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I've been bitten by the stroker bug.

 
Old 03-10-2018, 06:13 AM
  #31  
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Originally Posted by danglerb View Post
I've been told wear on the ring lands can be an issue with used 968 pistons.

Is there some mid range stroker combination that doesn't need custom rods and crank (using 968 pistons)?
You can just bore the engine out and use 104mm 944 pistons, but then it wouldn't be a stroker.

Greg Brown does offer a GTS style 928 crank that IIRC doesn't need new custom rods and can use the stock ones
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Old 03-14-2018, 12:26 PM
  #32  
Kevin in Atlanta
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I've been offered a 6.5ltr stroker kit. This is more than I thought I wanted. Before I pull the trigger I need to know if I must go with a custom manifold or I can use my current one.

Thanks.
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Old 03-14-2018, 12:33 PM
  #33  
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Originally Posted by Kevin in Atlanta View Post
I've been offered a 6.5ltr stroker kit. This is more than I thought I wanted. Before I pull the trigger I need to know if I must go with a custom manifold or I can use my current one.

Thanks.
Depends on how much power you want to make,. I found it nearly impossible to get past 400 rwhp without one
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Old 03-14-2018, 12:50 PM
  #34  
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Originally Posted by danglerb View Post
I've been told wear on the ring lands can be an issue with used 968 pistons.

Is there some mid range stroker combination that doesn't need custom rods and crank (using 968 pistons)?
on the 944 side a number of people have been running for about 6-7 years with offset-ground rod journals down to Mitsubishi size (45mm vs stock 52). small journals but good into the 600hp range so far.

944 2.5 stroke stock is 78.9 like a 5.0 928...the offset gets it into the mid-85mm range (almost 928GTS stroke)

Mitsubishi rods are a little narrower than stock 944 but not a big deal with side clearance.
928 rods are 944 rods with what, 2mm milled off one side?
I would think that since the Mitsu rods are built "centered on the pin" like a 944, you could machine meat off of one side on all the rods to compensate for the 928 cylinder offset.

Eagle-brand 4G63 H-beam rods are $350 for a set of 4.
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Old 03-14-2018, 12:54 PM
  #35  
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I've been driving around with a stock '91GT manifold on my 6.5 for eight years now. So it's a 4R manifold, carefully port matched to the heads, but not otherwise modified. Best it did on the dyno was 402/419. Not that I wouldn't like moar power, but it's more than adequate for street use.
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Old 03-14-2018, 01:01 PM
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What are your opinions on used104mm Mahle pistons?
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Old 03-14-2018, 01:22 PM
  #37  
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It all depends on the wear on the skirts. New ones from Porsche are only $550 each but they include new rings (which are $175 a set, separately) so you either spend $4400 on new pistons and rings, or $XXX (XXXX?) on used pistons and $1400 on rings. If you have used 968 pistons, post up pics and see how many different opinions you get.
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Old 03-14-2018, 01:29 PM
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Kit also includes Oliver rods and from what I read they can get out of round. I'd like to use the 968 pistons I have. I'll post pictures here later.

I am a babe in the woods with this venture.
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Old 03-15-2018, 12:59 PM
  #39  
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Originally Posted by Kevin in Atlanta View Post
Kit also includes Oliver rods and from what I read they can get out of round. I'd like to use the 968 pistons I have. I'll post pictures here later.

I am a babe in the woods with this venture.
"Chevy" offset or 928 offset?

In the "early" days, people purchased rods that were designed for use in a small block Chevy engine...instead of having custom rods made for the 928 engine. The "Chevy" offset rods end up not being centered on the piston.

Terrible mistake.

The side loading from this incorrect offset ruined most of these engines very quickly.
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Old 03-15-2018, 01:02 PM
  #40  
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Originally Posted by GregBBRD View Post
"Chevy" offset or 928 offset?

In the "early" days, people purchased rods that were designed for use in a small block Chevy engine...instead of having custom rods made for the 928 engine. The "Chevy" offset rods end up not being centered on the piston.

Terrible mistake.

The side loading from this incorrect offset ruined most of these engines very quickly.
What typically failed in those engines? Kiborts engine has the "Chevy" offset rods.

They are not "off the shelf" rods though, and the crank is unique.
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Old 03-15-2018, 02:14 PM
  #41  
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Originally Posted by Hacker-Pschorr View Post
Kiborts engine has the "Chevy" offset rods.
That proves he's human and does make mistakes, right?

I'm guessing he's smart enough to not make this mistake again....

In the "early" days, I built a few engines using the Chevy offset....just following what others had done.

Once I saw the math of the side loading on the piston and the rod, I recalled these engines and "rebuilt" them with the correct offset rod.

On an engine that is Nicosil coated, the bores are hard enough to withstand the side loading of the piston, up to the point where the rod fails from continual flexing.

On an Alusil engine, the bores are too soft to withstand the high forces from the rod not being centered and piston failure will generally occur faster than rod failure.
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Old 03-15-2018, 03:00 PM
  #42  
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Originally Posted by GregBBRD View Post
That proves he's human and does make mistakes, right?

I'm guessing he's smart enough to not make this mistake again....
What 'mistake' are you referring to?

Kibort's engine has now ran 10+ racing seasons with ZERO problems, a pretty remarkable achievement for 928 stroker motors. And any racing motor at that.

Given that statistic, where is the 'mistake' when there are no problems?
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Old 03-15-2018, 03:08 PM
  #43  
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Originally Posted by GregBBRD View Post
In the "early" days, I built a few engines using the Chevy offset....just following what others had done.
Greg, how many motors did you build with the Chevy rods?
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Old 03-15-2018, 03:08 PM
  #44  
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Discussion about connecting rod offset.
┼ke
https://rennlist.com/forums/928-foru...ker-crank.html

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Old 07-19-2018, 06:10 PM
  #45  
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Originally Posted by GregBBRD View Post
"Chevy" offset or 928 offset?

In the "early" days, people purchased rods that were designed for use in a small block Chevy engine...instead of having custom rods made for the 928 engine. The "Chevy" offset rods end up not being centered on the piston.

Terrible mistake.

The side loading from this incorrect offset ruined most of these engines very quickly.
According to Oliver these chevy rods have a 60 thousands offset.

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