Reving but down on power

[rsrdave]

Just had a rocker replacement and new rings and my 993 freshly dyno-tuned (running PMO Carbs) .
While doing my last running in around the track I noticed when I put my right foot down i noticed the revs build but car seemed to lack power.
When i drove into the pits the car was back firing and at idle ,engine was high (1100rpm) .I checked the pipes and they were a nice grey color ,so don't think i did a piston or running rich .I didn't check to see if a plug had fowled .

Can anyone suggest what my engine problem could be ?

cheers Dave

[DSPTurtle]

Did you check your vacuum connections? Sounds like you may have lost a fitting.

[rsrdave]

thank you ,will check

[Dave Kost]

Check alternator output.

[Walt Fricke]

Yeah, sounds like a vacuum leak somewhere. The test is to spray some propane - take off the nozzle and slip on a piece of rubber tubing, so you can direct the gas to the places you suspect easily, while not letting too much raw propane loose.

The gaskets on the bottom and top of the manifolds are suspects with carbs. And vacuum connections, if you have them. Carbs can also leak air when the throttle shaft bushings are all worn, but it is usually thought that on a race motor not enough leaks in to matter.

As a matter of habit, it is good to start off checking things with a leakdown. Or a compression test. Or both. Goes along with pulling all six plugs to check that they look the same. That gives you more information as you sleuth. Does for those trying long distance diagnosis also.

Carbs might not be set up right as well. New PMOs, jetted and adjusted as they suggest for a 3.6 motor?

[rsrdave]

Hey Guys ,thank you all for your valuable input .I have car at dyno shop now so hoping to find out the problem soon .cheers Dave