OK you should be OK I misunderstood. That should put all the air over the cylinders. I would not think the air over the SSIs would be significant in the short term but I dont know for a fact.

Back to what Grady said:

"Heat exchangers should always have
cooling air going through them. Only if replaced with headers
(no heat exchanger) can you block off the air supply from the
fan shroud.

Disconnecting the supply air from the heat exchanger causes
the exhaust to run too hot. This can start a fire. It also raises
the temperature of the catalytic converter possibly leading to
failure."

If this is the case then I am currently only cooling half of the engine.

With the exhaust running hot, woudn't that also heat the bottom of the engine?

You do not have a cat, so no issue there. The cool air flows over the top of the engine down thru the cylinders, then gets deflected by the "tin" up to the bottom of the cylinders, then out the bottom of the engine. I do not think over a short distance your exhaust temp is going to effect oil temps.

You have the "loop" cooler up front correct? Is that getting hot indicating that your thermostat in the fender is opening up? I've also seen (my brothers 77S) where the thermostat in the engine block was failing causing his oil temps to rise.

So 1) Make sure the thermostat in the pass side rear fender is opening and the oil is flowing to the "loop", should be hot. 2) Make sure the thermostat located on the top rear of the engine is operating correctly. He replaced his and eliminated his oil temps. IIRC it only goes in one way to avoid incorrect installation, but double check that.

Oh, feel free to call me if you want to discuss....

Tim,

I have the carrera style cooler with Elephant Racing finned oil lines (wide mouth). The lines get very hot so oil is flowing through them. I need to touch the cooler though to make sure it is flowing through the entire thing. Just b/c they get hot doesn't mean that they are getting full volume. The external thermostat could be opening partially ... sending some oil through but not enough to cool properly.

I did not check the internal thermostat because I used the one from the 80 engine and I used the temp sender from the 80 engine. I was getting the same readings on the 82 engine (old engine). The chances of BOTH internal thermostats being bad is not likely ... possible ... but not likely. Same goes for the temp sender.

I will test the gauge tonight but I am doubtful that this is the problem.

If it tests GOOD then I am going to change the dizzy and see what happens.

I appreciate the help. You are welcome to come over any time to take a look - we have chatted a lot but never met in person.

Back to what Grady said:

"Heat exchangers should always have
cooling air going through them. Only if replaced with headers
(no heat exchanger) can you block off the air supply from the
fan shroud.

Disconnecting the supply air from the heat exchanger causes
the exhaust to run too hot."

+100
That makes soooooooo much sense.
Why would anyone want to have the HE just acting as heat collectors on the hottest side of the engine and NOT have air flowing through them?

Please, use common sense.

My SS 3.2 with 9.8 : 1 CR has stock thermostats and a Carrera external oil cooler up front without fan and my temps barely leave the white area on the gauge.

You can see from my pictures that there is full air-flow over the cylinders as well as through both HE"s.
If you block one side, and only send air through the other side, the blocked side will not get as much air and again act as a heat accumulator and not as a heat exchanger.

Just think about it, it'll come to you. :)

Craig,

Ok, I'm officially confused. I think Tim and elombard had some good points, and you were correct in your assumption with the pic you posted...

1. you have SSIs with heat exchanges, ok fine... all that means is you have headers and a piece of metal over them... this is essentially no different than wrapping your headers with exhaust wrap. Hell, some people might even argue you're gaining power from that, although it's offset by the weight.

2. If you still have all of the fan shrouds and everything from your original motor, you have the blockoff plates, I know this because I installed them.

Based on that, I'm not sure why you are worried. The fan sucks are in from the engine compartment and grill and blows it over the cylinders via the air deflectors that you should have installed when you put everything back together.
Now, I would argue you definitely should have installed the seal over the engine tin to seperate the upper and lower portions of the motor, but with those blockoffs it's not like air is just randomly shooting out of the fan shroud. Wether or not you have the heat exchangers hooked up should make almost literally no difference whatsoever, besides if you had the heat turned off and no blower motor, it's not like they'd be moving large quantities of air through them. I'm not sure why everyone thinks this is a big deal, but like Tim said it shouldn't matter, and if anything the 3.0 should care less about it than the earlier motors.

I don't think this is your issue unless I'm missing something about how you have it setup and there's a gaping hole in your fan shroud or something?

If you really want you can always cut them off with a die grinder and tin snips... I've done it at least twice for Mike Lam's car, and on several others, but it's not going to make the car run maybe more than 3 degrees cooler if that. think about it, it is physically and thermodynamically impossible for a piece of metal on the bottom of the motor to affect airflow in a sealed environment above it.

Wow! :rolleyes:

Even without extra blower motor, the alternator fan blows large amounts of air through the HE's and is routed out of the flapper boxes when not wanted inside the cabin PROVIDED the HE's are hooked up as intended by Porsche.

Even without Grady's excellent statement about the function of HE's, this retired ME cannot believe some of the comments made here about air-cooling.

O.K. don't connect the HE's and watch the metal turn even more blue over time.

Tin snips to remove the tin on the SSI's?? :confused:

What next? :D :D

What Grady is saying totally makes sense...
Flow a little air through the exchangers to keep them from over heating.
The original set up still flows air even without the blower motor running, it (the heating blower assembly) just adds a bit of resistance to the flow.
If you didn't need the flow through them, Porsche wouldn't have bothered to put in the dump flaps to discharge the unwanted heat under the car.
The back date does allow some cooling air to be dumped, but it shouldn't rob you of cooling to the cylinders/heads due to the entire shroud being pressurized by the fan.
If you wanted to get really into this, you could measure the flow (temp) at the dump valves and choke back the flow to even out those temperatures.

what you guys don't seem to understand is that Craig (MCA) hasn't run heat exchangers for years. It's not like he just decided to not hook them back up. They're simply sitting there, and I don't believe it's possible to overheat SSIs... I've seen... seriously... 25-30 track cars all run that setup if they didn't feel like cutting the heat exchangers off, and not one of them was in any way detrimentally affected under severe track conditions, so it clearly wasn't affecting the engine's ability to cool... lol, and how could it, they have nothing to do with engine cooling.

As far as gunter being a former ME, I'm only an astrophysicist by schooling, but you're never going to convince me that those heat exchangers are in any way significantly disrupting engine cooling simply by being there let alone are raising opertating temperatures by nearly 100 degrees. That is not Craig's heat problem, and I don't see the point in convincing him to waste hours and hours of time on a fictional problem.

I appreciate the debate going on here. The only way to tell is to hook up the HEs and see what happens. Currently I only have the plate for the left side - has the hole in it so that I can run hose to HE.

When the high temps started happening on the 82 engine, it was after a tune-up and after installing the block off plate. Prior to this change, the engine never ran hot. Maybe it is coincidence ... maybe not. Deep inside I always suspected the block off plate as being a contributing factor to the increased temps. I have no degree or expertise in this area ... it was always a gut feeling I had.

Kevin and I checked out my temp guage today. It seems to be properly calibarated.

Our next step was to hook up Kevin's "numbered" gauge up to my car. Unfortunately it fried a bunch of instrument wires. Neither of us can really explain why this happened. Very puzzling indeed. All connections appeared to be correct. The only difference was the he had the ground on the pressure side of the gauge and I had the ground on the temp side of the gauge.

Regardless, I have to replace some wires.

Does anyone know the gauge for the instrument wires? 22? 18?

I went to Radioshack, Napa, and Lowe's with little luck getting answers. I took a piece of wire in to all three places. Two of them said I could use a lower gauge (14or 16 for example) and it wouldn't hurt anything. The lady at Napa said I can't do that b/c I will have to change fuses.

I am thoroughly confused and I despise wiring!

Could you post a picture of the wire with a known gauge to compare it with?
The fuse doesn't care what wire is behind it, just how much current is going through it.
Some of the old automotive wire had thick insulation on it so look at the size of the wire not the insulation.

I just went out to O'Reillys and got some 18 gauge wire. It should work ok. Anything lower gauge seems too big.

Tomorrow I am going to reinstall my heating components and see how it affects engine temps. This, of course, is contingent upon fixing the wiring.

FWIW, I am running my 2.7RS spec engine just like you are- fan shroud block off plates, no heater stuff, but my heat exchangers have had the heater part partially removed with a hammer and chisel (really) to cut down on the smoke from the oil leaks they catch.

My engine temperature is 180 Farenheit almost all the time. When it is real hot ambient and I am on the power aggressively, it holds about 190.

I have a front mounted auxiliary oil cooler, non-finned lines.

My car only weighs 2000 pounds, though, maybe that stresses it less?

You are not making me feel any better :).

Although I may not see any results by installing the heater hoses, at least I can rule it out as a possible culprit.

One thing at a time ... slow and steady until I figure this out.

Craig,

First of all, let's revist a few things. 1. I just thought about this and your heat issues didn't really start after installing the blockoff plate. I'm going over the list of things we had to fix on your car after we got it from Autometrics... forgetting the brakes, suspension, etc... your valves badly needed adjustment and the valve train wasn't even installed properly on the driver's side. Your fuelling was way off, and I seem to recall you had been running rich. We know the valve guides were about shot... there were issues there. But let's say all of these things might have contributed to seeing a higher operating temp than you had been used to.

For some reason I thought earlier in the post you were saying you were seeing higher temps than you were. Maybe I misread something where I saw the number 80 or 90 and thought you were 90 degrees too hot. You never hit the upper white mark, so you're below 120C/248F and you're above 90C/194F So for the sake of argument let's just agree you are, realistically, in the perfect operating zone. And this is the middle of summer in Charleston. Just keep this in mind... also, after we did all the work was when it started warming up too... I don't remember how it was running this past winter when you drove it, but....

What oil cooler are you running? I seem to remember you said you upgraded, but did you not? What oil cooler you are running will greatly affect your operating temps...

Also, I think I asked you this via e-mail and don't remember if you answered or not, what oil are you running? If it was my car I'd be running a relatively thin break in oil, and it'd be dino oil not synthetic until the motor was broken in... that will defintiely affect your oil temp in an oil cooled car. In a 964 Valvoline 20-50 racing vs. Mobil 1 15-50 is an 8 degree F difference.

So, 230's where I like to be on track, not on the highway, but honestly... dude with some oil coolers it's not unthinkable, especially if your motor is running a little hotter now due to compression increases, etc... To be honest without an upgraded oil cooler in the summer I'd probably expect to be seeing 220 easily in that car.

If you're still worried or overheating at idle, etc... then let's look at where the excess heat could be coming from:




Here's why I know this has nothing to do with your exhaust, and honestly, while I in no way doubt the work I/my shop did on your car, I feel I kind of need to defend myself as my shop did the work. When we installed the blockoff plate you had no heat exchangers on the car period, so airflow around a heat exhcanger should be the last thing you're thinking of.

You had the bottom half of a Dr. Pepper can bolted to the heat exchanger hose holes, and a blower motor and it's associated plastic hoses hooked up to nothing... the ones that were in one piece anyway.

Installing the blockoff and removing the blower tubing that was hooked up to nothing and blowing into a Dr. Pepper can in no way affected your engine's temperature. I promise you this. As Flieger said, there is nothing wrong with that setup. Even if there was you're talking about a jump in temp of like 50 degrees! That heat is NOT coming from whatever heat might be trapped and/or radiated by the heat exhangers. Your exhaust is not going to affect your oil temps to that degree.

Plus, let's say it did... at any speed over 15mph... the airflow around the exhaust is offsetting any increase in temperature from "heat shielding"

I don't know how many Subies I've built/tuned at this point. They have a giant intercooler under the hood scoop and directly under the intercooler is the freakin turbo, and a small heat shield around it (much like the heat exchangers in some ways)... I promise you that turbo is getting hotter than any part of your exhaust. if I drive at 60mph in a subie for 2 minutes pull over and pop the hood, the intercooler is ICE cold, and that doesn't even have tin cutting it off from the bottom of the IC! The intercooler is fed air from a scoop and directed via strakes and a seal into the intercooler core. This is the same as sealing off you fan shroud with the blockoffs! It is designed to aid cooling not impede it. It is physically and thermodynamically IMPOSSIBLE for the heat exchangers that have never been working on your car to raise your oil temperatures by 50+ degrees!, and anyone that says otherwise is flat out wrong. If you were talking 5 degrees I might go along.

You now have a completely different motor, a completely different exhaust, I'm assuming no Dr. Pepper cans, etc... and you're running "hot". First of all, you need to make sure the CIS is adjusted, I wouldn't look at anything before you do that. Then if you are tuned correctly my first though would be to look at the cooling system, although as I recal you replaced the oil cooler right? Your idea of the vacuum advance not working had merit... the car wouldn't knock, but it would't burn as well and ould run hotter without the advance... are the engine air defletors installed properly... I truly believe you are wasting time looking at your exhaust system which sounds like it is working perfectly.

There are only 3 things that can make your OIL temps too high. Remember this is an air and oil cooled motor.

1. the temps in your combustion chamber
As you don't know the mixture you are running or the timing this is entirely possible... I would verify those as they are easy to do.

2. a lack of oil cooling.
Okay, your oil lines are hot so you think it's flowing fair enough, is oil really circulating? Is the airflow to the cooler somehow impeded? Is the oil flowing to the cooler, but not going through it? Plus, I've seen this happen on 911s... the engine oil cooler could be clogged?

3. Your fan is not blowing on your cylinders...
this is impossible if it's spinning, you've got the fan shroud on and block offs! Absolutely ALL of your cooling air is being sucked through the fan and blown onto your motor, the only way this might not entirely be true is if you did not install or incorrectly installed the air deflectors/guides for the cylinders.

Those are the things you should be focusing on, not an exhaust that works on a thousand different 911s that are tracked around the country every month. You did the right thing and got the best exhaust setup for your car... lol, maybe a dual in/out Monte muffler would have been better, but you're not going to find a problem there. My advice is sit down think about everything I've brought up decide if you really think you have a problem, above all tune the car! Then decide if you need to really work on an overheating issue. But work on the heat issue, not an exhaust system that works.

Every little bit that helps in dissipating heat should be taken advantage of.

Sending air through correctly connected HE's can only help with cooling, especially when stuck in traffic or crawling along bumper to bumper.
At slow, or no speeds, headers don't provide real cooling but HE's will give you some provided they're hooked up.

Re-check correct installation of air baffles around the cylinders. (Page 151 in Wayne's book)

Also, if you're using a bra, the front oil cooler will get no air-flow.

Heat
 

I did not realize you had the same prob with your other engine. This is what I'd do to start eliminating possiblities -

1) Get air flowing thru the heat exchangers.

2) Test verify that the thermostat (pass rear fender) for the front oil cooler is opening all the way. Don't guess.

3) Test verify that the "block" thermostat is also opening all the way. I know you have two, and unlikely they are both bad, but you need to confirm to eliminate.

Unless you know 100% that the above are not an issue, we are all just guessing.

Tim

For the record so I don't have to repeat myself (Andy :)).

I have Elephant finned oil lines with a Carrera style external cooler - wide mouth connections and no fan.

My lines GET HOT so the external t-stat is in fact opening. Again, I should pull it and see how much it is opening in order to confirm that I am getting FULL flow.

I did not test the internal thermostat from the engine that I used for the rebuild. In retrospect, I absolutely should have done that. Last night I checked the internal thermostat from the 82 engine. It opened up as expected.

I got a hot flash for a second last night when I thought that I may have installed the internal thermostat incorrectly. However, I was able to look through my pictures and confirm that it is installed properly.

My engine mounted oil cooler has some seepage coming from the bottom of the cooler (VERY minor - maybe a drop would fall every week). Could just need to be snugged up.

Doesn't this indicate that the cooler is at least getting oil through it?

I am running Vavoline Racing oil 20/50.

My oil pressure is exceptional.

My fan has a few chipped blades but that should not make a huge difference on the magnitude about which we are speaking.

It is hot and humid here in Charleston, SC - 90+.

-------------------------

Next steps will be:

1) To get HEs hooked up. Confirm mixture and timing.

2) Swap out my dizzy and use the one from the engine that I rebuilt. Maybe it isn't advancing all of the way or something else is screwy. I have read that temps will increase at highway speeds if this is the case.

3) Pull the external t-stat and test.

4) Go on a murdering spree and drive my 911 off of a bridge with me inside.

Each step will be tested before moving on to the next step.

---------------

I appreciate the help from everyone. I will plug along!

Yes. Just make sure it's opening all the way. Same with the other one.

Mine never goes over the 194 mark on the highway with the AC on. If I turn the A/C off and open the windows and the S/R, this disrupts the air flow over the rear of the car and I then run just over the 194 mark.

Now if I slow down or hit traffic it then begins to rise, and will continue to do so until I get air flow again.

You should be running much cooler!!!!!

I kind of agree, but it is a tradeoff... for instance, on a 964 the engine tray quiets the car and verifiably improves aerodynamics above 140mph... is it worth the engine overheating? No. I just find it highly improbable that the heat exchangers are in any way raising the oil temps significantly... in fact, I firmly believe if Craig removes the blockoffs the engine cooling he looses to the HEs will probably just break even. I've never seen a disconnected HE cause an engine to overheat. especially when moving.