Rod ratio

[98spydert]

I didn't want to jack the 4g64/4g63 thread, i just wanted to know what the stock rod/stroke ratio is and what the ratio is if you add the 4G64 crank to the 4g63. I'd do that math myself I wouldn't know where to find the measurments. Thanks.

 

[bigjangin]

all dsm rods should be 150 mm(magnus long rods are 156mm)
4g63 crank stroke = 88mm
2.4 crank stroke = 100 mm (crank from 4g64, g64b, or g4cs)


so that gives you 1.5 for the 64 crank in a 63.

Stock is 1.7

 

[98spydert]

Thanks for the info!
So that sucks, you loose your near perfect rod/stroke ratio when adding .1 liters of displacment. Is the trade off worth it?

 

[bigjangin]

getting .3 or .4L of extra displacement is definitely worth it in my opinion. A 2.4 or 2.3 will definitely go to 7500 rpm, if not higher. Not many people need to go higher than that.

 

[leakyfaucet]

The issue of rod ratio isn't really how high it will rev, it's how fast you tear up your cylinder walls!

 

[rarson]

Blah blah blah. Everyone thinks that rod ratio will destroy your engine. Well here's a thought: Honda's D16 series engine, the one that comes stock in a lot of Honda Civics, uses 137mm rods with a 90mm stroke, that's a rod ratio of 1.52. In a Civic. A very reliable Civic. Granted, you're not shoving 25 psi of boost down it's throat but these engines have handled 300 whp on completely stock bottom ends. I think people make it out to be a bigger issue than it is. In my opinion, I'd be more concerned about the effects it'll have on cylinder filling than wear.

 

[anoldsman]

I agree with rarson. Another example is the ever popular 383 Chevy with 5.700 rods - 5.700 rod / 3.750 stroke = 1.52 Rod/Stroke Ratio. Or the stock Chevy 400 - 5.565 rod / 3.750 stroke = 1.484 Rod/Stroke Ratio. These things will last forever if built right.

Chris

 

[swordfish]

With the recent incident of water getting into my engine I had to tear my 2.4 long rod (1.56:1) motor down. The cylinder walls look perfect as well as the piston skirts.... aside from one bent wristpin from the water. I am rebuilding it with new parts jsut to be safe .. again.

jeff

 

[NDgsx]

In my opinion, I'd be more concerned about the effects it'll have on cylinder filling than wear.

Well you'll have to run a longer duration cam then you would in a 2.0 and it will always breath a little better at low rpms, but I wouldn't worry about that in most cases.