[kingbuzzo]

Wouldn't a pontiac starter be somewhat useless under that kind of heat emanating from the block...at least until she cools down?

[JLMounce]

Originally Posted by Gary H

If I understand your symptoms right, the starter turns the engine over fine, but it won't crank up when hot. My bet is that you have a low voltage issue going to the Sniper system. In the condition you are describing, if the radiator fans are variable and on the high setting, they along with the starter draw, this could be dropping the voltage too low for the Sniper to run. I have run into this exact same scenario before where the engine fires fine when cold but has an issue starting when hot and the fans are on, especially if you're getting the Sniper voltage through the ignition switch or off the fuse box.

The sniper runs the fan in stall and crank?

I guess that would create a pretty easy test for the OP. When the engine is off and heat soaked, disable the fan in the ecu, then attempt to start.

[JLMounce]

Originally Posted by kingbuzzo

Wouldn't a pontiac starter be somewhat useless under that kind of heat emanating from the block...at least until she cools down?

If the solenoid is in good condition and the power lead from the battery is properly sized and in good condition, it's probably not a huge issue.

I still run a factory type starter, but it's fairly new. My engine soaks to about 210 if I've been hard on it and shut it down. No issues with cranking the engine after sitting for 5-10 minutes or so.

[Randylk]

Originally Posted by JLMounce

You can try an insulating spacer under the sniper to help with that.

It sounds like this is a crank and no start issue after a short heat soak.

What may be happening is that as the car sits for a bit and soaks some heat, the fuel film that clings to the intake manifold runner and for which the ECU in the throttle body calculates some fuel usage, may be evaporating.

As a result, when you go to hit the key, the car cranks over but the throttle body is not providing enough fuel initially to both re-wet the intake manifold and start the engine. Typically you'd get a symptom of endless cranking, or the engine may fire, stumble and die.

If that's what is happening, you need to look at your hot cranking fuel in the tune. You may need to make some adjustments there. To figure out if you need to add or remove cranking fuel, complete the following test.

When hot and heat soaked, attempt to start the engine. If adding a small amount of throttle helps the engine start, you have too much cranking fuel and need to reduce it.

If adding throttle does not help the engine start, you are lean and need to add hot cranking fuel.

Pretty sure this is my exact problem. That was actually my next step. When I did the tune I wasn’t factoring in the heat soak. So I’m gonna put the 185 thermostat back in move my fuel lines and use a heat shield and spacer. I may adjust some on the fans on and off temp and see what happens. Thanks for the suggestions.

[Schurkey]

Originally Posted by Randylk

Has a $3500 radiator and fan set up from radiator entropy. New water pump

I don't know how a "radiator and fan set up" can cost $3500.

Originally Posted by Randylk

and a 165 thermostat.

Originally Posted by Randylk

Temp is 185-190 while running.

A 165 thermostat but it typically runs 20--25 degrees above the thermostat rating? The thermostat is not in control of engine temperature. The electric cooling fan MAY be in control--but perhaps not adjusted properly, or perhaps it's not in control either.

Originally Posted by Randylk

I may adjust some on the fans on and off temp and see what happens.

Your cooling system has genuine problems. PROBABLY related to the "$3500 radiator and fan set up". What temperature is the fan engaging? What temp does it disengage?

[bdk1976]

Originally Posted by Schurkey

I don't know how a "radiator and fan set up" can cost $3500.

My thoughts exactly. I have an iron head 455 that runs 180 all day with a stock water pump and a stock 4 row radiator. My entire drivetrain cost about a third of this guy's cooling system - AND runs way cooler. WTF?

[promptcritical]

Just curious…does it not turn over or turn over really slowly, or does it just not fire

[Formulajones]

I don't know, things are only getting more expensive. I just bought a radiator from Griffin for the Vega, that was $1200 alone, and it's not a very big radiator either.

[Schurkey]

Originally Posted by promptcritical

Just curious…does it not turn over or turn over really slowly, or does it just not fire

I asked about that way back in Post #2, and never got a response beyond "doesn't have a problem cranking".

[dataway]

Can you post a picture of the radiator/fan setup?

Hopefully you are not using one of those dual electric fan setups with the shroud about 1" deep. They only use about half the radiator.

[chuckies76ta]

Originally Posted by Randylk

Temp is 185-190 while running.

I'm wondering about this also like Schurkey. 165* thermostat and you say the engine runs at 185-190* It appears to me something is not doing a proper job in the coolant system. That's the other thing to that has been asked. What is the fan on/off temperatures. When the thermostat opens at 165* you better have the fans running. Do a test, turn your fans on when you start the engine and see if the thermostat controls your engine temp. Oh, put the new stat in first.

Like has been mentioned, change thermostat. Get a decent stainless thermostat from Napa. https://www.napacanada.com/en/p/THM1...QiLpSLPMSBSI4h

[HWYSTR455]

What kind of gauge are you running, or are you looking at the handheld for coolant temps?

Yup, pics would help a lot.

Water pump divider clearanced?

AC pulleys?

What BRAND T-stat? (And which one)

Are you running a bypass regulator or deadhead? (the Sniper internal regulators are known to be a problem)

Fuel heat soak usually isn't an issue at EFI fuel pressures so those changes aren't going to have any positive effect.

Look at the attached image, these are the relevant items, as well as the 'Cranking Timing' value.


.

[chiphead]

Originally Posted by Schurkey

I don't know how a "radiator and fan set up" can cost $3500.




A 165 thermostat but it typically runs 20--25 degrees above the thermostat rating? The thermostat is not in control of engine temperature. The electric cooling fan MAY be in control--but perhaps not adjusted properly, or perhaps it's not in control either.


Your cooling system has genuine problems. PROBABLY related to the "$3500 radiator and fan set up". What temperature is the fan engaging? What temp does it disengage?

Exactly this. If the actual engine temp is 180+ with a 165 thermostat, the cooling system has lost control of engine temperature. Either that, or the electric temp gauge has a wiring issue and is reporting incorrect temperatures. I'm struggling to see how a system gets 50+F temp rise on shutdown. There's a lot of latent heat or a radiator sizing issue. How much water does your system hold?

A cooling system with enough reserve capacity should be able to keep the engine at thermostat temp. I looked at "entropy radiator" and it looks like a very expensive billet version of the dual-fan setups we've all seen. I have NEVER had luck with a system like that. They don't flow enough air through the core, especially when the fans are off.

On my current '67, I just removed a dual paddle fan system like that and replaced with a stock clutch fan and shroud. Even with no thermostat it ran at the turn-on temp of the electric fans, 185-190. That's a sign of blocked airflow.

I ran the car with the clutch fan and no thermostat, and the hottest it got was 170 stopped in traffic and 150F going down the road. So with a good 180F thermostat, I know I have some reserve cooling capacity. It never gets over 185 when running, and when I shut it off, it climbs to 200 on a 96* summer day. Not bad for a used fan and shroud and a $50 fan clutch

The other thing to consider is sediment in the cooling system. If an engine has rusty or clogged cooling passages, the parts of the block sitting under sediment builds heat. Upon shutdown, that area sheds the built up heat to the water, which then spikes in temperature. If any rust or sediment is coming out during flushes, it needs to be flushed until the water runs clean. Also check the radiator for clogs due to crap coming from engine block.

https://entropyrad.com/collections/radiators

[HWYSTR455]

I believe the term for spike in coolant temp after shutdown is 'after boil'.


.

[Schurkey]

Originally Posted by chiphead

I looked at "entropy radiator" and it looks like a very expensive billet version of the dual-fan setups we've all seen. I have NEVER had luck with a system like that. They don't flow enough air through the core, especially when the fans are off.
https://entropyrad.com/collections/radiators

None of the product shown on the home-page has a way to bypass air through the shroud when the fans are off, and the vehicle is moving fast enough to create a pressure differential between the front of the radiator and the rear.

Very amateur design work in my opinion.

Those shrouds should have a metal- or rubber flap that can open at speed to allow "ram air" movement, but closes when the vehicle is moving slowly or stopped.

[Formulajones]

I've been down that road experimenting with setups like that. It seems there are a bunch of radiator/fan companies that design there electric fan setups like that and every one I've tried always had an issue passing enough air to control engine temps. What ends up happening when I tried it is eventually the fans just run all the time, even on the highway, because even at speed it's a struggle to get air through the radiator when so much of it is blocked off. I had a big thread about it the last time dad wanted to try it on his GTO and even had Cold Case involved, adding holes and rubber flaps all around the electric fans where I could fit them and it was just never enough to control the issue.

I completely got away from those setups years ago and now only use a good quality radiator with the factory shroud and a clutch fan setup. Now I can't even get the engines hot in the AZ desert heat.

[P@blo]

If a thermostat is rated to start opening at 180*, are we suggesting that the cooling maintain that temperature even when the valve is not fully open? I'll put my helmet on for this one as this makes no sense. It seems nornal to have the operating temperatures 15-20* above the thermostat rated opening point.

Some guys have probably over engineered their cooling system and can maintain coolant temperatures when the thermostat valve is only partially open and is what I think is actually going on here. And maybe to a lessor degree, guys with more modest cooling systems but with cooler air temperatures (less demand on system) see the same situation occuring. Seems to be a bit of stretch to say a cooling system has "lost control" not maintaining the thermostat rated starting opening temperature but never overheats the engine. My cars run 180* thermostats and typically run 195-200* no matter what I throw at them, driving style wise, and see almost zero ROI chasing something like this down.

[nUcLeArEnVoY]

Originally Posted by Schurkey

None of the product shown on the home-page has a way to bypass air through the shroud when the fans are off, and the vehicle is moving fast enough to create a pressure differential between the front of the radiator and the rear.

Very amateur design work in my opinion.

Those shrouds should have a metal- or rubber flap that can open at speed to allow "ram air" movement, but closes when the vehicle is moving slowly or stopped.

Who cares? It looks cool and costs a lot of money. Must work!

[nUcLeArEnVoY]

Originally Posted by P@blo

If a thermostat is rated to start opening at 180*, are we suggesting that the cooling maintain that temperature even when the valve is not fully open? I'll put my helmet on for this one as this makes no sense. It seems nornal to have the operating temperatures 15-20* above the thermostat rated opening point.

Some guys have probably over engineered their cooling system and can maintain coolant temperatures when the thermostat valve is only partially open and is what I think is actually going on here. And maybe to a lessor degree, guys with more modest cooling systems but with cooler air temperatures (less demand on system) see the same situation occuring. Seems to be a bit of stretch to say a cooling system has "lost control" not maintaining the thermostat rated starting opening temperature but never overheats the engine. My cars run 180* thermostats and typically run 195-200* no matter what I throw at them, driving style wise, and see almost zero ROI chasing something like this down.

Yeah, this is what I was always led to believe. A thermostat's purpose is to maintain cooling system pressure, and to set the minimum operating temperature. The cooling system's capability and efficiency is ultimately what determines the temperature the car runs at. If your cooling system is bulky and well-designed enough to actually open and close a 160 thermostat in closed loop operation, then great, If not, it'll operate at a higher temp and eventually stop at what the cooling system can support. The only issue with using a thermostat at too low of a temp that your cooling system can't maintain, is that said thermostat will always be open and you lose some of the system's ability to make pressure.

[chuckies76ta]

Originally Posted by P@blo

If a thermostat is rated to start opening at 180*, are we suggesting that the cooling maintain that temperature even when the valve is not fully open? I'll put my helmet on for this one as this makes no sense. It seems nornal to have the operating temperatures 15-20* above the thermostat rated opening point.

Some guys have probably over engineered their cooling system and can maintain coolant temperatures when the thermostat valve is only partially open and is what I think is actually going on here. And maybe to a lessor degree, guys with more modest cooling systems but with cooler air temperatures (less demand on system) see the same situation occuring. Seems to be a bit of stretch to say a cooling system has "lost control" not maintaining the thermostat rated starting opening temperature but never overheats the engine. My cars run 180* thermostats and typically run 195-200* no matter what I throw at them, driving style wise, and see almost zero ROI chasing something like this down.

Here is my experience with 160* thermostat in both vehicles. The 160* thermostat starts to open at 160* and it only takes a less than say 15 sec to be fully open. Having said that the cooling system in both cars maintains the 160 degrees give or take a few degrees. If the coolant system is design/ working properly there is no 15/20* swing in temperature. As the coolant temperature increases or decreases that is when the thermostat modulates to accommodate the coolant system.



I can run my car with the 160 * thermostat in any outside temperture and it never goes above 160*.


The Firebird with the IA2 at 789 hp is a different animal, only runs at the track.On the street in really hot, 85-90* F weather it cannot get enough air through the radiator when driving slow with the electric water pump and dual fans. At the track if only hits around 170-175* in same hot temperature outside. So it has a 160* thermostat and the system cannot keep up when the vehicle is driven slowly in very hot weather. At the track with heat it up to 160* and do the 1/4 mile run with it reaching 170-175* when back at our pit.



Morel of all this, if you have a 160,165,180,190 degree Stat the coolant system should maintain that temperature.