What connecting rods for an LT1?

Birdie2000

Birdie2000

Club Member
So what's everyone's favorite connecting rod? For a 383 stroker LT1 with a YSi. Needs to be 6.0 inches. Figure on 700rwhp unless it happens to make more once I finalize everything. Redline will most likely be around 6000rpm. Looking to keep this motor a little milder, lower my power goals, and hopefully add a little durability and streetability by keeping the revs and boost down. The car is going to be more of a high-power street car now instead of primarily drag. Crank is a Cola and pistons are JE.

Was thinking about Oliver Billet but was told they're over $2000 a set nowadays? :faint:I need something cheaper than that. Eagle is not an option, and I'm pretty sure I want to stay away from the Compstar rods as well. Had Manley forged H-beams in my old motor that came with the car, seemed like really nice rods and I don't think they were that bad in price.

The engine I bought now has Speedomotive Pro-I beams, not sure if I trust them or not. If I thought they'd hold the power I'd probably keep them and save the money. They say they've used them over 1000hp in engine competitions and such, but that they wouldn't use them that (1000hp) power level in a drag race application. They didn't give me a power range on the rods, but I didn't ask either.

Any opinions?
 
Lunati pro-mod billets $1334 a set and tough as nails.



Birdie2000 said:
So what's everyone's favorite connecting rod? For a 383 stroker LT1 with a YSi. Needs to be 6.0 inches. Figure on 700rwhp unless it happens to make more once I finalize everything. Redline will most likely be around 6000rpm. Looking to keep this motor a little milder, lower my power goals, and hopefully add a little durability and streetability by keeping the revs and boost down. The car is going to be more of a high-power street car now instead of primarily drag. Crank is a Cola and pistons are JE.

Was thinking about Oliver Billet but was told they're over $2000 a set nowadays? :faint:I need something cheaper than that. Eagle is not an option, and I'm pretty sure I want to stay away from the Compstar rods as well. Had Manley forged H-beams in my old motor that came with the car, seemed like really nice rods and I don't think they were that bad in price.

The engine I bought now has Speedomotive Pro-I beams, not sure if I trust them or not. If I thought they'd hold the power I'd probably keep them and save the money. They say they've used them over 1000hp in engine competitions and such, but that they wouldn't use them that (1000hp) power level in a drag race application. They didn't give me a power range on the rods, but I didn't ask either.

Any opinions?
Click to expand...
 
Which one is considered stronger for a blower app where lightweight isn't a necessity? I've heard so many things on the whole H-beam vs. I-beam debate I don't know what to believe any more.
 
http://store.summitracing.com/partdetail.asp?part=LUN-LAD2&autoview=sku

I like manely rods but they have not been pushed as far as the lunatis. they are a bit pricey but they are the best rod for the $$ out on the market. for a YSI application turning 7800 or so rpm this would be the rod I would chose for the budget.

As for the A-I-H beam argument its really sort of application specific. If you are building a high revving motor an I beam is ideal. If you are building a moderate rpm high nirtous engine an A beam is more suited to this. If you are building a blower engine or turbo motor for low RPM and H beam is the way to go.

Defining rpm 7500> is high rpm
Defining rpm 7500< is moderate RPM
Definign low RPM is 6800<

Hope this clears up the confusion.

Each beam design has its own benfit but for anything thats really high output per cube and displacement with lots of RPM A and I beams are the way to go.

Birdie2000 said:
Which one is considered stronger for a blower app where lightweight isn't a necessity? I've heard so many things on the whole H-beam vs. I-beam debate I don't know what to believe any more.
Click to expand...
 
I would run an I beam. Considering clearance for the camshaft etc for a SBC i would stay away from an H beam due to the width of the broach alone.

Birdie2000 said:
Which one is considered stronger for a blower app where lightweight isn't a necessity? I've heard so many things on the whole H-beam vs. I-beam debate I don't know what to believe any more.
Click to expand...
 
I'm thinking 6000-6500 rpm tops unless there's no reason for that limit. I'm mainly thinking for streetability and durability concerns, and just pulleying the blower up to make the desired boost, which I would figure in the area of 12-14lbs. I'm hoping to have a fairly efficient motor.
 
a 383 at 12-14psi is not going to get the ysi enough into its sweet spot to make it work well. I would figure running 18-20 would be apropriate for that blower and turning say 7500 rpm.

Birdie2000 said:
I'm thinking 6000-6500 rpm tops unless there's no reason for that limit. I'm mainly thinking for streetability and durability concerns, and just pulleying the blower up to make the desired boost, which I would figure in the area of 12-14lbs. I'm hoping to have a fairly efficient motor.
Click to expand...
 
Fair enough, I guess I'll have to think it over a little more. I am a bit confused by that though. I always thought that for a given blower rpm it produced a certain cfm, and the boost was simply a factor of the motor producing resistance to getting that volume of air through the motor, thus the reason a better flowing air pathway typically lowers the boost but keeps the power the same or better.
 
return on HP and TQ required to turn the blower vs the CFM output. IT is a parobolic type curve with a plateau in the middle of its airflow range for TQ input vs CFM. You want to get the blower to it's plateau of efficency.Blower Like turbochargers have surge areas as well where they have trouble having a nice continous flow of air without reversion and cavitation.

It's easy enough though to build a 7500rpm lt1 with 383ci and to turn the blower to 18-20 psi. Not a big deal. I would still recomend that Lunati rod anyways becuase if you ever get the need for speed you have the parts ready to rock.

Birdie2000 said:
Fair enough, I guess I'll have to think it over a little more. I am a bit confused by that though. I always thought that for a given blower rpm it produced a certain cfm, and the boost was simply a factor of the motor producing resistance to getting that volume of air through the motor, thus the reason a better flowing air pathway typically lowers the boost but keeps the power the same or better.
Click to expand...
 
Thanks for the explanation, makes sense. :)

On the other hand, I can see why the blower should be driven to a certain point, but why 7500 rpm on the engine? Why not make the blower reach that boost/rpm level at a lower engine rpm?

btw, not trying to be a pain in the ass, just trying to learn. :)
 
Becuase its better to split the differnce with rpm and TQ. lots of cylinder pressure breaks parts lots of rpm breaks part. picking a nice medium like 7500 keep the parts in the motor and the gaskets and pistons where they belong as well. That would be the best way to go IMO. Just run a solid roller.


Birdie2000 said:
Thanks for the explanation, makes sense. :)

On the other hand, I can see why the blower should be driven to a certain point, but why 7500 rpm on the engine? Why not make the blower reach that boost/rpm level at a lower engine rpm?

btw, not trying to be a pain in the ass, just trying to learn. :)
Click to expand...
 
People seem to have really good luck with the Oliver billet parabolic beam rods. That's what I'm using in my new motor.
 
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