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cb5331
MMT Super Elite Member
Joined: Fri Dec 18, 2009 8:10 pm
Posts: 16915
Location: Rowlett, TX
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 to shim or not to shim Dad has a 32 briggs. Having the heads ported and polished and the valves done. Also changed to the 36 carb. From everything I could gather, while working on the heads we should go ahead and shim the springs. Should we? If yes how many thousandths? Thanks.
Also, before the work he was turning around 4250 rpms when empty. He was using the wheel from a 27 and liked it because it planed out faster and carried a load a lot better. The valves were in pretty bad shape, so I'm assuming he should see some decent gains when he gets it back. I'm guessing he'll go back to the 32 prop, but should be close to 36 hp, so I'm guessing he'll be in the same rpm range. I knew pretty close to that range is where you are pretty close to floating the valves. So if it doesn't hurt anything to do it, I would think that we should. Just need to know how much.
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| Wed Jul 28, 2010 5:31 pm |
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craig
MMT Elite Member
Joined: Tue Jan 13, 2009 7:53 pm
Posts: 7515
Location: Chauvin
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Re: to shim or not to shim
_________________
1750 GatorTail Extreme/Stage 3 37 GTR HD
Procrastination is a lot like masturbation. Sure it sounds great at the time but, in the end your only f--k--g yourself.
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| Wed Jul 28, 2010 8:30 pm |
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cb5331
MMT Super Elite Member
Joined: Fri Dec 18, 2009 8:10 pm
Posts: 16915
Location: Rowlett, TX
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Re: to shim or not to shim Is it something we should do? Thanks man
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| Wed Jul 28, 2010 8:31 pm |
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craig
MMT Elite Member
Joined: Tue Jan 13, 2009 7:53 pm
Posts: 7515
Location: Chauvin
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Re: to shim or not to shim Yes...I would!
Your valves generally begin to float in the 4350-4450 rpm range on these engines and you stated your already turning 4250. Working these heads (decking...porting/polishing)will allow you to turn higher rpm's....especially if you add an aftermarket carb. in the future.
_________________
1750 GatorTail Extreme/Stage 3 37 GTR HD
Procrastination is a lot like masturbation. Sure it sounds great at the time but, in the end your only f--k--g yourself.
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| Wed Jul 28, 2010 8:38 pm |
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cb5331
MMT Super Elite Member
Joined: Fri Dec 18, 2009 8:10 pm
Posts: 16915
Location: Rowlett, TX
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Re: to shim or not to shim Thanks again. Appreciate the explanation.
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| Wed Jul 28, 2010 8:39 pm |
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Wilson
MMT F.E.
Joined: Thu Jan 15, 2009 6:35 pm
Posts: 935
Location: South LA
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Re: to shim or not to shim What sort of rpms is everyone running with carb/heads/exhaust?
I have the carb & exhaust and I'm debating about getting the heads. My dealer doesn't seem as impressed with heads as a lot of people on here and says it all depends on how well your current valves seat. He has consistently said that shimming the valves is a good and less expensive idea, if I'm bumping the rev limiter. I'm running 4150-4250 rpms now and only bump the limiter when grinding in the mud. Compression & leak-down tests are both fine.
I'm seriously considering the Iron Mountain heads because they seem reasonably priced with stainless steel valves included. Anyone have any opinions or suggestions about these?
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| Wed Jul 28, 2010 11:18 pm |
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deadbird8
MMT 1000 Club
Joined: Wed Feb 04, 2009 7:50 pm
Posts: 3833
Location: Old East Dallas, Texas
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Re: to shim or not to shim
_________________
Excel 1851F4 w/ MB35HD+R CDI with a little bit of this and little bit of that
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| Thu Jul 29, 2010 6:29 am |
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dpd
MMT Addict
Joined: Thu May 07, 2009 10:25 am
Posts: 714
Location: Thibodaux, LA
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Re: to shim or not to shim
_________________
16 x 48 Blanchard Bateau / 40 PD FPR
Eat,Sleep, Fish, Hunt. Repeat.
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| Thu Jul 29, 2010 10:39 am |
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dguidry
MMT Super Elite Member
Joined: Tue Jun 29, 2010 1:20 pm
Posts: 11166
Location: Cecilia, LA
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Re: to shim or not to shim These will help a lot, too:
_________________
Formerly:1648 Homemade Cypress Crawfish Skiff GTR23 Performance Cam and Heads; 17x46 Gator Tail with 35GTR and Hoyt's cam;s Currently: 17x48 Gator Tail with XD40 EFI.
“Wisdom is not just expertise. It is knowing how much of various areas of expertise you need to know in order to make the decisions that the world needs and that you want to do,” Columbia University President Lee Bollinger.
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| Thu Jul 29, 2010 12:21 pm |
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caddobrook
MMT F.E.
Joined: Mon Feb 01, 2010 11:01 am
Posts: 881
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Re: to shim or not to shim May be a stupid question... But..
If you shim would you still set the valve clearance at .005? or does that change?
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| Sat Jul 31, 2010 5:47 pm |
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anotherred
MMT Pro Member
Joined: Fri Jul 10, 2009 4:44 pm
Posts: 62
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Re: to shim or not to shim Set it the same, all the shim does is put more preload on the rocker so it don't float as quickly.
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| Sat Jul 31, 2010 6:31 pm |
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