1982 911 Euro SC performance issue

[911 Martini]

Steve,

I finally had the chance to get my 1982 911 E Stock car on the dyno on Friday. I knew I was down on power based on how badly I was getting pulled away from on the straights.

From a troubleshooting perspective I have:

* Checked leak down - worst cylinder was 3.8%
* Compression check was good on all cylinders
* Changed spark plugs
* Checked to make sure I was getting wide open throttle
* Checked relative injector flow - 5% delta highest versus lowest
* Injector spray pattern looks ok
* Checked CIS fuel pressure - 70 psi
* Checked warm operating fuel pressure 45 psi
* Cold fuel pressure 25 psi --- doesn't matter on warm operation
* Timing at 4500 rpm - was set at 36 deg BTDC on 98 oct race fuel - no knock issues

In the attached graph there are three dyno runs from three different cars. The blue line is my car, the orange line is from a car that had a loose head and wasn't achieving WOT, the third is from a mid-pack car with standard engine performance. I have adjusted the AFR and am now at 12.0 at WOT, I will be making additional adjustments to get it to 12.6 on my next run.

Can you give me some guidance on where to go from here?

Is it possible for the cam chain to jump a tooth and cause this type of problem?
Is there any history on cam wear that may lead to this type of performance lose?

911 3.0 Dyno runs.JPG

[Steve]

I would check your cam timing as well as review what exhaust system you have (makes a very big difference).

[911 Martini]

Steve,

I should have clarified that while I don't have a baseline dyno run I believe there has been a change in the performance. This car was a class leading car several years ago, but now mid-pack cars can pull +10 car lengths on the front straight at TWS (3300 ft straight).

The exhaust is an open system with race headers and a 2 into 1 stinger, there has been no change in the exhaust system.

I will check the cam timing next.

Thanks,

Tim