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Hey all. New here. I have a 1973 Mach 1 with a 1969 429/C6 swap in it. Originally had a 351/FMX. The problem I'm having is that the car overheats at idle or sitting in traffic. It runs cool when moving.

I have replaced the water pump with a Weiand High volume aluminum pump with the backing plate in place, a new 3 core aluminum radiator, new radiator hoses with a spring in the lower hose, 6 blade flex-a-lite mechanical fan, I have a shroud on the radiator. I have tried 195, 180 and 160 thermostats. I'm using a 13lb cap. The head gaskets look installed properly with the square edge of the gaskets towrds the lower front of the heads.

I have placed a 12" puller electric fan on the inside of the drivers side fender near the front. My next step is to replace the mechanical fan with dual electric fans with 4600 cfm rating.

The timing on this engine is set at 5 degrees BTDC initial atm (6 degrees was standard until 1971). Any higher and I get pinging under acceleration.

If I start the vehicle and leave it idling the temperature slowly climbs until it overheats. Or if I'm sitting in traffic it will do the same. Then I get pinging under load again due to the heat. It has never boiled over on me. I did shut the vehicle off after it idled in the driveway for a long time while I was doing other tasks and the coolant was boiling inside the overflow tank. It has done that once. It doesn't lose fluid and there's no smoking at all from the exhaust.

Is this strictly an airflow problem due to the fact that the 1973's weren't designed for the BB engines? I know there is almost zero room in the engine compartment on the sides and back of the engine. The engine is almost up against the shock towers on both sides which makes doing spark plugs etc a real chore. If so will the dual electric fans which should hopefully push more air than the mechanical fan at idle solve the problem?
Thanks for any assistance.
 

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You need more air at idle.
 

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The 71 and 72 came with 385 Series engines. It sounds as mentioned needing more airflow. Did you discuss the swap with the radiator vendor?
 

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Discussion Starter #4
The 71 and 72 came with 385 Series engines. It sounds as mentioned needing more airflow. Did you discuss the swap with the radiator vendor?
Thanks for the replies guys. I knew the 71 came with a BB but was unaware the 72 did. I didn't discuss tthe radiator swap. It had a 3 core stock type brass/copper radiator that sprang a leak after the water pump swap. The aluminum radiator has the same dimensions as the stock except a little thicker.

I'll give the dual electric fans a shot. I might also relocate the battery to the trunk and put a second 12" puller on the passengers side fender in the same spot that the 12" is in on the drivers side.

Have to change the stock factory guages also. It only has the stock guages so I haven't been sure what temperature exactly she has been running at. All I know is that big chunk of iron puts out some serious heat in my engine compartment. It's stock now but I want to rebuild it for a bit more horsepower next year and definitely have to get the cooling issues fixed before then.
 

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Thanks for the replies guys. I knew the 71 came with a BB but was unaware the 72 did.
I might have to correct myself here. I think 1971 MUST was the only year for the 429. But the front rails and aprons should be or nearly be the same (71/73).
 

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I might have to correct myself here. I think 1971 MUST was the only year for the 429. But the front rails and aprons should be or nearly be the same (71/73).
I didn't do the swap myself. Bought the car with it already done. It had been sitting for many years after a semi-restoration due to the PO having medical problems.

If I'm right the shock towers and engine mounts had to be changed on the 72/73 to fit and support a BB ford. Not sure what the original shock mounts looked like but mine are pretty close to the engine which leads me to believe that my problem is airflow due to restricted room for the air to actually flow past the engine itself.
 

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I didn't do the swap myself. Bought the car with it already done. It had been sitting for many years after a semi-restoration due to the PO having medical problems.

If I'm right the shock towers and engine mounts had to be changed on the 72/73 to fit and support a BB ford. Not sure what the original shock mounts looked like but mine are pretty close to the engine which leads me to believe that my problem is airflow due to restricted room for the air to actually flow past the engine itself.
I just checked the MPC and all three years used the same apron and rail assemblies irregardless of engine choice. It may be the previous owner made a few modifications to ease installation. It may be he also added reinforcing to prevent chassis twist.

Your assumption about hot air escaping may be correct. FORD did not seem to have this problem with assembly so something that has been done is the culprit (taking into consideration there is nothing wrong in the engine). It needs to exhaust heated air as well as it draws fresh out side air.

Here is an 1971 OEM 429 inlet air deflector that sits atop the core support and directs all incoming air through the radiator-


There is most likely a full surround of these deflectors in an original install.

One option you have is to shim the hood @ the the hinges to allow more hot air escape. This will give you some indication of heated trapped air. Just make sure the hood latches after this modification. Ask me how I know.

If so, then the obvious solution will be a hood with an exhaust cowl or teardrop design, maybe louvers. The rear apron skirts could also be louvered depending on how far you want to go.

71 429 CJ Mustang and Cougar Megasite
 

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Thanks for the info. At work so haven't had time to reply. Mine doesn't have those deflectors so I'll see if they are available or if I can find a set of 71's to fit. Looks like they might help out a bit.
 

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Thanks for the info. At work so haven't had time to reply. Mine doesn't have those deflectors so I'll see if they are available or if I can find a set of 71's to fit. Looks like they might help out a bit.
They help direct outside air through the radiator instead of flowing around it. I will try and find an illustration of all baffles. It will be a few days.
 

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I had this same problem with my 351C in our 70 Mach1 so when we did the restoration we did as you have and added a 3 core griffin aluminum radiator / edelbrock high flow water pump and a spring in lower hose then I added a dual electric fan with molded shroud that covered complete radiator, I hooked up the drivers side fan to run all the time with ignition on so sitting in traffic wouldn't be an issue and then I set the thermo switch to kick the second fan on at 185 degrees which is the temp of the thermostat I'm using, now as a added protection I installed FPA hedders that were ceramic coated inside & out and a trans cooler to my AOD as I've read alot of engine heat is due to heat from the trans.

Now this summer here in Missouri has been unusually hot 100 plus but it hasn't stopped us from going to car shows and some are a cosiderable distance, we went to Des Moinces,Ia. for the Good Guys show July 4th and it was HOT we cruised 70 to 75 mph for 2 1/2 hrs with the a/c running and never went over 190 degrees and when we hit Des Moines city traffic same thing never went above 190.

Just a thought that if your using manifolds or uncoated hedders with no trans cooler that might be your problem. Good Luck .... Jim
 

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A stock 69 429 is a high compression engine which you will probably not be able to run on today's pump gas.

More initial timing will make it run cooler. Put some race gas in it and add some timing and see what happens.

BTW it has nothing to do with a tight engine compartment. I run a 460 with headers and iron heads in a 73 convertible and it never gets over 195 with a stock replacement 3 core radiator, a stock fan shroud and a stock fan blade.
 

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Thanks for the information guys.

It has the tranny cooler on the radiator. I'm going to bypass that and install a delane external cooler with fan. I'll be replacing the stock power steering cooler with a delane fan unit also.

I run the highest octane gas I can get with an octane booster and lead substitute every fill up. I haven't gotten around to seeing if anyone near here sells race fuel. If so I'll have to try that out.

Hopefully the dual electric fans will fix the idling temperature problem. I like the idea of running just one fan all the time. Will be awhile before I get to find out. I'll have to try that out. Won't be home until the middle of October. Between the baffles and extra cooling it should hopefully do the trick.

I do still have the stock exhaust manifolds on it. Going to take it to the shop to install headers later this year when I get the temperature issue fixed.

It isn't so horrible that I can't drive it which is a good thing. It's got to be just a minor fix. If I'm idling or sitting in traffic and hold the rpms higher the engine will cool down to normal. Just at a complete stop and idling at 650-700 rpm's or so is when the temperature creeps up.
 
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