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Looks great David!  The front of your engine looks very interesting!  Are you using an electric water pump for engine cooling?  Not seen that type of timing belt adjuster before - the hexagon is larger than the types I have - custom made?

Pete

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3 hours ago, EXCEL V8 said:

Looks great David!  The front of your engine looks very interesting!  Are you using an electric water pump for engine cooling?  Not seen that type of timing belt adjuster before - the hexagon is larger than the types I have - custom made?

Pete

Pete,

 

yes I am using an electric water pump from Davies Craig, a local firm just down the road.

The adjuster is the one that was on the engine. The actual adjustment is done on the the rear eccentric hexagon, then it is held in place with the front eccentric hexagon and finally locked up with the centre through bolt. I have no idea if it is correct or not but it was easy to adjust once I made a suitable open-ended spanner and I cannot see it ever backing off. This was my first exposure to a 907 engine and in my opinion it is not a good design. There are many weaknesses.

1 hour ago, jonwat said:

Is that the Elite behind it? It'll ne a bit of a squeeze. :rofl:

That is our Type14 Elite. It already has a very nice Coventry Climax FWE engine in it so I do not have to squeeze the 907 into it 🙂 

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7 hours ago, dmottram said:

This was my first exposure to a 907 engine and in my opinion it is not a good design

Good to see you're nearly there David. What weaknesses do you see in the design. Wondering if the subsequent 912 engine addressed any of the issues?

Pics when installed please!

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2 hours ago, Clive59 said:

Good to see you're nearly there David. What weaknesses do you see in the design. Wondering if the subsequent 912 engine addressed any of the issues?

Pics when installed please!

Well to name a few easy ones............

1.      As the cylinder line is at 45 degrees to the horizontal, the thrust loads on the main bearing caps is concentrated on one main bearing retaining bolt (like a V8 engine). Most performance V8 engines have four bolt mains to counter the issue. Perhaps at only 80 HP/litre the stresses are insufficient to cause trouble  but I wonder if the later turbo engines were 4 bolt mains.

2.      There is no positive location via dowels between the cam carriers and the cylinder head. The fitting then becomes a real task as the cam wheels have to be clocked up against the crank to ensure perfect alignment of the camshafts with the crank. I know many people do not do that and just rely on a straight edge across the face of the pulleys but they should be dowelled. 

3.      The appalling cam cover fitting using tapered faces. What were they thinking. Due to the 45 degree angle the exhaust cam runs fully under oil due to the location of the drain-back hole, there are only six retaining bolts, too far apart, the wall thickness of the taper is too thin (given there is such a large distance between retaining bolts) and the exhaust cover is extremely close to the exhaust manifold which no doubt causes excessive expansion of that side of the cover due to the high temperatures involved. An engineering fail in my opinion. I will be trying to fit a heat shield in that area.

 

That's all for now..... David

 

We have been covid locked down here since early March so my time has been spent on restoring an old MG TC. I started in January and have almost finished. I drove it briefly for the first time last week. Lots of enjoyable garage time.

I hope that you all keep well as the virus surges in the UK and Europe. We now have it under control with a running 14 day average at 2.4 cases per day and deaths down to just a couple per day (mainly in aged care facilities). Now the Govt has to focus on the economy to get it cranking and back to good health.

TC 9.jpg

TC 10.jpg

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I'm building a 2.5 l supercharged 912 for my Elite and I'm 10-doweling the mains to reduce fretting of the main bearing cradle.  There are effectively 4 bolts per journal, but the outer ones are too small and too far away from the point of stress.  I agree - given their racing pedigree it should have a much stiffer bottom end - even the 912 is only a small improvement.

The cam housing dowels is an odd one.  My cam housings have dowel holes at the front and rear - the front ones have the roll pins/O-rings, but there is no corresponding hole in the head for the rear ones.  I hadn't noticed this until I read your post and had a look!  I will look at adding drillings to the head to use the rear locating holes.  Thanks for pointing that one out David.

Cam covers - utterly shocking and inexcusable!  Don't know what I'm going to do about it yet.  The pre-production engines that they used in the Vauxhalls had 10-bolt covers - still the same horrible design, but they might have been a little better?  I'd like to swap to the later design but they are now getting rare and very expensive.

Pete

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Pete, I thought of dowelling the cam carriers but it is a lot of work as you have to get them properly aligned in the first instance and then mill a new hole through the carrier into the head so that the holes align. Even using a roll pin at the front is fraught, what is needed at both ends is a proper solid ground dowel in a proper size hole for proper location after they are aligned. In the end I thought that I would wing it and see what eventuates. Hopefully the miracle of modern sealants might solve the issue. I have glued the gasket to the carrier in the first instance then used hi-temp Three Bond Super Sealant. It has worked for me on other difficult situations so I am hopeful.

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I'll have another look at the castings to see if there is room for tubular dowels around a few of the studs - much like I'll be doing with the MBP studs.  That then allows the carriers to be lined up and drilled/reamed with only a single stud removed at a time.

Pete

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  • 2 weeks later...

Interesting discussion here. I'm unclear what leaning over the lump at 45 angle means in terms of bearing work as G loads on the reciprocating assembly far exceed that of Mother Earth. What the slant design does in terms of restricting use of space on the exhaust side is another matter entirely, one I'm suffering in an effort to place an A/C compressor there in an S2 Esprit. Also, in situations of prolonged right turns at the limit, sweepers taken in the course of track day fun for example, the vector resultant of natural gravity plus 1 g cornering force essentially negates oil drainback from the top end. Many a 907 has had the big ends knocked out due to the combined influence of that, the preference for revs, and limitations of the early sump design. Essential to keep watch on the oil levels in these, at the very least.

True, the cam covers are an artful mess requiring great care in order to seal properly. Possibly the innate signature of Lotus' eternal quest for minimum mass once again yielding compromise in service. A treat to see DCOE in use, near and dear to an old Elan owner like myself.

Cheers 

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I'd not considered the cornering effects of oil drain-back from the cam covers!  Very interesting.  Steve - I'm also locating the A/C compressor under the exhaust manifold to make room for a blower on the other side - haven't done the brackets yet, and it will be a serpentine belt drive from a custom crank pulley.

Pete

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Well I'm at risk of not being the first to engineer a serpentine solution for 907 accessory drives! I salute your innovative spirit in having a go. The Esprit chassis presents real challenges in terms of clearance to the front areas of the engine, as I've examined ad nauseum for the past several weeks in my effort to accommodate a dry sump 910 and soundly resolve all mountings and drives for reliability. Just this afternoon I have determined to locate the driven pieces all on the inlet side much as I would have liked to keep some mass low on the x side. Just too much of a knife edge on clearance, line connections viability, compressor port clocking ( hence reliability ), access for service, shift linkage re-work and the 3 pulleys required to run a belt. Accepting the inlet side clears away that list of grave concerns and reduces the added pulley required of a serpentine layout to that of a single tensioner.

Peter, I hope you'll report on your program to supercharge the engine, another crafty idea indeed.

Cheers

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I do everything the hard way!  I'm currently building a high speed spindle for the lathe toolpost to internally grind the crank pulley - the original Lotus pulley is a sliding fit on the crank, but I want a bit of interference on there - probably only about 1/2 a thou - but grinding is the only way to get that sort of accuracy.  I'm planning on bolting the supercharger pulley to the crank pulley.  Making them separate gives me control over the pulley ratios for the blower drive.  Clocking the compressor ports is tricky!

So have you given up on your serpentine belt idea Steve, or are you locating all accessories on the inlet side and still going serpentine?

Pete

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Happy to report a breakthrough realised yesterday, culminating in decisions to vertically stack alternator above oil pump, above that the A/C compressor where the alt formerly resided. This allows the lowest placement of masses on inlet side as the smaller diameter alt pulley is key to dodging belt conflict with a chassis diagonal. Pieces are on order for finalising layout in the course of fabricating the brackets and I'm confident this is quite doable.

Cheers 

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  • 1 month later...

I have a restoration thread going on Excel.net - although there's been nothing to post for a while 🙄.  Stuff seems to be going glacially slow at the moment!  I'll post up the engine build on here though when I get properly started on it!  It will be good to see the parts you've had made as well Steve - thanks for that!

Pete

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  • 2 weeks later...

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