4.125 stroke and nitrous
12-22-2010, 04:24 AM
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4.125 stroke and nitrous Hey guys,
I have a couple of questions about my motor. It is a 423 ci motor with a 4.125 stroke and a 4.040 bore. I have it tore down right now and im thinking about changing the crank out for a 4.00 stroke. That would make me a 411-412 ci motor. Im building the car for a local class that only lets you spray an .082 jet (225?) but i think the motor will last a lot longer with the shorter stroke on gas. What do you guys think?
I have a couple of questions about my motor. It is a 423 ci motor with a 4.125 stroke and a 4.040 bore. I have it tore down right now and im thinking about changing the crank out for a 4.00 stroke. That would make me a 411-412 ci motor. Im building the car for a local class that only lets you spray an .082 jet (225?) but i think the motor will last a lot longer with the shorter stroke on gas. What do you guys think?
12-23-2010, 03:00 PM
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Thats what im on the fence about. I know it will be faster with the bigger motor but i dont want to tear it down again. The reason it is apart now is because after we put the gas on it ( for the first time) it had a slight knock. One of the ring lands was raised slightly but not really messed up. We also found one of the piston skirts looked like it was coming apart so its getting new pistons. The car makes great power now and i really want to find away to make it live like it is. Im running the 275 real street class and it will be alot of close cars so i need all the power i can get. What would you do?
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12-23-2010, 08:36 PM
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I would say go to a 4" stroke, for reference here is my old set of pistons compared to my new ones - 4" stroke and 4.125". The first ringland is moved down some. Also, if you can, get a set of pistons that don't have the eyebrows cut off the side of the piston.
12-23-2010, 09:46 PM
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thanks for the pics. Im just wondering how much power i'll leave on the table if i go with the 4" stroke. The car made 548rwhp through a th350, steel drive shaft, 12 bolt w/ 4.10's N/A. It would make around 590 with a M6. There aren't alot of 408's making that kind of power.
12-23-2010, 10:08 PM
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Yah, very solid power numbers. Couple of things:
The 4.125 stroke on an aluminum block isn't near as hard on the piston because the sleeves are longer than cylinder length on the iron block (as far as the piston rocking and messing up the skirts).
Depending on what heads, cam, and intake, you could always run a bigger camshaft and spin the motor a little higher with the 4" stroke setup. There are many guys running some solid times on 408 CI setups.
The 4.125 stroke on an aluminum block isn't near as hard on the piston because the sleeves are longer than cylinder length on the iron block (as far as the piston rocking and messing up the skirts).
Depending on what heads, cam, and intake, you could always run a bigger camshaft and spin the motor a little higher with the 4" stroke setup. There are many guys running some solid times on 408 CI setups.
Last edited by 03supercobra; 12-24-2010 at 11:48 AM.
12-24-2010, 12:03 AM
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Yah, very solid power numbers. Couple of things:
The 4.125 stroke on an aluminum block isn't near as hard on the piston because the sleeves are longer than on the iron block (as far as the piston rocking and messing up the skirts).
Depending on what heads, cam, and intake, you could always run a bigger camshaft and spin the motor a little higher with the 4" stroke setup. There are many guys running some solid times on 408 CI setups.
The 4.125 stroke on an aluminum block isn't near as hard on the piston because the sleeves are longer than on the iron block (as far as the piston rocking and messing up the skirts).
Depending on what heads, cam, and intake, you could always run a bigger camshaft and spin the motor a little higher with the 4" stroke setup. There are many guys running some solid times on 408 CI setups.
this is true. thanks for the advice.
12-25-2010, 02:11 PM
#15
Same Bore Same Stroke with CPs and have no problems 3 years spraying a 200 shot. They just have a kick *** piston that can take the beating!!!! Thats all i was saying.
12-26-2010, 04:14 AM
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I am far from an expert on this topic, but I would think the rod length is pretty important, with longer being better. The 4.00" has got to be a longer rod, so that is my vote.
12-26-2010, 01:14 PM
#19
I hear ya. I was just stating that no matter what you do sleeves stay the same length no matter what unless you change them. You are having luck because you piston were made more for that bore and stroke. Back 5 years ago you couldn't get a piston to work with that bore and stroke. It would consume oil tremedously. Now more pistons are made by piston companies to suit factory LS blocks. You will start to see a piston you would have to had ordered back in the day become an off the shelf piston in a catalog.
12-29-2010, 03:52 PM
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I was looking into running that class to start with. They were being pretty flaky on the rules for the ls heads. What times did your car run NA with the 422 in it.
Last edited by IH8FORD; 12-29-2010 at 04:54 PM.