Stanley

Looks like the tee connection might not work in the stock upper radiator hose - there's no straight section long enough to fit the tee. You could try it (on an old hose first) but it might tend to leak since you'd be clamping a curved section to the tee. The new silicon hoses have tighter radius curves - looks like a workable setup could be made from 2- 45 deg. angle hoses with the tee in the diagonal section. The 45 deg. silicon hoses are available online. I would go for black rather than the usual blue silicon. I've read both good and bad things about silicon radiator hoses. It will be a bit pricey: about $15 each for the angle hoses, $25 for the tee, $15 for a nice EPDM heater hose, plus clamps (special clamps recommended for silicon) and shipping. More with a valve or restrictor. As a possible alternative, there are hundreds of branched radiator hoses available for the newer cars - someone knowledgeable at the (independent store) parts counter might be able to find one that fits.

Depends on how it works and how it looks. You want a sports car or a GT car? Z can be either one, or both. The holes might be right for a WB gauge etc. or to have an ignition box inside where it's cooler.

That thing's out of there. Only took about an hour or so, would have been less if I hadn't unnecessarily removed the bottom of the box first. Found the leak - one of the heater hose connections at the valve was covered with corrosion. Don't know if the heater valve can be saved. The diamond pattern vinyl under the valve is all tan with the residue. The heater core looks strangely brand new, also the clamps. Maybe someone replaced the core and clamps and forgot to check it for leaks. Plenty of footroom now. A duct and holes in the firewall to plug, so I'll get some more shop towels. The AC unit looks ok except for cracked plastic on the bottom. Want to throw it in the dumpster but it might be worth money - anybody want to trade a Gilken OS head for it? Now I wish I hadn't cut off the hoses in the engine bay - or at least left enough to splice.

Excellent comment. Don't really get it, but having a good laugh anyway.

The AC? Should have known, there was a non-working compressor that was removed when I got the car. The non-working heater can stay, hope to fix it someday. Expect a few uncomfortable hours getting the AC box out. New AC would be nice, but only after some performance engine work is done, so way down the list, if ever. If it gets too hot I use a cool cushion, a 40 ounce ice tea, and open the window. Wonder if there's a cover available for that bunch of relays etc., on the right side?

Thank you, looks like my heater is different. I see a core, through the broken plastic, to the right and slightly below the blower. Doesn't look like what's in the Hayne's manual.

Radiator hose Tee fitting:V8 Chevrolet TPI & TBI, Radiator Hose Tees, Stealth Conversions

Googled "branched radiator hose" and this came up:branched coolant hose - Google Search

Tired of the heater, dripped coolant before I bypassed it, takes up all the foot room on the passenger side, looks crappy with all the broken plastic. Have a warm jacket and boots if it comes to that. Like having the fan, though - it helps defog the windshield in the winter, even without any heat. Can do?

Like it. The more frazzled it gets, the better it works.

I'd like to see a tech article on working the stock manifold. Looks easy enough but someone with the experience would have some helpful tips. I could do that while the real mechanic is overseeing the head work. I'm going for mid-range torque. Don't need to go 130 mph or keep it between 6000 to 7500 rpm. All the headers I've seen have the big primaries for racing. Unless I can find a header made for mid-range torque I might stay with the stock manifold.

Hard to believe it's vapor lock on a 70 F day. Mine only vapor locked once, it was 115 F in Blythe and overheating from other problems. Could be a number of things. A fan shroud helps in traffic. I removed the plastic vent connection (and shoved a shop rag in the vent) at the 3" diameter hole in the radiator support at the left side to get more cool air to the carbs. You could do that on both sides, but engine bay heat might not be the problem.

"It's a lot easier to reject heat through a radiator than it is a rubber hose." Good point. The thick heater hose insulates. The loop wouldn't be as bad if it were a metal pipe instead, the longer the better. The carb heater also takes hot water and runs it back to the intake (when the hot-off valve is missing) but it's metal so it sheds some heat. Running a hose from the head outlet to a fitting on the thermostat outlet, just in back of the radiator hose connection, doesn't sound too hard. If the outlet is too thin to tap in a fitting just braze or aluminum weld one on at an angle. A valve at the head outlet would take care of the warm-up problem - open for summer, closed for winter. More food for thought.

Fixed it, thank you. I was wrong about FSM. On my car, there's no thermostat in the heater tube, maybe the PO's mechanic removed it. Was going to get one someday, guess I won't now.

S30 coolant plumbing v2.pdfThe wrong way arrows were bugging me so I fixed them. Would have got it right first time if I'd looked at the engine manual. There's a small mistake in the manual where it says the carb heater provides consistent fuel temps at all times, but there's that hot-closed thermostat in the stock line. Also put small arrows in the heater in fig. 2, and removed the arrows for now in fig 5. My CAD looks like Custer's last stand with all those arrows scattered around. Is the coolant forced out (stock) of the head outlet by pressure in the engine from the water pump, or is it sucked out by negative pressure at the inlet? I'm guessing both. In the fig 5 setup it seems more likely that it flows from the T housing to the head "inlet" (reversing the stock flow) esp. when the thermostat is closed, but I don't know enough about the internal flow. I want it to flow to the radiator per Leon's suggested mod, but without doing the mod. I did a variation of fig 4 a few years back to my truck, after a July trip to Tucson: took a new heater core and mounted it in the loop, in the engine bay. It worked to reduce overheating - takes a slightly longer to warm up. One more thing, in that hybrid z thread it was stated that the external bypass helps the internal bypass to prevent water pump cavitation during high rev events during warmup. This could happen for a race car leaving the pits (or if your neighbor's waiting to street race as soon as you start up the car). I'm guessing this is a non-issue otherwise.

Thank you, I was pretty sure it wasn't 100 percent correct. All I know is from reading that thread and there are some varying opinions there. As I understand it, coolant stagnates at the back of the engine (compared to the front 3 or 4 cylinders) so anything that gets coolant from the back to the front helps. Regarding the arrows in the carb loop, I see how they would run the other way if the thermostat is closed, but what if it's open? Seems like the larger flow from the engine to the radiator would create a suction that would pull coolant from the smaller carb tube. But maybe not. Could there be a situation where the flow would slow down, stop, or even reverse? I also wasn't sure about the direction of flow in certain setups and conditions between the head and the water pump inlet.

S30 coolant plumbing.pdfHere's a pdf, some sketches to help me understand coolant flow with various setups, based on the hybrid Z thread John posted. That thread is about coolant flow, not heating the carbs, but it answered my question about John's setup. A lot of that thread is about high horsepower Z cars that are tracked - I left those setups out since they're over my head. Also I left out conditions where there's heater with a closed valve and a carb heating tube with a closed thermostat (in the tube) since not much happens. Fig. 1:Stock setup, heater on. Improves circulation at cold start (see that 24p thread for why it's important, esp for racing) and helps cool rear cylinders. Fig. 2. Stock, heater closed. Same as plugging outlet D and branch of tee F. Fig. 3. Heater hose looped, carb heater tube remains. What I've got now. This setup gets bad press because it sends hot coolant from the head back to the intake, but it helps cold start circulation and helps equalize engine temps. Fig. 4. Heater hose looped, carb heater tube gone. Helps equalize temp and improves cold start circulation. Proven to raise coolant temp, but maybe because more is circulated at rear of engine. Fig 5. John Coffey's setup if I'm correct. This is what I want to do with mine. Improves circulation at cold start and helps equalize engine temp.

Wow, 24 pages on the cooling system. Back to school. Don't think I'll do any mods like that to the head, I'm already running cool enough for Pike's Peak (the drive, not the race). Just need to dump the goner water tube in a functional and "cool" looking way.

Does running the bypass line provide better coolant flow than just plugging it? How did you run the line, under the intake manifold or behind the balance tube? Looks like you could do that with heater hose, although steel braided would look way better and be less likely to leak. Took a better look, it's leaking behind the nut, maybe evidence of some previous leaks between the nut and the tube at both ends. Also a leak at the back or the rear intake where the short hose it attached. Basically leaking all over the place. Guess I'm over having it there. Maybe I'm over having the heater, too, but I like the defroster. Wonder if the aluminum tee (that bolts to the right rear of the engine) it thick enough to tap some threads into. Looks sort of thin.

Off topic but since it was mentioned, I was wondering, what's wrong with silicon bronze valve seats? Not arguing, just want to learn something. Silicon bronze is tough material with a coefficient of expansion closer to aluminum than steel is. Have heard of performance engines using silicon bronze seats and guides.

Hi Bruce. Don't know, I'll get a look tomorrow with the magnifying glass.

Doubt if the water tube is available - Z therapy might possibly sell me one though. ZT website implies I don't need it which may well be correct. No stop leak in my new radiator. Possibly JB weld on the leak as a temporary fix. Before I start messing with it I'd like to assemble the hardware I'll need to plug the water system just in case - the Z's my daily driver and I expect to need the car this weekend. Wonder what size plug would fit the opening on the thermostat housing, maybe 1/4" BSPT? And what to plug the other side by the heater hose, maybe braze the unused end of the fitting? It only seems to leak when the engine's cold. BTW, it's a E46 not a E36.

73 Z with SU's. The water tube that goes between the front and rear E-36 intakes has a leak where it meets the rear manifold. There are hex nuts at each end of the tube. Don't know much about it so don't want to mess it up worse. Want to keep using the water tube. It's a small leak but I want to fix it before it gets worse. Temporary and/or permanent fix?

MSA Aluminum 3-row, and Nissan 180 thermostat, in my 240z. Stays right in the middle (180), even up the mountain on a hot day. Also using oil cooler. Sometimes goes up to about 190 after going 80 - 90 mph for an hour and then hitting a long 10 mph parking lot on the freeway. I wanted the 160 thermo, but the guy at Nissan parts counter talked me into 180, thanks for that.

And one does not simply tune SU's, I guess. Easy enough if you just want driveability, but it's taken me some doing, to get max performance without fouling the plugs. Using the IR did help me. Took the dead IR back to H.F. and they gave me a new one. Took a bunch of measurements and saw the front end (closer to the fan) was consistantly running hotter on both sides. Reset the mix, advance the distributor a little and took a ride. It's revving much better now (but I still think it's on the lean side, even at 3 1/4 turns down, the mileage is too good). Way cheaper than a WB or EGT's. Won't give a quick exact answer, but what would? It might help to take a lot of measurements and graph the results. Also thinking about putting a fuel pressure gauge. The Ztherapy video says F.P. affects the mix - more F.P. =richer. Makes sense to me. So many variables in a simple system. Drive, adjust, repeat is also the only thing that works for me in setting the timing. Lazeum, my Dad says the same thing, word for word.