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Refresh951's Hybrid Stroker - A Blown944 Design

 
Old 06-19-2012, 06:46 PM
  #31  
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Where was this idea a year ago??
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Old 06-20-2012, 02:29 AM
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Originally Posted by Dougs951S View Post
Fantastic, I'm really looking forward to seeing this project completed. My motor only has 45k on it, but when it finally needs to be rebuilt, this is exactly the type of hybrid project I've been dying to do. Can the bore be expanded a bit more to achieve 3 liters with this type of setup?
3.1 using stroke alone
Originally Posted by ChrisJ951 View Post
Where was this idea a year ago??
In my head
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Old 06-20-2012, 08:47 AM
  #33  
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Shawn, are you using the stock cam?
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Old 06-20-2012, 08:51 AM
  #34  
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Originally Posted by ChrisJ951 View Post
Shawn, are you using the stock cam?
Yes, at least initially..
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Old 06-20-2012, 03:31 PM
  #35  
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Very interesting project. One question; could you start off with a 2.5NA motor for this project?
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Old 06-20-2012, 06:40 PM
  #36  
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Originally Posted by blown 944 View Post
3.1 using stroke alone
What the heck would the stroke be for that??
Originally Posted by kghaas View Post
Very interesting project. One question; could you start off with a 2.5NA motor for this project?
Yes, the cranks are the same.
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Old 06-20-2012, 08:25 PM
  #37  
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Sid, how is that extra crank throw achieved? Is it simply by further grinding of the rod journals? Would one need to use and therefore source different length rods than for the 2.9 liter, or there still enough meat on the piston to move the pin up without creating interference issues. The change in rod angle is insignificant I assume. The pistons in this build are shorter than stock, right? Does that leave enough room to fly cut them and ensure a completely not-interference fit?
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Old 06-20-2012, 08:47 PM
  #38  
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Had to pull 0.006" off the stroke today at my machinists request, new stoke will be 3.380". Not a significant change but thought I would pass it along. He said he could probably pull off the 86 mm stroke but left very little margin for cleanup. Offset grind should take place tomorrow.

Just added up everything, parts and machine work totals $3,431. This includes everything except the head. Includes pistons, rods, rings, 86 block and crank (thanks Lart), ARP Head studs, Rod Bearings, Main Bearings, Cometic Head Gasket, Bottom and Top Seal Kits, Block Filler, and even MoCal Oil Cooler.

Final cost for the high flow head: Used head (bent valves), new guides, new intake valves (47mm), new exhaust valves, new seals, competition valve job, deck (0.010") was $693 complete.

Total Cost: $4124
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Old 06-20-2012, 08:55 PM
  #39  
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How much does a typical stroker motor usually run? I have never looked before.
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Old 06-20-2012, 09:07 PM
  #40  
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Originally Posted by 86 951 Driver View Post
How much does a typical stroker motor usually run? I have never looked before.
For comparison SFR lists a 2.8L short block for about $7000
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Old 06-21-2012, 01:30 PM
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Originally Posted by refresh951 View Post
Had to pull 0.006" off the stroke today at my machinists request, new stoke will be 3.380". Not a significant change but thought I would pass it along. He said he could probably pull off the 86 mm stroke but left very little margin for cleanup. Offset grind should take place tomorrow.

Just added up everything, parts and machine work totals $3,431. This includes everything except the head. Includes pistons, rods, rings, 86 block and crank (thanks Lart), ARP Head studs, Rod Bearings, Main Bearings, Cometic Head Gasket, Bottom and Top Seal Kits, Block Filler, and even MoCal Oil Cooler.

Total Cost: $4124
How much was the Mocal? Also, what brand of piston are you using? Summit sells a piston for the LS 6.0 (4.020"/102.11mm bore) made by Sealed Power for $26 each...
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Old 06-21-2012, 01:45 PM
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Originally Posted by blown 944 View Post
. I don't see much point in going beyond the off the shelf 105.5mm bore though.
Agreed... off the shelf is a good thing

Last edited by David Floyd; 06-21-2012 at 05:38 PM. Reason: spelling :-)
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Old 06-21-2012, 02:49 PM
  #43  
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Originally Posted by refresh951 View Post
Had to pull 0.006" off the stroke today at my machinists request, new stoke will be 3.380". Not a significant change but thought I would pass it along. He said he could probably pull off the 86 mm stroke but left very little margin for cleanup. Offset grind should take place tomorrow.

Just added up everything, parts and machine work totals $3,431. This includes everything except the head. Includes pistons, rods, rings, 86 block and crank (thanks Lart), ARP Head studs, Rod Bearings, Main Bearings, Cometic Head Gasket, Bottom and Top Seal Kits, Block Filler, and even MoCal Oil Cooler.

Final cost for the high flow head: Used head (bent valves), new guides, new intake valves (47mm), new exhaust valves, new seals, competition valve job, deck (0.010") was $693 complete.

Total Cost: $4124
Does that $3,431 also include sleeving the block? That's an excellent price if it it does...
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Old 06-21-2012, 03:40 PM
  #44  
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Originally Posted by Dougs951S View Post
Sid, how is that extra crank throw achieved? Is it simply by further grinding of the rod journals? Would one need to use and therefore source different length rods than for the 2.9 liter, or there still enough meat on the piston to move the pin up without creating interference issues. The change in rod angle is insignificant I assume. The pistons in this build are shorter than stock, right? Does that leave enough room to fly cut them and ensure a completely not-interference fit?

The rod journals are ground off center and much smaller.

The pistons are indeed shorter. That helps the counterweight clearance.

The pins can be moved up significantly over stock. The pistons that are being used already have very deep valve reliefs. That helps a bunch. Rod angle is still very good.

My current engine loves to rpm. A 3.1 would be good to 6500 rpm pretty easily.

I need to try a good head on mine as I think that it is the restriction right now.
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Old 06-21-2012, 05:35 PM
  #45  
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Right, you rotating assembly must be substantially lighter than stock. I would love to see this with 16 valves, or even just a big valve 8 valve. You say 3.1 is the limit with just stroke. What is the limiting factor? How much you can grind off the journals, or will internal clearances become the issue? I don't understand how you can get away with using the same rods though, wouldnt they need to have smaller and smaller big end diameters the more you increase the stroke and shrink the bearing surfaces? It seems to me like if it was done right, this build would be substantially more reliable than stock? Sorry to ask so many questions but these 2 hybrid builds absolutely intrigue me! I might be giving my 951 to my girlfriend to replace her 944, and if I did that I would look for one to replace mine with a wrecked engine, and give myself an excuse to build a machine like this.


Edit: Refresh's build does include a big valve 8 valve head. Need some dyno sheets now!
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