Elec87

iTrader: (49)

Is a 4.125 stroke to much for a street motor?
My current combo is a 422
I am using a lunati crank 4.125 stroke
Lunati pro billet Connecting rods 6.125
ross pistons 4.030 bore.

What I am curious about is can this combo last long in a street car or should this be a all out max effort drag motor?
I am just trying to figure out if I should put anymore money in this pit or call it a loss as I like driving the car alot and don't want a straight up drag car.
Thanks for any input.

gnx7

iTrader: (28)

Elec-

There are handful of guys running 4.125" stroke cranks in 4.125" bore blocks making 447ci.

Aside from the supposed increased wear with side loading the piston in the bores..... I wouldn't worry about it. It will certainly make a gangload of torque.

Elec87

iTrader: (49)

But will the motor be out of square and wear quicker?
It's a 4.030 bore with a 4.125 crank

Project GatTagO

iTrader: (7)

You better just pull that engine and send it to me. I will send you a nice stock LS1 so you can drive it everyday and not worry about it so much.

Andrew

Beast96Z

iTrader: (21)

The only problem is the legnth of the bore. When increasing stroke, and keeping the same legnth you have to go with tighter ring spacing. It's ok for a N/A motor, but not great for power adders. With a proper piston design you should be able to go 100k.

Grimes

iTrader: (3)

This is just anecdotal info from the internet, but people who run the 4.125 stroke tend to burn a lot of oil.

Elec87

iTrader: (49)

Hmm Is it not uncommon For this combo on a street motor then?
When we took this thing apart the pistons had some skirt wear and the bearings were beat to ****. I just don't want to invest the money if the combo won't last me a season or two.

Grimes

iTrader: (3)

I'm not sure why the bearings would be beat to **** along with wear. Since you have some major cash invested in those parts, why don't you have that motor rebuilt properly and even think about using coated bearings and pistons.

Elec87

iTrader: (49)

I have it at a large shop and they are telling me this is not a very street friendly combo and it will wear and tear fast. I should only use it in race applications with the short piston skirt design.

pist0lpete

iTrader: (3)

A common problem with 4.125 stroke setups is they allow the piston to come out of the bottom of the bore too much causing the piston to rock increasing ring wear and eventually resulting in more oil consumption.

PREDATOR-Z

Talk to "Canadian Performance" they have a solution for that. I like their approach.

Beast96Z

iTrader: (21)

Using the correctly designed piston is the way to go in a long stroke street motor. I talked to Brian at Wiesco about this with my motor. In this instance, I would call him and get a piston designed around the stroke. It can be made to last, you just have to have the correct parts. I would not build it again with the kits Lunati/JE pistons.

PREDATOR-Z

BINGO, custom piston and pin position.

Elec87

iTrader: (49)

it has ross pistons. How do I contact these guys?

pist0lpete

iTrader: (3)

Its all about the pin location in relation to the rod and stroke most definitely.

Gannet

Ok, I'm confused. For a given stroke, rod length, and block deck height, there is only one pin location. If you want to change the pin location you have to change one of those dimensions. You can change the ring location relative to the pin (within limits), but that's it. If I have this wrong, please explain.

Steve - Race Eng

iTrader: (1)

You are correct about the pin location. The only way one can move the pin higher is by lengthening the con rod. This of course bunches up the ring pack and can not be done if the pin is already as far up as practical with a 6.125" rod.

A longer sleeve is recommended to run a 4.125" stroke without problems. I had Darton increase sleeve length to 5.800" for all applications last summer to allow the longer strokes to be run in street applications. A longer sleeve provides the necessary skirt support at the bottom of the stroke.

Steve

Elec87

iTrader: (49)

Hmmmm I may just partially part this out and build a 408.