Lotus Elan

Cracked Block

PostPost by: elandoc » Wed Nov 21, 2007 10:29 pm

After spending a million dollars getting the Elan fast and reliable, I go and crack the block. The crack is between the welsch plugs on the exhaust side, on the outer table of the water jacket. It's a 711M.
I've looked at possibly repairing it, but what's around doesn't inspire confidence, so I'll have to dig up an old Escort engine.
Has anyone ever cracked a block there? I have an electric water pump, so I've been considering thermal shock, but maybe it's just a bad casting - funny how it's lasted 7 years and cracks now, though.
Any thoughts out there?

Patrick
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PostPost by: twincamman » Wed Nov 21, 2007 10:48 pm

hell its only cast iron any one should be able to weld it --there is very little pressure ----10 pounds maybe -ed
dont close your eyes --you will miss the crash
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PostPost by: elandoc » Wed Nov 21, 2007 11:37 pm

Well, Ed, I'm no expert, but people who are tell me that welding an iron block ain't a walk in the park. There are metallurgical issues with the edge of the weld, as well as thermal expansion problems. Apparently metal stitching is an option, but it looks even dodgier.
Patrick
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PostPost by: twincamman » Thu Nov 22, 2007 7:16 am

how about some of the space age epoxies ??? theres one for body panels thats supposedly stronger than weld --ed
dont close your eyes --you will miss the crash
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PostPost by: rgh0 » Thu Nov 22, 2007 8:20 am

Never cracked the outer water jacket just bores couple of times

Given the cost of a 1600 block easier to replace than repair i would have thought.

How much did you deck the block. Take to much metal off and the block can flex causing to crack especially if used at high revs with al the vibration inherent

cheers
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PostPost by: oldokie » Thu Nov 22, 2007 5:36 pm

An 'okie' might try to fix it with JB Weld. If you can find the ends of the crack, drill two holes (as small as possible), one at each end, fill them and the crack. If you weld it you'll still need the the holes to keep the crack from spreading, also use a shielding gas (Argon) inside the block.
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PostPost by: cabc26b » Fri Nov 23, 2007 1:30 pm

Hi Patrick,

I have not had a block fail yet but....

I would tell you to look into a new block - I have seen repairs fail and ruin a race weekend and in the end waste a lot of money. As long as you are building the most expensive elan - how about getting a Aluminium Cosworth BD block ? there are plenty available, you just have to pony up the funds.
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PostPost by: cabc26b » Fri Nov 23, 2007 1:30 pm

Hi Patrick,

I have not had a block fail yet but....

I would tell you to look into a new block - I have seen repairs fail and ruin a race weekend and in the end waste a lot of money. As long as you are building the most expensive elan - how about getting a Aluminium Cosworth BD block ? there are plenty available, you just have to pony up the funds.
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PostPost by: cbguerrajr » Sat Nov 24, 2007 1:59 am

Hello Patrick

Sorry about your block.
I'm also thinking about putting an electric water pump in my Elan.
Do you have the pump setup using the electronic controller so that it remains off until some temperature is reached? Or is your pump on all the time?
I was wandering if having the pump off at the start was such a good idea, as uneven temperatures surely will develop inside the head and block.
I don't know if it would be enough to crack the block though. I was more concerned about warping the head...
Something to think about

Carlos
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PostPost by: Bill » Sun Nov 25, 2007 6:52 pm

Patrick.

For what its worth! Perhaps a touch of old technology may work in this situation.

Years ago (early 60's) I repaired a similar situation on the TR3 I was competing - an old machinest friend had repaired exterior water jacket cracked castings (freeze ups on the Canadian praries) during WW2 - had to keep the farm machines going you know, no parts available.

He instructed me as follows;

Drill out the ends of the crack in the casting with a 1/8" drill to stop the crack from increasing in length.

Form a sheet of brass - 1/8" thick or so to the casting area profile to cover the crack with a 1 in. overlap all around.

Drill a series of holes in the brass patch piece (1/4" in from the outside edge of the patch piece and @ 1/2" centers).

Then using brass patch piece as a template drill matching holes in the block and tap out for 8 / 32 brass machine screws.

Install patch with 8/32 brass machine screws - use lots of gasket sealer (Permatex 45 years ago)

Bobs your uncle! It lasted the several years I had the car and was still sound when I sold the car!

This may be a solution, particllarly if you have largish $ investment in the block!

Besides - if you polish the brass repair plate you will be able to proudly point out to folk that early repair practices are applicable to early Elans.

I think Colin would go along with it - except for the added weight of course!

Whatever you do - good luck - and remember that in 10 years from now there may be no option. Or no spare blocks!

Bill (26/0538)
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PostPost by: ddddumas » Wed Nov 28, 2007 6:05 pm

The cast iron block can be repaired, but it should be brazed rather than welded, as is routinely done throughout industry. Generally, the block is stripped, cleaned, and thouroughly heated before brazing with an acetylene torch, bronze rod and flux. Of course, the block will have to be remachined, and perhaps, sleeved. Hope this helps.
Paul Garrett
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PostPost by: elandoc » Mon Dec 03, 2007 2:34 am

Thanks guys.

Repairing: the crack goes into both welsh plug holes, so even low temperature differential brazing might not do it. After heating the block to 600 degrees C, I might have to re-machine everythin anyway!

Replacing: I've decided to replace the block, and have stumbled across a late casting, with "xxxx" above the engine mount - apparently these are very thick castings, able to be bored out to 89mm or so, if anyone is interested. The FIA regs for tarmac rallying limit me to 83.5mm (+40 thou) - unless I use the famous Colin Chapman ruler...

Water pump: I considered thermal shock as a possible cause for the crack - it's unlikely, but I have made the following observations:

Modern engines have a bypass thermostat, which means that when closed (cold/warmup), a second passage is opened underneath, which flows back to the inlet of the water pump, thereby recirculating the water through the block and head, and preventing hot spots. When at operating temp, the thermostat opens, which closes the bypass circuit.

Our older engines don't have this (and yes, I've looked at machining the head to accept one), but the swirling action of the water pump probably helps move the water around the engine, even against the closed thermostat.

An electric water pump with the mechanical pump removed doesn't do this, although the controller will pulse the pump from 20 degrees below set point, gradually pumping faster until the set temp is reached. From customer feed back, Davies Craig has modified the controller to pulse briefly every 30 sec from cold, just to prevent hot spots (my earlier controller doesn't do this).

It's hard to imagine local convection not helping circulation during warmup, but I found it difficult to get my motor warm enough (eventually putting the thermostat back in), and several times at hillclimbs and sprints was concerned about suddenly working the engine from idle (ie the temp differential between the head and the bottom of the block). Anyway, here's what I'm proposing...

I'm going to run a very small booster pump between the heater outlet and the bottom hose. It will operate when the EWP is off (during warmup and between pulses) and maintain an even thermal gradient between the top and bottom of the motor at all times. I may even put an oil/water heat exchanger in the circuit (bottom hose). I've had one in the past - it cracked, of course and I now have the old oil cooler on, but I was very impressed with its space saving and temp control, so might get a new one (incredibly expensive, of course!).

There you go guys... What do you think?

Patrick
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64 Morris Cooper S (now sold)
85 Ferrari 308 GTSi QV
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PostPost by: rgh0 » Mon Dec 03, 2007 10:01 am

Patrick

I have recently posted a number of measurements of Ford blocks in the Yahoo LotusElan forum.

In summary I believe all Ford 1500/1600 blocks had the same cylinder casting and the maximum bore you can get from any casting is around 85mm by careful selection of the casting at the top end of the tolerance range. It is not physically possible unless you siamese the bores to get a much bigger O/D on the cylinder casting than 91.5mm +/- 1mm casting tolerance which is what Ford appears to have used in all blocks despite the myths otherwise.

Having some continuous water circulation on warm up is wise particularly in a highly stressed competition engine to ensure no hot spots or thermal stresses. The standard hole in the thermostat achieved this in the original engine and you need to simulate that in an engine with an electric pump I believe. I would keep the hole in the thermostat and run the electic pump at a minimium speed always.

regards
Rohan
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PostPost by: john.p.clegg » Mon Dec 03, 2007 3:59 pm

Patrick


Our older engines don't have this (and yes, I've looked at machining the head to accept one), but the swirling action of the water pump probably helps move the water around the engine, even against the closed thermostat.

Before the thermostat opens the pump is circulating coolant around the engine/block via the heater matrix....at least in my plus2.

John :wink:
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PostPost by: elandoc » Tue Dec 04, 2007 12:37 am

Hi John,
That only applies if you have opened the heater tap. Modern engines have another circuit as well. Besides, heaters are heavy, so therefore... I don't have one.
Cheers
Patrick
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85 Ferrari 308 GTSi QV
79 Ferrari 400i
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