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For turbo, which pressure plate
Posted by: goatsnvairs ()
Date: December 13, 2017 05:33PM

Have my turbo motor out, wondering if I should use the 140/180 pressure plate or a standard without the extra weights. I've heard the lighter ones are less moving mass for the 180 not under boost, and allow faster spool up. Any truth?

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Re: For turbo, which pressure plate
Posted by: MattNall ()
Date: December 13, 2017 05:36PM

Most use a stiffened / 1600 psi. standard plate.... the Weights have been found to cause hard shift under hi-rpm shifting..





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo




Edited 1 time(s). Last edit at 12/13/2017 06:48PM by MattNall.

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Re: For turbo, which pressure plate
Posted by: RobertC ()
Date: December 13, 2017 05:42PM

MattNall Wrote:
-------------------------------------------------------
> .... the Weights have been found to cause
> hard shift under hi-rpm shifting..

Huh??? Confused (again)?

Why would a 140 / 180 pressure plate cause a hard shift?

I guess I should ask what does "hard shift" mean?

Never had a problem shifting my 140 at 5500 rpm.

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Re: For turbo, which pressure plate
Posted by: jjohnsonjo ()
Date: December 13, 2017 05:51PM

Yeah, Matt, flat shifted mine at red line too many times to remember. So please explain. The weight of the disc should be the only thing that affects the syncro's The extra weight is a plus when side stepping the clutch.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

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Re: For turbo, which pressure plate
Posted by: MattNall ()
Date: December 13, 2017 05:59PM

I'm just repeating what's been written on FastVairs...and here.... iirc





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: For turbo, which pressure plate
Posted by: goatsnvairs ()
Date: December 13, 2017 06:04PM

MattNall Wrote:
-------------------------------------------------------
> Most use a stiffened / 1600 psi. standard
> plate.... the Weights have been found to cause
> hard shift under hi-rpm shifting..


So by std plate you're saying like a 110 plate? Not sure what the 160lb pressure means.
I mean I know what it means but is that like an off the shelf clarks part or some hypo version? Appreciate it.



Edited 1 time(s). Last edit at 12/13/2017 06:47PM by MattNall.

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Re: For turbo, which pressure plate
Posted by: jjohnsonjo ()
Date: December 13, 2017 06:28PM

The turbo and 140 have extra lugs cast into the pressure plate. The GM idea was to increase the pressure plate inertia to help with launches from engines that had low torque at low RPMs but plenty further up the band. Without the weight it would take more slipping and higher Rs to launch. The lbs has to do with the strength of the spring.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

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Re: For turbo, which pressure plate
Posted by: goatsnvairs ()
Date: December 13, 2017 07:14PM

jjohnsonjo Wrote:
-------------------------------------------------------
> The turbo and 140 have extra lugs cast into the
> pressure plate. The GM idea was to increase the
> pressure plate inertia to help with launches from
> engines that had low torque at low RPMs but plenty
> further up the band. Without the weight it would
> take more slipping and higher Rs to launch. The
> lbs has to do with the strength of the spring.

I've always been very nervous about aggressive launching, like dumping the clutch, on a corvair just knowing how the whole input shaft and transaxle work. Maybe unfounded but I save my burnouts for my gto. So if I am habitually a smooth launcher I may go with less weight on the p plste...

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Re: For turbo, which pressure plate
Posted by: gnvair ()
Date: December 13, 2017 07:58PM

I have always used the heavier 140/180 plate. The extra inertia on the launch really helps. It also helps keep the rpms up when shifting.
Lighter flywheels and clutches are best for road racing and accelerating out of turns. Light flywheels and clutches are also good for engines with a lot of off idle torque (which turbo Corvair engines lack......unless you have some kind of super fast spooling modern turbo).
As for what Matt was saying.........
there was a GM bulletin on the early models of gear clash issues (I believe on the 62-63) models and the fix was the smaller diameter clutch disc which was lighter.

Lee J

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Re: For turbo, which pressure plate
Posted by: RCSmith ()
Date: December 13, 2017 08:51PM

isn't the 140/180 PP made of nodular iron?

Ray C. Smith
'66 Corsa


Bergen County ,NJ

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Re: For turbo, which pressure plate
Posted by: irfgt ()
Date: December 14, 2017 02:41AM

Yea, use the wrong parts in your engine. What do those engineers who designed the car know!

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Re: For turbo, which pressure plate
Posted by: goatsnvairs ()
Date: December 14, 2017 03:14AM

irfgt Wrote:
-------------------------------------------------------
> Yea, use the wrong parts in your engine. What do
> those engineers who designed the car know!


Thanks for reminding me why I hesitate to use this forum.

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Re: For turbo, which pressure plate
Posted by: vairmech ()
Date: December 14, 2017 04:41AM

Here you go, personal information of just what you are asking!

Modified turbo engine, ran with stock clutch at drag strip. The boost was always noted and was very consistent. Put in my 15# dual disc clutch, boost was down but overall times and speed were the same or slightly better. Get the boost back up and times were better!

This is not a popular thing to do but a turbo with a lighter flywheel and PP with 3.27 gears and I bet you get a little boost in first gear!

Yes, the turbo PP faces were made of nodular iron, they did that for wear purposes. The best way to go there is to machine off the weight lugs on the 140/turbo PP's!

Stock is, is NOT always best! Slide rules worked but the bean counters ruled!

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: For turbo, which pressure plate
Posted by: v8vair ()
Date: December 14, 2017 04:47AM

Ole Blues Hot Rod 140 (Big Cam ) had a Aluminum flywheel and a 3.27 gear. It hauled ass, Stop light to stop light and went right up my steep driveway. Tune properly i would go with the light set up. Mike

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Re: For turbo, which pressure plate
Posted by: gnvair ()
Date: December 14, 2017 05:07AM

I would not go light with the turbo. I DO have a turbo and I do drag race it and I also get boost in first gear.

Lee J



Edited 1 time(s). Last edit at 12/14/2017 05:08AM by gnvair.

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Re: For turbo, which pressure plate
Posted by: jjohnsonjo ()
Date: December 14, 2017 05:23AM

goatsnvairs


""I've always been very nervous about aggressive launching, like dumping the clutch, on a corvair just knowing how the whole input shaft and transaxle work""

I don't do it any more, but the factory input shaft is one tough piece of steel. It is actually a torsion bar and meant to twist. Anyone who has ever attempted to straighten a bent one will tell you the memory is unbelievable.

With the turbo, I now feel full throttle with some clutch slippage gives a faster launch and quicker boost.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

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Re: For turbo, which pressure plate
Posted by: goatsnvairs ()
Date: December 14, 2017 07:15AM

vairmech Wrote:
-------------------------------------------------------
> Here you go, personal information of just what you
> are asking!
>
> Modified turbo engine, ran with stock clutch at
> drag strip. The boost was always noted and was
> very consistent. Put in my 15# dual disc clutch,
> boost was down but overall times and speed were
> the same or slightly better. Get the boost back up
> and times were better!
>
> This is not a popular thing to do but a turbo with
> a lighter flywheel and PP with 3.27 gears and I
> bet you get a little boost in first gear!
>
> Yes, the turbo PP faces were made of nodular iron,
> they did that for wear purposes. The best way to
> go there is to machine off the weight lugs on the
> 140/turbo PP's!
>
> Stock is, is NOT always best! Slide rules worked
> but the bean counters ruled!

I choose this one, gonna try it. All good input though and much appreciated.

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Re: For turbo, which pressure plate
Posted by: thewolfe ()
Date: December 14, 2017 07:16AM

I have the heavy PP with the weights machined off in my car. It does take more throttle to get going from a stop which if you're not used to it you may not like it. No problem getting 15psi in first gear but my engine is modified quite a bit. I have a 4 spider 3:27 ready to go in and I'm contemplating swapping pressure plates to one that has weights again when I pull the 3:55 out. Easier to drive around town with the added weights and probably more so with a 3:27.

Nate Wolfe
Portland OR
65 Corsa 180

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Re: For turbo, which pressure plate
Posted by: gnvair ()
Date: December 14, 2017 09:24AM

You can't compare a draw through Corvair turbo to a naturally aspirated engine. They are totally different animals! The draw through set up has several feet of tubing that the air fuel mixture has to flow through. The stock turbo does not spool very quickly either. From a stop a turbo Corvair engine is actually worse IMHO than even a 95 horse engine until it comes on boost.
I have found that best launches are via revving it high and slipping the clutch out. The inertia of the heavy flywheel and pressure plate really helps. The lighter flywheel and pressure plate results in bogging and revving it up and trying to slip it does not help. I have tried it both ways as I had a scalloped Yenko style flywheel (old Otto Parts modified) with an old Otto Parts 95/110 pressure plate.
At speed there are no issues with the heavy stock set up especially on the highway. Dip into the throttle a little and get boost and its off like a rocket.
The other big issue is the first gear ratio. Stock Corvair first gear does not offer enough torque multiplication (64-65 is 3.20 1st gear, 66-69 is 3.11). I kept the 3.55's for this r
reason. Would have loved to have a 3.50 or numerically higher first gear).
When racing the launches are very soft. My friends who have watched me at the track have said the same thing. It spools part of the way through 1st gear but takes off like a rocket in 2nd so most of the et and mph is made up in 2nd, 3rd and 4th gears.

Lee J

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