512 BBi engine rebuild expert question

Because the exhaust valves are inverted and heavily shrouded by the casting around the cam buckets. Oil cant run uphill. I dont put guide seals on the exhaust valves.

 

also there is no vacuum at the outlet valves

 

The SPCs indicate that they "learned" that they didn't need them (or got a little benefit from not having them) on the non-Lambda flat 12s, but reinstated them on the with Lambda flat 12s (that are less tolerant to having a little oil get into the exhaust stream):

365 GT4 BB (carb non-Lambda) = has them on the exhaust valves
512BB (carb non-Lambda) = has them
512BBi (K-Jet non-Lambda) = does not have them
early euro TR (K-Jet non-Lambda) = does not have them
US - CH - SA TR (KE-Jet with Lambda) = has them

 

Regardless of what they did then I would not run seals on the exhaust side because it doesn't cause visible smoke yet it provides some lubrication. Exhaust guide seals on a 2V flat 12 isnt doing the guides any favours due to how shrouded the guides are, they would have zero lubrication. It worked but there are better options and we know more now. The Testarossa is different, its very open around the exhaust valves so I wouldn't hesitate to put guide seals on one of them. A great example of what they thought was right back then buts crazy now is low compression pistons and 4 rings like a compressor.

 

Don't disagree -- they even thought it was a good idea on the TR design since they excluded them on the early euro version (but it must have mucked up the Lambda system and/or fouled the cats). Do you also exclude them when working on 365BB and 512BB heads?

 

No doubt it would increase HC numbers so they added them for us over here.

Correct, I avoid running seals on the boxers. Guide clearances are a standard thing regardless of the engine and the rule of thumb for any working clearance is tight equals failure. Running dry guides is just as bad as running something tight.

 

I can't understand the 4 ring pistons? Most engines have had only three rings for eons. Racing engines only have two! But they are rebuilt often.

 

The daytona's had a 3 ring piston. I don't see a reason for it in the V8's but I could see why they might in the 1970's on a flat engine only because maybe the technology wasn't there for proper oil control? If the V8 and flat 12 shared the same piston then for cost reasons it makes sense but they dont and its not just a slight machining difference V8 vs flat 12.

 

My RC30 has 2 ring pistons, suggested ring replacement interval is every 10,000kms or 4 races!