Advice on keeping my 4104 / 671 cool

[Gordie Allen]

Hi,
I'm new to this board (newbee status).  I bought a 1956 Gm 4104 in Feb.  Drove from Sanford FL to Augusta Mi with only one mechnical.  The relatively new fan with aluminum hub and polyurethane blades blew apart.  One blade let loose and the remainder followed.  This had happened with the stock fan previously which is why the $1500 replacement fan.  The previous owner put a bigger radiator in which actually hangs too close to the ground.  He put a skid plate under it, but still...   I made a roadside fix by calling an Autozone and paid a guy to come get me, bought two 16" electric fans which I mounted diagonally – pusher style, fastening with lots of zip ties.  That and the addition of a 6"x24" scrap of trim off the bus zip tied as an air dam behind the radiator got me home with minimal cooling issues from Atlanta to Michigan

The engine is a rebuilt 671 with 15000 miles and 4 valve heads.  Runs great, no leaks, and 10 mpg on trip home.  I have some questions.  1) Where can I get the proper radiator?  My only other option is to cut down the upper tank and raise it 4".  Not the best solution.  2) I'm considering aftermarket remote oil cooler and fuel cooler with fans to help out with cooling – maybe even a remote transmission cooler as well.  The issue in the back of my mind is why have two crank mounted fans failed?  Could there be a balance issue and can this be checked without pulling the engine?  I'm also rebuilding the original heater with a new core and  moveable ducting doors that would allow me to dump hot air outside via the stock heater as a backup.  This is no small unit.  Two - four row copper heaters 12" x 20" (Thomas bus cores) stacked in original housing with fan assembly torn apart, cleaned and reinstalled using 65' of 1" heater hose in PVC to replace copper pipe.  Obviously, I'm after the most dependable cooling I can get.  Nothing is more stressful than watching the temp gauge climb above 190*.  This is my first shot at a bus conversion, although I am a motorhead, and I built my own house, so I know I'm up to the project.  Just retired and other than building a new garage, finishing my custom 2000 Corvette, and building an original 1970 Chevelle Malibu SS, I have most every day to work on the bus.  Thanks in advance for your experience and recommendations.
Gordie

[Len Silva]

The stock 4104 had no cooling issues if everything is in good shape.  You didn't say, but I'm assuming someone has added an auto trans and that is why the system has been cobbled up. If it's a stick then you only need to restore the original.

The rubber mounted fan hub can be a problem and should be checked out.  The original fan shroud is also an important part of the cooling system.

[Gordie Allen]

Len,
Thanks for your reply.  This is a 4 speed manual.  I've just read a lot of posts regarding cooling issues requiring misters, etc.  I don't know what the past issues were with the cooling, but the previous owner installed a truck radiator after the fan disintegrated and destroyed the original.  It has a poor excuse for a shroud and the fan that blew up on me cost around $1500.  It has (had) a two piece aluminum hub with flanges that hold (held) 10 plastic blades.  To get it home I mounted electric fans (pushers).  I was worried that something may be out of balance to cause two fan failures.  I plan on replacing the over sized radiator with a properly sized one.  Still debating on whether to go with puller electrics with proper shroud or try another hub driven fan with proper shroud.  Which leads me to ask where to find a radiator.  I know it'll cost me around $1500, but if that's what it takes to do the job, it's worth it.
Gordie

[Len Silva]

If it's a stick, then you should not have any cooling issues.  Misters are for bigger buses with bigger engines and compromised cooling systems.

The fan hub is definitely something to check and I'll bet that was the source of all the problems.

If you don't already have them you can find a full set of manuals and parts book here:  http://manuals.lenstudio.com/

[gus]

The 671 fan hub is infamous for failing, yours is on its way or has probably failed in the past.

Failed fans are a pretty sure indicator of out of balance or misaligned hubs and/or bearings.

The 4104 never overheats if downshifted, lugging it on hills will overheat it, shifted down it will go on forever in a lower gear at full throttle and stay cool. I've driven mine five to ten miles up mountain grades in NM in third and second gear with no overheating.

It originally came with a radiator shroud. Mine was missing but when I fabricated one it didn't seem to make much difference.

[luvrbus]

Change the $ 600  harmonic balancer on the front of the 671 your problem will most likey stop

[Gordie Allen]

So, can I install a harmonic balancer without special tools and be sure it's installed properly?  Also, how do I find the correct radiator?
Thanks,
Gordie

[gus]

My understanding is that there is only one specific harmonic balancer for each engine which is determined when it is manufactured, wiser ones will clear this up!!