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Miata

To: spridgets@autox.team.net
Subject: Miata
Date: Mon, 6 Oct 2003 10:44:17 -0700 (PDT)
Certainly the thought of doing the top end with out doing the bottom, causing 
problems with the bottom end is long standing in both aviation and automobiles. 
The theory may not hold true regarding modern aluminum  engines however. I have 
personal experience with the Toyota 22r motor whereas I had the head redone at 
200k and have not seen failure or compression problems with the bottom end 75k 
later. That scenerio is not uncommon with the 22r. I don't know much about the 
Miata motor other than the ealier motors (thru '93 ?) had the habit of snapping 
off the crankshaft nose. Apparently when changing the timing belt, during 
installation of the crank pulley, the woodruff key can be installed incorrectly 
causing the pulley to become loose, stressing the end of the crank and 
eventually snapping off.  
 
I like the Miata. I drive about 140-150 miles a day commuting to work and back. 
I looked seriously at picking up a older Miata for the commute but with 6 LBC's 
and 3 modern cars parking around my house is creative at best! I'm now looking 
at retrofitting my 70 MGBGT with the 2.8 Chevy V-6 after I finish my Bug 
project for  my commuter. So, for now, my 97 Toy truck and 76 MGB will share 
the commute duties. 
 
I agree with Capt Bob, there are alot of good Miata web sites out there. Its 
best to check with those "experts" for the particulars.
 
Larry Pitts
60 Bug  (in progress)
ok., ok.......
60 MGA (pending)
70 MGBGT (next on the list)
73 MGB (on the list)
76 MGB (runs like a rapped ape)
74 TR6 (some where on the list)
 
 
"Robert E. Shlafer" <PilotRob@webtv.net> wrote:
Mike....

Normally, at a high mileage, ring wear to
some extent has taken place. So it is so
with valves, valve guides, etc. as well.

Matter of fact, on aircraft piston engines,
"top overhauls" are noted for causing
possible imminent "bottom" end problems.
when many hours are on the engine.

FUZZY (Larry Pitts) is an aircraft mech. so I'll defer to his wisdom as
this is really his forte....after all, pilots can only
break aircraft while mechs. fix them!

So, it can be expected that if you renew
the seal at the "top", you MIGHT increase
blow-by out the "bottom" (by the rings).

A lot depends on the sealing condition of
the rings before the head is taken off. I
suppose a leak down test prior to head
removal could tell where the compression
is going, if at all, to one extent or the other.

OTOH, I would think Mazda engines are better quality toleranced than our
Series A's. Maybe the Miata list is a better
place to ask this question of those with
experience and knowledge of this engine,
in view your engine's specific mileage?




Cap'n. Bob 
'60 :{)





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