rod length

[93grandprixse]

is there any difference in rod length between engines?

[bszopi]

Not until you get to the GEN4 engines. All other engines got 5.7" rods.

[93grandprixse]

well i have a 2001 3100, im trying to find a way to make low compression, building it to put in my 1990 STE Turbo...

i plan on building it low compression so i can run more boost than just like 6 lbs

what engines came with the shortest rods?

[bszopi]

With proper tuning, you can run more than 6psi on a stock CR 3100. And like I already said, everything from 80-04ish came with 5.7" rods. Once you get into the GEN4 engines (ie, 3500), then rod length INCREASED. In order to lower compression, you need to get custom pistons.

[Superdave]

people are running 10-12 PSI on the stock SCR for the 3100/3400.. like bszopi said, it's all in the tune.


you could lower the compression a little by modifying the combustion chamber on the heads but you can also really screw things up if you aren't carefull...

[Joseph Upson]

Low compression for boost is old doctrine. You should only lower compression as a last resort based on the levels you intend to run. If intercoolers and water injection make keeping or increasing your current compression ratio with the boost pressure you intend to run possible, that's the route that will net you the most efficiency with your power increase. Dropping compression will also affect your mileage as you extract less energy from the intake charge.

High compression actually increases your engine efficiency and is much more manageable with boost with todays improvements in electronics and cylinder head design.

I posted a link in the boost section to a BMW blower kit that produces 8.5 psi in an 11.3:1 compression engine as an example to show that it's being done.

[93grandprixse]

thanks for the great advice guys, but its really un needed, im just trying to find a unique way to build a 3100 up that no one has tried before. im doing this for my high performance machining class up here at college (im a college student going to ferris state university for automotive engineering) so i know the basics of how an engine work, what to and not to do for what i want, i understand its all in the tune, and i plan on doing very precise tuning work. but for now im concentrating on filling out my build sheet for class, and i want to find the most effecient way to make a sort of frankenstien high boost engine out of these engines... something no one has yet found a way to do...

hence why i was wondering about rod length...

thanks anyways guys... i appriciate the support and good advice... and il keep you posted on the engine build.

[RedZMonte]

Rod Length?!?!?!

Giggity Giggity GOO!

[onefastV6]

thanks for the great advice guys, but its really un needed, im just trying to find a unique way to build a 3100 up that no one has tried before. im doing this for my high performance machining class up here at college (im a college student going to ferris state university for automotive engineering) so i know the basics of how an engine work, what to and not to do for what i want, i understand its all in the tune, and i plan on doing very precise tuning work. but for now im concentrating on filling out my build sheet for class, and i want to find the most effecient way to make a sort of frankenstien high boost engine out of these engines... something no one has yet found a way to do...

hence why i was wondering about rod length...

thanks anyways guys... i appriciate the support and good advice... and il keep you posted on the engine build.

You could always build the following.....

3100 block bored .060, 2.8L crank,custom pistons, modified SBC rods, reground cam, SBC cam bearings, 3500 heads, 3500 LIM, 3100 large port UIM

[Superdave]

Since the combustion chambers are the same size from the old 3.1 to the 3100.. you could always put in a set of pistons for a gen2 3.1 to lower the scr back to 8.9:1.. then smooth/polish the chambers to lose a bit more.. maybe down to 8.8:1 depending on how much material you remove.

[93grandprixse]

You could always build the following.....

3100 block bored .060, 2.8L crank,custom pistons, modified SBC rods, reground cam, SBC cam bearings, 3500 heads, 3500 LIM, 3100 large port UIM

very intregued, but what would be the advanteges to doing so?... if i am correct, the 2.8l crank has the same stroke as the 3.1 crank i already have...

[Superdave]

very intregued, but what would be the advanteges to doing so?... if i am correct, the 2.8l crank has the same stroke as the 3.1 crank i already have...

the 2.8 has a 2.99" stroke and the 3.1 has a 3.31" stroke


so you'd lose displacement overall..

[onefastV6]

very intregued, but what would be the advanteges to doing so?... if i am correct, the 2.8l crank has the same stroke as the 3.1 crank i already have...

You could rev the engine pretty high with the 2.8L crank....

[93grandprixse]

what would you guys say would be a safe rpm you could rev it to with the 2.8 crank?

and also, what are sbc rods and cam bearings? us sbc a company or code for some other part from annother engine... (i ask this because i know quite a few honda guys and they seem to talk in code and i dont know weather its one or the other...)

also, what would the displacement be with the block being bored .060 over? would that bump it up to a 3.4 or 3.5l engine so to speak, if the crank was to remain the same?

im just curiouse as to whats the max these engines can be bored over for boost before it becomes unsafe...

[bszopi]

SBC = small block chevy

To see different displacements with various components, check out the site's CR calculator, as it determines displacement as well -> http://60degreev6.com/content/CR_Calculator