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Expert
Posts: 4458
  
Location: Jelling, Denmark | my a-series racer is burning through the headgasket between cylinder 3-4. I cant quite figure out why id does this. both the cylinderhead and the block has just been skimmed. it seems like I can drive along on the road without damaging anything, but when ever I race, it burns the headgasket between the two cylinders. but why? |
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Regular
Posts: 112
Location: Hamburg, Germany | poor quality of the gaskets has been a problem some time ago. IIRC with the black Payen it was due to relocating the factory and poor setup of the machine. depending on what type you use
in general i would say if it only happens during racing that may be a problem with cylinder pressure being high enough to lift the head a bit and than burn the gasket. using the Metro Turbo torquing procedure may help, lightly oiled threads and 70Nm.
or it may be ignition related detonation, damaging the weakest link first, in your case the gasket. retarding the ignition may help.
or one cylinder is running a bit leaner and hotter, damaging the gasket. you won't see that at an exhaust gas analizer as it only sees all exhaust gases from all cylinders, not from individual ones. |
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Elite Veteran
Posts: 664
Location: Herts | Do you have the heater tap hole open on the cylinder head? |
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Expert
Posts: 4458
Location: Jelling, Denmark | t3gav - 8/8/2016 11:21 AM
Do you have the heater tap hole open on the cylinder head?
no I don't. why do you ask? |
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Expert
Posts: 4458
Location: Jelling, Denmark | KLAS - 7/8/2016 6:17 PM
poor quality of the gaskets has been a problem some time ago. IIRC with the black Payen it was due to relocating the factory and poor setup of the machine. depending on what type you use
in general i would say if it only happens during racing that may be a problem with cylinder pressure being high enough to lift the head a bit and than burn the gasket. using the Metro Turbo torquing procedure may help, lightly oiled threads and 70Nm.
or it may be ignition related detonation, damaging the weakest link first, in your case the gasket. retarding the ignition may help.
or one cylinder is running a bit leaner and hotter, damaging the gasket. you won't see that at an exhaust gas analizer as it only sees all exhaust gases from all cylinders, not from individual ones.
Yes I use the black Payen bk450 gasket like most if not all mini racers. the gaskets were bought recently.
A guy suggested that the recent skim of the the cylinder head and block were enough to put the compression "over the top" and that the gaskets burn because of this, so this is in-line with one of the reasons you give.
He suggested a different torquing procedure and to torque it down harder. normally I torque it as haynes say, I believe its 7.5kg cold. he suggested to do that and then loosen all bolts a quarter of a turn, tighten them a quarter turn again and then torque them to 7.5-8.5kg with the engine hot. |
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drive it like its hired
| Defo plenty of thread left on the head bolts?
I had a payen gasket leak on an a series straight after fitting, all I did was pour water in and it shot out the front, never seen anything like it.
I use a cheap asbestos one off ebay and its been perfect.
How does the fire rings sit on the block or head, are they exposed?
Re-torqueing is a good idea in this scenario I think
Edited by petrol_head 8/8/2016 1:11 PM
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Expert
Posts: 4458
Location: Jelling, Denmark | petrol_head - 8/8/2016 2:09 PM
Defo plenty of thread left on the head bolts?
I had a payen gasket leak on an a series straight after fitting, all I did was pour water in and it shot out the front, never seen anything like it.
I use a cheap asbestos one off ebay and its been perfect.
How does the fire rings sit on the block or head, are they exposed?
Re-torqueing is a good idea in this scenario I think
good question with the thread on the bolts. I will check!
ok. that sounds extreme. I haven't previously had a bad experience with the black payen gaskets.
the fire rings are not on the very edge of the bore, but I guess about a mm from. on the cylinderhead they are very near the edge between the combustion chambers. |
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Expert
Posts: 4458
Location: Jelling, Denmark | petrol_head - 8/8/2016 2:09 PM
Defo plenty of thread left on the head bolts?
6-7mm of thread left. So this doesnt look like its the problem. |
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Elite Veteran
Posts: 664
Location: Herts | DotMatrix - 8/8/2016 7:21 PM
t3gav - 8/8/2016 11:21 AM
Do you have the heater tap hole open on the cylinder head?
no I don't. why do you ask?
It should be open, otherwise cylinders 3 and 4 tend to get hot as the water cant circulate. The stud holes are already tapped so drill the hole for the water and fit a heater tap or take off stub and plumb it from here back into the lower rad hose https://minispares.com/product/Classic/Engine/Cylinder_heads/Head_components/12G2534ALLOY.aspx?100402&ReturnUrl=/search/classic/12g2534alloy.aspx|Back to search |
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Expert
Posts: 4458
Location: Jelling, Denmark |
ah yes I see.
but by plumbing it this way wont I be putting hot water from the engine back into the colder water going back to the engine and thereby reducing the amount of water being cooled. shouldn't I either fit a small radiator on this hose or plumb it into the top of the radiator somewhere?
I guess an alternative could be plugging the holes in the thermostat end of the cylinderhead and drilling the ones in the other end larger? |
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Elite Veteran
Posts: 664
Location: Herts | Yeah some of the turbo guys and an additional rad there but originally it went to the heater matrix then back into the lower hose. It will stop cavitation and hot spots at cylinders 3/4 just by fitting the take off and re plumbing. |
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Expert
Posts: 4458
Location: Jelling, Denmark | t3gav - 31/8/2016 11:11 AM
Yeah some of the turbo guys and an additional rad there but originally it went to the heater matrix then back into the lower hose. It will stop cavitation and hot spots at cylinders 3/4 just by fitting the take off and re plumbing.
aah ok. good point on the cavitation and hot spots. I have seen the solution with the extra heater matrix/radiator in minis many times, but they have too small radiators to begin with unlike the metro so I think I will try this
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New user
Posts: 12
Location: Derby | Just wondered where and when the picture of the green & orange Metro was taken. Thats our old 1380 that we ran in the MG Metro Cup. Have been wondering where it got to. The flow across the head was much improved using the heater connection, we used that on all our engines. |
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Expert
Posts: 4458
Location: Jelling, Denmark | Purple00 - 14/9/2016 9:28 PM
Just wondered where and when the picture of the green & orange Metro was taken. Thats our old 1380 that we ran in the MG Metro Cup. Have been wondering where it got to. The flow across the head was much improved using the heater connection, we used that on all our engines.
hello. I don't know anything about where the car is now, I just googled until I found one that looked like what I had in mind. but since the picture is named ebay44995.jpg I would guess it was taken from an ebay auction. I do believe I sat it for sale a couple of years ago without engine.
regarding your answer, the solution I have done so far is to move the thermostat down from the sandwich plate to the head so that the sandwich plate is now on the radiator side of the thermostat and then route a hose from the mini heater take-off and to the old metro heater take-off in the sandwich plate which should ensure that more water is flowing from the far end of the head.
but in the winter I will send the radiator out to have a connection fitted in the other end for the heater take-off hose like it is done on your car.
what radiator is it in your old car?
did you drill out the water holes in the cylinderhead and block?
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New user
Posts: 12
Location: Derby | Sorry for late reply but its been many years since we messed around with A series. The radiator was a Turbo Challenge item but fitted with a high flow core. We always used the BK450 head gasket but added an extra coolant hole adjacent to no4 cylinder. The block and head were also drilled for the extra hole. If you compare the BK450 and the Group A Turbo head gasket on the Minispares web site you will see the extra hole. Other mods were to replace the steel bungs in the cylinder head face with brass ones. We didnt alter the other coolant holes in the head/block, although when we ran Turbo engines we would restrict the coolant flow on the front of the block, ie the non Turbo side. We always used 11 ARP head studs. The original engine on a scatter cam produced 135bhp @ 7750. |
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Expert
Posts: 4458
Location: Jelling, Denmark | Purple00 - 17/9/2016 8:21 PM
Sorry for late reply but its been many years since we messed around with A series. The radiator was a Turbo Challenge item but fitted with a high flow core. We always used the BK450 head gasket but added an extra coolant hole adjacent to no4 cylinder. The block and head were also drilled for the extra hole. If you compare the BK450 and the Group A Turbo head gasket on the Minispares web site you will see the extra hole. Other mods were to replace the steel bungs in the cylinder head face with brass ones. We didnt alter the other coolant holes in the head/block, although when we ran Turbo engines we would restrict the coolant flow on the front of the block, ie the non Turbo side. We always used 11 ARP head studs. The original engine on a scatter cam produced 135bhp @ 7750.
great info, thanks a lot for that. I see the extra hole in that head gasket. I never noticed that before. I think I will do this to my engine this winter.
when you restricted the flow for the front on the block on the turbo engine did you do that by blocking off some of the 8 small holes between the studs in the front of the block?
with 135 bhp it must have been a quite good cylinder head  |
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New user
Posts: 12
Location: Derby | On the turbo engines we had brass inserts fitted into the front cooling holes, with small holes to limit the flow. Regarding your detonation problem then have you checked the ignition timing on all four cylinders not just no 1. When you get the chance check the timing mark on the crank pulley to see if its really at TDC, you can also mark the pulley on the opposite side so you can check all 4 cylinders. If there is going to be a problem its nearly always on no.4 |
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Expert
Posts: 4458
Location: Jelling, Denmark | Purple00 - 20/9/2016 7:22 PM
On the turbo engines we had brass inserts fitted into the front cooling holes, with small holes to limit the flow. Regarding your detonation problem then have you checked the ignition timing on all four cylinders not just no 1. When you get the chance check the timing mark on the crank pulley to see if its really at TDC, you can also mark the pulley on the opposite side so you can check all 4 cylinders. If there is going to be a problem its nearly always on no.4
Thank you for all the info. It will come in handy when I decide to build a turbo engine at some point. No I have never checked the timing like that and haven't checked if the timing mark is at TDC either but I will when it is running again. Last weekend when racing the headgasket went again but the last two gaskets have given up between the number 4 cylinder and the water hole between cylinders 3 and 4 and previously it was between cylinders 3 and 4 it gave up. I don't know why this has changed.
What torque did you tighten the bolts to on the NA engine?
What compression and cam did you use in the turbo engine? I was thinking about 8:1 in compression,and either a mg metro cam or the minispares turbo special cam which has a duration of 256/284.
Edited by DotMatrix 21/9/2016 3:47 PM
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New user
Posts: 12
Location: Derby | We used the same set up for Turbo and NA engines. ARP head studs sealed with silicon sealant and torqued to 15 lb/ft. Nuts lubricated with ARP moly and
torqued to 40 lb/ft except the stud by the water pump at 30 lb/ft. The Turbo engine CR was limited by the race regulations to a maximum of 8.65:1 and a capacity of 1293cc. The Metro Challenge (and the later MG Metro Cup) regs were based on using the Omega forged +20 pistons and the MG Metro camshaft CAM6648
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burning through headgaskets
