Thinking About A Barnett Stroker Crank...

[icanfixall]

I was reading everything this site offers and was wondering how they do what they do for our motors. I'm wondering how my port work compares to theirs. I do the entire hot and cold air path. Not just part of it like their stage 1 or 2 porting. That stroker kit sounds interseting too. I'm wondering how much they drop the mains and extend the rod throws. Probably the same amount. I sent them some questions. When I get some answers I'll post them..

 

[towcat]

how about a linky to their site?

 

[NCheek]

Linky

 

[RLDSL]

Personally, I would like to know how you make a stroker crank for something that has pistons that are already sticking up into the heads? what goes down must go up Only way you could make a stroker is if you were making a low compression engine. Not exactly a daily driver soloution

 

[icanfixall]

Actually what can be done making a stroker is to lower the crank mains lets say .250 in the block. So now what you have is a crank turning 1/4 inch below where it used to be. Thats done by welding up the mains on the crank bearings and then machining them so the outcome is a crank that .250 lower than it was before. Now you have the rods that are now 1/4 inch low in the cylinders. So you weld up the rod bearings and machine them up the .250. Now you have a crank that is a 1/4 inch stroker. Its really not that simple but this is the idea. Sometimes its done only on the rod bearings but that wont work for us. We already are as much as 31 thousands out of the block. This work is done on the oppsite sides of the rods to the mains mostly. This cahnges the oem center line of the crank.

 

[RLDSL]

Actually what can be done making a stroker is to lower the crank mains lets say .250 in the block. So now what you have is a crank turning 1/4 inch below where it used to be. Thats done by welding up the mains on the crank bearings and then machining them so the outcome is a crank that .250 lower than it was before. Now you have the rods that are now 1/4 inch low in the cylinders. So you weld up the rod bearings and machine them up the .250. Now you have a crank that is a 1/4 inch strokere. Its really not that simple but this is the idea. Sometimes its done only on the rod bearings but that wont work for us. We already are as much as 31 thousands out of the block. This work is done on the oppsite sides of the rods to the mains mostly. This cahnges the oem center line of the crank.

Of course, by the time you do that, you weaken the main caps , screw up the balance and throw a few years of factory engineering and testing with zillions of dollars of equipment at their disposal out the window
Fine if you have deep pockets and just plan on racing the thing on the weekends and don't care if it blows up and have to do it again next week.

 

[icanfixall]

The above posting is missing the point. The crank shaft bearing are welded up, then machined at a differant place so the stroke is differant from where it was. Think about this. Take two circles. One of the is the main bearings and the other is the rod bearings. Move them out from each other and now you have a constant main circle and a rotating rod circle. Move both of them and you change the stroke. Thats what is done for any crank stroke on any motor. The mains have their constant rotation plain position and the rods circle that centerline. Its kinda hard to explain without a picture. The realibilty is not compromised done properly. The balance is worked out too and for deep pockets... Nope... Its not. Main caps are not machined... Unless you do a line bore or line hone. Then only 2 thousands is taken off the caps.. If needed. The famous chevy 383 was a 400 crank welded up and remachined, then it was fitted into a 350 block. A 20 over piston makes it a 383 stroker with plenty of torque and realiblity. I hope this helps in the understanding...

 

[69dieselfreak]

im shure barnetts stroker set up has some R&D for relibality

 

[NJKen]

I have never lowered a crank to make a stroker. You would never be able to bolt a trans to it agian without some seriously specialized hardware. Usually you get a crank with a bigger throw, a shorter rod and a set of custom slugs. If you get the 2 numbers rite you wind up with a piston that has more travel. I am not sure about these engines but in the gassers I have built there are things to consider with a stroker. The first is clearancing the block the make the noew crank and rods clear. That is usually not a big deal. The thing that you have to watch is piston skirt to crank clearance. Almost always you wind up with a shorter skirt that can in some engines (302 to 347 for example) can lead to excessive skirt wear and piston instability. Proper machining is imperitive for longevity. You need the bore to be perfect to support the piston.
Ken

 

[69dieselfreak]

I have never lowered a crank to make a stroker. You would never be able to bolt a trans to it agian without some seriously specialized hardware. Usually you get a crank with a bigger throw, a shorter rod and a set of custom slugs. If you get the 2 numbers rite you wind up with a piston that has more travel. I am not sure about these engines but in the gassers I have built there are things to consider with a stroker. The first is clearancing the block the make the noew crank and rods clear. That is usually not a big deal. The thing that you have to watch is piston skirt to crank clearance. Almost always you wind up with a shorter skirt that can in some engines (302 to 347 for example) can lead to excessive skirt wear and piston instability. Proper machining is imperitive for longevity. You need the bore to be perfect to support the piston.
Ken

thats a good point

 

[NJKen]

Actually what can be done making a stroker is to lower the crank mains lets say .250 in the block. So now what you have is a crank turning 1/4 inch below where it used to be. Thats done by welding up the mains on the crank bearings and then machining them so the outcome is a crank that .250 lower than it was before. Now you have the rods that are now 1/4 inch low in the cylinders. So you weld up the rod bearings and machine them up the .250. Now you have a crank that is a 1/4 inch stroker. Its really not that simple but this is the idea. Sometimes its done only on the rod bearings but that wont work for us. We already are as much as 31 thousands out of the block. This work is done on the oppsite sides of the rods to the mains mostly. This cahnges the oem center line of the crank.

Seriously though if you think about this very carefully it makes sense. The location of the mains are never changed though because you could not bolt it to a flywheel/flexplate anymore. The crankpin is moved in this manner though. Usually no more than 1/4 inch. That is the way that you make a stroker crank unless you go for custom new cast stroker crank (big big bucks). Do a google search on manufacturing a stroker crank and you can find some pictures that makes the above make sense.
Ken

 

[icanfixall]

See... I sometimes have a very difficult time trying to explain myself. What I see in my mind isn't what I expain. Thanks....

 

[typ4]

Rod throws Gary, longer throws, shorter rods, special pistons== the stroker equation.

 

[91f2504x4]

Most of the time, you either have a shorter rod or a piston with a shorter compression height, and by that I mean, the new pistons have the wrist pin located closer to the top, most of the time this causes issues with interference of the ring lands and wrist pin and eventually leads to burning oil and is not the preferred way of doing a stroker.

The preferred method is to build up the rod journal and then machine it down to move it farther out on the crank (farther from the center of it) then you take how much stroke you added, let's say .5" and you buy or make connecting rods that are .25" shorter, this will maintain your stock compression ratio and allow you to gain additional displacement.

Many times you can use connecting rods from another engine to fit the crank and pistons together rather than having to make new ones. Just like some ford 351w stroker kits use 302 pistons and rods or even some use Chrysler connecting rods, all you have to do is find something that fits.

 

[turbo_joe]

i have read somewhere somebody used a 6.9 crank but with i think 7.3 pistons and rods, what would that do, lower compression?