Why Pull the Plenum ?
The LT5 has a lot of parts under the plenum. In the midle of the V towards the front is the cylinder case ventalation bafle. The 13 (from memory) bolts that hold the cover down are know to come undone over time. I knew mine had as I was getting a small amount of oil dripping from the V drain. I managed to get the required gaskets from Geoff on dyno day and finaly got round to doing the work the weekend before Le Mans.
To remove the vent cover, clean and then replace the gasket and torque down the bolts (with loctite this time) was what had to be done.
To remove the plenum was easier than expected, although I marked everything as I went as I didn't want any suprises when it came to putting it all back together. The list of work involved is below :
Drain some coolant
Remove air intake
remove plenum
remove A/Con compressor
remove coil packs
remove vacuum assembly
remove starter motor(for cleaning V drain)
Clean mess up
remove secondary linkages and vac pumps
remove vent cover
clean and re-assemble
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Upon putting back toether I checked the secondaries to find that those on the right hand bank had not been operating as they should. Each secondary butterfly vavle has a lever attached to it. Each lever is controlled by a rod linkage, moving all 4 valves on each bank together and by the same amount. I found that only 1 valve was working correctly on the right hand side. When all four secondary valves should be fully open, only one was and the other 3 were all in different stages of open. When all should have been shut, only one was and the others were again open be various amounts. I found the problem to be with the plastic levers that attach to the valve linkage. They use an elongated metal washer with a squared off hole to locate the lever. They had been over tightened enough to round the flat off and move the lever out of position by a few degrees. After what felt like hours I managed to repair each tab washer and got every thing working as it should......Always did run rich on the right hand side.
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