Cracked Block

[elandoc]

Hi Rohan, I've PM'd you, but forgot to mention this.

I had a block measured and it will have a bore thickness of 100 thou at its narrowest casting after a 40 thou over bore - incidentally, it was marked "xx", not "xxxx", as I thought; I believe "xxxx" is still the duck's nuts casting, though.
From what I can gather, you need at least 125 thou wall thickness in the bore for reliability - is this right? I'm neither a metallurgist nor an engineer, so I would like to hear some input from someone who knows (preferrably with some sound reasoning). In any case. I think I'll junk this block and look for another one (unless someone tells me differently).
A friend had a "xxxx" block ultrasounded and it was 380 thou, which apparently allows an 89 mm bore.
Cheers
Patrick

[rgh0]

Patrick

My understanding is that around 3mm is the minimum you want in the bore wall thickness and this minimum is approach in the standard blocks given the casting and measuring tolerances on occassions. goinbg down to 2.5 mm .100 inch is starting to be risky from a wall thickness perspective bore from porosity in the casting as well as splitting the bore. I have split a bore in a 85mm racing engine at 3mm wall thickness.

To have 380thou / 9.5 mm walls in an 81.5 mm bore or to get an 89mm bore with 3 mm thick wall and the 96mm bore spacing you need the bores to be touching at their outside. Possible to do but not the way the cores for these blocks were designedand assembled. You also have the minor problem of what to do about the cross drilling between cylinders 2 and 3 as you have no space left for it. Again possible to work around but not without major block work. I dont believe any block even with xxxx on it would go to 89mm without major work. Cosworth certainkly had to cut out all the bores and welded in a new block of cylinders with siamesed bores and reran the cross drilling oil line to make it possible to go to this bore size.

cheers
Rohan

[garyeanderson]

Ford of England cast up some special 701 blocks for Cosworth that were never crossdrilled for the oil passage between bores 2 and 3. These engine blocks were dry sumped and used a 4 port oil pump and an external oil line to feed the main oil gallery on the left hand side of the block. One of the motor mount bosses (top rear, I think) near the oil gallery was drilled and tapped to except a fitting for the external oil line.
My friend has one from his old Cosworth BDJ which used an 85mm bore and 48.4mm stroke. If I remember right, any of the larger bores that Cosworth used in there BD engine program were furnace brased where the old cylinders were completely machined out of the block and a new set of 4 cylinder siamezed bores droped in and furnace brazed or new cast alli blocks that were a siamese design from the start. Any engine block that can go over 85 mm is more than likely something special. I bought a old 831c block that was at 86 mm, when I tried to have it bored 86.5 the cylinder walls were moving away from the cutting tool. big bores are hard to do on most kent blocks.

Gary

[mikealdren]

Patrick,
running without a heater may work in your climate but it isn't an option in the UK and I suspect that it's a life and death issue in Canada. Yes I'm envious at this time of year.

The +2 has an air mixer heater so it doesn't have a water valve - we ought to tell the guy who keeps advertising them on Ebay.

Mike

[paros]

Fascinating thread which I will print out to keep.

Talking of brazing in liners, I remember a friend in the late 60's, who initially worked for Charles Lucas in the UK, and as a semi illegal immigrant [ from Holland ] his task was to deal with the brazed blocks. These were as mentioned machined out to accept liners which were brazed in with welding rod.
A day later when cool he had to then retap all the threads, and the cost of all broken taps was deducted from his pay.
I seem to remember the blocks also cracked under use from the grain growth and brittleness.

As to cracked blocks, then a replacement is sadly the safe answer BUT just what is the real advantage of an electric pump - other than creating this thread?
The Elan standard pump, driven by a slack notched belt has been my approach and to date no problems. And recently with a thermostat installed - which does have a bleed hole in it.



Richard

[msd1107]

Richard,

The standard water pump is a square law device, which means flow and pressure are low at low RPM, and the pressure and HP losses are high at high RPM. It depends on which site you look and whose lies you might choose to believe, but large V8 water pumps are reputed to soak up to 20 HP, and our smaller water pump up to 10HP. In contrast, the Davies-Craig uses a maximum of 7.5 amps, which is about .15hp.

In high temperature conditions, the controller runs the water pump as fast as necessary to keep the water temperature within limits - no more over heating in stop and go traffic. Also, the controller can be programmed to continue to run after shutting off the engine, so you do not get a temperature spike in the engine after a fast run.

The water pump is rated for 2000 hours, so its life is probably in excess of a regular water pump. One of our members has already replaced an early unit. Replacing an electric water pump is a screw driver operation as opposed to replacing a TC water pump.

A previous post (http://www.lotuselan.net/forums/viewtopic.php?t=15596) allows you to model the effects of using an electric water pump on performance.

I doubt that anyone would make this change on a concours destined car, though.

David
1968 36/7988

[garyeanderson]

Ford of England cast up some special 701 blocks for Cosworth that were never crossdrilled for the oil passage between bores 2 and 3. These engine blocks were dry sumped and used a 4 port oil pump and an external oil line to feed the main oil gallery on the left hand side of the block. One of the motor mount bosses (top rear, I think) near the oil gallery was drilled and tapped to except a fitting for the external oil line.
My friend has one from his old Cosworth BDJ which used an 85mm bore and 48.4mm stroke. If I remember right, any of the larger bores that Cosworth used in there BD engine program were furnace brased where the old cylinders were completely machined out of the block and a new set of 4 cylinder siamezed bores droped in and furnace brazed or new cast alli blocks that were a siamese design from the start. Any engine block that can go over 85 mm is more than likely something special. I bought a old 831c block that was at 86 mm, when I tried to have it bored 86.5 the cylinder walls were moving away from the cutting tool. big bores are hard to do on most kent blocks.

Gary

Russ Newton and myself were inspecting the 701 block at lunch yesterday, this is the block I was refering to in the quoted post. I brought the camera and got some photos so its easier to understand. This solution is two fold, it allows for bigger bores by eliminating the cross through bores two and three. The second thing it does is allow you to run an external line this is larger in diameter than the 5/16 inch crossfeed drilling that is delivering oil to the main oil gallery.

[lotuselanman]

Gidday Patrick,
Jeez you pick a good topic here.
Interesting.
See ya,
Les

[elandoc]

Hi Les,
I've found a block from our friend GS, who charged me a fortune (I think he still has his lunch money from grade three). Whatever - he reckons he can get $800 for one. Anyway, it's costing me more in getting my mechanic to run up and back and get each block ultrasonically tested (I'm on my third). Maybe I should buy a Porsche...
Cheers
Patrick

[Barney]

I asked around some of our Marine Engineering associates and they have suggested the Metalock process that works with all castings. This company has a presence worldwide and are very experienced having dealt with this problem for many years.

Website = http://www.metalock.co.uk/castingrepairs.asp

Benefits of using such a system are listed on the site together with lots of great photos of previous repairs. I've listed the benefits below.

I?m interested in finding out about these processes - I hope that somebody (if not in this particular case) may gain from this info.

Benefits stated are:
Maintains alignment and original surfaces.

Dampens and absorbs compression stresses and spreads tensile strains.

Provides a good expansion joint on such jobs as cylinder liners.

Distributes the load away from fatigue points.

Maintains relieved condition of inherent internal stresses where these were the cause of the fracture, or partial cause.

Provides a low co-efficient of expansion in the relation to the repaired metal.

The repair being completely cold does not require the application of hear which could, and often does, introduce fresh stresses

[billwill]

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

A thought about this old message..

If you have no heater, maybe one could connect the heater output pipe to the heater input pipe of the engine to create a warm up circuit.

[elandoc]

Hi Bill,

Pretty much what I've done, but with a small electric pump.

Patrick

[johnsimister]

Probably a bit late in the day, but have a look at the Jim Stokes Workshops website via Google. L&S is a metal-stitching company which is part of the Jim Stokes Group, the people who make replica Alfa 8C engines and can repair or recreate practically anything. Their work is perfection itself.

I tried to include the URL in this post but was told I couldn't because I haven't been a member long enough or made sufficient posts, even though I have. Technology...

John

[elansprint71]

If brazing or welding is out of the question (if "welsh" plugs means core plugs, I can understand this) have you thought about getting it stitched?

My choice would be a new ally block but, hey, that's a lump of money.

Cheers,
Pete.