z-ya Posted April 17, 2013 Author Share Posted April 17, 2013 On my motor it was blowing bubbles into the cooling system. After a few laps it started getting hot, and the overflow tank was overflowing. There was still pressure in the system by the time I go to the paddock, but the radiator was about 1/2 air. I am also using the AZ radiator with ducting. Quote Link to comment Share on other sites More sharing options...
Bob_H Posted May 8, 2013 Share Posted May 8, 2013 (edited) We have done all the air flow tricks including sealing gaps, ducting, going with a smaller oil cooler (sits in front of radiator). We had a fan on it, but we removed it thinking that it was blocking flow. We also have your fiberglass hood tilted in the rear about 1" to let air out of engine compartment. The radiator is a new Arizona Z unit (Griffin), which is much larger than the Datsun competition one we were running before. The behavior is the same with either radiator. ... Pete This is from a much earlier part of the thread - but it stood out to me - the fiberglass hood tilted up 1" at the rear - my understanding has always been the high pressure at the base of the windshield will push air INTO the engine bay, not help evacuate hot air OUT. How was it working for you? You obviously found the issue to be the head - but I was wondering about this particular comment. You and I have a very similar power engine. Mine is now sitting for about 2 years before it will see the track again - and I intend to do the head mods,(I can tap into it unlike you, not historically valuable other than it was a Sunbelt modified head). This has been a thread I have watched closely and I appreciate your sharing the troubleshooting and eventual,(hopeful), solution. Bobby Edited May 8, 2013 by Bob_H Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 9, 2013 Author Share Posted May 9, 2013 The solution so far has been a new head build using the BSR head as a guide from a porting perspective. We didn't go crazy with long valves, tall springs, machined spring seats, and shimmed towers. It is an E31 with the BSR porting, N42 valves, performance springs, and a Norris 490/280 cam. The head was only lightly resurfaced. So the compression ratio is probably around 11.5 - 12:1. Before we were closer to 13.5:1. So far no issues, but we really need to wait for warmer weather to be sure. Still goes like hell. I don't know for sure if tilting the hood is good or bad for getting hot air out of the engine compartment. A freind who worked on the BSR team in the 70s suggested it at a vintage event. Heck, we were willing to try anytihing at that point, and it was easy to do. Quote Link to comment Share on other sites More sharing options...
bigbreak_2000 Posted December 14, 2013 Share Posted December 14, 2013 What could be potential negative impacts if I run the LD28 waterpump? I got hold a brand new Aisin pump and getting ready to install it, but now not certain if there are other impacts I may need to compensate for. For ex. is it going to cause gasket leaks over time, would it also be a strongly recommended to upgrade the lower radiator hose to the style that has the inner spring to prevent hose collapse at higher rpms? I bought the pump because I liked the idea of extra insurance against knock and overheating related issues but now not sure installing the pump is worth the effort and money installing it in my scenario. Once you go through the effort to modify the front cover to fit this pump there is no return to using the stock L28 petrol engine pump (more freely available). This question pertains to my 3.2 stroker motor, using a stock 280zx cooling system (radiator, rubber hoses, 50/50 blend water/coolant, no mods to water passages). Only mods I have is a 160 degree F t-stat, replaced the fan clutch and took shroud off in lieu of a large electric fan (set to turn on if I remember correctly at 170 degrees F). Most time the motor turn between 3000 and 5000 rpms but occasionally 6500rpms. I don't run it over 7000 rpms and never constant (for longer durations) over 6000rpms. The next owner might, but I don't (not for now). In the humid summer days and at stop lights I would see the water temp go as high as 81 degrees C (178 F), and it appears the ave operating temperate of the motor is around 76/77 degrees C (170 F, or just below the point where the fan turns on). Quote Link to comment Share on other sites More sharing options...
Xnke Posted December 14, 2013 Share Posted December 14, 2013 You seem to have adequete cooling for your needs. 178F water temps are just fine. Quote Link to comment Share on other sites More sharing options...
Bob_H Posted January 4, 2014 Share Posted January 4, 2014 Worst case - it doesn't work for you, buy a used replacement front cover and put a stock pump back on. I promise you will find a buyer for the old setup here. I agree - unless you are on the track,(road course), you shouldn't see any issues with the stock pump despite your power. That being said, on my motor,(260 rwhp), on a full throttle run from 3rd through 5th, at the top of 4th shifting into 5th, the temp just starts to rise on the gauge,(still the stock 240z gauge), and I would say it rises about 10-15 deg,(rough WAG), imm. comes back to normal in about 30 seconds after letting off. So unless you are on the track, you should be fine. Quote Link to comment Share on other sites More sharing options...
z-ya Posted January 4, 2014 Author Share Posted January 4, 2014 (edited) We are running a stock OEM pump now. No issues. Block must of had a crack in it that started to open up once the engine got past 180F. I've run stock pumps on my turbo car an never had cooling issues on the track. IMO the diesel pump is only needed for extreme racing applications. The stock OEM L28 pump moves plenty of fluid for most all applications. Edited January 4, 2014 by z-ya Quote Link to comment Share on other sites More sharing options...
duragg Posted May 23, 2014 Share Posted May 23, 2014 I'm still deep in this battle. Was on the verge of too hot with the race motor, then when it blew up and running the mild-motor in 100f temps I would get up to 220f water and have to back off to hold 210f. Now the race motor is back in. I have removed the oil cooler which lived in front of the radiator. Mounting dual Tru-Cool L7B coolers in front of the wheel wells fed by ducts. Radiator is all shrouded in and has full access to airflow. I had a 180f "high flow" therostat in and did some testing with it. In about 210f water it opens up to about a .2" gap and math says that is something like a .86 square inch hole. Some friends said to run a 5/8 restrictor which is only a .3 square inch hole. Some websites say get the max flow possible. Hoping the relocated oil coolers will improve airflow enough so that I can run the car properly. Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 29, 2014 Author Share Posted May 29, 2014 We went to the L7B because it was smaller than the aircraft cooler we had in there. We also shrouded the radiator, and lifted the back of the hood an inch or so. Check for combustion gases in the coolant. Also check for air in the system. I added a separate surge tank to bleed any air from the top of the thermostat housing. I think we are running a 3/4" restrictor in there now with the L24. No cooling issues, but then it is a different block, and at least 1.5 points less CR. The problem with my motor I believe was a crack somewhere in a cylinder wall that opened up when the engine hit around 190F. Then it just pumped combustion gases into the coolant. I have not tried to find the crack, but the block is the only thing I didn't change, and the same head I ran on the L28 has no issues on the L24. Pete Quote Link to comment Share on other sites More sharing options...
duragg Posted June 1, 2014 Share Posted June 1, 2014 After removing the oil cooler from the front of the radiator and relocating it with dedicated airflow the temps are now perfect. It was 100f today in Phoenix, ran 3 Time Trial sessions with a new 3L Rebello motor and a high flow t-stat (180). Water temps stabilized around 195. Oil temps around 235. Hope this thread helps others down the road. Tj Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 1, 2014 Share Posted June 1, 2014 Just a note from the dyno test sessions JeffP and I were doing on the engine dyno. We were running 5 minute pulls at 475HP level. Our goal was to see what the oil temperature did. We, as well as the dyno operator were amazed that without the oil cooler, the temperature rose linearly, and stabilized relatively early in the pull, never really getting any higher than 240F in the sump at the sensing point of the Nissan Comp Oil Pan. From those pulls, Jeff decided an Oilstat was in order. If you get the cooling flow to the head correct, it really helps stabilise the oil temps, FWIW Quote Link to comment Share on other sites More sharing options...
duragg Posted June 1, 2014 Share Posted June 1, 2014 This "cooling flow to the head" concept still eludes me. I have searched and not certain what I am looking for. I have a plain cooling system with the heater core lines capped and no fancy returns or bypass stuff. What am I missing? Quote Link to comment Share on other sites More sharing options...
johnc Posted June 2, 2014 Share Posted June 2, 2014 An extreme simplification: the coolant has to flow from the right side of the head to the left and then forward to the thermostat housing. The coolant flow around the back three cylinders tends to stagnate because it has to flow past the front three cylinders to get out of the head. By drilling holes in left side of the head at the coolant galleries you can pull the coolant directly out of the back three cylinders and route it externally forward to the thermostat housing (or the radiator). This eliminates the stagnation in the back three cylinders and also increases the flow in the front three. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 2, 2014 Author Share Posted June 2, 2014 (edited) This "cooling flow to the head" concept still eludes me. I have searched and not certain what I am looking for. I have a plain cooling system with the heater core lines capped and no fancy returns or bypass stuff. What am I missing? Nothing. You should not have any issues with cooling with your setup. It is the same setup they have been running on racing Z cars since the 70s. If you want to over engineer it, then look at this thread: http://forums.hybridz.org/topic/59029-head-cooling-on-cylinder-5-solutions/ We ran the 240Z and 1200 this weekend at a COMSCC time trial. The 240Z had zero cooling issues with ambient temps approaching 80F. It was the first time I've had the 1200 on the track. Here are some track videos (sorry about the vibration, I need a better phone mount) http://trackattackapp.com/?raceid=9bd0f97c-1aff-41ab-9ea9-e45c79ce7340&lapid=2ce4ad56-4a54-4a52-8198-4a4279c48c43 Edited June 2, 2014 by z-ya Quote Link to comment Share on other sites More sharing options...
duragg Posted June 3, 2014 Share Posted June 3, 2014 (edited) Oh.. is it video time?? Here is me with my new radiator setup on a 100f+ day with 30 heat cycle R6 275/35-15s haha Water stayed below 200f. Motor was popping above 5000 so I had no power. http://youtu.be/4g6i19dIg6k Thought I had the save, but got the marbles. Edited June 3, 2014 by duragg Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 5, 2014 Share Posted June 5, 2014 (edited) I would disagree that the head mods are 'over-engineering' --- it might be with low specific output engines (under 300HP), but over 300HP output, even Nissan changed the way the head flowed water. If you're running in 80F with tarmac (cooling airflow) temperatures under 110F, that's a totally different environment and cooling requirement than the desert southwest and 80F with tarmac temperatures of 160F+. Remember what was done in the USA to racing vehicles was the result of private teams and budgets not equivalent to works racers doing the job for Nissan Directly. Both the LY Head, and the FIA Head have significantly different flow patterns (the FIA head, like John Coffey says, is Up, Over to the Left, and out, while the LY Head reverses that flow coming out the Intake side on the Right...carrying exhaust heat to the 'cold' side of the head.)--arguably they can be said to bring water 'from the bottom to the top and out' rather than try to move it forward from the back of the engine inside the head. I cited the examples of the 5-minute pulls and stable oil temperature (without an oil cooler) as an example of what the benefits of proper cooling flow to the head can accomplish without adding significant weight and complexity to the oil system. Ask any expert if you "need" an oil cooler on an L-Series making 475HP... What if the oil temperature stays stable and below 230 no matter what you do? If someone sees his temperature rise, and then go back down during short spurts of activity...that technically I suppose means the cooling system is sized 'correctly' -- or one could say 'marginally' as well. Seeing elevate quickly and then remain at steady temperatures for extended pulls means the system has reached eqilibrium. It would take less than a minute to reach the max temp on the pulls, then it stayed there. There was 'reserve'. The one thing the Electramotive people steered us toward no matter what we asked about and thought our problems were was "we never had a DNF for a cooling problem", and as we worked on the cooling, it seems all the other problems took care of themselves. Over-engineering? I don't agree. "Big Picture Engineering" might be more like it. Again, over 300HP. All it does on anything below that is 'give margin' IMO, which is a good thing. Edited June 5, 2014 by Tony D Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 7, 2014 Author Share Posted June 7, 2014 (edited) Thought you guys might like my cute little 1200 . It's only making power from 6k to 8k at this point. Carbs need tuning. The smart phone doesn't like the solid mounted motor. Need a better camera mount. I agree Tony, over lets say 400HP, I would agree. Especially if it will see track time. For the street, it is probably not needed. Edited June 7, 2014 by z-ya Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 7, 2014 Share Posted June 7, 2014 Again, caveat being WHERE the street might be! Climbing the Baker Grade into Vegas at 85 ambient, with 160-170 thermal layer on the radiator cooling airflow level is a lot more strenuous than running up the local Hillclimb at 85 with a 90F radiator cooling airflow. I've had people tell me there is NO WAY my breather melted off my R180, too. Running stock engine...it was 120F into Phoenix in June and I was climbing the grade to Chirraco Summit at 85 mph... No, you don't need a differential cooler for street use. But when th even MELTS OFF, it might .... Maybe.... Be suitable to street use! When I went to TI Zedaway in 2001, those jaunts were 16-18 hours daily, doing 85+ (maybe triple digits for hours on end but that would be illegal, and I'd never do anything like that...) stop for 20 minutes to fuel up, then back at it. Outside endurance racing, I don't know many places you will do that. And it's my "street reality"... Once I got to the aerosol-covered grey sky Mideast and East Coast...everything ran cooler. But in the desert southwest, even on a "street car"... "Margin in the cooling system is a good thing"! Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 8, 2014 Author Share Posted June 8, 2014 I've never had an issue on the track or street (and anywhere in between) with my 300WHP turbo car. Not endurance races, just 30 minute sessions. Stock long block and cheap aftermarket replacement radiator. Still had the heater core connected as well. I've run many track events with this car with ambient temps over 85F and never had the coolant temps go over 200F. The oil temps got a bit too high (280F). So are you saying that 85F in the desert is hotter than 85F in New Hampshire? When I get to the point where I can't keep it cool, I'll consider that mod, but until then, I'll just keep running what is working. Quote Link to comment Share on other sites More sharing options...
Xnke Posted June 8, 2014 Share Posted June 8, 2014 Yes, that's what he is saying. The air temp a foot or two over the asphalt is much hotter than 85F when you get out in the desert... Quote Link to comment Share on other sites More sharing options...
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