MG MGB and MGB GT Tech Talk
I have 1973 engine with a good bottom. A friend of mine has a 1979 with a good head and bad bottom. Can he use my bottom and his head? Also, I would like to use the head from the 73 and put it on an 80. Whatdayathink?
tx for the help in advance.
tom
I may be wrong - but I think all the heads are interchangeable. I'm not sure if the 3 and 5 main heads are different. There are some valve size differences, but the stud locations are all the same (I think).
You may need to check what push rod you need to use, but not sure.
You can put any 18v head on the 1980. However, it eliminates the water choke. Not a bad thing, just something to know. If you put a water choke head on an earlier one, make a blanking plate.
Yep, you can use the late head on the 73 block without any trouble. Both are 18V engines and have the same size combustion chambers. All MGB heades are interchangable to a point. They all have the same bolt patterns, BUT combustion chambers are different and the wrong swap may cause unwanted results. Everything made before the 18V engines used a large cc and had smaller dishes in the pistons. 18V engines used a larger piston dish and smaller cc size. So, if you used a 18V head on an early engine, you would see a rise in comprwssion ratio. Use a early large cc head on a late 18V large dished piston engine and you will see a drop in CR. Difference amounts to about one point in the cr, so while the difference is not drastic, it may be enough to further lower a low comp engine and loose a bit of performance or raise the cr on an already modified engine to the point of requiring premium gas or an additive to prevent knocking. Oh, and there is an issue of the exause valve on a 18V head hitting the edge of the cylinder on a non-18V block to consider, but there are also other considerations with this issue as well like cma lift and head thickness
Wasn't there some issue with the rocker arm oil passages between the older heads and the later heads?
Later heads used an offset hole location on the rear rocker support, so you must use the correct tower for the head you choose. Use the wrong one and you will get no oir to your rockers
I have been running a '70 head with a late model block for three years now and no probs so far. Little guy runs really smooth for what it's worth.
With the 73 head. If it's not cracked I would stay with it. The water choke heads are real subject to craking. Much more so than the 74 1/2 and back heads.
the water holes are slightly different from 74 1/2 onwards.....but the head gasket will take care of it....the 73 block will line up with the 79 head except that the holes in the head are more that the 73 block and the head gasket will plug them....with no harm done.....count thecooling holes. And note the locations
