Heads cracking between valves.

[KAL SPL]

Im suspecting this is a common fault , I have 2 spare heads and both are cracked  , the 1 on my motor currently is running but continually has misfiring issues which I assume is also cracked.

[KAL SPL]

Thanks guys this forum has been a great help I assume im the only person this has ever happened to ...

[Rusty's Uncle]

I think that the lack of response is down to the fact that this is not a common problem. Not one I have come across before anyway. I can see by the shape of the combustionn chambers that it is a later type head. Could they have been from a bad batch of castings ?

[ChrisRLewis]

The usual cause of a crack between the valves is an overheating engine. May be worth checking thermostat, ignition timing, fuel mixture, slipping fan belt.. etc

[michaelodonnell500]

never had this happen before, sorry!

[thepuddlejumper]

I was told this is a common problem with the panda 30 heads, I have had three panda 30 heads and two were cracked between the valve seats.  Took one to a local alloy welding co, they gave it to an apprentice to weld, when I was there at the time, the guy took an angle grinder to it and cut down the crack and through the valve seats and destroyed it.  Lucky white heather!!!!!  anyway I spoke to an Italian mechanic, he builds 500 engines, and he said that on the panda head it is not a problem because the depth of the valve seats are 10mm thick and the crack would have to go that deep before it would affect the performance.  A friend in the 500 club took a cracked panda head to a local vehicle machine shop where they removed the valve seats and welded the crack and fitted new valve seats think it cost about £75.  The panda head on my gamine has cracks between the seats and I have been running it like that for the last 11 years, touch wood.  I took it on the tour of europe, 50th anniversary and launch of the new 500 in 2007, wheels fell off at 60mph, drive shaft couplings lasted about 700 miles, condensers about the same but the engine never lost a beat during the 3200 mile return trip.

[KAL SPL]

It has been suggested that running it to lean will cause it , back in the day when I had no idea how to set the timing and keep up regular maintencance it used to ping its head off , I just tried to drive it through a certain rev range without it pinging but suspect it was always to lean , that make sense ?

Just thought it odd that the 3 heads I had all have the same crack between valves , 1 being worse than others the crack was right up into the inlet runners.

The good head has been cleaned and ready to rock now.

[Pete126]

It has been suggested that running it to lean will cause it ,  back in the day when I had no idea how to set the timing and keep up regular maintenance it used to ping its head off ,

Yes that could have caused it or maybe trying to run the bugger on Aviation fuel or Aussie Lager
Nice job on the head Daryl

[smallcox]

Sorry for the slow response,(missed this question) I hold my head in shame.

Panda heads seem to suffer more from this problem than the siamese head that you have. As mentioned above this is rare, but I have to had this crack between the valves and when it happens it's always both sides that go. On the plus side althought this is not recommended you can run with the crack without any symtons for quite some time. Thermal stress is the cause (suddern heat changes) as mentioed above the main reason would be lean mixture on the fueling. Normally if pre-ignition has happened the head will have small holes in the squish area that look like some one has used a centre punch on it. Did you find out if your head is cracked as you mentioned missfiring, This also indicates possible weak mixture, now you have a repaired head to fit I would check the mixture/carb that it is not leaning out as the revs increase.

Happy motoring Smallcox

[KAL SPL]

Thanks for reply , Im a full bottle on every square inch of these engines now (self taught) after having weekly problems from ignition module to carby float collapsing to earth straps loose and setting the timing correctly plus rocker gap being non existant.

The timing is now spot on and the car runs perfect , I havnt as yet swapped the new head in as the original motor has been re bearinged/gasketed and detailed to be swapped out as soon as a I get a few more small bits sorted.

Even now with everything spot on I still here the occasional backfire/missfire which Im assuming is coming back through the carby as it isnt that loud to be coming from the exhaust.

Im assuming the exisiting head also has the cracks and could potentially be wherre the noise is coming from.


The motor this head came from was basically run into the ground until it jumped a rocker off the pushrod , I have learnt much since then

[nrg19uk]

Kal spl what's all the pitying in the top pic of the skimmed pictures?? Poor quality head??

[KAL SPL]

Honestly couldnt tell you , that head came off an engine I got in a crate already in pieces , I assume the previous engine had a rough life.

[KAL SPL]

Still got a fair bit to do but its getting there

[smallcox]

Kal spl what's all the pitying in the top pic of the skimmed pictures?? Poor quality head??



As I mentioned this is pre-ignition, this will distroy cyclinder heads and pistons. You have been warned

Engine above looks good

[bis13]

kal what car is this engine going into? only i notice you have a 500 thermostst housing (or you have altered the original 126 housing?).