Welding Cast Iron

Is this a repair or for increasing the CR?

Tom

possibly

umm, cast iron ones are best in my experience for welding cast iron. lol, in all seriosnes, get some Murex cast iron rods, and warm them gently in the oven before you use them (shhh i wont tell if you dont lol) also pre heat the whole (or as much as possible) of the job as this will reduce the tendency of cracking due to thermal shock, then weld away to your hearts content, but DO NOT use anything to cool it with when you have finished, or you may find yourselve with more problems than you started with.

Hope this is of some help

Tim

Welding is not my forte. Anything that gets hot enough to hurt me is not really my thing. I have a little Clarke gasless mig for emergency repairs but avoid using it like the plague. Everything I try and weld turns into little lumps of pigeon crap which may or may not stick to the job. The usual advice with cast iron is get it as hot as possible before welding and let it cool slowly afterwards. Your chances of ending up with a cracked head are fairly high though and I wouldn't entertain it personally. Someone else may have better advice.

-- Dave Baker - Puma Race Engines

Increasing the CR of a sidevalve head from an Austin 7

Charles

Charles,

Welding cast iron can be a b***ch. Problem areas for a used castings are:

1/ oil in the pores - even baking for hours at 300 deg C doesn't always get it out

2/ lack of tensile strength. When the weld pool solidifies it obviously shrinks and the surrounding material is too weak in tension. Often a repaired casting may look sound, but fails parallel to the weld in the heat affected zone.

Nickel rods seem to be best, and as soon as the pool solidifies in needs to be peened to relieve the stresses. Best to work in small areas distributing the thermal stress.

Can you not machine a flat on the combustion chamber, and fix a suitably shaped piece of cast iron with bolts? If you want to increase the compression ratio why not skim it, or modify the piston crowns ?

AWEM

It all sounds fraught with danger doesn't it.

Not really This is a similar head:

The material needs to be added around the base side of the spark plug to reduce the volume over the cylinder. Skimming may work up to a point but you've still got the plug in the middle of the cylinder.

Charles

In the 1950's I seem to recall having the head of the Seven surface ground to raise the CR but cannot remember how much was taken off. At that time you could also buy alloy high CR heads but they were above my budget. I remember experimenting by fitting two amal motorcycle carbs, which worked well and then bought an adapter to fit a twin choke Stomberg from a Ford V8. I also recall hearing that one could change things such that the exhaust ports became the inlets and 4 Amals could be fitted. Colin Chapman (Lotus) was into A7's at the time and sold various mods to improve braking and handling including a split front axle.

Cars were fun in those days.

Donald, South Uist

Another thing I remember is that you have to be careful when raising the CR too much because the two bearing crank deflects at high revs and you could end up with the middle pistons hitting the head. Changing to a three bearing block and crank was not a solution because introducing the third bearing weakened the crank and these later engines were no good for souping up because of that.

Donald, South Uist

the problem of welding bits inside the combustion chamber is that the burning pattern of the fuel combustion will not be even...thus will shorten the life of the engine,,it will also end up pinking a the raised weld will glow hot as the engine heats up thus ignighting the fuel mixture before the normal piont of ignition ei if the spark occures 8degrees before top dead centre then it will end up at any point between 12 to 8 degrees tdc (top dead center) this will then end up causing failer of the bigends ,,bores etc

combustion chambers are designed to keep the combustion presser even over the top of the piston as much as possible thus giving equal pressure all around the top of the piston so as not to push to hard on one side which will cause exccessive waer in one side of the rings and bore,,

another problem is that if you weld abit into the combustion chamber then you can loose power as the fuel burns quicker at one end before the othe thus the presser caused by the ignition is thus weakend,,

the only save method is to get the head scimmed,, obut whether u need one mill or less depends on the engine,, get a presser guage and put it in place of the sparkplug and turn over the engine will allow you find out your pressent combustion level..but on this type of engine i would not raise it to increase the power as it will end up (as some one else on here said) dammage the main bearings and possibly break the crank

if you want abit more power why not change the engine?? these rear wheel drives are very easy to do

Charles, Instead of playing with engine tuning take the trafficators off, this will add another 5 mph to it.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

You jest but folding down the windsrenn does exactly that....

c

a diff. opt. iff head not cracked is heat head hot then fill wit

brazeing rod. down side is cannot be welded with nickel rod after a brass sinkes in and will mess up further welding. :rolleyes

-- royal

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this thread:

Have you ever come across this:

Williams, L.M. (Bill)

"Austin Seven Specials. Building, Maintenance and Tuning" Williams, L.M.

Tom

O

Yup - On the shelf!

Charles

Not tried welding on an Austin seven head but a friend of mine used to raise the compression ratio on Talbot heads by adding weld with cast iron rods and then machining. You have to heat the head to almost red hot first to reduce thermal shock.

Early Austin seven heads were not very good and didnt have enough meat to skim. The later, 1937 onwards, head gave a higher compression ratio (5.8 : 1 instead of 4.9 : 1) and you can take up to 1/16 inch off the surface. I used one of these on my special for road use. Better still is to get hold of the head from an Ulster, Nippy, or Speedy which can have up to 1/8 inch machined off. These have the advantage that it will still be acceptable to the VSCC if applicable.

The alloy heads made post war are best if you can find one.

Russell.

You could also look for the cyl. heads for an early Reliant as the early ones were the Austin 7 engines.

It can work and is done on American cast iron heads by drag racers. The weld material is used to fill the combustion chamber and is then ground out to get the desired shape and volume.

I read about it recently but can't remember where, but IIRC the head is heated to a dull red color and held at this temperature. Cast iron rod is used to build up the combustion chamber and the head is then slowly cooled in wood ash, vermiculite or wrapped in a thermal blanket material..

In some cases this technique is even used to relocate sparkplug holes.

Hope this helps.

Cheers,

Kelley

There you go then Charles, there should be a pile of old Reliants to look through in Long Eaton, with just light shotgun damage & a few bloodstains. ----------------------------------------------------------- snipped-for-privacy@boltblue.com

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I think this was done to some Cleveland pro stock engines, the heads only had to survive a few runs though. They relocated the plug and with hand finished piston crowns got 14:1. it has probably been done to every other type of engine raced in prostock before they used aftermarket heads.

furnace brazing iron heads was common enough, Swaymar used to chop a chunk out of Cologne heads and put a new bit in to give three ports and people used them on road engines!!!!!!!!!!

why not have Arias knock up four pistons.