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Engine Related Items / Re: Engine Identification
« Last post by JohnTwist on February 14, 2020, 03:23:57 PM »
Here are some photos that have information about engine identification.  Here is a bit more:

The three main MG engines have a tach drive at the rear of the camshaft.

The 18GB engine is set for a dynamo, the newer engines also have a set of vertical 5/16-24 threads to accept the rear mount of an alternator. 

The 18V engines use a very different front engine bearing plate and a single row chain and sprockets for the cam.

The 1968/69 rear engine plate has a hole about the size of a silver dollar on the LH bottom.

Hope this little bit helps.
John Twist


Engine Related Items / Engine Identification
« Last post by march2020 on February 14, 2020, 03:14:31 PM »
I bought a 1963 MGB completely dissembled back in June. The previous owner had the motor rebuilt and indicated it was a 5 main engine. I have not pulled the pan to verify. My challenge is determining if it is an 18 GB or 18 GD because there is no engine ID tag. Can you provide some help?

Tom Bishop
Westerville, Ohio
Engine Related Items / Re: Breather Tube to Aluminum Valve Cover
« Last post by JohnTwist on February 14, 2020, 03:28:24 PM »
A;   Drill a pilot hole then follow with a ¼” NPT tap into the valve cover exiting the right rear of the valve cover pointed towards the windscreen washer container.  Use a ¼” pipe nipple (grind off the excess that protrudes into the interior of the engine so there is no chance of fouling the valve springs).  The ¼” inside diameter is much too large for proper ventilation. 

It must be reduced to 5/64”.  I found it easiest to use my torch and solder several washers of descending size on the end of the pipe nipple, ending up soldering the pipe shut.  Then drill that 5/64” hole through the solder in the middle of the smallest washer

Use a ¼” pipe nipple, it needs not be barbed – it’s a 95¢ hardware store item.  That’s ¼” inside and ½” outside.  It’s a taper fit into the valve cover so it’s tightened VERY snugly.  But, again, grind off the excess that protrudes into the inside of the VC so it has NO chance of fouling the rocker assembly.

Hope this helps.
John Twist
Engine Related Items / Breather Tube to Aluminum Valve Cover
« Last post by march2020 on February 14, 2020, 03:15:41 PM »
I need help regarding adding a breather tube to an aluminum valve cover. The hose connected to it will come from the charcoal canister.

David Braun
Engine Related Items / Re: Engine Compression
« Last post by JohnTwist on February 14, 2020, 03:29:55 PM »
A:   Back up a couple of steps.  When an engine comes to rest, two valves remain open.  If the engine sits for a period of time –months / years – then those two valves develop some rust on their faces and cannot perfectly seal.  So, before I determine compression, I run the engine for ten minutes and then check the compression.  If something’s amiss – a variation of more than 10% cylinder to cylinder, then I adjust the valves (0.015” in your case), and check the compression yet again. 

If the compression is extremely low in one cylinder, the problem could be the valves, the piston/rings, or the head gasket.  In ALL these cases the head needs to be removed to fix the problem – so I never squander time trying to figure it out from above.  Once the head’s off the problem is usually easily seen.

Support the head upside down on the bench and fill each of the combustion chambers with fluid.  Gasoline is handy but dangerous.  Fuel oil / mineral spirits are effective.  If one of the valves is leaking, you’ll see the fluid drip out of an inlet or (more likely) an exhaust port.

Position the pistons at the same height.  Pour that same fluid into the cylinders – say one inch above the surface of the piston.  Over the next fifteen minutes look at the fluid height in each cylinder.  If the rings are faulty in a cylinder (or worse) the fluid will escape down the sides of the piston and into the sump more quickly than the others.

Cylinder compression – the raw number – is a function of the valve lash, the integrity of the valves/rings/gasket, the heat of the engine, and the speed it’s spinning over.  I’ve never noticed a difference in compression by the position of the throttle.  The important thing is that they’re within 10%.  Of course, a true figure of less than 90 psi indicates something amiss (list above) or cam timing.

There are cylinder heads available on eBay and at swap meets.  For example, the Chicago Area swap meet every late winter, early spring always has cylinder heads there.

Hope some of this helps!
John Twist
Safety Fast!
Engine Related Items / Engine Compression
« Last post by march2020 on February 14, 2020, 03:17:07 PM »
I've been watching some of your awesome MG repair videos on youtube.  First of all - thanks so sharing so much great content.

I have a question regarding a project a friend and I just picked up.  We have a '70 MGB with virtually no compression in front cylinder and low <90 in the other 3.  We pulled the head and first off noticed a crack.  The engine has been rebuilt as it has +.030 pistons in it.  Unsure how many miles it has on it since the rebuild.  The crack doesn't really explain the low compression especially in front cylinder.  We will be pulling the valves to see what lies underneath soon.

Anyway - what would be your recommended course of action in this situation?  I assume at the very least we will need to source a good replacement head.  We are trying to minimize cost but still want to build a quality motor.

Let me know your thoughts.

Thanks so much
Steve Betzhold
Upkeep and Performance Hints / Koolmat Insulation
« Last post by JohnTwist on February 14, 2020, 03:37:01 PM »
The below is for everyone’s information!
John Twist

If you ever have an area that needs heat and or noise reduction, check us out. No, we are not one of those suppliers that offer low-cost thin aluminum foil on one side and cotton padding on the other. This entry-level product will wear out underneath your brake and accelerator pedals over time.

Ours is a product made from Owens Corning Silicon and bonded to Owens Corning fiberglass. The result is a thin matting that can reduce noise up to 23 decibels. Sold in rolls 30" to 60" wide or we can die-cut to your supplied dimensions. Koolmat is burn tested and certified to FAR 23.853 and 25.853.

Another feature of Koolmat is that it can withstand heat up to 500 degrees on the silicon side and 1,100 degrees on the fiberglass side. Making this lightweight product desirable for extreme heat management.
Used by NASA (Hubble Telescope), NHRA, NASCAR, FAA too.

If you would like free samples or more information please let me know.

Thank You,
Bill Jarrett
Koolmat, Inc.
149 Rolling Hill Rd.
Mooresville, NC 28117
Body Work Related Items / Re: Replacement Frame/Chassis
« Last post by amgba on February 14, 2020, 03:38:31 PM »
There is NO frame on a MGB... it's a monocoque vehicle. If the "frame-like" members (such as the king rails) are rusted out, they have to be rebuilt by carefully welding on new metal in a way that attains original strength.

Barry Barnes
Body Work Related Items / Replacement Frame/Chassis
« Last post by march2020 on February 14, 2020, 03:09:13 PM »
I found out the frame / chassis on my 1980 MGB (LE) rebuild is gone. Anyone know where I can find I replacement?
Michael Ben David
Engine Related Items / Re: Weber Carburetor Tuning
« Last post by amgba on February 14, 2020, 03:39:11 PM »
Ignore the purists who demand that you put SUs on your car. They think the HS4 was designed for the MGB, actually, its design goes back to 1904.

Also, be aware that any carb can develop air leaks due to worn parts. HS4s are just as bad for air leaks and worn parts as any other carb.

A well tuned Weber DGE 32/36 carb in good condition is very economical and will give you an extra jump when you want it due to its 2-stage design. I drove mine years getting a consistent 27 mpg.
Barry Barnes
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