9 replies to this topic

[axnutty]

I have a freshly rebuilt 1293 engine. Its using a mg metro head, freshly skimmed, and the block i had decked, so both mating faces are (or where at least) true and flat, with no corrosion or marks. Its running 10.55:1 CR

it has a 9 stud setup and this should be fine at CR figures such as this apparently.

The water system is all new, apart from the water pump and rad cap. It was running a 88C stat.

On running in, all was fine, but the water temp was sitting high on the gauge at 90C / 95C. After 500miles I fitted a super low diff ratio which meant engine revs were high at 4500/6000 most of the time and it subsequently got very hot on a spirited drive later that week. No visible coolant loss, but got the gauge up to 105, stopped with electric fans on and it climbed to 130C. Got it towed home, fitted a cooler stat, new high capacity water pump and a larger cooper s pulley to stop cavitation. It then seemed ok, and i went and did a classic navigational rally. Water temps were getting high again, i noticed at this point that the water level was low in the rad despite being absolutely full the night before with all air locks removed. So i replaced the rad cap, which i noted had a much softer spring than the replacement. It then blew its head gasket (geg300). I stripped it down and replaced the headgasket (geg300 again). It blew that in the same place within 5 miles. (Back of number 4 cylinder to outside right where extra stud hole would be). I wiped the head off and put it on a milling machine deck. It has 0.003" deflection in the middle, but really i cant see this being the culprit. A headgasket should allow for that.

what else could it be?

the water system is now entirely new.

are geg300 hg just not up to the job?

with it failing around the extra stud hole, do i infact need the extra studs int his case?

[GraemeC]

They're not my favourite gasket - I much prefer the BK450 (TAM1521), but they should still do the job.

 

How confident are you on the calibration of your torque wrench?

[TehMarchant]

Any leaks around the heater unit?

 

Are you using a 2 core rad?

 

Is the top hose getting hot? IE good coolant flow

[axnutty]

Matrix is fine, i actually deleted that though after first hgf anyway.

torque wrench is new. Originaly set at 40ft/lbs, second time went to 50. Am retorquening if necessary after first heat cycle as well.

Should also say, its a head without bypass so ive drilled two 7mm holes in stat body.

[Spider]

With the revs you've been doing and the temps you have been seeing, I'd say there's an issue in that alone. High Revs with a low diff should mean low engine loading, so low engine temps.Has

 

Is the right carb set up and right dissy, I'm guessing something here is well out of where it needs to be.

 

Is the head cracked? That too will lead to over heating and sometimes subsequent gasket failure.

 

Following on from Graham's comment on the torque wrench, are all the head studs and nuts the same? A mix here means clamping is not consistent, which again, can lead to gasket failure.

[Wrgreen]

I would say get a payne head gasket. Also you say its blowing on cylinder four and if i remember correctly the metro heads did not have the hole drilled out near cylinder four for the heater valve. This means the water does not flow around the head correctly and cylinder four gets hotter than the others. I would sugest drilling the hole out.

[dyshipfakta]

I agree think your head gasket is a symptom rather then the actual issue. Your temps are way high. Is your fan on the right way around?? Simple but seen it happen to many folk. I would also strip and clean the coolant system again make sure there is no crud.

[MRA]

I would say get a payne head gasket. Also you say its blowing on cylinder four and if i remember correctly the metro heads did not have the hole drilled out near cylinder four for the heater valve. This means the water does not flow around the head correctly and cylinder four gets hotter than the others. I would sugest drilling the hole out.

 

Not actually true, the flow around these heads is more than adequate, more 7mm holes in the stat would help, but again 2 is normally sufficient, I would go with fuelling or ignition, what distributor are you using ?  as your curve could be giving you a retarded top end thus causing your overheating issue, also if you have a manual fan is it the correct way around ?

 

Cavitation will not be an issue up to the revs you are using.

 

The copper head gaskets really need a ground not milled surface to get the best from them, use a Payen BK450 much better and much much much more reliable.

Edited by MRA, 08 May 2016 - 12:53 PM.

[axnutty]

Fan is on correct way, both of them as i re fitted the mechanical one. The car in question is actually an mg midget, so block is akin to a 1275gt id guess, head is definetly metro though.

dizzy is an aldon yellow, designed for a 285 cam and hif44, which is what im running. I will admit that the breather pipe on the hif44 had not been blocked, as i hadnt realised its existence till this morning. So i guess it could have been running lean which wouldnt have helped. Although it is running a very rich needle in there which may have compensated a little. Either way its now blocked a back down to a bdl

the head gasket has failed both times in the same place, which is near to a hole thats in the block is sealed off. I shall try get a picture shortly. I dont know if thats of importance as its obvioulsy a new engine and one made from bits, so maybe i have some incompatibility issue....

[carbon]

Couple of suggestions. First check block and head faces again for any warping, I know you have had them both decked but running a motor up to 130C may have caused some warping. Anything more than a few thou could be suspect.

 

Second does your head have any brass plugs fitted on the deck face? Some 940 heads have these fitted, and the one between cylinders 2 and 3 can sometimes shift, and ends up about 5 thou recessed. Unfortunately it's pretty much right on the gasket sealing rings between the cylinders.