overheating after installing headers

[dberman]

I have an '85 911. The car has always ran relatively cool at the track, never getting over 230 degrees F. Over the winter I replaced the stock heat exchangers/exhaust with European headers and an M&K exhaust. I also removed the duct work for the heat and added a block off cover for the left side of the fan where the hose used to attach. I did a DE at the Glen this past weekend and during a 20 minute session the car was getting up to 250 F and I had to get off the track before it went higher.

Is it possible that the heat exchangers insulated the engine from the high exhaust temperatures previously and the higher temperatures are due to the addition of the headers? Or should I be looking for the cause elsewhere? Thanks for the help.

[fred cook]

Could be any of several things. The first that comes to mind is that your engine might be running lean since adding the headers. Also, you could wrap the headers with heat shield cloth to lower temps right under the engine. Changing the heater duct for a block off plate probably is not the cause. Good luck!

[Steve@Rennsport]

You'll need to run your car on a chassis dyno to be sure, but it sounds like its very lean. I've never seen any car that didn't go excessively lean after adding headers and a sport-type muffler so we always install a custom chip at the same time.

Do NOT wrap those mild-steel headers,....have them coated with a ceramic-metallic, heat barrier coating if you want them to contain heat and last a lot longer.

[uwanna]

With the HE shells wrapped around the stock exhaust you get some extra cooling. The cooling air from the fan is routed thru the heating ducts to the HEs at all times. If the
heat levers are in the off position, the air just passes thru the HEs to the outside.
I think the 3.2s on also have a thermostat on the breather hose plate that turns on the
heating fan when the engine gets hot, giving more cooling to the HEs.
Don't know if eliminating all the "heater stuff" is causing your problem, but it's food for thought!

[dberman]

Steve, thanks for the info. I did install a Steve Wong chip based on the headers and the sport exhaust. Is the dyno the first thing I should do before looking into anything else?

[Steve@Rennsport]

Originally Posted by dberman

Steve, thanks for the info. I did install a Steve Wong chip based on the headers and the sport exhaust. Is the dyno the first thing I should do before looking into anything else?

My pleasure! Did Steve make the chip for the headers, or the stock system? If not, I would give him a call and have him make the corrections for your current set up.

Then, you can go to the dyno to make sure the AFR's are safe.

[GaryR]

Originally Posted by Steve@Rennsport

My pleasure! Did Steve make the chip for the headers, or the stock system? If not, I would give him a call and have him make the corrections for your current set up.

Then, you can go to the dyno to make sure the AFR's are safe.

If Steve did burn that for the new headers, find out if there is a dyno in your area that Steve works with that will send him the data so he can make adjustments based on what the car is doing now (assuming it's not right). You may have to pay him additional for a custom chip as he might have to burn you another one if yours isn't spot on. Or maybe you will find out it's A-OK and look elsewhere!

[dberman]

The chip Steve Wong sent was the standard chip he makes for headers and a sport exhaust.

Sounds like I'll get the car dyno'ed and if it is lean, send Steve the dyno data and have a custom chip made. Hopefully that's the issue. If not I'll look elsewhere as you suggest.

Thanks again for the help.

[dberman]

I brought my car to a dyno and the A/F mixture is fine. So, the car isn't running lean. I believe the thermostats are working properly although I will have to pull them to be sure. There is certainly oil going to both coolers.

The block off plate actually is the same as it was last year. I shouldn't have mentioned this above. So, the only changes I made this year was the headers and muffler and the oil line reroute needed with this setup. Previously I had the stock heat exchanges along with a different sport muffler.

It has been suggested to me that the heat could just be from the engine producing more HP.

I'm going to the track next week so I've pulled the fog light and cut a hole in the back of the headlight bucket to get more air to the front oil cooler. I'm thinking of putting a block off plate under the cooler parallel to the ground so the air hitting the cooler can't escape underneath the chasis. Is this something commonly done?

[wayner]

In the Harley Vr1000 super bike racing days, the team found during wind tunnel test that the air path of least resistance was AROUND the rad rather than through it.

They solved it with a 1" lip along the edge of the rad. That's all it took to make the rad the easier path for the air. I think that example applies nicely

[toddu]

Originally Posted by dberman

I'm thinking of putting a block off plate under the cooler parallel to the ground so the air hitting the cooler can't escape underneath the chasis. Is this something commonly done?

Great idea, and easy to fab up with some aluminum sheet. I've done this with my 3.2SS (300hp) and with just a fender cooler I never get over 210. I don't have a before comparison however, but the air in my set up has 1 place to go.

Todd

Btw - my cooler is aftermarket and I believe a bit larger than stock.

[dberman]

I was at Limerock the past 2 days. I ran the first 2 sessions with the same setup as Watkins Glen except for the fog light removed. The car got hot - probably around 260 F. I then pulled the headlight out. As I mentioned above, I cut out a rectangular shaped hole about 5 inches by 3 inches in the headlight bucket. After that time, the car never got above 250 F. I estimate I probably got up to about 240 F and it was stable at that point. So, I'm pretty happy with that solution. I probably put that block off plate underneath the front cooler to see if that makes any difference.