95Blackhawk

I have an issue with my LT in the RX7. Only when road racing in ambient temps above 80 or so, I get the coolant rising slowly to 220 F, as read on the head by a Cyberdyne gauge. The system has never gone above that because I have the car going into limp mode (AFR increases to 10.5 and timing is pulled 10* across the board) at that point and I also back off. Let's not get into a discussion of optimal place to run the temps. I don't want to run above 210 while racing. Also, all other issues have been looked at and corrected (aftermarket radiator, high air flow, air dam, EWP, water wetter, etc.).

If I were to modify the vents to flow more back to the radiator, would this help my problem? The AFR 190's I am using came without some head-to-block holes that stock heads have. This was supposedly for more strength but may be the cause of my issue. My stock headed Hawk never had this problem.

Thanks all,
Ben

Jditlfm

Did you try a 160 degree stat? I don't see how a bigger stem tube is going to help as its only meant to carry away the steam that forms in the head from reverse cooling. In a normal cooled engine the liquid coolant carries away this vapor and unless your having a excessive amount of vapor in the head forming which would cause drastic overheating i cant see it helping. You should also look into leaning that out 10.5 is awfully rich especially when running low timing that's a good way to take out a ring land. Also a lot of road racing guys prefer the stock water pump over a EWP for road racing as it flows more at higher rpms. Just a thought.

95Blackhawk

Yes 160 is in there but I understand enough to know that a 160 vs a 180 or 195 will not impact temperatures that creep up under heavy consistent loads. That is why I did not mention it.

I respect your opinion on the AFR but not here to discuss that. My intent was to explain that I am trying to do what I can to keep it from getting hotter. BTW, limp mode is AFR 11:1 in a stock PCM just at a much higher temperature.

Regarding the steam vent lines, when I have burped the system, you can see that when cold, coolant does come through the steam vent line (please note I understand this is open to the atmosphere at the time I am looking). So this must be a short circuit back to the radiator. My theory is to increase the flow of the short circuit and take away heat from the heads easier. So, is this theory and practical application sound?

Ben

mdacton

tap the back of the heads and put -6 lines to the front....

I don't think its going to make a huge difference though. What fans are you using? how much cfm do they pull?

95Blackhawk

Using the Taurus fan. 18" diameter supposedly able to pull upwards of 4500 CFM. Damn things take so many amps, I had to double up on my relays to get it to work

<Puck>

I am running thicker then normal steam vent lines and noticed no difference whatsoever in my temps. It just is not a problem spot on the lt1s cooling system.

95Blackhawk

Puck,

Thanks for that input. I would guess you wouldn't see a difference in temps if you are running the 1/4 or if you are going around town. Where I am wondering is in the arena of heavy consistent loading. Will making that tube bigger (hence more flow to radiator and not through the block) be beneficial?

Ben

<Puck>

I know that road racing is pretty much the worst torture to subject all parts of an engine, but I believe the back vent line is a lot more steam and air then actual fluid flow so I do not know if it would help in your case.

It is a cheap and easy mod to try out yourself and test though - I fabbed mine up with some high temp+high pressure "great white" thread sealant paste, some npt plumbling connectors, and high temp/high pressure hoses. Everything from home depot. It was maybe 2 years ago so I don't remember exactly but it was probably like 15 bucks...I know for sure everything together was under $20.

I did it becuase the factory vent tubes were not only on backorder but the dealer(and even online) wanted rediculous prices, so I just made my own and tried out a wider ID to see if it would maybe lower the load temps. I did not notice any difference but saved a bunch of cash, had a little fun tinkering, and learned a little bit

powerslide350

I had an EWP on my 94 Formula along with complete new cooling system (rad, hoses ect.) Everynow and then like we all do, I would take it out for a cruise and end up driving the wheels off it. Multiple long pulls on long counry roads. Anyhow, the engine temp would start to rise like you describe when otherwise it wouldnt move off of the 160* mark, even at the drag strip.

I also had a home made steam pipe made of 90* brass elbows at the back of the heads(tight fit!) with 3/8 hoses running to a "T" and then to the Radiator. I made this because I broke the original while disassymbling the engine, and didnt like the price of a new pipe+new banjo bolts+4 crush gaskets. AN would have been nice but it would have cost more than the OEM unit and increasing flow wasnt the objective.

I see your point though in conditions like road racing, every little bit helps.
You would also have to plumb the larger hose or fittings into the radiator. I bet you have an aluminum radiator too.

What im getting at is I went back to a mechanical WP and the temp gauge never left the 160* mark even on long "spirited" drives.

After a day or two of driving I didnt notice the slight decrease in power. Running at sustained high RPMs is just too much demand on cooling system for a EWP to handle IMO. I would consider ditching the EWP and give the mechanical a try befor yanking the heads to instal new fittings. If this is the problem, lets say you lose a few hp (6 or 7hp?) and slows your times, you still get to at least finish w/o overheating.

My bad for the long verse... Hope this helps.

95Blackhawk

I hear what you are saying on going back to mechanical. I cannot since I have a dual chain now. Taking that off and replacing would be more of a hassle than just "tinkering". Tinkering is my option because it is fun and not such a hassle.

Thanks for the input.

powerslide350

[QUOTE=95Blackhawk;5695763] Tinkering is my option because it is fun and not such a hassle.QUOTE]


Agreed.

Random idea.

I wounder how much material you could remove from the waterpump ports on the block and on the WP itself to increase flow efficiency. Or weather or not this is a restriction area.

The_Bishop

Your problem is the electrical water pump. They just do not flow enough to support sustained heavy loads. On my '94, driving home from work on the highway (Slight uphill grade for nearly the whole 50 miles) I was seeing 210+ temps, with a new 160 thermostat, radiator, completely flushed and bled cooling system when I was running an electric water pump.

It drove me crazy.

I swapped back to a stock pump. No other changes. Problem *gone*. Even after swapping to 4.10 gears, running at 3000+ RPM on the way home from work (yeah, I was speeding a bit...) the temp sits right around 160-165.

z275plus

I had the same problem with the EWP, went back to the stock water pump and my problem was solved.

95Blackhawk

OK, I hear what you are saying on going back mechanical. Here is the problem:

My 95 Hawk, I went with a CSR and road raced it. Same exact tracks and same conditions, also a 383. No problems. Temps never got past 200 when racing.

This is what makes me think I can solve the problem without going back to mechanical.

Any thoughts?

seawolf06

It seems like you are running a high CR with the rx7. What is the firehawk at? I'm not sure how you are with your tunes, but you may need to get it dyno tuned. That could be the difference between running the ewp on the firehawk and on the rx7.