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Old 07-13-2015, 07:06 PM
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Overheating small block chevy

My 68 Camaro is running a .060" over bore 350 with a Weiand 142 blower, 700cfm Holley carb, crane hydraulic roller cam part number 119841-intake 359 at valve 539, exhaust 372 at valve 558 with 1.5 rocker ratio, msd 6 series ignition with a 3 stage retarder., headmen headers 3" collectors , coated with jet hot coating, to dual exhaust 3" pipes with black raven mufflers that dump in front of rear axle. Rear end used to be 4:10 gears but has since been reduced to 3:42. Transmission is an aluminum powerglide that runs trans cooler lines to the stock radiator. I have a TCI 2800 stall converter. I run a mechanical fan with a stock water pump and a 180 degree thermostat. My issue is this overheats according to my temp gauge which climbs 210 to 220 running around town and idling during hot summer days can see 230 and higher. I am seeing poor gas mileage and lots of black out the pipes. I run timing about 8 to 10 degrees. I am wondering what is causing the overheating? Bad timing, too much fuel, too low water flow, not enough fan cfm? I have run with and without the thermostat but yields same results. I also have a 100 hp Nos super power shot plate below the carb and used it only at the track when I use to drag which was years ago. Anyone have any suggestions on how I can cool this hot car down?

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Old 07-13-2015, 08:47 PM
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Everything sounds good, but you didn't mention the size of your radiator? With what you've got going with this HOT ROD, You should have at least a four core. Maybe that radiator needs to be cleaned out. Hard to believe how much junk builds up in those radiators. Helped mine a lot.
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Old 07-13-2015, 10:53 PM
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y thoughts are the same...you don't have enough radiator if it is a stock piece unless it is from an Air Conditioned or Big Block combination....HP is heat, the more HP you make, the more heat you have to deal with...you'll need either a 4-row of 5/8" wide tubes core Copper/Brass radiator or a 2-row of 1" tubes aluminum radiator.

I would also expect this combination to need 14-18 initial timing, and using the retard functions to keep timing from getting too high under boost.

Is the retard rpm activated or is it tied to a MAP sensor so it retards based on manifold pressure(boost level)??
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Old 07-14-2015, 07:20 AM
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I also say you need more initial timing. I would have initial at least at 18 with mechanical limited to 32-34 for starting. Can sneak up on the timing if you watch the tune.

Get a high flow thermostat.

If you car runs a good temp down the road, then most likely you dont have enough fan.

The black smoke says its rich. Bumping the timing will help. Running too rich will also cause heat.

Make sure you have a retard for when boost is applied.
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Old 07-14-2015, 07:46 AM
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Put more initial timing in it but with the blower you will need to limit the total initial + mechanical to about 32-34*.

More timing will cool it down a little. The radiator may be to small but you need to fix the timing first.
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Old 07-14-2015, 02:42 PM
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Quote:
Originally Posted by Camaro1968 View Post
My 68 Camaro is running a .060" over bore 350 with a Weiand 142 blower, 700cfm Holley carb, crane hydraulic roller cam part number 119841-intake 359 at valve 539, exhaust 372 at valve 558 with 1.5 rocker ratio, msd 6 series ignition with a 3 stage retarder., headmen headers 3" collectors , coated with jet hot coating, to dual exhaust 3" pipes with black raven mufflers that dump in front of rear axle. Rear end used to be 4:10 gears but has since been reduced to 3:42. Transmission is an aluminum powerglide that runs trans cooler lines to the stock radiator. I have a TCI 2800 stall converter. I run a mechanical fan with a stock water pump and a 180 degree thermostat. My issue is this overheats according to my temp gauge which climbs 210 to 220 running around town and idling during hot summer days can see 230 and higher. I am seeing poor gas mileage and lots of black out the pipes. I run timing about 8 to 10 degrees. I am wondering what is causing the overheating? Bad timing, too much fuel, too low water flow, not enough fan cfm? I have run with and without the thermostat but yields same results. I also have a 100 hp Nos super power shot plate below the carb and used it only at the track when I use to drag which was years ago. Anyone have any suggestions on how I can cool this hot car down?
Unless this blower is pumping pressure when your just boppin' around just off idle you need a lot more timing advance in this range. This is a common problem with supercharged engines on the steet it takes some sorting out.

You probably need about 18 to 20 degrees initial advance with an additional 14-12 in the centrifugal. This needs to combined with a pressure retard that takes some of this advance out as the pressure comes up. This tends to be about 2 degrees of advance for every pound of boost, some times less sometimes more depending upon the engines detonation tolerance.

This should get some noticeable control of you low speed temperature problems and maybe your rich mixture which probably is a combination of too late ignition resulting in to much of the burn occuring after the point of best force transfer into the crankshaft. The late timing runs the engine hot because the energy is not being used to push the piston and the burn is still hot in the lower part of the stroke so that unused energy is going into the cooling system. The sooty combustion can also be the result of the late timing where the exhaust valve is opening before the fire has consumed the fuel so as blow down occurs the unburnt portion goes out the exhaust.

Once you get this sorted out you can work on the fuel curve. Getting the fuel curve right on a blower motor can drive a sober man to drink but it can be done.

Mind you I don't often give advice on supercharged engines as it's super easy to get into trouble with these things and as an advice giver compared to being the tuner I don't have any control over what's going on.

Installation of detonation sensing if not using it to control the ignition is a very beneficial way of not scattering the engine. Otherwise the only advice I have is listen carefully for detonation. But getting some advance timing on this should cool it off and clean it up but you've got to keep your wits about you as you do it.

Bogie
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Old 07-14-2015, 03:33 PM
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Engine knock detection and indication for all vehicles

I don't think that you can hook this up to the MSD, but seeing a bright LED illuminate letting you know that it's detonating, long before you can hear it or feel it, could be a lifesaver. I'm running one of these on a turbo application and it seems to be working fine. I initially didn't have it hooked to the ECU, but is presently and when the light comes on we know something is wrong with the tune and it needs to be fixed RIGHT NOW.

I'd recommend it to anyone as it works. I looked at it as a $100 insurance policy on our investment.
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Old 07-15-2015, 08:29 PM
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It's a 3 core rad. See pic. Think that's too small ?
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Old 07-15-2015, 08:31 PM
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Quote:
Originally Posted by dwwl View Post
Everything sounds good, but you didn't mention the size of your radiator? With what you've got going with this HOT ROD, You should have at least a four core. Maybe that radiator needs to be cleaned out. Hard to believe how much junk builds up in those radiators. Helped mine a lot.
It's a 3 core , I attached photos in the thread
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Old 07-15-2015, 08:40 PM
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Boost only kicks in about 3500 rpm and gives about 4 psi of boost pressure.
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Old 07-16-2015, 08:19 AM
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Quote:
Originally Posted by Camaro1968 View Post
It's a 3 core rad. See pic. Think that's too small ?
It appears from what little I can see in the photo that a couple tubes are obstructed with solder. If that's an average for the remaining severals of tubes there is a flow issue.

Check this out since you're there and I'm not and let me know if that's an accurate observation.

Bogie
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Old 07-16-2015, 05:03 PM
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It has some sludge in there but not solder, I do have crush damage in the middle of the rad where the water pump hit on an engine pull.
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Old 07-16-2015, 05:20 PM
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Quote:
Originally Posted by Camaro1968 View Post
Boost only kicks in about 3500 rpm and gives about 4 psi of boost pressure.
Blowers don't kick in they start building boost at very low rpm and increase in a fairly linear fashion with engine rpm. I would be very surprised if you are not seeing boost before 3500 RPM if teh engine is loaded.
You can not look at this while just revving the engine and not driving. The boost will have more significant impact with the engine under load.
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Old 07-16-2015, 05:36 PM
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I should say the boost hits positive pressure on the gauge when I get to 3500. Anything lower than that shows in vacuum.
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Old 07-17-2015, 05:06 AM
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For what it's worth, my N/A 355 in my 68 Camaro was overheating as well and it wasn't unusual to see 190 just driving around town. It would climb up to 215-220 when sitting at the stop light. Timing was where it needed to be, jets were just fine and I made sure the radiator was filled with a proper proportion of water and coolant but it still overheated.

Replaced the radiator with one from Griffin that was 26" wide and that dropped the temps to no more than 170 when driving around. Worst I saw was 190 sitting in traffic on a hot 100 degree day.
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