Offset crankshaft grinding

[CHB]

Guys,
out of curiosity, let say I got a crank of 52mm rod journal which has a stock stroke of 91mm. If I am going grind the rod journal down to 48mm, and by doing the offset grind on the rod journal, do I get a full 4mm extra stroke or just 2mm extra stroke?

[roadsailing]

Guys,
out of curiosity, let say I got a crank of 52mm rod journal which has a stock stroke of 91mm. If I am going grind the rod journal down to 48mm, and by doing the offset grind on the rod journal, do I get a full 4mm extra stroke or just 2mm extra stroke?

Assuming a total offset grind (that is you don't remove any material from the outermost part of the journal) you will gain 4mm extra.

[CHB]

thanks for the tip!

[Cuzzo]

What exactly is offset grinding?

[CHB]

offset grinding on conrod journal is actually reduce the size of the conrod journal to fit a smaller rods, but instead of using the original center point as reference, you move the center point further out, thus increase in stroke. here is very good explaination of what actually it is

http://www.fordmuscle.com/archives/2003/09/stroker/

[trdee]

what effects does that have to the balance of the crank and whatnot?

[Cuzzo]

I believe the crank would then get rebalanced like it would with any machining.

How much material would be "grinded" off? I would have though this would weaken the crank.

[Dangerous Beans]

How much material would be "grinded" off? I would have though this would weaken the crank.

He is talking about going from a 52mm rod journal to a 48mm one, which is 12.56cm2 difference by whatever the length of the journal is.

It would weaken the crank, but the increase in stroke would also reduce the ability of the engine to rev as high so it might not matter.

[Bronald McDonald]

People have been doing said mini-stroke techniques to old school 308's for yonks.

They tend to run fine. Remember bearing journal sizes change, so the rods obviously need the correct sized holes too.

People with 308's often use Hemi 6 cylinder rods (due to Journal size).

What rod would you run if you offset ground your crank?

[roadsailing]

winsor/cleveland V8s tend to have big end journals that are way to big to start with, so you can grind them down and use chev rods with few problems AFAIK

what engine is it for?

[jonathan yee]

goin for the 2.3L 5sgte i assume......

[oldeskewltoy]

there may be an issue.... hypothetical

the oiling passages may lead to a failure only because they will no longer be in the center of the "new" journal

[roadsailing]

there may be an issue.... hypothetical

the oiling passages may lead to a failure only because they will no longer be in the center of the "new" journal

hmm, maybe but it has been done plenty of times before, not on toyotas i'd guess.



I wouldn't bother for such a small capacity gain personally.

[rick q]

Offset grinding the crank is how the 1900 and 1950cc stroker motors are made up from the 1800cc 7AFE blocks / 4AGE heads. They offset grind the crank to increase the stroke, and bore them out as well. The cranks are nitrided to help regain some of the strength lost.

A bit more info here :- http://www.speedracersportscars.com.au/

[jonathan yee]

i personally wouldnt do it as then you'd have to use shorter rods and the rod/stroke ratio will be getting worse....funny i'm trying to find out if i can destroke the 3s.........