HTD Belt Upgrade - worth it?
11-10-2003, 02:29 PM
#1
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HTD Belt Upgrade - worth it?
I've got all the parts now to convert my '81 engine to a '83 HTD (high torque design) belt.
FLENNOR HTD belt and round tooth gears
After doing all the recent cam stuff, and running without the covers, I realized that I could replace the square tooth belt 'in about an hour'.
So the question is, do I bother replacing the gears, or should I just replace the (less expensive) square tooth belt, say, once a year? (And replace pulleys/water pump only as needed.)
I check the tension all the time, so with constant tension, replacing the belt more often should not affect the water pump life?
FLENNOR HTD belt and round tooth gears
After doing all the recent cam stuff, and running without the covers, I realized that I could replace the square tooth belt 'in about an hour'.
So the question is, do I bother replacing the gears, or should I just replace the (less expensive) square tooth belt, say, once a year? (And replace pulleys/water pump only as needed.)
I check the tension all the time, so with constant tension, replacing the belt more often should not affect the water pump life?
Last edited by PorKen; 11-10-2003 at 02:49 PM.
11-10-2003, 02:40 PM
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If it were me I'd probably stick with the square tooth version. I'm sure Porsche changed the design for a good reason......maybe twice as many valves on the later engines, but it wasn't like a factory recall or anything.
It would be interesting to see how many square vs. HTD belt failures there have actually been.
I don't think you need to go the "once a year" extreme. The 4 year/45K mile interval is just fine. As always, I think that keeping the tension and associated running gear in spec is the best insurance.
It would be interesting to see how many square vs. HTD belt failures there have actually been.
I don't think you need to go the "once a year" extreme. The 4 year/45K mile interval is just fine. As always, I think that keeping the tension and associated running gear in spec is the best insurance.
11-10-2003, 03:09 PM
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"It would be interesting to see how many square vs. HTD belt failures there have actually been."
MikeN - that would be nice to know.
One thing I found is that as the belt ages, it stretches, which changes the camshaft timing by a few degrees, cam to cam and cams to crank. This may be why the car feels 'fresher' after a belt change.
On the 32V cars, you can adjust the camshaft gears to compensate (although the procedure does seem to be a bit arduous), but not on the 16's.
MikeN - that would be nice to know.
One thing I found is that as the belt ages, it stretches, which changes the camshaft timing by a few degrees, cam to cam and cams to crank. This may be why the car feels 'fresher' after a belt change.
On the 32V cars, you can adjust the camshaft gears to compensate (although the procedure does seem to be a bit arduous), but not on the 16's.
11-10-2003, 07:55 PM
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HTD -or not (to be) : That is your question? {apologies to , you know,that English playwright}
It proably doesn't matter substiantially staying w. the square tooth vs. changing to the HTD, as you practice 'good belt managment'. The one caveat is that the HTD design favoures hi rev/torque: it's all in how you (choose to) drive.
Therefore, one enters the realm of opinion, theory, and 'free' advice: we all know the value of the latter! BTY, the HTD was introduced in '83.
I changed the '80 to a HTD 11 yrs. ago, doing the 4 cogs + belt - it seemed to be a good thing to do on the basis, "it's probably better, certainly not worse". In addition, it was an opportunity to replace the cam seals, spacers, and O-rings.
Before spring, I'll install the remainder on the cam drive 'updates' from assembled parts: namely, '85 Tensioner/block gasket, carrier arm (with the latest black polymer bushings),crank guide roller, and back cover. The '85 tensioner has all the bits to provide a 'low belt tension alarm' , as long as I can figure out how to wire in a facsimile of the factory 3 min. delay( hints, anyone?)
This car still has it's ORRIGINAL water pump, @ 117,000Km. Reluctantly, I'll (probably) replace it this go round. I mention this, because, having done the TB/ water pump thing on my '88 recently, it would appear that, for the cost of an '87+ carrier arm/idler roller, one can fit the S4 waterpump to the 16v and benefit from the wider pivot stance of the S4 carrier arm (on the pump pivot stud vs. cast-in boss), and the stabilizing cross brace spanning the pivot stud to pump body. (anyone got an arm to spare- for testing purposes?)
All of these components, regardless of model year, maintain an identical rolling center, so I've not yet seen any problem in 'enhancing' the HTD updates with S4 generation parts.
On the subject of belts, the latest issue from 'OPTIBELT' HTD has a'dimpled trapezoidal' interpretation of the round tooth, claiming that retensioning is not req'd. Well, no one believes that; However, on the 1500 Km retensioning on an Optibelt installed on the '88, it was spot on! - no adjustment req,d. Guess what, the same belt is going to the '80.
Ken, I've spent this nickle on your thread, in part Because of the interresting cam timing issues you're developing, in part as 'advancement' of the HTD question posed for pre '83 cars, and lastly, for (worthwhile) update potential beyond the belt/cog issue, Comments anyone??
It proably doesn't matter substiantially staying w. the square tooth vs. changing to the HTD, as you practice 'good belt managment'. The one caveat is that the HTD design favoures hi rev/torque: it's all in how you (choose to) drive.
Therefore, one enters the realm of opinion, theory, and 'free' advice: we all know the value of the latter! BTY, the HTD was introduced in '83.
I changed the '80 to a HTD 11 yrs. ago, doing the 4 cogs + belt - it seemed to be a good thing to do on the basis, "it's probably better, certainly not worse". In addition, it was an opportunity to replace the cam seals, spacers, and O-rings.
Before spring, I'll install the remainder on the cam drive 'updates' from assembled parts: namely, '85 Tensioner/block gasket, carrier arm (with the latest black polymer bushings),crank guide roller, and back cover. The '85 tensioner has all the bits to provide a 'low belt tension alarm' , as long as I can figure out how to wire in a facsimile of the factory 3 min. delay( hints, anyone?)
This car still has it's ORRIGINAL water pump, @ 117,000Km. Reluctantly, I'll (probably) replace it this go round. I mention this, because, having done the TB/ water pump thing on my '88 recently, it would appear that, for the cost of an '87+ carrier arm/idler roller, one can fit the S4 waterpump to the 16v and benefit from the wider pivot stance of the S4 carrier arm (on the pump pivot stud vs. cast-in boss), and the stabilizing cross brace spanning the pivot stud to pump body. (anyone got an arm to spare- for testing purposes?)
All of these components, regardless of model year, maintain an identical rolling center, so I've not yet seen any problem in 'enhancing' the HTD updates with S4 generation parts.
On the subject of belts, the latest issue from 'OPTIBELT' HTD has a'dimpled trapezoidal' interpretation of the round tooth, claiming that retensioning is not req'd. Well, no one believes that; However, on the 1500 Km retensioning on an Optibelt installed on the '88, it was spot on! - no adjustment req,d. Guess what, the same belt is going to the '80.
Ken, I've spent this nickle on your thread, in part Because of the interresting cam timing issues you're developing, in part as 'advancement' of the HTD question posed for pre '83 cars, and lastly, for (worthwhile) update potential beyond the belt/cog issue, Comments anyone??
11-10-2003, 08:04 PM
#5
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Garth,
TWO brown 928s? You're my idol!
What I don't see is why you've done all that belt upgrade work. Is there any data that the HTD belt is really better than the old belt? The lore is that it is the stretching, not the snapping, that leads to most failures. Are the belts really made from different stuff?
TWO brown 928s? You're my idol!
What I don't see is why you've done all that belt upgrade work. Is there any data that the HTD belt is really better than the old belt? The lore is that it is the stretching, not the snapping, that leads to most failures. Are the belts really made from different stuff?
11-10-2003, 08:29 PM
#6
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GarthS - "the HTD design favoures hi rev/torque"; sold.
Actually I did hear that the HTD was phased in for the bigger cams of the later engines and then the thirsty-two valvers.
I bought a 42" 300ft/lb 3/4" drive torque wrench at Harbor Freight, but I forgot to buy a gear puller set. Now of course the crank gear is not cooperating, so I can't change the leaky crank oil seal until tommorrow.
I didn't think to get an '85 tensioner, I'm only upgrading to the '83 (with oil fill ports and a larger shoulder bolt).
...
I have an appointment for Wed. morning for the dyno. Nothing like leaving things to the last minute, eh!
Actually I did hear that the HTD was phased in for the bigger cams of the later engines and then the thirsty-two valvers.
I bought a 42" 300ft/lb 3/4" drive torque wrench at Harbor Freight, but I forgot to buy a gear puller set. Now of course the crank gear is not cooperating, so I can't change the leaky crank oil seal until tommorrow.
I didn't think to get an '85 tensioner, I'm only upgrading to the '83 (with oil fill ports and a larger shoulder bolt).
...
I have an appointment for Wed. morning for the dyno. Nothing like leaving things to the last minute, eh!
11-10-2003, 08:39 PM
#7
While on the subject of belts, can someone post a pic of the cam gears with the marks showing. I pulled off one of my covers and could not see any alignment marks on the gears or the block. Also, where is the crank supposed to be when checking. I believe mine has a 0 and a 2l3 on the dampner. I am still learning about this subject so any advice is helpful. Thanks.
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11-10-2003, 09:01 PM
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Porken .... the original square belt typically lasts at least 5 years 60,000 miles . Plus if it breaks, it breaks you stop moving . Put on a new belt and away you go ....it SHOULD not bend valves. The photo of the used round gears appears to show some wear it is hard to tell . If your square gears are worn then it might be time to "update" otherwise I see little benefit . If the original design was adequate for the task it does not need higher torque capabilities .
11-10-2003, 09:44 PM
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G Man,
Don't have a picture, but I just pulled the belt off my 80'. The following is assuming you are at T/0 on the damper. The cam gear marks are tough to see. The right side (passenger's side) is a little more obvious. With the cover off, shine a flash light from the top looking down and you will see an arrow. It should line up with a v on the cam gear (facing toward the engine). The left cam gear when looking straight at the gear is a little more to the left, same type of arrow, same type of v. The best way to find them is to rotate the crank to T/O and lock it there. Then look for the arrows and then you should see the little groove. When you find them, mark em with white touch up paint. If I get my camera going, I'll PM a picture where they are, since my belt is still off.
Don't have a picture, but I just pulled the belt off my 80'. The following is assuming you are at T/0 on the damper. The cam gear marks are tough to see. The right side (passenger's side) is a little more obvious. With the cover off, shine a flash light from the top looking down and you will see an arrow. It should line up with a v on the cam gear (facing toward the engine). The left cam gear when looking straight at the gear is a little more to the left, same type of arrow, same type of v. The best way to find them is to rotate the crank to T/O and lock it there. Then look for the arrows and then you should see the little groove. When you find them, mark em with white touch up paint. If I get my camera going, I'll PM a picture where they are, since my belt is still off.
11-11-2003, 12:25 AM
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I guess I'm glad I asked.
Wally was right. Taking a more objective look, compared with my existing gears, the '83 eBay specials are quite worn. It looks as if the belt tension was way too high, as some of the teeth are actually flattened somewhat. The flat tooth gears still have the coating on all the teeth.
(Long string of four letter words edited.)
Conclusion: No update required.
Wally was right. Taking a more objective look, compared with my existing gears, the '83 eBay specials are quite worn. It looks as if the belt tension was way too high, as some of the teeth are actually flattened somewhat. The flat tooth gears still have the coating on all the teeth.
(Long string of four letter words edited.)
Conclusion: No update required.
11-11-2003, 12:28 AM
#11
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Glen,
I'd certainly agree with jim Bailey's comment on the adequacy of the square tooth design - so why 'update'?
The design evolution makes sense, there are enough used/donor parts available in good condition and affordable, and the belt/water pump/roller costs are effectively identical, regardless of model year. It is ~$20 to rebuild any variant of tensioner, standard over the counter bearings press into all rollers except the primary tensioner roller - but that roller is the same part # for all model years. ie., it,s not a major expense beyond normal PM.
As far as time/effort - as you (all) know, once you get past fans/ignition /covers/slave cyls and crank bolts, the rest is even fun, not to mention -easy!
So, why not 'update'?
Seriously, it was/is easy, economical, and certainly didn't degrade anything.
As to belt integrity, I'm confident the identical high standards/specs of materials & fabrication are applied, regardless of tooth design.
I'd certainly agree with jim Bailey's comment on the adequacy of the square tooth design - so why 'update'?
The design evolution makes sense, there are enough used/donor parts available in good condition and affordable, and the belt/water pump/roller costs are effectively identical, regardless of model year. It is ~$20 to rebuild any variant of tensioner, standard over the counter bearings press into all rollers except the primary tensioner roller - but that roller is the same part # for all model years. ie., it,s not a major expense beyond normal PM.
As far as time/effort - as you (all) know, once you get past fans/ignition /covers/slave cyls and crank bolts, the rest is even fun, not to mention -easy!
So, why not 'update'?
Seriously, it was/is easy, economical, and certainly didn't degrade anything.
As to belt integrity, I'm confident the identical high standards/specs of materials & fabrication are applied, regardless of tooth design.
11-11-2003, 09:12 PM
#12
G Man,
When I did mine, about six months ago, the markrs simply weren't there....
I posted about it and Dennis Wilson suggested I look on the back side of the gears... he was right! Someone in the past put them on backwards...
Just clean a little and you should see em.
Great time to clean things and the gears/block face can take a few pounds of lubricated dirt out of the hp to weight ratio.
Say...
My next belt change I want to change sprockets -wear- Am I correct in assuming you break torque before belt removal?
In the past I simply cleaned and marked for alignment with the cam marks on other cars -used thin paint pen on the sHARk when I couldn't find the marks, referenced the crank in same manner.
If I were to get bright enough to use the flywheel locking tool where and how do I get to the lock location - BTW is there slop when using this 'gear jammer' or is it close tolerance?-. I would guess that I'd need to drop the exhaust, maybe the TT, -shields?-.
Also planning on a rebuilt TT install/TC converter bearing, seals...
Where is the mystery inspection hole for the TT clamps and what comes off to get at the TT clamps. There is an inspection hole on the top aft side of engine when you pull the Air cleaner box and I felt one on the drivers side of the Trans/TC -need to be a snake to see anything let alone work on the aft one.
Later.
When I did mine, about six months ago, the markrs simply weren't there....
I posted about it and Dennis Wilson suggested I look on the back side of the gears... he was right! Someone in the past put them on backwards...
Just clean a little and you should see em.
Great time to clean things and the gears/block face can take a few pounds of lubricated dirt out of the hp to weight ratio.
Say...
My next belt change I want to change sprockets -wear- Am I correct in assuming you break torque before belt removal?
In the past I simply cleaned and marked for alignment with the cam marks on other cars -used thin paint pen on the sHARk when I couldn't find the marks, referenced the crank in same manner.
If I were to get bright enough to use the flywheel locking tool where and how do I get to the lock location - BTW is there slop when using this 'gear jammer' or is it close tolerance?-. I would guess that I'd need to drop the exhaust, maybe the TT, -shields?-.
Also planning on a rebuilt TT install/TC converter bearing, seals...
Where is the mystery inspection hole for the TT clamps and what comes off to get at the TT clamps. There is an inspection hole on the top aft side of engine when you pull the Air cleaner box and I felt one on the drivers side of the Trans/TC -need to be a snake to see anything let alone work on the aft one.
Later.
11-11-2003, 09:36 PM
#13
John,
The lock goes into the flywheel cover. If you have an AT the hole on the passenger (right) side will have a cover on it. If you have a 5 speed, the clutch slave cylinder will need to be removed to install the lock. If you set your engine at top dead center there shouldn't be much slop. It is a good idea to loosen the cam gear and oil pump gear (if appropriate) bolts prior to removing the belt. If you need a lock I have one you may borrow.
BTW does 65-13 or 77-0 ring any bells?
Dennis
The lock goes into the flywheel cover. If you have an AT the hole on the passenger (right) side will have a cover on it. If you have a 5 speed, the clutch slave cylinder will need to be removed to install the lock. If you set your engine at top dead center there shouldn't be much slop. It is a good idea to loosen the cam gear and oil pump gear (if appropriate) bolts prior to removing the belt. If you need a lock I have one you may borrow.
BTW does 65-13 or 77-0 ring any bells?
Dennis
11-11-2003, 10:01 PM
#14
Thanks Dennis
Thank God I'm a lost citizen of western Pennsylvania - Pitt & the Steelers both won -77-0 is that a record? I'd hate to show up for practice at A&M for awhile.
My boss is a graduate of A&M and -he didn't take my ribbing to well- he said he'd bet $50.00 at least 1/3 of the squad was from Texas.
I told him the operative word is: 'WAS' !
Thank God I'm a lost citizen of western Pennsylvania - Pitt & the Steelers both won -77-0 is that a record? I'd hate to show up for practice at A&M for awhile.
My boss is a graduate of A&M and -he didn't take my ribbing to well- he said he'd bet $50.00 at least 1/3 of the squad was from Texas.
I told him the operative word is: 'WAS' !
11-11-2003, 10:12 PM
#15
John,
77-0 just tied the Big 12 record. There is a large number of Texas HS players on the OU squad but not as many as in the past before the scholarship caps. Funny how the better players migrate to the better programs. Don't tell your boss that, as he might do something drastic. BTW my grandfather was from western PA but I still like Penn State better than Pitt.
Dennis
77-0 just tied the Big 12 record. There is a large number of Texas HS players on the OU squad but not as many as in the past before the scholarship caps. Funny how the better players migrate to the better programs. Don't tell your boss that, as he might do something drastic. BTW my grandfather was from western PA but I still like Penn State better than Pitt.
Dennis
