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Can belt excessive stretch and wear Rev Rot engine
Posted by: DaveO90s4 ()
Date: December 18, 2017 10:27PM

Hi all, my new Otto belt ex Clarks has stretched to maximum idler adjustment in about 300 miles and there is fabric shredded off the sides in places. Mindful of the need to not overtighten Corvair Belts I'm wondering if these symptoms are typical of a belt that has not been right enough?

This is on my Revetse Rotatipn 140 - any words of wisdom from - so any words of advice from rev rotation users would be most appreciated.

If it is a belt tension issue is the spring loaded idler replacement going to help?

Thanks indeed.

Dave O

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: MattNall ()
Date: December 18, 2017 10:58PM

Rev Rot. is not usually a problem.... are all the pulleys aligned?

Are you running the correct belt? US 3/8" x 56" Wrapped?





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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: RobertC ()
Date: December 18, 2017 11:02PM

Might try Gates 3V560 and see if it works better

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: DaveO90s4 ()
Date: December 19, 2017 12:16AM

Hi Matt & RobertC, I'm hoping this is just a leaning curve issue on my part. I bought 4 belts from Clarks , two Clarks and two Otto. So can only assume these are correct. The Otto one got to the point that it had stretched so far that I ran out of adjustment.

(Now the stupid bit on my part. Put new belt on. Because engine is the other way around, this requires dropping the new belt down a narrow black chasm and somehow looping it around the crank pulley. Ok. Did that. Fitted belt, adjusted tension, tightened all up, started engine. But if rubber belt flying everywhere. Mm methinks, that can't be quite right. Of course the idler Pillay belt saver was way way out of place (hidden near the top of the chasm) and was happily ripping my brand new $40 belt (15 to buy, another 15 to post, plus exchange rate) to shreds. Try again - having leant something important. Laugh at me too - I am)

I now wonder if previously when I fitted the original belt, ran caradjusted after one hour as per instructions, if possibly I had failed to adjust that belt saver then too and that had been rubbing on belt.

Any 3rd of 4 new belts now fitted, only one left, and none that I can find in Oz.

Wish me luck (and common sense) ha ha

DaveO

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: vairmech ()
Date: December 19, 2017 04:51AM

You cannot use the auto tensioner on a reverse rotation engine!

If you were to re-engineer the alternator mount to the other side and the tensioner go on the other side then it would work.

In a reverse rotation engine you are pulling down on the idler pulley with the crank pulley. A spring will not hold the pressure.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: BobV66Vair ()
Date: December 19, 2017 09:40AM

maybe the crank section was actually around the crank instead of the pulley?

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: DaveO90s4 ()
Date: December 19, 2017 12:50PM

Hi Ken, thanks for your advice that the auto tensioner won't work in a RR for the reasons you stated. Whilst it would probably not be too challenging to develop a mount that swapped the alternator and idler pulley side for side, I think that clearance between the relocated alternator and existing distributor would be very challenging.

The fact that others have successfully run RR engines gives me much hope that the problems are merely 'user error'. I've checked all pulleys for alignment, bearing wobble, binding, not running true etc and think I can discount such mechanical issues.

The vertical 'slack' side of my belt does run very close to one of my AN10 remote oil filter fittings on the alt. housing. I need to verify that that is not suspiciously shiny. If so out with a fine file on the offending part of the hex.

Bob- very sure the belt was correctly positioned around the crank pulley - one thing I check thoroughly.

Now, with 3rd new belt on, plus a bit more tension than previously, the strange tinkling noise as the engine idles has gone, engine seems to be idling better / more smoothly and the alternator pulley is not quite as hot as previously. I think.

(And apologies for all spelling errors. Blasted iPhone auto UN-correct)

Thanks again for all the helpful replies.

Dave O

Dave O

1975 Porsche 914 with 140 HP Corvair reverse rotation engine, zenith 40 TINS, Otto 20 (or 30?) cam, etc, Australia



Edited 1 time(s). Last edit at 12/19/2017 12:57PM by DaveO90s4.

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: OttawaCorvairGuy ()
Date: January 10, 2018 04:21AM

While doing research and asking questions. Someone was kind enough to share a link to Deserter GS build.

I came across the following info and pictures about his reverse setup.

He mounted a belt guide on the oil cooler side of the crank.



He also used a deep ALT pulley and raced hard with this setup.


Here is a link about his project with some more good info.
Deserter GS

Hope this helps,

Tony
(Ottawa Area - Canada)

(1) Marie's 1962 Convertible and our 1966 Ultravan #248 (aka Itchy Feet - Long Restoration)
(2) Our 1963 Rampside (Sold 2014) and 1967 Ultravan #256 at Upper Canada Valley car show in 2009.
(UV256 aak Itchy Feet II - corvair power plant came out 2012 - plans with donor for a GM 3.8L FWD conversion, as a gas pusher, in the back of UV256)
(3 & 4) Are some of our 11 Corvair parts cars - to help keep our stuff on the road - hopefully as long as we live. ;-)
(5) Is one of our Wayne 100 boats (Corvair powered)
(6) Nov 14, 2012 Ultravans #362 and #512 arrived. We are getting closer to our goal of having an Ultravan museum.
We now own; UV248, UV256, UV362, UV512, and UV520 will hopefully be here July 2013.
(7) I saved Ultravan #231 from the scarp yard this year. It arrived May 9, 2013 and I plan to flip this one with a mid-engine Subaru power plant.



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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: Huntsville ()
Date: January 10, 2018 10:17AM

If you haven't already, check all your pulleys for rust. It will sand a belt down in a few hundred miles.

Also, you should be able to turn the alternator pulley with one finger when the engine is cold.

I had to sand mine down, I also had the belt too tight for the first few months I had my car. Once I corrected that, the same belt has been in use for over 20,000 miles.



Danny Robertson
Huntsville, Al
'64 Spyder (Daily Driver)
'63 Rampside (Rotisseried and in Progress!)

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: DaveO90s4 ()
Date: January 13, 2018 02:49AM

Hi Gents,

Thanks for the two most recent posts in reply to my issues - I'd not seen either until now.

I think (fingers crossed) that I've got my problem resolved (Many thanks to Ken Hand for taking time out to help a complete stranger in another country!!) . My thoughts are as follows: -

1. The belt tightening idler pulley, when adjusted to make the belt tighter, moves the pulley primarily horizontally away from the engine albeit with some minor vertical lift as it swings through its arc.

2. For a normal rotation engine this is great (of course - the Chev engineers had a think or two about this) - the belt can LEAVE the crank pulley on a bit of an angle but still ARRIVE at the fan pulley within an acceptable angle.

3. For a Reverse Rotation engine the more the belt is tightened, the greater the angle that the belt ARRIVES at the crank pulley - and with significant tightening the angle of arrival is too great for the belt to survive.

I think (assuming I am correct in the above) that this means that avoiding excessive fan belt tension on RR engines is even more important than for normal rotation engines.

I have now done another 300 miles or so and the belt is not showing any signs of wear - and belt seems to be ARRIVING at the crank pulley at a nice straight angle, centred in the groove and with adequate tension.

Should I have any more problems (fingers crossed I don't) I think I'd be inclined to re-engineer the adjustment idler pulley bracket so that when the belt is tightened the idler pulley has a primarily vertical height increase. That would keep it ARRIVING at the crank pulley correctly and increase the less critical angle of departure as the belt LEAVES the fan pulley.

I think I'm overcoming teething problems, am getting my zenith carb jetting sorted out (slowly), installing CHT gauges etc. I am really liking my Corvair engine. My 914 (previously 4 cylinder 1.8 L) now really performs very nicely indeed.

Cheers all

Dave
Oz

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Re: Can belt excessive stretch and wear Rev Rot engine
Posted by: MattNall ()
Date: January 13, 2018 07:55AM

Great Progress!





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Click HERE for My Website...Click HERE for My TechPages!
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