Fan-radiator spacing, fan clutch, and overheating

[XH29N0G]

The charger overheats when stuck in traffic at temperatures above 90-95 F.  I know there have been a lot of recent posts on this, but I have not yet solved my issue so here goes.

It did not do this before the 383 was rebuilt.   It used to have the pulleys for A/C and now has non-AC pulleys.  I am trying to identify the cause of the overheating. 

Possibilities I am considering: 

(1)  It has a fan clutch that spins when cold and hot (thermal design).  It seems to spin slightly easier when hot.  I do not think it is HD.  I do not have the part number, but can take it off and look for one.  Could the fan clutch have gone bad.  When cold, it holds a towel up against the radiator.  I have not yet checked when hot.

(2) the radiator is a 26" I think 3 row std A/C unit.  I think it is OK so am not looking here.

(3) the flow of coolant is fast once the thermostat opens.  I think this means the thermostat and pump (the original unit) are OK.

(4) the spacing between the fan and the radiator (there is a shroud) is presently about 2 inches.  I do not know if it was closer when the pulleys for A/C were being used.  I am wondering if it is too far back (even though the towel test seems to indicate flow). 

(5) I am wondering whether the engine is just generating more heat than it was before.  It has been stroked to 450 c.i. and has aluminum heads and headers (had headers before).  The underhood temperatures seem higher.

So I am wondering about 1 and 4.  I am considering getting an HD thermostatic fan clutch as a test, but thought I would send a note to the board in case there was another thing I should do first.

Thanks.

[firefighter3931]

Ideally, the clutch should be 3/4- 1 inch from the rad core for best cooiling and the fan blades should be inside the shroud for maximum air pull through the radiator 

If it stays cool at speed out on the highway yet heats up in traffic, it's not a cooling capacity problem....it's a heat transfer issue. Basicly, in that scenario you're not pulling enough air to properly disssipate the heat load. The fan clutch should be pretty solid once the engine reaches operating temp....yours sounds suspect 

Possible tuning complications that contribute to incresed temps are retarded timing and lean A/F ratios.


Ron

[XH29N0G]

Hi Ron,

Thank you.  The A/F is something I am working on, but it is not running lean.  Idle is 12-14.  Normal operating conditions are similar.  I will try to replace the fan clutch first.  In another thread you mention  HD Hayden 2765 clutch.  I will try that unless there is an issue.

[John_Kunkel]

When a well-designed shroud is used the distance from the fan to the core doesn't matter, many Brand-X cars have shrouded fans that are several inches from the core.

The FSM states that the only way to know if a fan clutch is good is to replace it with "a known good unit"....IOW, there's no way to test one. If in doubt, replace.

[XH29N0G]

Thanks John,

I'll get a replacement and post a note if it is successful, or not.

[justcruisin]

If you have the room I would use the Chrysler clutch - (hayden 2747 or equivalent - I think) The 2765 is a Jag clutch and is not an HD unit and it may not have enough beef to drive a heavy fan blade. Also it has a smaller bolt flange and your bolts will over hang the edge of the clutch mount, a spacer ring can be fabed up to solve this problem. The 2765 is only an option if you have a distance to radiator issue.

[XH29N0G]

I tried an imperial HD clutch after looking up and gathering that they are the same (or similar to the Hayden ones) that I ought at the local car parts store.  While it has not been as hot as it was (yet), I have not seen the same high temperatures.  In fact, it seems like they are reading slightly lower and more stable on the gauge, but still around 200. If the overheating returns (or not) when the weather turns back into the mid/high 90's I will let you know.

Thanks. 

[A383Wing]

if you had AC pulleys on there, you also probably had an AC pump..change to non-AC pump also

[XH29N0G]

Thanks for the idea.  If the issue returns, I will check that. 

[XH29N0G]

Finally had a warm day.  No problems with overheating or spiking.  The fan clutch replacement and the topping of the coolant did the trick.