I just got my 74 tuned in and running decently after spending over 2 decades completely dormant without turning over in my parent's garage. Took me a couple of years, but I am close to getting this baby lined out!

Was enjoying driving it a couple of weeks ago, when the original radiator finally sprung a leak. Not just any leak, but the neck where the cap goes on broke and it would no longer hold pressure.

Long story short, not being set on keeping completly original I purchased a Texas Heat aluminum radiator. For the long story behind that decision - read the PS below.

When I went to measure to verify before purchasing - wouldn't you know - mine is an oddball. Evidently, when they started producing the 1800cc spiders, they didn't have all the details worked out, or they just wanted to use up old stock - because the dimensions on my 74 match the pre 74' year models. So I ordered one of those. I did not order a new fan - as my old one seemed to be working fine.

When fitting the new radiator, I ran into two or three problems that make it not "plug and play".

1) hoses didn't work....I had to trim the bottom hose. I had to lengthen the upper hose. I did this by cutting the upper hose and splicing in a piece of aluminum pipe I had left over from an old project. Problem solved - no big deal.

2) no room for the charcoal canister. I was brainstorming a solution for this when I had the bright idea to take a break and pull the radiator back out to check the stock fan fit-up. No dice. The tabs on the new rad were not close to the original fan bracket. Off by about 3-4inches. Toyed with the idea of altering the fan housing/brackets, but instead I have opted to go ahead and order an aftermarket high cfm and lower amperage fan to fix this. I am throwing this one in in case it helps someone contemplating the same replacement. I am in process of ordering a 12" fan that attached directly to the radiator. In retrospect - I wish I had done this from the get-go since they offer a little discount on these when you purchase a radiator.

3) back to the charcoal canister...by giving up on the original fan and bracket, I think I will be able to cut the tabs off the new radiator for the fan bracket and mount it in its stock location.

I will try to post pictures if I ever get around to it.

I don't think I need yall's help with this one - at least not yet. Just hoping to help someone out there save time/money!

Happy

P.S. here's the long story behind the decision to upgrade the radiator - when I was in high school in the 1980's, I had the great honor of using my Spider in a parade to carry - get this - Miss Arkansas! Talk about a 17 year old's dream multiplied by a Forest Gump moment! In that parade, I remember not being able to truly enjoy the moment because I was stressing about the car overheating in the slow stop and go in the heat of a an Arkansas July - it didn't totally overheat and melt down, but it got uncomfortably hot as I recall - that was a long, long time ago. As Paul Harvey used to say...now you know the rest of the story!

HappyHog wrote:P.S. here's the long story behind the decision to upgrade the radiator - when I was in high school in the 1980's, I had the great honor of using my Spider in a parade to carry - get this - Miss Arkansas! Talk about a 17 year old's dream multiplied by a Forest Gump moment! In that parade, I remember not being able to truly enjoy the moment because I was stressing about the car overheating in the slow stop and go in the heat of a an Arkansas July - it didn't totally overheat and melt down, but it got uncomfortably hot as I recall - that was a long, long time ago. As Paul Harvey used to say...now you know the rest of the story!

I hear you, Happy. I had a similar story from my HS days in Virginia around 1980, but it was "Miss Somebody" (I forget exactly what) in my spider in the parade. I made it, but the engine also came dangerously close to overheating. Thank goodness for the heater core and heater fan providing a little bit of extra engine cooling, although it made me pretty uncomfortable.

I think foreign sports cars of that era just weren't designed for stop-and-go traffic in 90+ degree temperatures.

-Bryan

Ain't small-town America great, Mr. Bryan!

Update on the radiator....Instead of ordering a fan and waiting on it, I made a run down to O'Reillys and bought one today.

Got it rigged up no problem. I looks pretty good against that aluminum radiator. I cut the tabs for the fan mount off the drivers side of the alum rad - kept the one on the passenger side....never know when you might need to bolt something up. By cutting those tabs, it gave my charcoal canister room to live where FIAT put it - tucked in nicely between the new rad and the horn compressor.

Filled the thing with coolant and started it up and ran it until the fan kicked on and off a couple of times. All seemed good. New fan seems to blow more air, is definately quieter, and seemed to pull way less on the 12V system. Note: Fan came rigged up as a pusher, so I had to flip the fan around in its housing and wire it up correctly. Think I'm ready to rock and roll with it now!

Happy

One trick when overheating is to turn the heat all the way up. It will be uncomfortable, but the heater is a small radiator, and can make a difference.

True....assuming you haven't by-passed your leaking heater core!

I have been running it some in thick 100 degree temperatures. First time in probably 30-plus years this car has driven in those conditions. New radiator and new electric fan. All seems to be working ok, and fan seems to pull plenty of air. Once it kicks on, at idle, it will no lower temp enough to kick it back off. I shot the outside with my temp gun. Radiator seems to be around 140-150-ish degrees. Block/heads seems to be around 200-210 for most part - except down around exaust side near exhaust ports of cyl. 2, 3, and 4. I figure this is nothing to worry about except transient heat from ex manifold....although I did notice the manifold itself #1 seems to be cooler.

Question - could lack of heat transfer be due to a bad water pump? It doesn't seem to be leaking, but I feel like maybe I'm not moving enough coolant through the new rad. I'd probably also be wise to run a flush thru to clean out coolant passages in the block - but this sort of makes me nervous because I might cause leaks in the motor. Thoughts? Should I replace the water pump? Should I run a flush? If so, before or after I replace the water pump? Any recommended flush product that work especially well?

Also - how difficult is it to replace heater core? Will be months before I need that, but I'd like to know how involved it is so I can get mentally prepared for it. Before I dive too deep into a project on the spider, I need to focus my shop time on the broken exhaust valve on my commuter car - my 150k mile 2007 Mini Cooper S! (the fact I own one of those AND I own a FIAT shows what a glutten for punishment I am!)

Happy

Happy and Bryan…CLEARLY you both did not take into account the risk and exorbitant cost of having to replace the front bow of a Spider top by having someone seating on it…(very envious here of you both)

When it was time to replace my radiator—about 6 months ago—I opted for a OEM type. But I did replaced the OEM fan with a 16” low amp electric fan. Happy to report that despite the high humidity and 95° current temperatures, the temp gauge sits still at 90°

Anbele wrote: Happy and Bryan…CLEARLY you both did not take into account the risk and exorbitant cost of having to replace the front bow of a Spider top by having someone seating on it…(very envious here of you both)

Ha! Anbele, your guest of honor must have been, well, gravity challenged as we say these days...!

HappyHog wrote:Thoughts? Should I replace the water pump? Should I run a flush? If so, before or after I replace the water pump? Any recommended flush product that work especially well?

Happy, here's the way I'm looking at it. It sounds like your block might be somewhat full of crud, and if the water pump has not been replaced in the last 10 years, it's not a bad idea to replace it. Especially since you got a new radiator. For flushing, I remove the water pump, open the drain on the exhaust side of the block, remove the top radiator hose, and blast water from a garden hose everywhere I can through the pump opening and coolant neck on the cylinder head. Down the heater hose connection as well, the one right in front of the #4 spark plug.

You can use a radiator flush, but I'm not sure it's necessary since you have a new radiator, although it might help with the block. I think it takes a few days or weeks of driving with the flush in the system, so you might not want to wait that long. If the container says "Flushes radiators clean in 10 minutes!!!" they are lying to you, the low-down vermin. 10 minutes won't do squat.

HappyHog wrote:Also - how difficult is it to replace heater core?

It's not terrible, but it's not a job that I look forward to. Here's how I do it. Remove the passenger seat and put a thick blanket over the various bumps in the seat area. Remove the lower center console (the one with the radio speaker grill). Undo the 4 clips that hold the plastic ducting below the heater core (2 on each side). Lie on your back in the passenger area, being sure you have all the tools you will need: flashlight, rags, screwdrivers, razor blade, pliers, 10mm wrench and 10mm socket with an extension. Remove the heater hoses (I just use the razor blade to cut them off since they will be replaced anyway). Remove the clip that holds the heater valve control wire. Lower the heater box ducting from the bottom of the heater core. Undo the bolts that hold the input and output pipes to the heater core. Curse as you do this. Once everything is removed, clean up the pipes, check the heater valve, install the new heater core with new gaskets, watch it leak, curse some more, tighten it up, and quaff a beer when finally all is well. Don't forget to reinstall the passenger seat!

-Bryan

Agree with Bryan’s procedure…although I’d add a couple of more beers to the process…hopefully at the end of the repair! Good luck!

Anbele wrote:I’d add a couple of more beers to the process…hopefully at the end of the repair!

In some cases, it might help more in the beginning, but since we are safety-first, I'd stick with your approach.

-Bryan

Awesome - I will likely do the flush and replace the 30-plus year old water pump one of these summer weekends and punt the heater core replacement into fall/winter months when it will be needed (for heat, not car cooling ).

On new development since the radiator replacement is that when it gets to full operating temperature 190-plus, it stumbles under load - like when ulling up a hill or moderate acceleration. I have had a slight stumble since I got the carb lined out at gear shift from 1 to 2, but it was very slight and picked right back up. Temperature didn't seem to change it. Now, after the radiator change, this stumble is much more intense and long in duration - but only after it starts to get near operating temp. Is is possible I screwed something up in the charcoal canister when I had it off for radiator fitment? Any other ideas? I haven't pulled plugs yet, but plan to do that soon to make sure my carb adjustments are really as good as they seemed to make it run.

BTW - I opted for a 14" electric fan. Maybe I should have went a tad bigger????

Happy

Do you have the internal thermostat (in the cooling outlet neck at the front of the cylinder head), or the external one (the thee neck thingie by the water pump?

A few things come to mind:
- You could have an air pocket in the coolant line that operates the automatic choke (not relevant if your choke is electric, of course), so the choke isn't opening up all the way.

- You might have disconnected a vacuum line to the intake manifold when working on the charcoal canister. Or a vacuum line to the distributor, if it has a vacuum advance (I can't remember for 1974).

- How is your spark plug gap? The early spider ignition systems seem to like about 0.025" for the gap.

By the way, operating at 190 oF seems normal. The fan shouldn't kick on until you get to 210 or so, and it shouldn't come on at all unless you are stuck in slow traffic on a hot day, or doing a lot of idling.

-Bryan

Finally back on here after several months. Have been busy with job, flip house project with my wife, a mini-cooper rebuild and finally got around the last couple of months back to the Fiat.

I had one of those snow-ball experiences.....replacing the heater core and I thought - while I've got this out, I'll .....

Next thing you know I had installed a cover over the center console, made a piece of walnut to match the recent dash replacement, found and fixed an inner rubber shifter boot, cleaned up floors, added sound deading - performed metal repair and reattached drivers seat mount to flooboard where it had rusted away, went by carpet place and bought $8 of carpet remenents for the front floorboads, bought a retro looking blue-tooth reciever and installed it with better speakers than the 1980's era sound that was in it....then I was finally able to move to the water pump.

When I pulled the water pump, I couldn't believe it was moving water at all - half the old one looked like I had pulled it off the ocean floor! Now I have coolant flowing and actual heat in the cabin - which is a little nicer now.

I'm back in business. Took if for a hundred mile top down ride in Ozark Mountains with my bride on eclipse day. Still have a few running issues, but she's running good - and cool.

Oh yeah - meant to add - I do have the internal thermostate - mounted on top front center of cyl head.

One other thing I did was to modify my home made mount for the ignition control module - made it where more air gets around it to help cool it. Looks pretty trick considering I fabricated it from shop junk. I'll try to remember to post pics sometime.

And yes - many beers (I call it ciphering fluid) were consumed before, during, and after all this work (over numerous work sessions)

Happy