>My name is Grant,
>
>I am currently building an engine from my Hunter and I believe I have
>a
>little problem.
>
>After assembling the bottom end (Stroked .350 crank, Rods & pistons
>out of a
>Mitsubishi Starion Turbo) and cc-ing the combustion chamber (20cc in
>pistons, 43cc in head) I have a comp ratio of 8.93:1. (500 ccin
>swept
>volume)
>
>This would be alright for a normally aspirated car but as I intend to
>supercharge the engine, I would lie a comp ratio of between 7 - 7.5:1.
>
>The head (alloy) appears to have been modified with the combustion
>chambers
>similar to that of a Holbay head, with larger exhaust valves. I do
>not know
>what can be taken out of these heads. I need to gain about 12-17cc to
>bring
>the comp ration down to what I need.
>
>If anyone out there knows of (or has attempted) a modification which
>might
>work, I would greatly appreciate your input.
>
>Is a spacer a good idea?
>
>Regards,
>Grant Crough
>Email: Mutters(at)bigpond.com
>
>Please address all replies to messages from the Hillman List to:
>
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>
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>information in your reply.
Grant,
Boy I hope those starion Rods are at least 5.8 inches center to center,
or
you are in for one wild vibrating motor with that kind of stroke.
Sounds like you ought to make pistons for this beast.
This will allow you to use SB chevy rods "longer than stock",
and make the crown of the piston to whatever volume that you desire.
Have you allready bored the block, and ground the crank?
What is the journal size of the crank now "after stroking it?"
The Starions standard crank journal dimension is 2.087, which
is a nice grind from a standard rootes crank, but even then
you cant get .350 additional stroke with this "starion" rod.
You could get about .050 though via an offset grind.
The 2.000 inch chevy bearings will allow up to a .230 increase
in stroke.
I would use the rings from the Starion, and thats about it.
Use widened chevy rods with 2.100 or 2.000 bearings,
carrillo type rods. Rods should be at least the 5.7 inch
or even 6.0 inch if you want more torque and a smoother
engine balance.
Chevy wrist pins "different diameter than rootes", and of course
clevite 77 SB chevy bearings.
The ultimate compression ratio that you feel you need will require
that you remove a bunch of material, and based upon the bore and
stroke that you have selected, looks like you will be running
about 2.2 liters "that is if you can really stuff these starion slugs
in the rootes bore".
I think that you may be in worse shape than first you thought on your
compression ratio.
Perhaps you miscalculated your "swept" volume.
I calculate it to be around 550ccs, assuming 3.59 inch pistons,
and 3.300 stroke.
Looks like you may want to run a reduced compression height on the
piston cause there just aint enough meat in that head to do the job.
Are you sure you can get 3.59 inch bore pistons into a rootes block?
Iffen so, have you though about how to seal off the head gasket?
The stock pieces only work to 3.270 bore.
I would be far more inclined to drop the Starion motor into
the alpine for the trouble your about to face.
Hope this helped.
Jarrid Gross
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