Valve Clearance Question: .009 to .011 for exhaust only?

[el-saturn]

BMW we once had the honor to make parts for the F1 1500cc turbo engines - at first it was bmw and later megatron. i'd say THAT engine was MUCH better than the renault - we made the carbon fiber plenums: they COULD explode!! .... so we added more fibers!! sandy those 2002 engines were fantastic and simple! (i don't mean the turbos) and bavarians are the best type of germans!!

[2cams70]

I know the standard ford crossflows had exhaust valves that were two piece construction - i.e stainless head friction welded to a carbon steel stem. This was done because carbon steel is a better bearing surface for a valve guide than stainless steel hence it's preferred where durability is a design aim (durability in the sense of the valve guide having a long life as opposed to the head separating from the stem!)

Maybe Lotus started with two piece and then went to a single piece stainless design for cost or durability (in the sense of the valve head staying attached to the stem!) reasons.

I checked the old exhaust valves out of my 1970 engine and they are one piece stainless (as checked by magnet). They look original but don't know for sure.

I checked some data and I see that stainless does have a higher thermal expansion rate than carbon steel so this fits with the theory but it's just a theory with no hard evidence

It's a bit disappointing to see that Rob the original poster of the topic question has ghosted us on this forum. Not a word of thanks despite all the effort people have made to help and offer advice about his question.

Fair enough some of us had a bit of a dig at his BMW illness but that's ok because we aren't all perfect and he should have been able to take on board a bit of harmless banter especially given this is a Lotus forum.

[vincereynard]

BMW we once had the honor to make parts for the F1 1500cc turbo engines - at first it was bmw and later megatron. i'd say THAT engine was MUCH better than the renault - we made the carbon fiber plenums: they COULD explode!! .... so we added more fibers!! sandy those 2002 engines were fantastic and simple! (i don't mean the turbos) and bavarians are the best type of germans!!

I read that the best blocks for the F1 turbo were old, "well seasoned" blocks that has many hot /cold cycles to relieve them of stress. New blocks were more fragile.

1500cc / 1400bhp (maybe) = amazing

[2cams70]

1500cc / 1400bhp (maybe) = amazing

Top fuel engines are even more amazing 8,000cc / 10,000HP

Personally though I don't like forced induction engines as it takes more smarts to get high HP out of a NA engine plus they sound better!

[alan.barker]

Years ago when i was at the Goodwood Circuit with Club Lotus someone had an Elan with a Turbo fitted.
This was maybe 35 + ago and i don't remember who the owner was. Maybe the Elan was a dark colour brg or something. He was a bit worried about all the heat the Turbo was making near the grp.
Alan