Mercruiser 4.5 versus Chevy vortec Base 4.3

[ghettosmurf83]

So I've been doing research and I know that the 4.5 mercruiser is based on the 4.3 V6 Chevy but mercruiser cast their own block I've also figured out that it has a longer stroke My question is did they achieve the longer stroke with a longer rod or a crankshaft with more throw ie is the crankshaft the same as the 4.3 except for being forged and they just used a longer rod or did they use the same rod as the 4-3 and put a crankshaft in that has a longer throw?

 

[Pmt133]

Rod length doesn't change the stroke. The crankshaft is a different stroke and I think the bore slightly too....

 

[ghettosmurf83]

Rrod length absolutely changes stroke, ie: say you have a crank that has a 3-in stroke and you add a rod that has a 4-in stroke you now have a 7-in stroke

 

[ghettosmurf83]

Rod length doesn't change the stroke. The crankshaft is a different stroke and I think the bore slightly too....

I don't know if you're only about mechanic or if you build cars too but everybody knows there are two ways to build a stroker motor you either want a high RPM stroker motor or high torque stroker motor, if you want to increase the torque of an engine you add the increase stroke to the crankshaft, if you want a higher rpm you increase rod length

 

[ghettosmurf83]

Rod length doesn't change the stroke. The crankshaft is a different stroke and I think the bore slightly too....

But that is not my question My question is where did they gain the stroke in a 4.5 l it is 2 in greater and stroke I don't know if they increase the rod or the crankshaft throw I'm taking the rotating assembly out of a 4.5 because it is forged and putting it in a 4.3 so I can turbo it

 

[matt167]

you cannot gain stroke from a longer rod. You get stroke from the crank only. Changing rod length affects your rod ratio which does effect your ‘ power band ‘ if you will because it does change the geometry. But with the rod ratio you need to have matched pistons because if you use a longer rod, the piston will need its pin location higher in the piston, to keep the piston from protruding the hole..

Little reading I found for you quick

Understanding Rod Length, Piston Compression Height, and Crankshaft Stroke

The inside of an engine is a fickle ecosystem where every component directly affects another. Rod length, crankshaft stroke, and piston compression height are three variables that are key to choosing the perfect rotating assembly. Here's a deep dive into their definition and effects.

blog.diamondracing.net

Fwiw, the only way your getting a stroker 4.3 is if you could get a 4” stroke crank

 

[Scott06]

Rrod length absolutely changes stroke, ie: say you have a crank that has a 3-in stroke and you add a rod that has a 4-in stroke you now have a 7-in stroke

no as mentioned by Matt not how it works Stroke increases by the crank.

what are you trying to do ? Are you trying to increase the displacement on a 4.3? If so take it out and put in a 5.7 ..

 

[Scott Danforth]

The 4.5 and the 6.2 both use the same rods and pistons. They have the same bore and stroke

They have the crank custom made. It won't fit the 4.3 block