Carrelo con rods

[Harpo]

Does carrelo balance their con rods (rod to rod and end to end)

Thanks

David

[Spenny_b]

My new Carrillo's didn't have any balancing grinding marks on them; I don't know how balanced they were from factory (I didn't ask the question of the guy doing my balancing work), it may be that they were within Porsches specification, which is generous versus what can be achieved.

Looking at mine, I wouldn't say that huge amounts were removed from either end, but there's scope for them to be optimised

[faapgar]

Their new matched sets are usually very close.Fred

[Trackrash]

Not that hard to check.

[Harpo]

Does someone have a con rod balancing fixture I can rent?

Thanks

David

[Spenny_b]

Originally Posted by Harpo

Does someone have a con rod balancing fixture I can rent?

Thanks

David

It'd probably cost you more to ship somebodys rig, than to have your own....I bought one of these:

https://www.amazon.co.uk/gp/product/B01DGLFVS0/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

and one of these:

https://www.amazon.co.uk/gp/product/B01N323E64/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

Just so I have both bases covered with smaller and larger parts, less than £10 each with free shipping form Amazon. A set of 90º brackets like Trackrash posted (ingenious!) for a couple of quid each from your hardware store, and boom, you have a rudimentary rig.

[Harpo]

Agreed. I already have a scale so I will see what I can come up with something from work

David

[Trackrash]

FWIW, I used a ball bearing in the big end and made sure the rod was level when in the jig. As mentioned I had some large angle brackets that worked out perfectly. The scale is accurate to less than a gram. Some guys will go to 1 /10 g. I don't think that is necessary.
You can do a google search and there are a number of examples of end to end balancing of rods.

[lvporschepilot]

Juice is definitely worth the squeeze with these rods though. Carrello’s weigh some 150g less each on top of being much lighter. That loss in rotating mass is worth 5-8bhp in a 3L ish engine. Combine that with forged JE pistons which weigh some 150-200g less than stock and you’re really into some nice gains from weight losses.

[Spenny_b]

Originally Posted by Trackrash

..... Some guys will go to 1 /10 g. I don't think that is necessary.

Yeah the guy who did my balancing work, ex Brian Hart (in fact was best mates with him) and very experienced with top level F1 engines, also holds the opinion that going to 0.1gm levels of balancing is entirely possible but not really required, other than for OCD-reasons. The amount of oil flying around skews the equation massively; I guess that cornering loads or accelerative/deccelerative forces on the chassis, also means that oil-slosh is never going to be consistent across the crankcase.

(...but it didn't stop me getting it spot-bollock-on!)

[lvporschepilot]

I believe that was part of the reason the Kremer oil bypass mod was taken by the factory in 76, less windage losses in the crankcase.

[911pcars]

FWIW, after balancing the con rods w/the diy rig, how are you going to balance the crankshaft, the flywheel, crank pulleyj, pistons, etc.? What I'm getting at is engine balancing is performed with specialized machines. Send all reciprocating parts to an engine balancing service, preferably one that understands Porsche, or in lieu of that, you confirm with them the needed tolerances and specifics. Ask questions, but you also need to know the correct answers. Do not assume all balancing services are equivalent.

[Spenny_b]

Originally Posted by 911pcars

FWIW, after balancing the con rods w/the diy rig, how are you going to balance the crankshaft, the flywheel, crank pulleyj, pistons, etc.? What I'm getting at is engine balancing is performed with specialized machines. Send all reciprocating parts to an engine balancing service, preferably one that understands Porsche, or in lieu of that, you confirm with them the needed tolerances and specifics. Ask questions, but you also need to know the correct answers. Do not assume all balancing services are equivalent.

That's why I did indeed send it all out to be balanced by a specialist. Not the crank, as I wasn't tearing the bottom end apart for Build#2. But we know from measuring a stock crank that they come from factory extremely well balanced. I got the SMFW, clutch housing, front pulley and crank position "wheel" I'm using balanced, along with pistons/wrist pins and rods.