Thinking About A Barnett Stroker Crank...

[RLDSL]

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...

I've delt with plenty of stroker engines and I've never heard of a crank where they moved the main journals either.
Type4 hit the nail on the head , plain and simple. Easy to do on a gasser where you are usually starting with lower compression numbers to begin with and have a lot of room to play with . I ran an engine shop many many moons ago, Lots of custom engines. granted, I've forgot, most everything since then, but not everything

 

[IDIeselman]

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..

Call the # and ask for Tim, He will be willing to talk to you and answer any questions you may have

 

[Freight_Train]

mmmmm,Stroker....mmmmm.someone loan me some money before I put a 6V53 in white lightning!

 

[hesutton]

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?

The 6.9 and 7.3(N/A) IDI have the same crank and rods. It wouldn't change anything. I read some weird stuff like that in "TheDieselStop" recently.......some of those guys just make things up I guess.

Heath

 

[VanBoy]

Linky

Interesting......

Not much pics on their diesel section...

 

[Alex S]

for that kind of $$ you could just put in a cummins or a dt466 or a small nucluar power plant

 

[david85]

for that kind of $$ you could just put in a cummins or a dt466 or a small nucluar power plant

The funny thing there is you would probably get in trouble for not paying highway taxes on the enriched uranium fuel.

Its one thing to make claims of a stroker 6.9/7.3 IDI, but has such an engine ever even been built? Don't believe everything you see on the internet. At the very least I would ask for some videos or pictures of this stroker they claim to offer.....

 

[VanBoy]

The funny thing there is you would probably get in trouble for not paying highway taxes on the enriched uranium fuel.

Its one thing to make claims of a stroker 6.9/7.3 IDI, but has such an engine ever even been built? Don't believe everything you see on the internet. At the very least I would ask for some videos or pictures of this stroker they claim to offer.....

Yup.

I'm a novice on the internals of engines. I know how they go together and can "assist" in putting one together. I've read how a 350 Chev can be 'stroked' using a different crank... don't recall the rest.

Now, when you stroke the engine using a different crank, lower the travel, everyone is assuming using the same rods and piston, right?. So, that would mean, the piston would shoot ABOVE the current location... so it would not work. (As I said, I read how a 350 Chev is stroked to a 383 [I think 383], but don't recall all the details.) Like I said, a newbi here- what if the height of the piston from the wrist pin to the top was decreased to match the new throw? It would still be flush to OEM location at TDC, but it would be a longer travel down, hence it would be "stroked", right??

Or am I missing something..... what can you do to stroke this engine w/out changing the block crank location?????? Could this be done by just a different crank and a 'custom' piston design??? Or a shorter rod also? (If you can stroke a 350 Chev, why can't the same principals be used to stroke a 6.9/7.3L IDI?? )

 

[icanfixall]

Stroking a motor is basic math. Alonger stroke needs a differant pin location or pistons need to be custom made sometimes. Sometimes its a combination os stroke, rods and pistons. I have seen top fuel cranks being created from billit rounds of material. Really interesting steps they need to do as they are maching it and stress relieveing as they go along. Years ago you could take a small block chevy 400 and bore and stroke it to a 454 motor. The motor had to be assembled in a certain way or it wouldn't turn. A small block 350 chevy has about 50 thousands clearance between the rod nuts and the cam lobes. It one of the tightest V8 motors ever built. Stroker motors sometimes need the piston skirts trimmed so they don't hit the crank throws. The crank rotational orbits change, not the psychical location of the crank. Remember its the distance between the rod and main circles that are changing.

 

[VanBoy]

Ah...

Oppps....didn't notice you mentioned the 383 in a earlier post. I tend to speed read ......

Has that company replied to your inquiry yet? I'm wondering what kind they are doing to stroke it out.....

 

[91f2504x4]

If I were going to do performance mods to a 7.3l, I would focus more on compression ratio, head studs and possibly fire rings, to allow more boost. You have to remember that the 7.3l and 6.9l motors are already lower RPM engines and when you stroke an engine normally it lowers the RPM threshold meaning it will "safely" turn fewer RPMs than it did before you "stroked" it.
7.3l's have plenty of displacement to make unreal amounts of power, you just need to get the compression ratio and gasket strength to hold the kind pressure a good turbo would make to equate to the kind of power you want. Especially with the kind of money a stroker kit would cost, you could make lots of other improvements that would lead to lots of power.

But stroker kits are nothing new, I have no doubt you could stroke any engine you want to for the right amount of money, sometimes you even have to take a grinder to the inside of the block to make room for crank clearance. There are a few old Super M and 400 farmalls running around with 400-500+ cubic inch stroker engines and they were only 264 and 281 cubic inches from the factory. Whenever you stroke an engine if you want to keep the same compression ratio you just have to maintain the same distance from the center of the crank to the top of the piston. What you add to the crank in stroke you make up for by using shorter rods or pistons with the wrist pin closer to the top.

 

[Agnem]

Wouldn't increasing the stroke increase the compression? Seems like a waste of effort without a lot of other mods to go with it.

 

[91f2504x4]

If you increased the stroke without changing rods or pistons, then yes it would increase the stroke, but it would probably also force the pistons through the heads if you increase it more than about 1/4" of an inch due to the very narrow clearance of these engines.
You just cant change the stroke without also changing the rods or pistons, or rods and pistons, if there is a stroker engine where the rods or pistons where not changed then it must have been extremely low compression to begin with and they must not have added much stroke. When it comes to stroking a motor you can make it whatever compression ratio you want, stroking a motor could also lead to lower compression if you make the piston not travel as far up the cylinder.

 

[IDIeselman]

Here's a little stroker info for the masses, While not Diesel specific the principal still applies. Has anyone mentioned opening up the head combustion chamber for lower compression?

By adding a stroker crankshaft, the following occurs:

1) For every 50 cubic inches added, the rpm at which torque and horsepower peak at will drop about 600 rpm. So, if your 460 horsepower peaks at 6000 rpm, a 545 will peak at 5000 rpm. This assumes not changing anything else in the engine combo.

2) If you wish to maintain the same horsepower and torque peaks when you increase the stroke, you need to add between 12 to 16 degrees of additional intake duration for every 50 cubic inches added in displacement. Respectively, exhaust will have to be increased also.

3) The amount of torque below the torque peak, and at peak, will increase. This is a good thing, especially for street cars.

4) The larger the engine, the faster it will pull rpm. The weight of the rotating assembly is almost the same on all strokes, from a 460 to the 545 assembly, but as you increase the stroke, the engine now has more displacement pushing that assembly.

5) If you keep the same cylinder heads on the larger motor, you need to add overlap by using a tighter lobe separation, usually 1 to 2 degrees for every additional 50 cubic inches, until you get to 270 degrees @ .050" lift. Above 270 @ .050" duration, you need to bring lobe separation wider to limit overlap that is inherent after that duration. BSFC numbers go up needlessly with too much overlap.

The tighter lobe separation angle adds the necessary overlap to feed the additional inches, however, it does close the intake valve earlier. The horsepower peak numbers will be similar, but will occur at a slightly lower rpm with the tighter LSA. It is usually good not to advance the cam as much as usual.

If your compression ratio is "on the edge" running on pump gas, it may be inapproopriate to tighten the LSA because it increases lower rpm cylinder pressures. The tight LSA adds low and mid range torque because of the lower end cylinder pressures, but may not be needed if the vehicle combo is traction limited. As an example, a street vechicle only running on street tires.

 

[tractorman86]

Here's a little stroker info for the masses, While not Diesel specific the principal still applies. Has anyone mentioned opening up the head combustion chamber for lower compression?

By adding a stroker crankshaft, the following occurs:

1) For every 50 cubic inches added, the rpm at which torque and horsepower peak at will drop about 600 rpm. So, if your 460 horsepower peaks at 6000 rpm, a 545 will peak at 5000 rpm. This assumes not changing anything else in the engine combo.

2) If you wish to maintain the same horsepower and torque peaks when you increase the stroke, you need to add between 12 to 16 degrees of additional intake duration for every 50 cubic inches added in displacement. Respectively, exhaust will have to be increased also.

3) The amount of torque below the torque peak, and at peak, will increase. This is a good thing, especially for street cars.

4) The larger the engine, the faster it will pull rpm. The weight of the rotating assembly is almost the same on all strokes, from a 460 to the 545 assembly, but as you increase the stroke, the engine now has more displacement pushing that assembly.

5) If you keep the same cylinder heads on the larger motor, you need to add overlap by using a tighter lobe separation, usually 1 to 2 degrees for every additional 50 cubic inches, until you get to 270 degrees @ .050" lift. Above 270 @ .050" duration, you need to bring lobe separation wider to limit overlap that is inherent after that duration. BSFC numbers go up needlessly with too much overlap.

The tighter lobe separation angle adds the necessary overlap to feed the additional inches, however, it does close the intake valve earlier. The horsepower peak numbers will be similar, but will occur at a slightly lower rpm with the tighter LSA. It is usually good not to advance the cam as much as usual.

If your compression ratio is "on the edge" running on pump gas, it may be inapproopriate to tighten the LSA because it increases lower rpm cylinder pressures. The tight LSA adds low and mid range torque because of the lower end cylinder pressures, but may not be needed if the vehicle combo is traction limited. As an example, a street vechicle only running on street tires.

this is some good info thanks! Did you write that?