[6pack] More POWAH

Robert Lang lang at isis.mit.edu
Mon Mar 23 09:06:58 MST 2009


Hi,

So, I strapped one of my cars on a dyno expecting "big numbers" or at the 
very least bigger numbers than what I had seen before. Assuming things 
like 12:1 compression and proper cam timing, I should def. see 150 fwhp 
and that should translate to maybe 130 at the wheels. I eventually got 
there (135.8 to the wheels), but less than what I really want.

So, where did we go wrong?

I took the motor apart a couple of weeks ago. Bear in mind that I need to 
start driving this car in a week or so from now. The "tradition" 
continues, e.g. Bob starts major car repair / improvement just before 
needing to use said vehicle. I think I like the excitement of the 
last-minute "gotta get 'er done" thing.

At any rate, 12:1 should mean roughly 36 cc combustion chambers. Note - 
that includes the head gasket. Fearing that taking off too much head 
material, I cut the head to  3.315". That should have been 3.295 according 
to the TR6 Comp. Prep book.

Turns out I was waaaaay too conservative. I measured the head w/o the 
gasket and I have 38cc chambers. Add the gasket (and factor out a tad due 
to the dome pistons), and we're close to 41cc chambers. Even with a .040 
overbore, this is something like 10.4 or 10.5:1...

So, I'm making the exact amount of power that I should be making 
considering all the parts of the system.

Oh well. I'll put that motor back together and go to plan B which is to 
finish the other motor. That one is def. over 12:1!!

In the words of H, Simpson...

DOH!

On the plus side, I def. don't need 110 octane fuel with what I have right 
now. :-)

rml
p.s. having a burrette is awesome. CC'ing the heads is a 20 min job and 
well worth it if you take the time.
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Bob Lang              NER/SCCA                 |  This space for rent
Solo Chair 2008       TR6 40 F Prepared        |  Triumph!
Voice:781-438-2568    FAX: 617-258-9535        |  Cell: 339-927-4489
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