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Running hot issue, BBc

General engine tech -- Drag Racing to Circle Track

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GRTfast
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Re: Running hot issue, BBc

Post by GRTfast » Mon Jun 10, 2019 1:59 pm

F-BIRD'88 wrote:
Mon Jun 10, 2019 1:56 pm
GRTfast wrote:
Mon Jun 10, 2019 12:57 pm
What timing curve are you running? Vacuum advance?

If the timing is too retarded at idle and during cruising, it will dump a ton of heat into the exhaust port and make the car run hot.
Heats up the exhaust port and the cylinder walls also.
yup. Any heat that isn't being converted to work has to go somewhere.

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Re: Running hot issue, BBc

Post by F-BIRD'88 » Mon Jun 10, 2019 2:02 pm

Truth. Truth

67 Nova
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Re: Running hot issue, BBc

Post by 67 Nova » Mon Jun 10, 2019 4:38 pm

F-BIRD'88 wrote:
Mon Jun 10, 2019 11:36 am
Change to a 120cc open chamber head will drop cr to 10.6:1 for street pump gas.
That might be where this is going. Will pull the restrictor out and change to 50/50 coolant/water and new hi flow t stat.

As for timing curve? That will have to look back into. Not sure off top of my head.

Thanks

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Re: Running hot issue, BBc

Post by 67 Nova » Wed Jun 12, 2019 9:51 am

GRTfast wrote:
Mon Jun 10, 2019 12:57 pm
What timing curve are you running? Vacuum advance?

If the timing is too retarded at idle and during cruising, it will dump a ton of heat into the exhaust port and make the car run hot.
Timing is locked at 32. This is the first time since the 90's I'm running an actual distributor in a motor again. ALL my other deals had crank triggers and MSD boxes. So no timing with them. Recall my buddy who built my motor and help set up my FIRST performance BBc (396/375 ++++) back in 1996 did this for me. Then first night out, when hot, car would like to start, very hard. I called him the next day and first thing he said was "car doesn't like to start HOT does it"? Went on to explain full timing with crank trigger and why he "rolls" the motor on his dragster over BEFORE tuning on the box. So I have had a box/ignition power in every car since then, INCLUDING this one.

So maybe need to get ahold of Petronix, as I'm using a Ignitor III distributor and coil, and get some insight and the parts that I HAD from them to put some sort of curve into this and not locking it out.

Hope to be able to load pictures later today or tomorrow.

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Re: Running hot issue, BBc

Post by GRTfast » Wed Jun 12, 2019 10:07 am

67 Nova wrote:
Wed Jun 12, 2019 9:51 am
GRTfast wrote:
Mon Jun 10, 2019 12:57 pm
What timing curve are you running? Vacuum advance?

If the timing is too retarded at idle and during cruising, it will dump a ton of heat into the exhaust port and make the car run hot.
Timing is locked at 32. This is the first time since the 90's I'm running an actual distributor in a motor again. ALL my other deals had crank triggers and MSD boxes. So no timing with them. Recall my buddy who built my motor and help set up my FIRST performance BBc (396/375 ++++) back in 1996 did this for me. Then first night out, when hot, car would like to start, very hard. I called him the next day and first thing he said was "car doesn't like to start HOT does it"? Went on to explain full timing with crank trigger and why he "rolls" the motor on his dragster over BEFORE tuning on the box. So I have had a box/ignition power in every car since then, INCLUDING this one.

So maybe need to get ahold of Petronix, as I'm using a Ignitor III distributor and coil, and get some insight and the parts that I HAD from them to put some sort of curve into this and not locking it out.

Hope to be able to load pictures later today or tomorrow.
I think you will find that a vacuum advance that allows 10-12 degrees of advance will cool things down at idle and cruising. I currently have a curve in my HEI that is about 30 initial, and is all in at 39 degrees around 3500 rpm. I also have a vacuum advance that adds about 8 degrees. This results in an idle advance of 40 degrees, and a highway cruising advance of 45 ish degrees depending on the speed. If I disconnection the vacuum advance, the car runs hotter, and will run-on after I turn the key off because the exhaust valve is hot enough to keep firing the mixture.

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Re: Running hot issue, BBc

Post by F-BIRD'88 » Wed Jun 12, 2019 10:13 am

You can keep the locked diz but should add vacuum advance too. About 10-12 at high vacuum pt cruise.
What you really need to address is the excessive CR.
And the water flow, air flow issues.

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Re: Running hot issue, BBc

Post by MadBill » Thu Jun 13, 2019 10:34 pm

67 Nova wrote:
Mon Jun 10, 2019 4:38 pm
F-BIRD'88 wrote:
Mon Jun 10, 2019 11:36 am
Change to a 120cc open chamber head will drop cr to 10.6:1 for street pump gas.
That might be where this is going. Will pull the restrictor out and change to 50/50 coolant/water and new hi flow t stat.

As for timing curve? That will have to look back into. Not sure off top of my head.

Thanks
Keep in mind that a 50-50 antifreeze mix has ~ 20% lower specific heat than straight water...
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

67 Nova
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Re: Running hot issue, BBc

Post by 67 Nova » Fri Jun 14, 2019 10:09 am

Sorry couldn't get pictures. Trans guy was leaving for his grandson birth. But on the hoist it does look like lower rad hose needs "attention". NO SPRING and sitting cold it probably 12% reductions in size at the bend.

Like I said, it's a alum 2 core that seems to flow well when it's running. My concern is car heats up fairly fast stilling. Then I figure it should cool once I'm moving. IT'S NOT. Just keeps climbing in temp.

If I sit and idle say to 180/190, then move the car, keeps climbing to 210 even with airflow thru rad. It's like my other car with electric fan. At idle with fan off she heats up, but soon as fan turns on it cools well.

I have messed with a vac advance or timing curve in 30 yrs. Guess it's time to get back to the basics...........

THANK YOU ALL

John

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