Yesterday's daily today - the J69 version

[Leonard Hatred]

Pleasing!


I know of a place where there's a big pile of NOS pistons.

[Vulgalour]

I wonder if Sheepbridge Engineering still exist? Sheepbridge is only a few miles from where I live and the industrial estate there does still have a few engineering companies on it as far as I know.

[tone_depear]

Eaten by GKN in 1979!

Works closed in 2007.

http://www.gracesguide.co.uk/Sheepbridge_Engineering

http://www.flickr.com/photos/comradethompski/sets/72157616822880188/

[Amazo]

If only we could bottle the smell that no doubt eminated from opening this box (and the smell of slightly musty old magazines), someone would make a small fortune.

[Vulgalour]

The new Fragrance from Ian - Fusty Old Smell.

[Jonny69]

Camshaft ordered. I decided to go for 4500-8500rpm instead of 5000-9000rpm. I went for a bit more lift and a bit less duration than the old Cosworth A6 all-out race grind.

I wanted an old style grind with lots of duration, but my only choices from back in the day were the Cosworth A3 or A6 grinds. The A3 isn't a lot more lift than a stock cam and it doesn't run a lot of duration so it's not much of a cam in my opinion. In complete contrast, the A6 which is the next one up runs an extreme amount of duration and there's nothing in between to choose from. Burton have filled the gap though with their own grind - the BLF18. I wanted over 300 degrees of duration and a bit more lift is an advantage because it'll bump up the bottom end a bit.

A3 http://www.burtonpower.com/camshaft-ohv ... eg-a3.html

Users must expect some loss of flexibility in the lower rev range. Good power band between 4000-8000rpm. Valve spring platforms should be machined to give a fitted valve spring length of 1.300”/1.310” (33/33.25mm). X/flow types may also require deeper valve pockets in the pistons. Ensure a minimum clearance of .160” (4mm) between piston at TDC and the valve head face. Power band 3000-7000rpm. Valve lift .349". Duration 286deg. Timing figures 35/71/71/35. Inlet timing 108deg ATDC.

Burton BLF18 http://www.burtonpower.com/parts-by-fit ... blf18.html

Power band 4500-8500rpm. Valve lift .415". Duration 318deg. Timing figures 42/96/74/64. Inlet timing 106deg ATDC.

A6 http://www.burtonpower.com/camshaft-ohv ... eg-a6.html

Good power between 5500-9000rpm. With appropriate valve gear, will rev to 9500+rpm. Front journal has additional slot for increased oil feed to rocker gear. Valve spring platforms must be machined to give a fitted valve spring length of 1.400”/1.410” (35.56/35.81mm). X/flow types will also require deeper valve pockets in the pistons. Ensure a minimum clearance of .200” (5mm) between piston at TDC and the valve head face. Power band 5000-9000rpm. Valve lift .400". Duration 304deg. Timing figures 46/78/78/46. Inlet timing 106deg ATDC

[Jonny69]

Might be ready for some more pics in a couple of days. The short block is finally complete and Robyn should be sticking it on a pallet to send it back down in the next day or so.

[Jonny69]

The postman stuck this through my letterbox on Friday.





Ok, so that's a three bearing crank, for anyone who doesn't know what one looks like. The crank is supported by those big shiny steel caps and the main bearings are in there. The standard cast main caps are very puny in comparison, so I am confident they have strengthened it up a bit.

I had the rods lightened and balanced. Below you can see the bit that has been ground off the big end - this is normally a thick boss which is there for quick balancing in the factory. It's much thicker than it needs to be so most of it can be ground off if someone wants to spend a bit more time with the balancing than would be efficient to do in a factory. There's a similar amount at the small end:



The new Lotus pistons are slightly bigger and have a shorter deck height, so I had a rebore done and the top of the block machined down to suit:





I wanted a light flywheel but I couldn't find anything second hand. I didn't want to use a steel flywheel because that would mean using a special clutch and I wanted to stick with a standard Escort style clutch for ease of replacement. So I opted to have the standard one lightened. Some people are a bit scared of lightened cast flywheels but as long as you're sensible with them they are perfectly safe. Here you can see the back face has had a skim and a chamfer around the outer ring:



On the clutch side it's had a light skim and a chamfer put around the outside:



I put the engine next to my 1700 block so you can see the differences:



So the Kent engines are pretty much the same with a few key differences:
-The 1200 block has three crank bearings while the bigger 1500cc and later 1600cc crossflow block have five.
-The bores are the same throughout the Kent range and the different capacities are achieved with different length strokes. So mine has a pretty short stroke - good for revs. The 1600cc block is slightly taller to clear the longer stroke - which you can see.



I thought I'd take a snap of the new cam profile next to the standard profile to spot the differences. Standard one is on the right, high lift and long duration is on the left:



You can see the much wider curve on the one on the left so the valve opens early and stays open for a long time before snapping shut. Lift is governed by how high the pointy bit goes, but you might have noticed the lobe doesn't look any any higher than the standard grind. There's only a certain height you can grind the pointy bits to before you can't fit the cam through the bearings so, to create more equivalent lift, the back of the lobe is ground smaller so the difference is greater. You need a slimmer shaft to do this and you can see this in the pic below:



Hopefully, with the nice weather we're having, I'll get it screwed back together and maybe back and running before I disappear off to Bonneville. Famous last words, should know better by now etc etc.

[Seth]

All looking fab there Jon.

The postman stuck this through my letterbox on Friday.

...before I disappear off to Bonneville...

Ooh!

[Jonny69]

Yeah, it's been an expensive year but long overdue