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I haven’t been here for a long time, so many of you will not know me. I have had a few issues to sort out and cars hard to take a back burner. They still are not the priority since surviving financially in a coronavirus world is a challenge for me given the area we are involved in. However my wife’s car needed it’s engine rebuilt as that had never been touched and you are probably aware old head gaskets are like hand grenades with loose pins. So it’s a 928S with the 4.7liter engine but we in Australia got the low comp pistons. So I changed them out and now have the high compression euro versions. We decked the block 10 thou and the heads were decked 11 thou. So compression should be good.
Prior to getting an 11 thou decking. New angles on the valve seats.
Notice the back cut on the valve
Checking the shrouding situation. Ready to test. Polished used valve springs Parts checked, valve stems have very minor wear. That wear was generally 3/10th of a thou to a max of 4/10ths. New guides fitted and honed to suit that wear. This was a more highly optimized port in a different engine
Last edited by slate blue; 07-11-2022 at 03:46 AM.
Nice to see you again. Polishing of valve springs is not for everyone unless you have access to a polishing machine that you have. Can not see that it is absolutely necessary even if it looks good.
Seems to be a heavy duty device for opening of the valve during the flow test. A specially made plug instead of the spark plug.
Åke
Åke, the polishing was certainly not necessary but they needed cleaning up for various reasons. We have had an extreme amount of moisture here and the springs had to be cleaned of residues also. I cleaned up two sets and Peter picked the best ones. The better description of the polishing is Superfinishing.
Super finished tappets and springs
Last edited by slate blue; 07-11-2022 at 06:49 AM.
I was just asked via PM about corrosion in this engine. I haven’t got photos of the block after it was cleaned up on me just now, here are the valves and heads prior to clean up showing it was basically corrosion free. Cleaning off almost 40 years of build up. Pretty much corrosion free The block after head removal
The superfinishing really makes it nice. The clinder heads look like new. You told me once that you guys in Australia have more problems with corrosion than we have here in the cold north. Remember the humidity and corrosion in Florida, probably the same conditions in Australia where you live.
I really do not understand why Porsche delivered the 928 with low compression pistons to Australia.
Åke
Hey Fred, just fixed the inbox. The engine had never been apart. I still have the head gaskets. Not sure about the studs. Every single stud and dowel was removed from this block and threads were cleaned. The studs basically need to be removed to deck the block accurately as the block then sits on a plate and the back of the block against a stop. This allows very accurate set up.
The superfinishing really makes it nice. The clinder heads look like new. You told me once that you guys in Australia have more problems with corrosion than we have here in the cold north. Remember the humidity and corrosion in Florida, probably the same conditions in Australia where you live.
I really do not understand why Porsche delivered the 928 with low compression pistons to Australia.
Åke
So in 1986 Australia switched to unleaded petrol for new cars. The manufacturers were worried about our fuel quality. At that time I was working in a petrol station. We had standard, super and unleaded. If you had a new car you got unleaded. The nozzle of the super pump would not fit into the new unleaded vehicles. Plus it would damage the cat.
Hey Fred, just fixed the inbox. The engine had never been apart. I still have the head gaskets. Not sure about the studs. Every single stud and dowel was removed from this block and threads were cleaned. The studs basically need to be removed to deck the block accurately as the block then sits on a plate and the back of the block against a stop. This allows very accurate set up.
Greg,
If you have a photo of the head side of the gaskets that would be of interest.
Your example is of particular interest in that we rarely see original examples with so little damage these days- whether or not there is anything to be learnt remains to be seen.
So in 1986 Australia switched to unleaded petrol for new cars. The manufacturers were worried about our fuel quality. At that time I was working in a petrol station. We had standard, super and unleaded. If you had a new car you got unleaded. The nozzle of the super pump would not fit into the new unleaded vehicles. Plus it would damage the cat.
Greg,
They did the same over here, introduced unleaded fuel, but our cars still have the high compression pistons. The nozzle was also changed to fit into the smaller fuel filler pipe on cars with catalytic converters. As you know, I have removed the catalytic converters on all our cars. Also the reduction in the fuel filler pipe. The only one of our cars with catalytic converters is the BMW Alpina with V8 engine. However, I always drive it without the catalytic converters which are only fitted for the annual safety and smog test.
Åke
07-11-2022, 03:40 AM
Reconditioning 2V heads with little tweaks
