Gasket and Block Problems

[baynes]

Currently working on a friends MGB he had the head machined and refitted this with a new gasket, fortunately the car had very little use since due to a head gasket water leak mainly front LH side.

Removing the head I found two contributing factors on the block.(1)Stud threads had pulled up by 0.1mm/.004" I have now chamfered these off with a 90 degree cutter.(2)The main problem was a build up of "gunk"a heavy and hard rust deposit surrounding the water passage holes through the block, mainly around the five large gasket holes, 3 LH and 2 RH side. This deposit was 23mm/.905" dia.and approx. .25mm/.010" thick. The disturbing aspect was the new gasket fitted was seated on these deposits the corresponding holes being 19mm/.748" dia. with the rolled over sealing ring being 22mm/.866". so clearly the new gasket could not seal. The earlier gasket fitted must have had larger holes around these water passages than the new one. I would have thought these gaskets would be made to standard dimensions, no doubt materials could differ. Possibly one was an El Chepo ?

Have since levelled these areas off using a flat steel block and 400 W&D paper, this also removed a slight burn mark on the block at the top of #1 cylinder at 10 o'clock from the front,ie in the direction of the water leakage. Good thing the engine was not run for long, as obviously there was water and gas leaking out together.

I am puzzled by the different hole sizes around the water ports is this common ? Maybe some one with with a MGB head gasket laying around would like to check and comment.

Being a "newbie" this is my first postlng I don't if I can attach a photo of the area in question, have one which shows the problem even the flow path of the water.Will try.

 

[Steve_S]

I had a similar "gunk" experience which we are guessing was due to the block being hot tanked and not properly flushed before rebuilding. See photos at https://www.lbcnuts.com/engine

 

[Dave Russell]

Hi Baynes,
Welcome to the forums.
It is pretty common for gaskets to be made with oversize water holes. This prevents the possibility of the gasket restricting the water flow. Often the gasket will be made to fit several variations of engine which often have slightly different water hole sizes & locations. I don't think that the various gasket makers have any standard on this, so two different brands of gasket could very well have different water hole sizes. The various locations can even vary a bit in the same production run. It usually doesn't present a problem as long as the gunk is removed as you did.

Good move on the stud holes. They should always be slightly chamfered to remove the possibility of lifted top threads. A heavy flat file run over the mating surfaces will level things pretty well.
D

 

[WJM]

I have had a few gasket problems and have found the only gasket to fit is a copper one. Since I have fitted a copper gasket I have had no problems. Have had no problems with the holes in the gasket but I think as it has been said it depends on the maker. Good luck with yor rebuild. Regards John.

 

[baynes]

Thank you all for your replies. looks like the "gunk" problem is not unusual. Re head gaskets certainly pays to check the hole configurations. Will be back for some ideas on block flatness, when I get a suitable photo marked up.

 

[baynes]

A follow up to above. A photo is attached to this which shows the block with stud holes chamfered and "gunk" around water ports levelled off. The location of the "gunk" deposits can still be seen in the photo after being levelled off, a light hard deposit still remains.left alone.

The main purpose of the photo is to show straight edge positions and corresponding feeler gauge readings for a flatness check. The area of concern is the .002" to .003" between 1 and 2 cylinders and extending for about 45 degrees around each cylinder to LH side, then back to .002". See sideways check.

The question is the reuse of the block without resurfacing ? Possibly if the block is marginal it may be worth a try to avoid the work and cost of resurfacing. Only the cost of a gasket is lost, time not that urgent.

Over to the more experienced on this question. If reused any thoughts on a head gasket, make and type ? Also the pros and cons of a gasket goo ?

 

[baynes]

RE last posting, missed the attached photo. I'll learn

 

[baynes]

Clicking on attachment in my last posting to look at the photo, it may come up a bit small and text not clear.
Depending on your computer set up go to FILE and PRINT PREVIEW you will get a better view.

 

[Dave Russell]

[ QUOTE ]
The area of concern is the .002" to .003" between 1 and 2 cylinders and extending for about 45 degrees around each cylinder to LH side, then back to .002". See sideways check.

The question is the reuse of the block without resurfacing ? Possibly if the block is marginal it may be worth a try to avoid the work and cost of resurfacing. Only the cost of a gasket is lost, time not that urgent.


[/ QUOTE ]
It's border line on whether the block will seal or not. Depends a lot on the condition of the head which isn't mentioned. Your best chance, if there is any, is to use a Felpro composition head gasket which has metal rings around the holes. I have found this type of gasket to give superior sealing over the two sided metal types. The Felpro gasket # 21183C is available for MGB's if you look around.

The fact that the block threads were pulled up tells me that the studs have likely been stretched too much also. I strongly suggest getting new studs, nuts, & hardened washers, if the gasket is to have a chance of holding.
D

 

[baynes]

Dave Russell Thanks. The head was checked on a surface plate with a light repeat light coating of bearing blue and appears OK, apparently was resurfaced recently.

Will replace the head studs, by the extractor marks these had been out at least twice before. Believe these should only be put in " wrist tight", say 4/5 ft-lbs

Any thoughts on gasket cement with the Felpro gasket. ACL in Australia make a similar gasket I understand,ACL Mono Torque they say no additional gasket cement required, then later on in the web site they say if Holomar is used the head gasket must be retensioned. Conflicting

 

[Dave Russell]

The Felpro gaskets claim to have a heat set lacquer coating & should be used dry. I think that the head should be retorqued after one heat-cool cycle, but hopefully, you may find that there is no change when you retorque.

I don't know if ACL is the same as Felpro or not. You should be able to mail order Felpro on the internet.

I use Hylomar for most other applications but not head gaskets. On a metal faced head gasket, I have found that Permatex "Copper Spray-A-Gasket" works very well.

If the studs go into the water jacket, use a sealer such as Permatex Aviation Sealer on the threads & set them very lightly as you say. All new studs should be torqued to tension & released several times (maybe three) before final tightening.
D