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PostPosted: Thu Jul 20, 2017 8:38 pm 
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4 BBL ''Hyper-Pak''

Joined: Sat Aug 20, 2011 8:32 pm
Posts: 27
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I'm putting my /6 together and have had new cam #819 from Oregon cam grinders done. .030 overbore on the pistons 1.77 and 1.44valves and new guides put in. .010/.010 on the crank. (78 model so it's cast), also have a wideband A/F gauge going in the exhaust to help me monitor things. But I am concerned that the stock ring gap may be a bit too tight if I add a turbo to the system and hit 8 possible 10 psi boost. How much more than the stock of .012-.017 and should I also go into the second ring also and how much added. over stock?
thanks


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PostPosted: Sat Jul 22, 2017 4:30 am 
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 12136
Location: Blacksburg, VA
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Stock pistons and rings?? 8-10 psi is not too much, as long as you keep the charge cool (meth/water injection and/or intercooler) and do not run too much timing advance (18-20 deg under max boost and WOT).

I would run a bit more gap, though, yes. I would go 0.001-0.004" over the stock spec maximum for that level of boost. Probably just top ring, but maybe 0.001-0.002" higher on the 2nd too.

I do not have much experience here, but those seem about right to me. My stock rebuild 175k 0.030" over motor has stock ring gaps and I have run up to about 12 psi. I have not run sustained boost, only on a dragstrip (12-15 sec) or at most 15-40 sec on the hwy up or a mtn.

Lou

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PostPosted: Sat Jul 22, 2017 6:27 am 
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4 BBL ''Hyper-Pak''

Joined: Sat Aug 20, 2011 8:32 pm
Posts: 27
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Dart270 wrote:
Stock pistons and rings?? 8-10 psi is not too much, as long as you keep the charge cool (meth/water injection and/or intercooler) and do not run too much timing advance (18-20 deg under max boost and WOT).

I would run a bit more gap, though, yes. I would go 0.001-0.004" over the stock spec maximum for that level of boost. Probably just top ring, but maybe 0.001-0.002" higher on the 2nd too.

I do not have much experience here, but those seem about right to me. My stock rebuild 175k 0.030" over motor has stock ring gaps and I have run up to about 12 psi. I have not run sustained boost, only on a dragstrip (12-15 sec) or at most 15-40 sec on the hwy up or a mtn.

Lou


thanks Lou
I'm looking over at the turbo forums and seeing a similar pattern but wanted to double check here for real time info. high winding 4's vs 5k reving /6 might be a ton different .


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PostPosted: Sat Aug 05, 2017 10:50 am 
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Turbo EFI

Joined: Tue May 17, 2005 4:26 pm
Posts: 1083
Location: CBS Newfoundland Canada
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I have run as much as .024" on top ring .018 on second ring with 14psi boost. ran .022" and .018" on the 11.1 comp n/a engine.


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