8.1 liter forged rods and pistons
#3
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Joined: Aug 2011
Posts: 1,696
Likes: 2
From: Metro Detroit
Use a 6.7 inch rod with a 2.2 .990 These are off the shelf rods, get any brand you want, get an H beam.
For pistons, use a Wiseco PT121A1. Also, you can have the relief fly cut the piston another 30 thou, from .280 to .310. Straight from Wiseco they are 677.32 with the fly cutting. They are the better 4032 alloy and have coated skirts.
If you want to keep the stock rods ( they have a 1.04 pin) you can get Wiseco or diamond. I don't know of anyone that makes replacement rods for the 8.1.
There ya go, let me know if you have questions.
For pistons, use a Wiseco PT121A1. Also, you can have the relief fly cut the piston another 30 thou, from .280 to .310. Straight from Wiseco they are 677.32 with the fly cutting. They are the better 4032 alloy and have coated skirts.
If you want to keep the stock rods ( they have a 1.04 pin) you can get Wiseco or diamond. I don't know of anyone that makes replacement rods for the 8.1.
There ya go, let me know if you have questions.
#4
Scat is making the stock stroke, 4.500 & 4.750. This is a USA forging, they take about 10-12 weeks. I needed on with-in 4 weeks. Mike @ MK Hammer, sold me one he had coming in to help me out. He also gave me a fair price, real nice person to deal with.
I did a 496 over the beginning of the summer with a 3.3 Whipple, Dart heads (iron) 770 hp @ 5800 760 torque, with 4.5 # boost. We are changing the crank due to wanting to increase boost without worries. Marine Kinetics, did the cam. I used; 6.700 rods, custom CP pistons 8.1 CR, I have another set; perfect for blown application. Here's the deal; you do not need any special rockers, guide plate or poly locks, if the valve lengths are Darts spec length and you figure rocker arm geometry correct. It will fit under the stock valve covers, I used Scorpion Endurance rockers, I bought from Marine Kinetics. Dart adjustable guide plates.
You can buy; the factory reluctor wheels from GM just got some in. I was lied to by someone; saying they bought them all and they are no longer available. Darts cranks are a import and use their own specific reluctor wheels. I'll tell you that's what I found out on my own, and from MK Hammer. I tried to buy; heads from Raylar; I was given the run around and later found out from them they were skeptical of my knowledge on who, designed them, who cast them and the person that completed the cnc work to finalize the heads. I wanted; cnc castings with valves, they wanted me to buy; everything else I didn't want. Like I was some dumb-ass, that didn't know what I needed. So I used Darts or Raylars heads would have been installed.
I don't know what your project is, before you get rolling. Talking to others with experience on the 8.1 will save you time and money.
I did a 496 over the beginning of the summer with a 3.3 Whipple, Dart heads (iron) 770 hp @ 5800 760 torque, with 4.5 # boost. We are changing the crank due to wanting to increase boost without worries. Marine Kinetics, did the cam. I used; 6.700 rods, custom CP pistons 8.1 CR, I have another set; perfect for blown application. Here's the deal; you do not need any special rockers, guide plate or poly locks, if the valve lengths are Darts spec length and you figure rocker arm geometry correct. It will fit under the stock valve covers, I used Scorpion Endurance rockers, I bought from Marine Kinetics. Dart adjustable guide plates.
You can buy; the factory reluctor wheels from GM just got some in. I was lied to by someone; saying they bought them all and they are no longer available. Darts cranks are a import and use their own specific reluctor wheels. I'll tell you that's what I found out on my own, and from MK Hammer. I tried to buy; heads from Raylar; I was given the run around and later found out from them they were skeptical of my knowledge on who, designed them, who cast them and the person that completed the cnc work to finalize the heads. I wanted; cnc castings with valves, they wanted me to buy; everything else I didn't want. Like I was some dumb-ass, that didn't know what I needed. So I used Darts or Raylars heads would have been installed.
I don't know what your project is, before you get rolling. Talking to others with experience on the 8.1 will save you time and money.
#5
Use a 6.7 inch rod with a 2.2 .990 These are off the shelf rods, get any brand you want, get an H beam.
For pistons, use a Wiseco PT121A1. Also, you can have the relief fly cut the piston another 30 thou, from .280 to .310. Straight from Wiseco they are 677.32 with the fly cutting. They are the better 4032 alloy and have coated skirts.
If you want to keep the stock rods ( they have a 1.04 pin) you can get Wiseco or diamond. I don't know of anyone that makes replacement rods for the 8.1.
There ya go, let me know if you have questions.
For pistons, use a Wiseco PT121A1. Also, you can have the relief fly cut the piston another 30 thou, from .280 to .310. Straight from Wiseco they are 677.32 with the fly cutting. They are the better 4032 alloy and have coated skirts.
If you want to keep the stock rods ( they have a 1.04 pin) you can get Wiseco or diamond. I don't know of anyone that makes replacement rods for the 8.1.
There ya go, let me know if you have questions.
#6
Registered
Joined: Aug 2011
Posts: 1,696
Likes: 2
From: Metro Detroit
Scat is making the stock stroke, 4.500 & 4.750. This is a USA forging, they take about 10-12 weeks. I needed on with-in 4 weeks. Mike @ MK Hammer, sold me one he had coming in to help me out. He also gave me a fair price, real nice person to deal with.
I did a 496 over the beginning of the summer with a 3.3 Whipple, Dart heads (iron) 770 hp @ 5800 760 torque, with 4.5 # boost. We are changing the crank due to wanting to increase boost without worries. Marine Kinetics, did the cam. I used; 6.700 rods, custom CP pistons 8.1 CR, I have another set; perfect for blown application. Here's the deal; you do not need any special rockers, guide plate or poly locks, if the valve lengths are Darts spec length and you figure rocker arm geometry correct. It will fit under the stock valve covers, I used Scorpion Endurance rockers, I bought from Marine Kinetics. Dart adjustable guide plates.
You can buy; the factory reluctor wheels from GM just got some in. I was lied to by someone; saying they bought them all and they are no longer available. Darts cranks are a import and use their own specific reluctor wheels. I'll tell you that's what I found out on my own, and from MK Hammer. I tried to buy; heads from Raylar; I was given the run around and later found out from them they were skeptical of my knowledge on who, designed them, who cast them and the person that completed the cnc work to finalize the heads. I wanted; cnc castings with valves, they wanted me to buy; everything else I didn't want. Like I was some dumb-ass, that didn't know what I needed. So I used Darts or Raylars heads would have been installed.
I don't know what your project is, before you get rolling. Talking to others with experience on the 8.1 will save you time and money.
I did a 496 over the beginning of the summer with a 3.3 Whipple, Dart heads (iron) 770 hp @ 5800 760 torque, with 4.5 # boost. We are changing the crank due to wanting to increase boost without worries. Marine Kinetics, did the cam. I used; 6.700 rods, custom CP pistons 8.1 CR, I have another set; perfect for blown application. Here's the deal; you do not need any special rockers, guide plate or poly locks, if the valve lengths are Darts spec length and you figure rocker arm geometry correct. It will fit under the stock valve covers, I used Scorpion Endurance rockers, I bought from Marine Kinetics. Dart adjustable guide plates.
You can buy; the factory reluctor wheels from GM just got some in. I was lied to by someone; saying they bought them all and they are no longer available. Darts cranks are a import and use their own specific reluctor wheels. I'll tell you that's what I found out on my own, and from MK Hammer. I tried to buy; heads from Raylar; I was given the run around and later found out from them they were skeptical of my knowledge on who, designed them, who cast them and the person that completed the cnc work to finalize the heads. I wanted; cnc castings with valves, they wanted me to buy; everything else I didn't want. Like I was some dumb-ass, that didn't know what I needed. So I used Darts or Raylars heads would have been installed.
I don't know what your project is, before you get rolling. Talking to others with experience on the 8.1 will save you time and money.
Kellog crankshaft was making 8.1 cranks. They are in Jackson, MI. U sure if they sell to public.
#7
Registered
Joined: Aug 2011
Posts: 1,696
Likes: 2
From: Metro Detroit
The CP Piston, they made for me are a 2618 with a .990 pin. No offset in pin location is needed, the stock piston is; if I recall .030" we put .006" piston to wall clearance. I told Dustin, just turn the knock off. I used a 4.255" bore size, they made it from the Bullet forging, due to size. That interference fit piston was only put in there for start-up noise, and going the extreme mileage. I had a long discussion with my engineer @ CP over my concerns on these blower pistons, needless to say ; I worried for nothing. We used a .200" wall wrist-pin also.
#8
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Joined: Aug 2004
Posts: 430
Likes: 3
From: Whitefish Chain - Crosslake, MN
4032 is not "better", it is for a certain application. N/A tighter clearances, minimal NO2 and maybe a very small amount of boost. 2618 typically expands more but is better suited for harsh environments such as endurance motors, blower motors, NO2 motors. They are not as hard as the 4032 so they don't shatter as easily when detonation is encountered. My N/A 383 had 4032 wiseco and SRP pistons. My blower 413 motor has Diamond 2618 pistons.
#9
Registered
Joined: Aug 2011
Posts: 1,696
Likes: 2
From: Metro Detroit
4032 is not "better", it is for a certain application. N/A tighter clearances, minimal NO2 and maybe a very small amount of boost. 2618 typically expands more but is better suited for harsh environments such as endurance motors, blower motors, NO2 motors. They are not as hard as the 4032 so they don't shatter as easily when detonation is encountered. My N/A 383 had 4032 wiseco and SRP pistons. My blower 413 motor has Diamond 2618 pistons.
#10
Darin designed the Raylar head, not sure how you feel about him, but I think he is a true wealth of knowledge. They are final machined I think at Roush. I believe the place in Ohio is casting them.
Kellog crankshaft was making 8.1 cranks. They are in Jackson, MI. U sure if they sell to public.
Kellog crankshaft was making 8.1 cranks. They are in Jackson, MI. U sure if they sell to public.
At one time Roush, did their machining, before that it was someone else. Greg Burkhart, owner of GT Racing Heads completes the full machining operation. He originally got the contract, for developing the rectangular Sniper CNC program. He is a excellent cylinder head porter, he has done heads for me back before the cnc operation went into full swing. The current cnc Sniper of course is Darin's at this time.
At this time the Raylar, casting is not done by Profiler, nor is the machining done by GT. Those were the words from Larry,( owner of Raylar), to me after the fact of explaining; his reason for avoiding my questions and knowledge of his heads. He stated; shipping from east- west was the cost issue. Here's my take; cheaper casting, same for cnc machining. Guess; I'll call Profiler, and get the other side of the story now.
The cost on the Profiler Sniper CNC head is about $1400.00 each Bare ready for heads.



