Balance shaft delete info

[kevrobert]

For those considering deleting balance shafts and purchasing one of the kits available, be advised of the following..

The lower balance shaft is incredibly difficult to remove in situ it required the removal of a an aluminium lug with a hacksaw on the casing, even then was very difficult to remove.

Now LR or 9apart sell you a neat little kit with I believe m8 bolts to blank off the oil feed and return.. well these are going to be very useful when the feed on my 8v is a 2 mm gudgeon pin which I blanked off with a screw and the return is a triangular shaped hole (I don't think they make triangular bolts!)

So back on with the casing and I used a roll bar bush of the correct diameter blanked off to seal the casing.

Do not waste your money on one of those kits.
There's a reason they don't come with instructions!

Now because I have deleted PS, have no Aircon and a lightweight Alternator I have no issues with engine balance whatsoever (additionally my engine is blueprinted)

I have not done enough testing yet to give a definitive answer but I believe any inherent imbalances are mainly due to running ancillaries.

[v2rocket_aka944]

PS, air con, alternator have nothing to do with what the balance shafts are there for.

engine balance has nothing to do with what they're there for.

deleting the b-shafts in the car, with a hack saw, using a rubber bushing to seal an oil-rich environment...yikes.

talking bad about vendor kits for having parts that you don't even know where they go, assuming they go somewhere else and of course wouldn't fit there...jeez.

note to all future readers, do not follow the original post.

[IdahoDoug]

Commenting on the "It's just fine without the balance shafts" implication. I will be interested in your feelings after you've driven the car like this. I have some experience with this difference, as I've been a part of testing of engines with and without balance shafts and the versions without were annoying, stuff in the interior shakes and vibrates and the engines were "buzzy". I also helped design a consumer test of this feature using random customers who came and drove the cars and answered statistical surveys of their impressions. The non shaft engines were universally panned. By contrast the same engine with the balance shafts were smooth, quiet and transformed the vehicle back from "annoying constant engine awareness" to "hey this thing's fun to drive."

Personally, if I removed the balance shafts from my beautiful 944, I'd feel like I had to apologize to every passenger and explain that no my Porsche is not about to self destruct, but I decided to increase its horsepower by about 1.2567HP and tolerate the annoyance.

If you're racing - sure. But I would not even consider doing something like this on a 944 driven on the street.

[wildcat077]

What would be the reason for removing the balance shafts ?
Is it for a horsepower gain , loss of rotating mass ???

The cutoff on my race engine is 6700 rpm , i could just imagine the vibration
during a 30 minute session without balance shafts ... yikes !

[IdahoDoug]

Also, your motor mounts were specifically designed to absorb and counter the known vibration profile of the 2.5L engine with twin balance shafts. Creating an engine with a completely different vibration profile means you could see if someone sells a motor mount for that different profile, but I honestly don't think it's out there. You'd be stuck with it.

[v2rocket_aka944]

Originally Posted by wildcat077

What would be the reason for removing the balance shafts ?
Is it for a horsepower gain , loss of rotating mass ???

The cutoff on my race engine is 6700 rpm , i could just imagine the vibration
during a 30 minute session without balance shafts ... yikes !

5-8hp, less mass, less belts and rollers...tradeoff is buzziness (subjective to each person) and potentially loosening fasteners and broken oil pickup tube.

but if someone doesn't even understand what the balance shafts do, they're not qualified to delete them.

heres a good summary.
https://www.youtube.com/watch?v=hwigSbyQ7AI

[wildcat077]

Originally Posted by v2rocket_aka944

5-8hp, less mass, less belts and rollers...tradeoff is buzziness (subjective to each person) and potentially loosening fasteners and broken oil pickup tube.

but if someone doesn't even understand what the balance shafts do, they're not qualified to delete them.

heres a good summary.
https://www.youtube.com/watch?v=hwigSbyQ7AI

I'll make sure i carefully install them in my new race engine build ... oh, i already did that !
No further comment ... perhaps you can slack off on the sarcastic remarks

[IdahoDoug]

For a race engine, obviously the sky's the limit and the lack of shafts is meaningless. I'm envisioning a stripped, loud interior, an aggressively stiff suspension and seats with a quarter inch of padding! Heh - not even going to notice an engine vibration over the visceral storm of a race prepped 944. It will just be the "new pattern" of the car's behavior that you'll then note any deviations from when feeling/listening and remaining in close touch with your steed. Have fun, be safe and send pictures!

[v2rocket_aka944]

it's certainly doable to delete them, you just have to know what you're doing and what the side effects will be. long story short, if you can build the engine to suit you can get away with it. lightweight pistons/rods and the longest rods you can fit with the shortest stroke you can tolerate.

that said, the 944 LeMans ran balancer shafts, FWIW.
and below this is one of the original 944 GTR trans-am racers...notice something?

[IdahoDoug]

Holy crap - is that huge hunk of aluminum stock by the strut a sway bar mount? I don't think I've ever seen a thicker piece of aluminum on an automobile outside of the block!

[v2rocket_aka944]

that IS the sway bar.

big aluminum ends like that with a large tubular piece across the front of the car, the aluminum piece has a slot and clamp to grip the tube.

like this.

[IdahoDoug]

Wow - that's a beast of a chunk. It's actually the sway bar end, and connects the sway bar to the sway bar link which is the vertical smaller chrome bit going straight down. Beefy stuff. I heard or read somewhere that torque on a sway bar can easily be in the 6000 ft-lbs range for a modern SUV. So these bits obviously need to be stout but that hunk o' aluminum exceeds anything I've seen. Wow.

[wildcat077]

I have a post on Rennlist where i showed a picture of one of the balance shafts actually twisting and blowing out the cover on my previous race engine ... nobody was able to come up with a reasonable cause , anyhow i'm still baffled as everything else in the engine was OK including rods, bearings, cam, pistons etc ...
I'll try to post the picture this week.

Although my new engine has JE pistons and Molnar rods, i'm keeping the balance shafts as i would never consider not using them !

[djnolan]

The only thing different about that lemans engine is the distributor on the back end of the cam!

[kevrobert]

Yes thanks for all the great comments, your right without the kit in my hand I deduced wrongly how it worked. All sussed now, rear plug stays, I've blanked the oil hole for the bearing and blanked the front off with washers and seals bolted through. Cost to me to delete zero.
What confused me was an article which mentioned nothing about oil return apertures, these spit oil so you cannot
delete the covers unless either you weld them up or maybe there's a way to blank these off internally?