Steve's Triumph Spitfire 1600
The ongoing saaaaaaga
Cooling System:
Coolant Flow To The Mixing Chamber:
This is the best image I could find for now of the Miata original set-up for the Mixing Chamber, By-Pass Pipe and small Thermostat Water By-Pass Fitting.
As expected and planned for, now that the Exhaust was routed forward of the Engine Mount there would be clearance issues with the Mixing Chamber; this had to be the next priority.
As mentioned, I like the way Dan did it but I wasn't up for that kind of aluminum welding just yet. I also hoped to keep the hydrodynamics as close to factory flow as possible.
I studied the flow and function of the system and decided that my choice was to flip the Mixing Chamber upside down and then make things work from there.
Mixing Chamber:
Radiator Input:
Input from the rad was going to be dirt simple from the new position, with some scrap bits of pipe and hoses we put together a pretty simple "s" bend.
Small "Water By-Pass Hose" (as Mazda calls it) and it’s Fitting on the Mixing Chamber:
As you can see in the image above, the little By-Pass Fitting that gets some coolant from the Thermostat Housing was now facing almost directly at the Engine Block and would need to be rotated to allow us to attach the hose.
The metal pipe is just pressed into the aluminum Mixing Chamber and I was very tempted to try to pull it out and reinsert or just try to twist it. Then figured that I'd likely end up trashing the only one I had at the time so I went with what I thought was the highest probability of success, cut it and weld it back on.
Before cutting I put a small bead of weld around the pipe; this is easier than welding the open end of the pipe and it would give me more meat to weld back onto or worst case we could leave it like that to slide the hose over it and secure it with a clamp. That would just mean a slightly longer hose to make up the curve. Welding it back together went fine though, so back-up plan not required.
Of course as another back up it would be pretty easy to just tap the hole and insert a brass fitting.
Weld Bead Before Cutting Bead Ground Down and Pipe ready to be re-welded Final Orientation
Engine Coolant Return Pipe – (“By-Pass Pipe” as Mazda calls it):
The Miata has the warmed Rad Fluid exit the back of the Engine Block, pass through the Heater Core, and then forward to the Mixing Chamber...to....mix and return to the front of the engine (through the rad if required).
My choice at this point was to just get the thing running so in the interest of expediency we elected to simply bypass the heater core and run that line
right to the Mixing Chamber. Although Cabin Heat is currently not a big priority for me, hopefully before autumn 2016 I'll have more to add on the subject.
I priced out some cool stainless steel hoses that I could run above the Exhaust Manifold and down to the Mixing Chamber, but in the end I felt that running under the header like Mazda did would be better. I think it would stay cooler and keep the engine bay a little more tidy. Ended up just using some 1/2" copper house pipe with a few scrap hoses to connect stuff (more later).
Probably the most difficult task in this part of the build was figuring out how to get that By-Pass Pipe around to the front and have it go securely into the Mixing Chamber Assembly.
Originally both the Mixing Chamber and the metal By-Pass Pipe were solidly affixed to the engine so Mazda just used a metal pipe with an "o" ring fitting that pushed into the Mixing Chamber and that was adequate to seal it and hold it in place. Because we used only a small portion of that original pipe with a different routing I had to fabricate a bracket that would allow us to secure it tightly in position; I choose to secure it back onto the Mixing Chamber mounting bolts. Then once more, some scrap hose to join it to my copper house pipe.
Lastly, before I'd feel comfortable mounting a hose to that By-Pass Pipe I needed to put a "Hose Bead" on it. Just welded a bead at the end and ground it down a little smoother. Naturally I did something similar with the copper pipe; soldered a very small portion of a coupling onto it's end and ground it smooth as well.
Actually quite fun to do and fortunately another success story.
Fancy Copper Pipe:
This first image shows the small Thermostat By-Pass Fitting with Hose attached.
Also hopefully you can see the forward part of the copper pipe. It is attached in two places with almost identical simple Brackets, Rubber Insulation, and Hose Clamps. The forward Bracket is attached to an otherwise unused threaded hole in the Block.
This shows the aft part of the By-Pass Pipe.
The Bracket used to secure it to the Engine Mount has a nut tack welded to the back so I'm not flailing around with tiny bits.
Again, just some Rubber Insulation and a Hose Clamp.
The top aft part of the copper pipe.
For now this is my by-passing of the Heater Core. When I get around to it, that hose will run through a Valve and the Heater Core before joining that copper pipe taking coolant forward to the Mixing Chamber.
Heater Valve Concerns (in case you didn't read the last section):
While studying both cooling systems I noticed that the Miata does not shut off flow to the heater core, rather the heater box just shuts off airflow to the cabin. This might not sound important but it is very important.
The Miata relies on that coolant to circulate otherwise the only fluid going back to the rad or the forward part of the engine is the small amount that goes through the Idle Speed Control System. I believe that this would mean very poor coolant circulation especially toward the back of the engine.
Please go to my tab “Cooling System Differences” for more details.
Mounting the Radiator:
I couldn't find a way to get the Miata rad installed totally vertical under the bonnet, so I removed the factory brackets that were welded to the Spitfire frame and started bracing the rad in there and manipulating it to see if I could do it at a forward-leaning angle like the later Spitfires. This forward tilt did of course prove helpfull when we got to fitting the Air Intake System. Naturally the Gas Bonnet Struts I installed a few years back were a concern, but in the end everything just fit.
I managed to prop the rad in place enough to build my own triangular brackets out of angle iron. The set-up floats with the bottom of the Rad just above the frame rails.
To secure the Rad I had to make a near-vertical piece to provide something on which to mount it.
At the bottom attached to the Miata’s frame there were hooks that the rad slides down into and then it's secured at the top with bolts. I cut the hooks from the donor car and mounted them to some angle iron with some small bolts and nuts. After moving the pins and bushings on the rad from one side to the other it slid in nicely.
The image to the right shows the right side of the Radiator with the pin re-installed facing forward.
Also clearly visible is the Factory Rubber Bushing that fits nicely into the Hook.
Right Side Inboard
Next the bottom piece of angle iron was cut, notched out to go around some sheet metal, and drilled so that it could be attached to the lateral parts of the car’s forward frame members (the part that curves up slightly to hold the bumper). I drilled down through both the top and bottom of the box frame then enlarged the lower hole to accommodate a socket. This way I could really tighten those bolts without concern of squeezing the top and bottom of the frame together. Welding tubes in like I did for the Engine Mounts would certainly work here as well, but this didn't require the strength of an Engine Mount.
To put the bolt in from underneath I set it in the socket with the largest washer possible and slide it up to put a lock-washer and nut on the top. Of course should I drop that bolt and washer inside the frame, it would be very difficult to get it out... I think a tube might be worth it.
Left Underside
The last thing to do was complete the Triangle with a forward piece and add one more point of contact to secure the Brackets.
The geometry was such that forward vertical piece had a slight gap where it met the lower part of the triangle so rather than imparting a preload on any part of the structure, I simply tack welded 3 washers on that piece.
I originally was mucking about with loose washers, but when I tripped over the welder a better solution became obvious.
A couple more fasteners through the Spitfire vertical bracket and it turned out to be a super-solid frame. With the lower rubber bushings around the posts as well as the Factory Miata upper ones for the bolts, as seen in the image on the left, everything is working great.
The intent is to eventually weld one up in aluminum or even just trim and tidy this one up. But for now I'll just drive it! :)
Filling The System:
Tilting the rad forward did present one other issue; the rad filler cap was now lower than the top hose from the thermostat. Like this there would be no way to completely fill the system with coolant. I found a few remote filler caps for sale on-line, but the time and money seemed less than ideal. The guys at 77 Autoparts again sent me to the right place, the guys at Nitro Industrial Sales (8520 Jane St. Concord ON) were great and helped me assemble all the right pieces to weld up my own, all for about $7; great guys.
The Bits
Will post the new sizes when I get them.
G60405-0808 or 8BO-8MJ - Hydraulic Fitting, I think...... Male JIC 37 Flare to Female Braze-On
304C-08 or #8 JIC - Cap
LPM-20 - Hose Mender Plated - 1 1/4"
Before welding I just used my bench grinder with a wire wheel to remove the plating where applicable and the stuff was easy to weld together.
Also, in the past I've dealt with such metal pieces with very sharp barbs; I elected to grind them down a bit smoother. They easily hold the 13 PSI or whatever, but they also still come apart when I want them to.
I didn't want this thing too big so I opted for some small fittings that really look decent and fit nicely, however......
Topping off the last little bit of coolant in the system wasn't too bad through the small hole, but it was too small to get my hydrometer hose into! Pretty impractical so something else to redo a little later.
I just used some old Prelude rad hoses I had lying around for now to connect it all together.
I think that just about does it!