Molnar Rods?

[Jonny042]

Well, the plot thickens, the specs are not a typo..... Molnar doesn't make a 964 Rod at all, it's a 964 RSR rod. Which is a 964 rod with a 993 width small end. From what I can tell this is useful if you wanted to use 993 pistons and a 964 crank.

They also make a 993 Rod which also fits 996 Turbos.

What they don't make is a 3.2/3.3/964 rod.

Unless someone knowledgeable can advise me that the narrow pin end of the 964 RSR spec rod is OK to use with the off the shelf 3.2/3.4 JE pistons I've ordered, I'm going back to plan "A", to use rebuilt and balanced stock rods with ARP bolts.

[Jonny042]

Originally Posted by winders

Why not get some Carrillo rods and be done with it?

The money you save with other options just ended up costing you more down the road....

Short answer - money. Longer answer below:

The bigger picture on this motor is it's a street/auto-x motor and I've chosen to give it a nice meaty torque rich powerband, which means it's never going to be an 8KRPM screamer.

$1700 Aftermarket rods are most definitely overkill. But if I can install something for a few hundred bucks more than stock rebuilts and lose 100g+ per hole of reciprocating mass, that would be money well invested.

As far as connecting rods costing money down the road? Not sure how that is, as we are discussing viable options.

[Neil Harvey]

Your choice should always be based on your engines performance. Then budget.

I assume the engine's performance is going to be around the mid 300 BHP? That's around 55- 60HP per cylinder/rod/pin/pin boss. Not a lot. The stock rod will work if rebuilt correctly. The weight will be the only consideration.

Many of the current options are still heavy for this type of engine. You stated a "meaty" torque band. I'm not sure what that means. You will be limited to the amount of torque produced by air intake limitations and displacement. The engine's VE is going to be at the lower end of the scale. So what you need to consider is the time it takes for the engine to reach the usable torque. The quicker you can rev the engine into the Torque that will accelerate the car forward the better. This is where the component weight makes a difference.

You need to consider trying to get all cylinders making the same torque. Heavier rods won't do anything to help get more air into the cylinders.

Lighter rods will cost $$$. another factor to consider now is, delivery time. You may be a shock on how long it will take.

[Jonny042]

Originally Posted by Neil Harvey

Your choice should always be based on your engines performance. Then budget.

I assume the engine's performance is going to be around the mid 300 BHP? That's around 55- 60HP per cylinder/rod/pin/pin boss. Not a lot. The stock rod will work if rebuilt correctly. The weight will be the only consideration.

Many of the current options are still heavy for this type of engine. You stated a "meaty" torque band. I'm not sure what that means. You will be limited to the amount of torque produced by air intake limitations and displacement. The engine's VE is going to be at the lower end of the scale. So what you need to consider is the time it takes for the engine to reach the usable torque. The quicker you can rev the engine into the Torque that will accelerate the car forward the better. This is where the component weight makes a difference.

You need to consider trying to get all cylinders making the same torque. Heavier rods won't do anything to help get more air into the cylinders.

Lighter rods will cost $$$. another factor to consider now is, delivery time. You may be a shock on how long it will take.

Hi Neil, thanks for the thoughtful reply.

The below quote is a better overview of the plans from this thread: http://forums.pelicanparts.com/911-engine-rebuilding-forum/1109850-hot-3-4-build-max-safe-rpm-stock-rods-w-9mm-arp-bolts.html

Originally Posted by Jonny042

I'm starting on a build for my autoX car (The "Rot Rod"). Most of the hard points are determined:

The 3.2 will end up a 3.4 with:

98mm re-plated stock 3.2 Cylinders (EDIT - sent to LN engineering)
98mm Pistons 10.5:1 (EDIT - JE 353287's on order)
46mm PMO ITB's
Heads - Stock 3.2 Ports/Valves/Twin plugged
DC43-102 Cams/Aasco ti/springs (EDIT - maybe DC44-106?) (EDIT 2 - DC43-106 on order)
1-5/8 exhaust (41mm SSI or 42mm Eisenmann)

The above specs should support a 7200 (or more) redline with peak power a bit lower than that. Street/track use.

Will the 3.2 rods be OK at those RPMS with ARP 9mm bolts? I'm not opposed to spending the money for better rods but seems like it would be a waste if not required.

Thanks in advance!!!

Jon

I'd be happy if the engine made 300Hp and had good wide range of torque (or at least isn't super peaky). I always prioritize light weight where I can, car currently has a Patrick Motorsports DME flywheel, and aluminum pressure plate but planning to switch to an RSR style flywheel which takes a few pounds off current configuration.

The ECU, 46mm ITBs and 12 COP units are in hand and I'm working on the heads right now as parts trickle in from around the world..... yes the supply chain issues are real. And yes I'm already over budget!!!!

I'm aware that the phrase "building a 911 on a budget" makes as much sense as "Fuc%#@ for viginity".......

The car also has close ratio gears in 2nd and 3rd and weighs 2335 pounds empty so getting to that torque is a little easier than some cars.

[LukasM]

Hi Jonny,

What rods did you end up with now for your hot 3.4 build, are you going to stick with stock ones? I think that Neil is working with an Italian company to produce some that are strong enough for a NA application and lighter than Carillo and Pauter? Not sure about the price however..

Cheers,
Lukas