The Lotus Grand Tourers

Excellent work as usual Pete. I'm lining my jobs up for when you finish

Yes - hardly anything left to do now!!

Pete

Great work. Like the trunnion mod. Very neat.
What's next on the todo list then?
Tony

MetBlue wrote: Mon Apr 27, 2020 19:09What's next on the to do list then?

Probably finish off all the brackets/column etc for the electric power steering.

Pete

Now the body is on I thought I'd spend some time on the new engine block I bought a couple of years ago for this project. It's a brand new block in a Lotus box but was obviously one of the blocks that should have gone back for re-machining for +0.015" over-size main bearings. The seller would not have known. The problem with it is that two of the main bearing bores are over 0.0015" out-of-round - factory limit is supposed to be 0.0005" out-of-round (although of the blocks I've measured to date I can't see any of them being this good!), and the other bores were far from perfect. I'd got four choices - sell it on, get it line-bored to original spec, get it line-bored for over-sized bearings (these are readily available again) or try to fix it myself. Obviously I'm going to do it the hard way!

I had a tool maker in Sheffield make me up a hardened and ground tool to exactly the smallest main bearing bore size (there is a tiny range that is acceptable) to fit my horizontal milling machine arbor. I used this as a hone with some 10 micron diamond lapping paste to slowly hone the bores round, or at least rounder.

This shows a light shining through the gap below the honing tool



This is the tool: The spacers on the arbor allow the honing block to be placed over each bearing. The pilot at the far end keeps the tool in line (pilot needed at both ends when honing the centre bearings)





It's worked!

What I couldn't predict was whether the bores would all line up, so it was a bit of a gamble, but after two days of slowly honing the block and girdle all the bores are rounder, give the correct clearance, and line up! The crank rotates beautifully smoothly.

Delighted with the result (and saved about £700).

Pete

Nice work. Very creative thinking.
Must be nice to have the machine tools at you disposal. Very envious.

Tony

Pete Boole wrote: Sat May 02, 2020 18:20 ...over-sized bearings (these are readily available again)...
Pete

I wish they were 3 years ago, could have saved me a LOT of grief!!

Very elegant solution Pete, nicely done.

Thanks guys . I thought about your plight Richard when I was researching what to do! The +0.015" bearings are expensive, but at least they are available now.

Pete

Pete, while you are working the block, may I suggest you check the water pump housing for good coolant flow.
In my Elite block I had serious flow restriction from casting burrs, a little work gave at least 30% more flow and solved
excessive coolant temperatures.
You probably have already done this.

Also oil ponding relief on the exhaust cam carrier to avoid gasket leaks. I assume you have saddle type carrier covers.

Dave the cog.

Thanks Dave. I have already done the coolant thing - there are pictures somewhere in this thread showing the difference between the 907 and 912 blocks. The exhaust cam carrier oil drain holes I haven't done yet - I'm really hoping to find some SE-type cam housings, but they are like rocking horse poo! I'm going to have a few chats with gasket manufacturers after the lockdown to look at modern gasket materials for the saddle-type cam housings as well - I've got a couple of ideas.

Pete

Bolted the first bit back on today! Woo Hoo!






Pete

Not really progress - but just in case I decide to fit some ICE in the car at a later date I've added a couple of flanges to locate a bass drive unit in the area vacated by the vacuum reservoirs:



Pete

Neat fiberglassing there Pete - I'm going to be needing some of those skills!

By the time you've repaired all that bodywork you'll have them!

Pete

Thanks for the reminder

Honing my metal working skills right now, avoiding fiberglass.

Neil.