[6pack] Compression Ratios TR250 Heads

TR250Driver at aol.com TR250Driver at aol.com
Tue Jan 27 16:29:04 MST 2009


Hey Guys,
The 250's engine is in pieces  as part of the ongoing rebuild.  I  am sort of 
at a decision point on the cylinder head.  Current head original  to the 
motor is 3.420" and the block is bored .030 over. They are telling me  that this 
is giving a compression ratio of 9.5 to 1. We will need to bore  the original 
block to .040 which would raise the compression to 9.7 to  1.  
 
My goal with this Triumph is to build a stock  motor.  Previously the 250 was 
pretty powerful from 3,000 revs to the  redline. It was fun and I tore it up 
pretty good. It was also  impossible to tune for an acceptable idle. With the 
stock goal in mind, I  have been given the following options.  An uncut 69 
early TR6 head is  available for rebuild which is claimed to return the 
compression to the desired  stock 8.5 to 1.  Actually I believe stock may have been 8.6 
to  1. Those heads would be the same correct? This claim seems to omit the  
oversize bore as a function of compression?  Confused about that. Also  what if 
the block has been decked?  Should I inquire? 
 
Also I have asked for a stock grind on the camshaft.  Would that  profile 
effect compression? In addition I have a complete TR250 motor from  another car 
that has never been touched but numbers don't match my car.   Too many choices 
and I don't want to regret what get's done so I would  appreciate the 
advantage of having the wisdom of the List.
 
Thanks in Advance,
Darrell
 
 
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