-
Hi Guest!
You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
There are some perks with a member upgrade!**Upgrade Now**
(PS: Subscribers don't see this gawd-aweful banner
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
SaxMan's Cylinder Head Overhaul / Head Gasket Replacement Thread
- Thread starter SaxMan
- Start date
Share this page
Some pics from tonight's conquest.
This is what greeted me once the head was pulled. If you look closely, you can see antifreeze in the center of the pistons of cylinders 2 & 3
DSC_1102 by onyxsax, on Flickr
The gasket break is pretty apparent in this picture and you can see the pool of antifreeze in cylinders 2 & 3 a bit better
DSC_1105 by onyxsax, on Flickr
Bottom of the cylinder head. Those valves look a little bit toasty?
DSC_1107 by onyxsax, on Flickr
Close up of the head gasket break:
DSC_1109 by onyxsax, on Flickr
This is what greeted me once the head was pulled. If you look closely, you can see antifreeze in the center of the pistons of cylinders 2 & 3
DSC_1102 by onyxsax, on Flickr
The gasket break is pretty apparent in this picture and you can see the pool of antifreeze in cylinders 2 & 3 a bit better
DSC_1105 by onyxsax, on Flickr
Bottom of the cylinder head. Those valves look a little bit toasty?
DSC_1107 by onyxsax, on Flickr
Close up of the head gasket break:
DSC_1109 by onyxsax, on Flickr
Cylinder head on the workbench:
DSC_1111 by onyxsax, on Flickr
Engine block with head gasket removed and cleaned up a bit:
DSC_1113 by onyxsax, on Flickr
Cylinders 1 & 4 at top of their stroke. Note the differences between the pistons.
DSC_1114 by onyxsax, on Flickr
Close up of cylinder #1. I'm not sure what I'm looking at, but it doesn't seem to have any affect, as Cylinder 1 registered the highest compression and lowest leakdown when tested.
DSC_1115 by onyxsax, on Flickr
DSC_1111 by onyxsax, on Flickr
Engine block with head gasket removed and cleaned up a bit:
DSC_1113 by onyxsax, on Flickr
Cylinders 1 & 4 at top of their stroke. Note the differences between the pistons.
DSC_1114 by onyxsax, on Flickr
Close up of cylinder #1. I'm not sure what I'm looking at, but it doesn't seem to have any affect, as Cylinder 1 registered the highest compression and lowest leakdown when tested.
DSC_1115 by onyxsax, on Flickr
AN5Sprite
Jedi Knight
Offline
David,
A good source for the preferred head gasket:
https://www.bpnorthwest.com/mg/midget/engine-gaskets-seals/head-gasket-black-1275-payen.html
A good source for the preferred head gasket:
https://www.bpnorthwest.com/mg/midget/engine-gaskets-seals/head-gasket-black-1275-payen.html
Thanks for the tip on the gasket. The pictures do make it look like the brass plug is closer to being recessed than it actually is. I went back out and looked again...it's definitely well clear of the cylinder walls.
When you put the gasket back on, do you use sealant like Permatex, or will the torque from the bolts keep everything in place? Same question for the intake and exhaust gaskets.
When you put the gasket back on, do you use sealant like Permatex, or will the torque from the bolts keep everything in place? Same question for the intake and exhaust gaskets.
By recessed we mean it is lower than the flat surface of the head. When you look at the cleaned head it should look like an integral part of the head except brass colored. Most fit the gaskets dry. For some stupid reason I still like to use a little copper sealant on the head gasket.
Kurt.
Kurt.
Trevor Jessie
Yoda
Offline
I suggest you go ahead and have the head rebuilt by a machine shop. Give then instructions on fitting a threaded plug there. Then they can skim the head to be sure it is 100% flat. They can also install/grind some exhaust valve seat and new guides. Do it once and do it right.
58Custom
Jedi Warrior
Offline
Saxman,
I think you are making assumptions about the plug that are not true. You say the center plug is recessed 1mm. That means the plug needs to be replaced or you will blow the new cylinder head. As for placement, it is exactly where they all are. Same 1275 head design, same plug, same recession problem, same point of failure. It's dead, Jim. Get it fixed now or you will be doing this job again within a month. That is how I leaned about this issue. Make sure the shop uses a solid plug or find one on your own. Home Depot and Lowes have the hollow plug so go to an Ace or an independent hardware store and get the good solid one.
I think you are making assumptions about the plug that are not true. You say the center plug is recessed 1mm. That means the plug needs to be replaced or you will blow the new cylinder head. As for placement, it is exactly where they all are. Same 1275 head design, same plug, same recession problem, same point of failure. It's dead, Jim. Get it fixed now or you will be doing this job again within a month. That is how I leaned about this issue. Make sure the shop uses a solid plug or find one on your own. Home Depot and Lowes have the hollow plug so go to an Ace or an independent hardware store and get the good solid one.
Yes, I think you guys have convinced me to take the head to a shop. I have all new valves and valve hardware coming in, so I'll probably let them set that up as well. The extra bucks I spend now will probably save me several times that later if it isn't done right. I'll give the guy who did the brake work on the car a call first to see if his shop can handle it. Should I go ahead and yank the valves now? I do have the compressor spring tool to release them.
Tom - it's funny because I was comparing pictures of the head in the thread about the recessed plug and then looked at my own head and they didn't seem to match.
Tom - it's funny because I was comparing pictures of the head in the thread about the recessed plug and then looked at my own head and they didn't seem to match.
58Custom
Jedi Warrior
Offline
Saxman,
Since you have new valve hardware might as well disassemble the head and maybe save a few labor bucks. While you are hunkered down under that low, low hood, how is your water pump? (Am I a trouble maker?)
Here's a nasty ol' blanking plug and it's effect on the gasket:
Since you have new valve hardware might as well disassemble the head and maybe save a few labor bucks. While you are hunkered down under that low, low hood, how is your water pump? (Am I a trouble maker?)
Here's a nasty ol' blanking plug and it's effect on the gasket:
58Custom
Jedi Warrior
Offline
The text below is from Hap's post:
"I've posted about doing this repair before, I even done it for other shops. You remove the recessed plug, which I do by drilling and tapping 1/4"-20 hole in it, and then use my slide hammer and a adapter I made to do this, and pull it out. It comes out easy enough using this method. Once the plug is removed, I use a brass male square peg 3/8" pipe plug, I have to drill the hole slightly bigger to do this, you would use the suggested drill size in a NPT drill tap chart, there are many on the internet to refer to. Then I would seal the NPT plug with JB Weld, thread it in, let the epoxy set up, then use a cut off wheel to cut the plug as close to the head deck as you can get without touching the head deck, then have the head resurfaced to the point the plug cleans up. You end up with a solution better than what the factory did, because the threaded plug will never recess. "
"I've posted about doing this repair before, I even done it for other shops. You remove the recessed plug, which I do by drilling and tapping 1/4"-20 hole in it, and then use my slide hammer and a adapter I made to do this, and pull it out. It comes out easy enough using this method. Once the plug is removed, I use a brass male square peg 3/8" pipe plug, I have to drill the hole slightly bigger to do this, you would use the suggested drill size in a NPT drill tap chart, there are many on the internet to refer to. Then I would seal the NPT plug with JB Weld, thread it in, let the epoxy set up, then use a cut off wheel to cut the plug as close to the head deck as you can get without touching the head deck, then have the head resurfaced to the point the plug cleans up. You end up with a solution better than what the factory did, because the threaded plug will never recess. "
I think I know what caused all this trouble: I changed the thermostat because the car wasn't getting more than 1/4" off the "Cold" mark. When I replaced the thermostat, I didn't put sufficient coolant in the car (it only filled to the thermostat, when it opened there wasn't enough coolant in the system. The car began to overheat and pegged the temperature gauge briefly before, but I got it home before it could boil over. I didn't think I did any damage, but obviously this must have been the incident that caused the plug to recess and the head gasket to give way. The irony is the thermostat change had no effect whatsoever, and now I have a head gasket issue to address. I would have been better off leaving it alone. Live and learn.
sqbsprite
Jedi Trainee
Offline
We all learned some things the hard way. I just wanted to remind you that when you put everything together, put the studs in first. They should not have come out. I think you asked that question in one of your early posts. I can't stress cleanliness of the gasket surfaces enough and be sure to follow the torque sequence and values for the head bolts. Use brass nuts on the exhaust studs with never-seize applied to the threads. Also, that yellow plug needs to go. The 1275 must have proper crankcase venting. I have a line going from that fitting to an after market PCV and then to the canister on the front cover. Make sure the PCV is oriented for vacuum from the front cover canister. Without proper venting, it will blow oil past the rear crank scroll. There are some old posts on here regarding this problem. I have photos of my setup that works well, but others have done similar fixes. Having the vacuum line broken from the distributor to the carbs probably wasn't letting it run very well.
Keep up the hard work. You will succeed and it will feel good having done it yourself.
Keep up the hard work. You will succeed and it will feel good having done it yourself.
I have found a machine shop near my office that is going to do the work. I drop the head off on Monday.
Otherwise, it's been so cold (nighttime temps in single digits) that I haven't been able to get any work done on the car since I got the head off. I have a huge box of new parts for the cylinder head and exhaust system that I haven't even opened yet.
Otherwise, it's been so cold (nighttime temps in single digits) that I haven't been able to get any work done on the car since I got the head off. I have a huge box of new parts for the cylinder head and exhaust system that I haven't even opened yet.