where are the horses?
My engine was dyno'd after it was professionally rebuilt, and it had 199 RWHP. This is what I expected, and was about 3 years ago.
This is a 1981 911 SC Euro, stock, other than headers and muffler.
Since then, I added Buckley Racing Headers, to replace the rusted European Racing headers it had. I was hoping for 205 to 210hp after the header swap.
I raced for a season (2013) with the new headers, but at the first race this season I could tell something wasn't right power wise.
In preparation for digging into this problem, I did a valve adjustment. Almost all were too tight for the feeler gauge which is somewhat interesting, I visually inspected the spark plugs, cap and rotor, and replaced the air filter.
I also did a leak down. Each cylinder has between 2% and 5% with the engine cold.
The timing was at 33 deg total advance after the rebuild. I use super unleaded (91 or 93 octane in these parts) so I set the timing down to 31 degrees BTDC at full advance. There are no vacuum hoses connected to the distributor or WUR.
Now for the amazing (SAE corrected) dyno numbers. My best run was 184 RWHP.
The air/fuel ratio was in the 14s and 15s at idle, was in the 13's until mid RPM range, then went down to the mid 12's for the last 2000 rpm. Each side of the exhaust showed the same A/F.
I tried several other timing settings - 33, 28 and back to 31. None improved the situation.
All of this looks to be as expected, other then the power. And, I don't have an idea as to what the problem could be.
A few other details. The dyno pulls resulted in 184, 175, 170 and 170 rwhp, in order, with timing of 31, 33, 28 and back to 31 BTDC. It seems like it got worse as we went and it seemed timing adjustments didn't make the changes we expected.
Any ideas as to what I might check next?
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