Well, that was inconclusive -
Blackstone by
Chris Conrad, on Flickr
While they're assuming an A-Series engine in their analysis (probably due to old records I have on file with Blackstone), what I'm able to gather is that there appears to be nothing structural or mechanical that is out of sorts.
The leakdown I performed before we left for Bonneville also indicated no issue with ring or valve sealing.
Nick is going to be in Wisconsin for the Bears-Packers game in a few weeks. Before then, I'll give Fordboy a call as well. It would be my preference to not pull the head, but that I can do with the engine in place, and in-chassis tuning might just be what we need to suss out the issues.
I'm very glad to not see indications of excess wear - it speaks to the precision that Mark, Steve Demirjian, and T&T put into the machining work ahead of assembly. Thanks again, guys.
My order from Moss Motors is being filled today - parts are on the way for the new/old Midget clutch arrangement, and, unfortunately, my MGB as well.
I hadn't driven the MGB in over a year due to work on the Midget. When I last drove it, if I rolled into it too hard, I would get a backfire into the supercharger manifold. I checked timing and fuel and looked for leaks around the intake/exhaust gasket. Nothing there, so I pulled the head.
And there's the leak . . .
20211112_171037 by
Chris Conrad, on Flickr
Due to pandemic related international shipping issues, the Payen gasket set that I would have preferred to install is not available stateside at the moment. I was able to secure a copper head gasket - it's on it's way.
A mystery was cleared up by me pulling the head on the MGB. From 1972 until 1974, British Leyland B Series heads, casting # 12H2709, utilized a larger intake valve, but did not have hardened valve seats. I've put 40,000 miles on this engine - about 35k of which have been under boost - and only once had to adjust the valves. No valve recession, which indicated that a previous owner had done the heavy lifting and installed hardened seats.
The mystery was why the head did not have air injection holes or plugs, which were a feature of the 12H2709.
Turns out that whoever took care of the head swapped in an earlier 12H1326 head and had it fitted with hardened seats.
20211109_143335 by
Chris Conrad, on Flickr
I'm both a bit miffed and grateful, in that the earlier head has a 1.562 intake valve vs. 1.625 for the smog casting. In a stock application, the larger valve head provides more hp toward top end, but loses about 2 hp in the 3k range. And while the 1.625 valve head is desirable to racers, it's noteriety in the dependability department pales to that of the 12H1326.
With the supercharger, horse power has never been an issue with this car, so I won't dwell on it.
I'm just going to replace the gasket, screw it all back together, and be happy that I've got a 50 year old car that I've completely enjoyed escorting Kate around in for the last 18 years.
