less.

Seriously, have you ever done any circle track racing or road racing? You need a fan, a shroud and a chin spoiler. Particular the chin spoiler if the nose of the car is more than a few inches off the track surface, even then a lip straight down from the core support will do more for cooling than most think. A shovel nose Camaro will overheat at 130 MPH without a chin spoiler, fan or no fan. If you ask me, I will tell you how I know.

[user-23911]

Like I said, a fan is for 15 mph and less.

A shovel nose Camaro will overheat at 130 MPH without a chin spoiler, fan or no fan.

[KnightEngines]

Water pump cavitation.

You need to slow the pump down - stock style pumps are designed to work well from 600-5000rpm, turn it to 8000 & it'll cavitate.

I'd typically use 50% underdrive (smaller crank pulley or larger pump pulley).

Or you could just fit an electric pump.

[mag2555]

Your 406 it telling you that at 60 degrees of air temp it's running lean !

[tracyracin]

What else about the weather? From 85 with a low barometer and high humidity to 60 with high barometer and low humidity can swing the A/F about two jet sizes. If you were close to too lean to begin with the weather change could move it into A/F more likely to result in detonation.

What cylinder heads, compression ratio, cam timing? Many recently designed cylinder heads have 'fast burn' combustion chambers and do not need or want as much timing advance as traditional 23 deg. Chevy heads, some are good with 28 or even less with higher compression ratios, 13/1 + . Nearly all new heads need less timing than old-school stuff, in fact are allergic to too much timing. Advance you can get away with on a drag strip will burn a motor down on an oval.

4 Blade Steel Fan
26” Aluminum Radiator
Run a restrictor in lower hose
Good formed hoses, the ones with wire so they don’ t colaspe.
Open nose no air box or ducting
Add 6” piece of plastic from bottom of rad towards ground.
Make sure your pulleys aren’t slipping
Check temperature gauge

Are you nuts? Why would you put a restriction in the lower hose, you want the pump to cavitate?

15 degree Headed 13.7 to 1 sbc, close to 750hp. Timed at 36 degrees. I dont have any other specs on the weather. The motor has ran hot 2 other times and it just seems to not be week to week.

[blown265]

Hello mate.
Do you run an advance curve, or is the timing locked? If the ignition has an intermitant advance mechanism, then the engine temp may follow suit. Notwithstanding the temp/humidity/AFR relationship, the advance (or lack of) could be something to check.
Regards
Paul

[tracyracin]

Thanks all for the replies. I did a compression and leak down test with no questionable results. I dont see or hear any movement in the radiator when i air up the cylinders (like there would be with a bad head gasket). It is a freshly built engine with only 6 races on it. Over heating 3 of the six. It has a stock type aluminum water pump on it. We have tried a mix of water and antifreeze, straight water, and water with a cooling additive.