Some pics of previous engine failure

[richardcox_lotus]

Those of you with long(ish) memories may recall me posting pics of a busted spark plug.

Well, several months and a replacement engine block later, here's some pics of the crack in my block that caused the damage. Still no clearer to understanding why it went.

The damage was in #2 Cylinder. The crack runs from about 4mm from the top of the cylinder & just keeps going all the way down. The other side of the crack is visible in the water jacket when peering down the hole in the top of the block, so it's gone right through prety much all the way. We think it started below the piston skirt but that's mainly conjecture.

Enjoy (In a perverse kind of way.....)

[twincamman]

sickening --TAKE IT AWAY ---may be you could get the block sleeved ???? ED

[rgh0]

Wat was the bore of the block. Hard to repair that as the sleeve is likely to crack due to lack of support where the crack in the casting is. You can get high strength Chrome Moly sleeves that dont need the back support but cost is about US$1000 per bore so not justified versus chasing up a block if you can find one.


cheers
Rohan

[richardcox_lotus]

All Bores Standard. Never raced/ralllied or abused. Less than 60K miles in total.

Bugger, innit.

BTW, I managed to track down a replacement block & the car's now back on the road. Watch this one appear on ebay in a couple of years time.
What am I bid ?

[rgh0]

My bet is thats it an unusually thin standard bore block at this point in the bore due to the casting cores having moved when the casating moulds were made. Wall thickness below about 2.5mm can crack and you only need a casting core to move a couple of mm of centre to get down to this thickness. The wall thickness on the oppossite side will be great about 7 or 8 mm but that does not do you much good

cheers
Rohan

[Tonyw]

Richard,

To prove Rohan's theory you could try to borrow an ultrsonic wear indicator your local Caterpillar or Komatsu dealer will have one as they use them to measure undercarriage. This device will measue the wall thickness.

I saw this thread eariler when your engine failed and thought perhaps your block had a heap of rubbish in it and it somehow accumilated in one spot causing localised overheating, just a thought.

tony W

[garyeanderson]

Might this be one of the 701 blocks that were cast late in the twin cam production that was a "Lotus Reject" that went into Fords engine exchange program. This could have been found years later in a Cortina or Anglia and possibly given a .060 overbore to stock twin cam pistons thus making for thin cylinder walls?

http://www.lotus-cortina.com/library/block/wood.htm
http://www.lotus-cortina.com/library/block/warner.htm

Gary

[rgh0]

There are lots of myths about blocks and wall thickness. Since I started chasing blocks and bought my own ultrasonic gauge I have now measured up around 20 blocks for wall thickness and found no systematic variation between any of the various block type numbers from early 116E to late 711M including L blocks and standard Ford blocks in 1500 and 1600 capacities. The only reason to buy an L block versus a standard Ford 1500 block is because you like the big L on the side for originality purposes there is no other systematic differences in the blocks that I can measure.


When I measure the blocks I measure the wall thickness top to bottom of the bores and around the bore at 45 degree steps to look for thin spots. What you see is systematic variation with the walls being thinnest at some point around the bore due to the offsetting of the bore with the cylinder casting.

The design outside diameter of the block cylinder casting appears to be the same for all blocks within a small variation in diameter due to the casting process itself. The only systematic variation I can find is due to the amount of corrosion present in the blocks being measured. The fresh castings appeared to have had a cylinder bore O/D of 90 to 91 mm. With many blocks now down to 89 to 89.5 mm due to corrosion. I am sure some special blocks for racing purposes or these mythical South African 711m blocks may have been deliberately cast with a larger casting O/D but I have never measured or seen any of these. It is only possible to go to around 92mm O/D in the bore castings with the sand casting process Ford used, beyond that you would need to Siamese the bores.

There are certainly variations in the blocks over the years in terms of the lug sizes and reinforcing ribs with the blocks getting more robust in these areas over the years but the cylinder bore casting itself appears to have not changed.

Minimum wall thickness does however vary considerably depending on how central the bore is in the block cylinder casting. This can vary in position from central up to around 3 mm due to shifts in the casting cores and I have found lots of standard Ford blocks with a minimum wall thickness due to the offset of around 3 to 4 mm in a 81 mm bore standard Ford engine.

Offset boring to recentralise the bore in the casting core means that almost all blocks can safely go to the standard Lotus 82.5 mm bore and maintain a 3 mm wall thickness and most will go to 83.5mm. Only a few will go beyond that as you are relying upon the block being at the upper end tolerance of 91mm plus no corrosion to get a 3mm wall thickness in a 85 mm bore. At 85 mm you also have to be very careful to miss the oil passage between cylinders 2 and 3.

cheers
Rohan

PS I just pick up a load of 8 more old 1500 and 1600 engines to strip for the blocks and when I add these lot of measurements I will let you know if the statistics change but I don't expect them to. Also pickup up 3 more very good quality Stromberg heads so it looks like another shipment to John McCoy for conversion when I can afford it.

[rgh0]

Forgot to mention that the articles from the Lotus cortina site listed in the earlier posting shows that the grading for Lotus of the blocks was very crude and would not pick up a lot of the possible variation in wall thickness due to shift cores. You cant properly assess a block with calipers through the various opening you do need to do it using ultrasonic thickness measuring.

You can get a good quality ultrasonic thickness device for around US$1000 these days. The devices I used back in the 70's were much cruder less reliable and cost around $30,000.

cheers
Rohan