Circle track cooling tips

[Racing68]

What heads, i've never run more than 32 deg timing in any 15 or 18 deg head

[KnightEngines]

Stock type alloy water pump - there's the problem.

Every speedway/circuit/hillclimb engine I've built (there has been a few, or a lot) that runs a mechanical pump needed underdrive pulleys.
That impeller won't pump spinning that fast, it'll just thrash around & make steam pockets.

Underdrive it, cheap, simple - problem will go away.

[tracyracin]

What heads, i've never run more than 32 deg timing in any 15 or 18 deg head

15 degree hvh pbm heads. Edelbrock castings

[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?

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.

I think 36 degrees is the main problem, and perhaps the carb is near enough to too lean the weather is influencing it. Do you know what detonation looks like on spark plugs? The problem on a dirt track is determining detonation from tiny bits of dark glass (fused dirt).

What heat range plugs are you using?

What heads, i've never run more than 32 deg timing in any 15 or 18 deg head

I agree with this, but I would start at 28 deg. and see if the driver complains about it being lazy, I bet not.

The cylinder head folks are doing their homework and producing ports and chambers that are much more efficient than even just a few years ago. Part of more efficient translates into more rapid combustion that doesn't need or tolerate as much advance as previous designs, and particularly doesn't need as much advance at the torque peak as at the HP peak, and so benefit from a several degree advance curve over the power band (and that ain't easy to do with a MSD distributor).

The other "ghost in the machine" is the slew rate of the electronic ignition is causing the timing to retard as RPM increases, so the RPM where you set the timing is very important because the timing is more advanced below that RPM and retarded above that RPM. The mechanical advance can be arranged to compensate for the electronic retard and provide some timing advance from 3000 to 8000 RPM, where with locked advance the timing is retarding about 1 degree per 1000 RPM.

Locked advance or 'all in at 2500" combined with the electronic slew rate gives the undesirable situation of more timing at the torque peak than at the higher RPM power peak, but the engine actually wants the opposite, maybe 24 (or less) at the torque peak and 28 at the power peak.

[ZIGGY]

Some thoughts: Since you're describing problem as intermittent and just with new engine, I'd tend to agree that
it's a tune or engine mechanical issue as others have said. Crack or headgasket can fool you. Ignition been fully checked out?
Do under drive pump. Worn or cheap aluminum or misaligned pulleys will slip belts but this should be consistent.
You said radiator - "no rust (it's steel?), no restrictions, good air flow". Overheating or age can allow tubes to balloon
and reduce airflow, which can be hard to determine. Dirt accumulation the same. (BTW for coolant run distilled water and a water pump lube.)
Restrictor (gutted thermo ok) and hard wire hoses good (wires can move though). (BTW good practice to run pressure warning light.)
Any hose/routing changes related to new engine? - make sure you can bleed system 100 percent.
Is it a stock block? (I hope not with your hp and rpm statement.) Keep us updated please.

[tracyracin]

I am running AR3933 Autolite plugs. No signs of detonation on the plugs. I run sunoco 112 fuel.

[tracyracin]

Some thoughts: Since you're describing problem as intermittent and just with new engine, I'd tend to agree that
it's a tune or engine mechanical issue as others have said. Crack or headgasket can fool you. Ignition been fully checked out?
Do under drive pump. Worn or cheap aluminum or misaligned pulleys will slip belts but this should be consistent.
You said radiator - "no rust (it's steel?), no restrictions, good air flow". Overheating or age can allow tubes to balloon
and reduce airflow, which can be hard to determine. Dirt accumulation the same. (BTW for coolant run distilled water and a water pump lube.)
Restrictor (gutted thermo ok) and hard wire hoses good (wires can move though). (BTW good practice to run pressure warning light.)
Any hose/routing changes related to new engine? - make sure you can bleed system 100 percent.
Is it a stock block? (I hope not with your hp and rpm statement.) Keep us updated please.

Dart Little M block. Good wire hoses. Will check out the radiator further to make sure it looks sound. It is aluminum. No rust coming from the block, water always drains out clean and clear. What percentage of an underdrive should i be looking for? Im going to measure pulleys tonight.

[ZIGGY]

30 to 50 percent reduction. I'm linking to a Stewart site that's been referenced many times here before.
It appears to have been changed some though. http://www.stewartcomponents.com/index. ... ation_id=6
While checking radiator, if you haven't already done so, look at condition of fins(not bent, flattened). (Never blast water straight into the finned area.) Shine light through core and look at tubes, dirt. Soaking alum. dirt race rad in a kid's wading pool is better way to clean. I recommend periodically
replacing these radiators as I think surface corrosion and tube/fin degradation take a gradual toll. Again, let us know how it goes.
P.S. to previous ramble - restrictor is to increase system pressure, not to slow flow. 25 lb. cap is good IME.

[treyrags]

Locked advance or 'all in at 2500" combined with the electronic slew rate gives the undesirable situation of more timing at the torque peak than at the higher RPM power peak, but the engine actually wants the opposite.......

Is this true in general or more specific with this type of head?

[billet]

First off I will say I'm far from a engine expert (do have my own dyno but still consider myself a hobbyist on engines) but I do have almost 25 years experience with Dirty Late models as a driver, owner and crew chief (which it sounds by the engine may be what your running) and not to step on any toes but this is just my experience.

1. Check the pulleys, if you can grab the fan and turn it without turning the engine then you need to look at the pulley's. Common for unanodized pulleys to wear rather fast and get to a point where the V belt does run on the sides of the belt but the bottom of the groove due to the pulley wearing. The lower pulleys seem to wear more then the uppers, so check that one closely. If using serpentine pulleys make sure the belt runs around each of the pulleys far enough to have sufficient belt surface/contact. One problem with the first ones was the small diameter of the pulleys and lack of rap around the pulleys so they have very little belt/pulley contact and would slip easy. Also once they did slip they would wear and you couldn't fix without replacing the pulleys and add an idler for more rap.

2. As said check radiator. I prefer to remove it and hold parallel to ground about 6 to 8" above clean concrete and drop, if you see a ton of fine dirt under radiator repeat until you don't. Then clean in a kiddie pool but letting it soak for an hour and light rinse off with a hose. Don't spray with high pressure. Radiators are a consumable item and need to be replaced, installing a stick on honeycomb in front of the radiator will help it live longer from clods and getting fins bent over as well as holes poked into it.

3. Use a good water pump. Not sure about the stock or cheap ones cavitating at higher RPM's but a race pump like steward should turn 7000 RPM, so overdrive or under drive to get that RPM. Most of the time with our big engines (430ish 900HP 8700RPM stuff) we run at 10 to 15% underdrive to get slightly over the 7K mark (may be over 7K but engine not always turning max RPM after track slows down).

4. While most of the times we can run without a shroud and not have a problem, it's beneficial to do so for sure.

5. If not running a shroud, fan should be within 1.5" of the radiator, too far away and it pulls air from side and not thru radiator.

6. use a 4 blade GM fan, not a copy as many of them copies are junk. They are no longer available as AC Delco discontinued them just in the last couple months so not sure what to tell you but we are all struggling to find a good replacement.

7. Make sure the cap on radiator isn't on the upper hose side of radiator, this is where the old wives tell of running no thermostat will make a car overheat comes from. When the thermo is removed the high pressure is now on the upper hose side of the tank instead of before the thermo housing/engine block and can cause the cap to lift and lose coolant and appear to be overheating but will eventually lose enough coolant to actually overheat. This was common in old vertical flow radiators as the cap was on the upper hose side. Most of this is or was explained on stewards site at one time.

8. I personally don't care for multiple pass radiators, 2 pass is ok but not a 3 pass IMO. Again just off my experience with late models.

9. inconsistent cooling: Is or was the tracks really dusty on those nights you had problems, if so look at #2.

10. Make sure cap/fill point is highest point on system, otherwise you can/will trap air in system.

11. Use highest pressure cap you can, we won't use anything under 28# and some are close to 40# but make sure you double clamp the hoses

This is obviously not including engine issue like all ready said like the timing and etc.

Good luck hope this helps

[tracyracin]

Measuring my pulleys puts me around 30 percent underdrive (2.4 crank 3.35 pump). Is that correct math?

[billet]

8000 crank rpm is 5714 water pump speed


Did you grab the fan and try to see if it slips, with that diameter pulleys it has to be a serpentine set up. If it is driving a power steering pump the rap around the water pump is probably lacking unless you have an idler.

[Tuner]

Locked advance or 'all in at 2500" combined with the electronic slew rate gives the undesirable situation of more timing at the torque peak than at the higher RPM power peak, but the engine actually wants the opposite.......

Is this true in general or more specific with this type of head?

True in general and I think more so with the newer fast burn heads. 1 to 2 deg per 1000 RPM advance from 3000 to 8000. Each engine has its own appetite. When they would talk about it, both Smokey and Grumpy said 1.5 deg per 1000, but what would they know.

One benefit is isolating the trigger from the engine/cam/oil pump oscillations by driving through the weights and springs, which act as a pendulous absorber, results in more consistent timing, less jiggle looking at it with the timing light.

Another thing I would do is use vacuum advance, 15 deg from 8" to 12" or 14".

[tracyracin]

8000 crank rpm is 5714 water pump speed


Did you grab the fan and try to see if it slips, with that diameter pulleys it has to be a serpentine set up. If it is driving a power steering pump the rap around the water pump is probably lacking unless you have an idler.

I cannot move the fan at all, the belt is good and tight. 6 rip serpentine belt with a power steering pump.

[geraldtson]

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?

I have a dirt late model in the shop that i gave my son its still race ready. Ran it for years with steel 6 blade 17 inch fan. Stewart stage 3 water pump with triple pass 27 1/2 inch x 19 radiator. Pulley's are 1 to 1 ratio meaning water pump and crankshaft pulley's are same diameter. Home made fan shroud. I don't really think the triple pass radiator is necessary it also cooled fine with double pass but upgraded to triple pass. Radiator cap is a racing 29-31 lbs pressure cap.Engine is sbc 357 cid (362 cid rule). Car normally runs 8200 rpm. With this setup car NEVER had an overheating problem. Oh,i also never run anything but STRAIGHT WATER. Tried everything in the world,nothing cools as good as water. Water is wetter! This fan-pulley setup pulls a lot of air and may cost a tad of HP but it works for me in Florida summer heat! Also, no restrictor in system anywhere.Also take billet's advice on everything he said, sounds like he know's his stuff!