ok i have beed reading and trying to educate myself in the v8 world and i see things like "i stroked my 350 to a 383" but i thought that when you make a block bigger you have it bored out , so i am now confused and what is a stroker engine?

P.S.= i put this in advanced so that i could get a real good explanation on this so that i dont feel like such a

 

A 350 Chevy has a 4" bore and a 3.48" stroke. If you bore it .030", you end up with a 355 due to the slightly larger bores. If you were to replace the 3.48" stroke crank with a 3.75" stroke crank, you then end up with a 383. This combination gets a few extra cubes from the .030 overbore, but most of the increase is from the greater distance the piston travels due to the longer stroke (swept volume).

Small block Chevs can't take much of an overbore, .060 max on 350's if the block is sonically checked, would be about it. That is why longer stroke cranks are used to get bigger cubes, without having to go to a 400 block or an expensive aftermarket hi-perf block.

 

i understand the bore, and i understand the crank, why do people using longer connecting rods when they stroke? i would think that would defeat the purpose of the crankshaft, cause wouldn't longer rods shorten the stroke? does the wristpin on the piston move when you lengthen the rods? bleh....anyone feels like giving me an explanation how all those things affect eachother etc id appreciate it

 

Rod length doesn't affect the stroke at all. The reason a lot of people like to use longer rods is because they reduce the angle of the rod at mid-stroke and therefore reduce wear on the bore and strain on the piston. When you use a longer rod it causes the piston to sit higher in the bore, so you also have to use a piston that has a higher wristpin (shorter piston deck) in order to keep it from smacking the cylinder head.

It's also possible to get "tall deck" blocks (head surface is farther from the crank centerline), so you can run even LONGER rods (or bigger cranks), but they're the pricey aftermarket blocks that were mentioned before, and they require special adapters for the intake manifold.

 

I gotta find out the exact specs of the block im buying, all blocks have an engine code milled correct? If I get the number can I figure out the year and specs on the block?


Bleh, gonna need to find this out before I try to select parts....

 

Rod lenght has nothing to do with the stroke, cubic inches or anything of the like. What determines how far up and down the crank will travel is the stroke of the crank and nothing else. If the connecting rod was a mile long and the crank stroke was 3.48", the piston would still move 3.48". Only 2 things determine the cubic inches, bore and stroke.

There is something called rod to stroke ratio, and the theory is that a bigger ratio is more desirable. The thinking is that a longer rod will cause the piston to dwell at TDC firing longer, giving the burning charge more of an opportunity to put force on the piston before piston gets too far down the bore and pressure drops off.

So if you have a 5.7 rod and a 3.48 stroke, the ratio is about 1.64. If you throw in a longer stroke crank, e.g. 3.75", that drops to 1.52. So the idea is to move to a 6" rod to "fix" that, and end up at 1.6.

Only one problem, it's just a theory. I've never seen anything that proved a longer rod made more power. I remember reading on a message board earlier this year that someone had actually done extensive testing and come up with zip as a power increase with longer rods.

Another theory is that a longer rod will have less angularity, so it puts less stress on the cylinder wall. Don't know, maybe. But what I do know is that a big time Pro Stock engine builder (forgot who) told Hot Rod way back in the 80's that in his experience, if the connecting rod hooked the piston to the crank, and was long enough to keep the bottom of the piston from hitting the crank counterweight, that was good enough, no need to sweat how to stick in a longer rod.

As far as identifying your block, there are codes stamped on the block pad in front of the passenger side head. They will read something like "TDJ". This will give you the original application. You can also look up the casting number here:

http://www.mortec.com/castnum.htm

 

Well I am guessing the block came out of a pre 80's car, I've seen it and it's clean. As clean as one could claim by looking at it.

Do most 350's have enough clearance for a 3.75 Crank and 6" rods? Or is there a serious clearance issue with 6" rods....l'll find out for sure what year the block is and all that good stuff, but is the general rule of thumb that you don't assume until you know, or that most 350's can clear 6" rods.

I am interested to know if the 6" vs. 5.85" is BS or real....if a longer rod does help reduce stress then I would do whatever I could to use a longer rod, power really isn't an issue, I'm not going for really high HP, so it's not like I'd be nitpicking every possible way to get power. But if I could extend the life of my block that's always a plus.

Thnx for all the good info guys.

 

Any 350 block can be made to clear a 3.75" crank, but most require some grinding at the bottom of the cylinders on the cam journal side to clear the rod bolts. When you put the rotating assembly together do it with the block upside down and bolt the maincaps down snug and rotate the crank to see where it needs to be clearanced. You may have to put the bottom end together and take it back apart a couple times, but it's worth it in the end.

6" rods can be made to fit easily, you just have to get a set of pistons with a short enough deck height...when you order your pistons just ask specifically for a set that work with 6" rods and a 3.75" crank. Your wristpin will be so high that it sits behind the oil control ring, but I haven't heard of anyone having problems with this.

 

Thnx for the info, the only thing my buddy could tell me about the block is that it's a 2 Bolt Main, he has no idea what it came out of or the year....I'll have to wait till I see the block and run the code.

 

AWESOME......thanks for all of the info......this is what i needed.........some real info.........thanks again