Refresh951's Hybrid Stroker - A Blown944 Design
06-20-2012, 02:29 AM
#32
Race Car
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?
In my head
06-20-2012, 08:25 PM
#37
Race Car
Join Date: Mar 2012
Location: Austin TX, drinking beer in the garage
Posts: 3,602
Likes: 0
Received 7 Likes
on
7 Posts
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?
06-20-2012, 08:47 PM
#38
Rennlist Member
Thread Starter
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
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
06-20-2012, 09:07 PM
#40
Rennlist Member
Thread Starter
06-21-2012, 01:30 PM
#41
Rainman
Rennlist Member
Rennlist Member
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
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
06-21-2012, 01:45 PM
#42
Addict
Rennlist Member
Rennlist Member
06-21-2012, 02:49 PM
#43
Nordschleife Master
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
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
06-21-2012, 03:40 PM
#44
Race Car
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.
06-21-2012, 05:35 PM
#45
Race Car
Join Date: Mar 2012
Location: Austin TX, drinking beer in the garage
Posts: 3,602
Likes: 0
Received 7 Likes
on
7 Posts
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!
Edit: Refresh's build does include a big valve 8 valve head. Need some dyno sheets now!