Balance Belt alignment: S2
04-26-2018, 04:42 PM
#16
Rennlist Member
Thread Starter
I'm sort of wondering if it's always shaken like a dog at idle and I just didn't notice until I decided to get ultra-paranoid following the BB replacement. My car has semi-solid (some would call them solid) motor mounts, basically billet aluminum with a little solid rubber isolator. Pelican called them "Super Mounts" back when you could buy them.
As I said, it's smooth above 1000, but really rough at idle. Could be normal?
As I said, it's smooth above 1000, but really rough at idle. Could be normal?
04-26-2018, 04:50 PM
#17
Race Car
When the sprockets were removed they were put in separate bags marked "upper" and "lower" to make sure they didn't get confused. In another thread ("Guess the age of this timing belt") the subject is discussed and there are some pictures available. There's a lengthy exchange on the condition of the lower sprocket, which has some mild burring on the outside belt retainer along with some tooth wear. From the photos we concluded the part was re-usable after some polishing, which is good since it's NLA.
It is very interesting to know there's a functional difference between the upper and lower parts, along with knowing the lower is somehow NLA while the upper can still be ordered, since they have the same part number. Very strange.
So I don't think there's been any confusion in the part use. For what it's worth, the subject was carefully researched in advance, all the parts were marked as they were disassembled, and many, many photos were taken.
It still shakes like a dog. The only confusion at present concerns the difference between Spencer's orientation guide and Clark's. As I mentioned, I chose to use Spencer's and, in retrospect, that appears to be correct since it agrees (see above photo) with the factory registration marks.
It is very interesting to know there's a functional difference between the upper and lower parts, along with knowing the lower is somehow NLA while the upper can still be ordered, since they have the same part number. Very strange.
So I don't think there's been any confusion in the part use. For what it's worth, the subject was carefully researched in advance, all the parts were marked as they were disassembled, and many, many photos were taken.
It still shakes like a dog. The only confusion at present concerns the difference between Spencer's orientation guide and Clark's. As I mentioned, I chose to use Spencer's and, in retrospect, that appears to be correct since it agrees (see above photo) with the factory registration marks.
The front guide washer has a tab that inserts into a key way slot.
In essence, this aligns the washer to make two separate assemblies, a top sprocket and a lower sprocket.
The free key slot not occupied by the washer's tab allows you to locate each on the balance shft properly.
T
04-26-2018, 05:11 PM
#20
Rennlist Member
Thread Starter
It's not that you used the wrong parts,it's how you assemble the parts to make up a unit that is a sprocket.
The front guide washer has a tab that inserts into a key way slot.
In essence, this aligns the washer to make two separate assemblies, a top sprocket and a lower sprocket.
The free key slot not occupied by the washer's tab allows you to locate each on the balance shft properly.
T
The front guide washer has a tab that inserts into a key way slot.
In essence, this aligns the washer to make two separate assemblies, a top sprocket and a lower sprocket.
The free key slot not occupied by the washer's tab allows you to locate each on the balance shft properly.
T
After thinking, it seems the sprockets are keyed in two positions, one for upper, the other for lower.
If the sprocket is mounted on the upper spindle, the "guard" washer on the front of the spindle should be oriented to show the "O" mark on the spindle through an open hole in the washer. This correctly aligns it to the upper (ober) spindle.
The lower sprocket is exactly the same part, with two key-ways machined into it. To mount it to the lower spindle, the mechanic must first orient the "guard" washer on the front, or outside face of the sprocket, so the slot on that washer partially eclipses the "O" mark on the sprocket. It's not OK for the lower sprocket to be oriented on the spindle key in a way that allows the "O" to be seen through a hole, it needs to be only visible through the slot, otherwise the sprocket is keyed to the spindle incorrectly.
It's a very subtle problem.Thank you for explaining it to me. I hope I've correctly explained the problem so others can avoid it.
Best Regards,
Scott.
Last edited by Otto Mechanic; 04-27-2018 at 02:57 AM.
04-26-2018, 06:25 PM
#21
Rainman
Rennlist Member
Rennlist Member
...i wonder if you might be able to loosen the super mounts, jack up the engine a bit and slide a piece of say 1/8 or 1/4" squishy rubber between the mounts and crossmember and then re-tighten.
might have "some" damping effect?
might have "some" damping effect?
04-26-2018, 09:04 PM
#22
Race Car
Never really a fan of solid mounts.
In an event where they may be adjustable for height, which some are, and you were looking to lower COG a 1/4" there
may be a use for them but I'll say again, if there's a driver anywhere on this 944/51/68 board who is so at the top of his
game that a quicker responding or shimmed engine mount is all that's standing in their way of a faster lap time,
please raise your hand.
Some of the mods I see on here are laughable.
Bigger than 996TT brakes.....for the street.....gotta have 'em,
While a Spec 944 with stock NA brakes would embarrass them at 10/10nths.
Put stock mounts back on the car.
T
In an event where they may be adjustable for height, which some are, and you were looking to lower COG a 1/4" there
may be a use for them but I'll say again, if there's a driver anywhere on this 944/51/68 board who is so at the top of his
game that a quicker responding or shimmed engine mount is all that's standing in their way of a faster lap time,
please raise your hand.
Some of the mods I see on here are laughable.
Bigger than 996TT brakes.....for the street.....gotta have 'em,
While a Spec 944 with stock NA brakes would embarrass them at 10/10nths.
Put stock mounts back on the car.
T
04-26-2018, 09:09 PM
#23
Race Car
BTW Scott, from back to the 80's, a lot of manufacturers mounted Randomly placed (I'm sure there was engineering study) weighted discs, isolated to the frames, crossmembers, etc. by rubber.
Vibration dampers.
If you look around a salvage yard for Ford Taurus, GM FWD cars from 85-present, you will find them.
May be a cheaper solution,
T
Vibration dampers.
If you look around a salvage yard for Ford Taurus, GM FWD cars from 85-present, you will find them.
May be a cheaper solution,
T
04-27-2018, 03:02 AM
#24
Rennlist Member
Thread Starter
T - I tried to post a reply but managed to only update another earlier reply. It's on this thread, but you won't get any notice since it was just an update. Sorry.
I think figured out what you and Spencer were trying to say about the sprocket, spindle key and the front guard. It does make sense to me now. I sincerely appreciate your guidance.
Best Regards,
Scott.
I think figured out what you and Spencer were trying to say about the sprocket, spindle key and the front guard. It does make sense to me now. I sincerely appreciate your guidance.
Best Regards,
Scott.
04-27-2018, 03:28 AM
#25
Rennlist Member
Thread Starter
Hey T -
I can't say I have any reason to be a fan either. After looking at the maintenance history of the semi-solid, or liquid filled, factory mounts, I went searching for an alternative. I admit I intended to build a car for the track and was willing to sacrifice comfort for a reduced maintenance cycle. Nothing more than that.
From what I understand, the semi-solid mounts will produce a reliable geometry with the transaxle and might shake like a dog. Since I already own a very nice 1985 928 S3 for those Sunday drives to the Crow's Nest with those buxom blondes, I figured I could get practical with the training wheels.
Best Regards,
Scott.
I can't say I have any reason to be a fan either. After looking at the maintenance history of the semi-solid, or liquid filled, factory mounts, I went searching for an alternative. I admit I intended to build a car for the track and was willing to sacrifice comfort for a reduced maintenance cycle. Nothing more than that.
From what I understand, the semi-solid mounts will produce a reliable geometry with the transaxle and might shake like a dog. Since I already own a very nice 1985 928 S3 for those Sunday drives to the Crow's Nest with those buxom blondes, I figured I could get practical with the training wheels.
Best Regards,
Scott.
04-27-2018, 03:46 AM
#26
Rennlist Member
Thread Starter
Now I think it's normal. It's what I was warned about. Not a problem.
Sorry for making an issue of it and thank you for your advice, I was unnecessarily worried. At least we've revealed (with pictures) the correct procedure for replacing these parts.
Thanks for you help and Best Regards,
Scott.
04-27-2018, 04:00 AM
#27
Rennlist Member
Thread Starter
But even so, I don't think I'll be returning to OEM mounts on this car anytime soon, it's always been destined for the track and as long as it's running right I don't really care if the ride is harsh. Believe it or not, there are some very selective ladies out there that actually look for successful engineers.
Keep the faith,
Scott.
04-27-2018, 10:57 AM
#28
Race Car
Yep. I think you and I may be on the same page here Paul.
But even so, I don't think I'll be returning to OEM mounts on this car anytime soon, it's always been destined for the track and as long as it's running right I don't really care if the ride is harsh. Believe it or not, there are some very selective ladies out there that actually look for successful engineers.
Keep the faith,
Scott.
But even so, I don't think I'll be returning to OEM mounts on this car anytime soon, it's always been destined for the track and as long as it's running right I don't really care if the ride is harsh. Believe it or not, there are some very selective ladies out there that actually look for successful engineers.
Keep the faith,
Scott.
That said, full blown race cars competing at the most top level of two SP classes, we run factory mounts.
The price of rigid mounting, IMO, places unnecessary stress to the block.
T
04-27-2018, 12:15 PM
#29
Rainman
Rennlist Member
Rennlist Member
the 944S2 doesn't have a throttle air bypass screw like the 8v cars did (it uses the idle air valve and probably variable spark timing to control idle speed) but i wonder if you could mess with the throttle-stop screw slightly to crack the TB open a little, thereby raising the idle speed and smoothing out the shaking?
04-27-2018, 08:06 PM
#30
Rennlist Member
Thread Starter
the 944S2 doesn't have a throttle air bypass screw like the 8v cars did (it uses the idle air valve and probably variable spark timing to control idle speed) but i wonder if you could mess with the throttle-stop screw slightly to crack the TB open a little, thereby raising the idle speed and smoothing out the shaking?
Regards,
Scott.