One man's opinion:
Most of the time the steel shim gaskets will not work with variations
this great. TOn the other hand, the stock sandwich gasket will
usually tolerate variations of this size and will seal.
Some owners really want to use the steel shim gasket just to get the
increase in compression ratio. But, consider the fact that the stock
sandwich gasket compresses to maybe .050, the steel shim gasket
compresses to maybe .025, so you can get the same compression ratio
increase by just milling the head another .025.
There is another consideration as well, and that is in regard to the
hp increase you get by increasing compression ratio with no other
changes. Changing from a .050 gasket to a .025 gasket will increase
your compression ratio by about 0.7:1 -- that is, it will increase a
10:1 CR engine to about 10.7:1. How many hp is that worth? Well, the
generally accepted relationship is that each one point on compression
ratio is worth about 3% hp increase (If there are no other changes
made). Therefore, if you have a 150 hp engine, that CR change will
yield about 4 hp. That's nothing to sneeze at, but most of us TR
drivers can't feel the difference that four hp makes.
Along with that, I've found that some TR engines kind of "max out" in
the compression ratio vs. hp trade-off. On some engines, if you can
run 11.5:1 CR and use 32 deg ignition advance without detonation,
upping the CR to 12.5 will force you to reduce the ignition advance
several degrees to avoid detonation. My experience with chassis dyno
numbers is that being able to increase ignition advance has a pretty
significant effect on hp and torque -- therefore, in some engines,
you end up with the same hp either way.
There are other reasons to use a steel shim gasket for the folks who
want to make some more changes to the liner tops to get more flow,
but that is a separate subject.
At 06:11 PM 6/7/2006, you wrote:
>Amici,
>
> A fellow FOT'r whose computer broke asked me to post
>this question.
> What is an acceptable liner height setting for steel shim
>head gasket on 4cyl TR engine? Seems the one he's
>building has a variation of approx 2 thous from right
>side to left of block on the 3 and 4 cylinders.Right
>side is 3 thous, left slightly more than 5. After first
>try assembly and startup it leaked even after retorque.
> The block seems to be the culprit as a low spot
>seems to reside next to the liners. He's now trying
>a copper sandwich style to see if he can make a
>race this weekend but looking for feedback on what
>anyone else has been able to get to work.
>
>Thanks,
>Bill D
>Triumph Rescue
>
>
>=== Help keep Team.Net on the air
>=== http://www.team.net/donate.html
uncle jack
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