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Discussion Starter #1
Im thinking of having the crank shop cut the head and add the cyl shim. What will that help low end or top. Will i have to rejet or clutch it. My sled is a 97 machz all stock. Thanks for any help.
 

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You should also consider trail porting and bore carbs while you're at it, it really improved my 670 throughout the powerband.

PS:put in your location if you're not running from the law

I had to write this before Paul Yarek did  
 

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how many thousands is the shim and what will your squish and compression ratio be. What you are doing with the shim is your raising your port timming which will give you more top end but you will have to bump up your rpm's or it wont help much,as far as the shaved head this will give you torque,be careful not to go above 13-1 for your comp ratio or you will have to run 93 or better octane. Let us know how it runs. happy sleddin.
 

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Actually adding the shim to a stock non piped mach z lowered the rpm at which peak power ocurred.I have a dyno sheet from Polar Motorsports that shows hp and torque up signifigantly and peaking between 7800 and 7900rpm.As far as being a good mod I would say its a better bang for the buck then pipes.While you have your jugs off and your head is either replaced or milled to allow  the chamber to hang down into the clyinder, carefully deburr all casting flash, and port match your upper half to the jugs.(there is alot of over lapping metal sticking into the transfers)We have done several of these kits at our shop and the only problem we have is finding enough weight to keep the motor under 8000 . You will be very pleased and only sharp eyes will pick out the thicker base gasket.   good luck
 

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Discussion Starter #6
Thanks John. Yes I was going to smooth and match the ports when i had the cyl off.But what about jetting and clutching .Right now im running stock 380 jets, also my clutching is stock 286 ramps bl gr spring, clicker on #4 and i do shortshift it,8000 rpm seems to pull harder.What im looking for is more top end ,i have run 110 on radar 2000 ft which i thought was pretty good for a long track.Im still running b10ev plugs , and have only ever fouled 1 plug. One more thing my compression is only 110 ,on all 3 cyl ,cold motor is that ok. Thanks for the help.
 

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Im not too sure about setting up a long track as compared to a short track, my own personal mach is a 98 with above mods plus a little exhaust port clean up and v force reeds.A couple of weeks ago at a 1000 foot radar run it ran 112 mph and we could only hold it below 8000 rpm for about 800 feet. Weve put in so much helix that it wont hardly back shift and it still over revs. Ive ordered a set of thunder shift arms and am looking forward to trying these and posibilly an rer secondary. As far as jetting goes,for z we usually run 45 pilots, with stock jetting and tempaflow(which work awsome) I would think that 110 in 2000 feet would be pretty good for a long track but the mods you are thinking of should add at least 5 mph to your top end if not more.
 
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