What's the consensus on running heavy pressure plates these days?
Folks seem to like lightening the flywheels sometimes but it doesn't make sense to do that and still run a heavy pressure plate.
Did all 140 and 180s come with a heavy pressure plate?
I'd like to hear again the theory behind them. I have an idea in mind but I don't want to propogate bad information.
I've usually associated a heavy pressure plate with LM but came across an EM yesterday. Was that more of a FC thing or a Spyder thing? It was in a VD 102 Van but hard to say where it originally came from.
I find myself with more LM heavy pressure plates than regular ones and wonder what might be the best application for them. I don't believe they have more clamping pressure but would be happy to hear about that too.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Spyders had them as well, its to improve launching do to less low end torque of these engines. They are also made of better material for improved strengnth and heat properties

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2023 KIA K5 GT/GT1 turbo-AKA ZIPPY II (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

I'm running a HD Pressure Plate with the weights machined off and 1800lb spring, and a lightened flywheel, 6 puck ceramic disc. It launches pretty hard...


Eric P.
DeWItt, IA

The heavier pressure plate also made the cars with the wilder cams idle smoother.

running a HD Pressure Plate with the weights machined off

me 2

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
62' Wagon rebuild MY Build Thread
65' Monza MY Build Thread
73' NovaSS 454 Big block (Sold)
86' BMW 325es
67' UltraVan 211 "Violet"
NFCC, UMCC
Grand Island, NY

So the HD does have more spring pressure?

Jim Brandberg
Isanti, MN
CorvairRepair.com

JimBrandberg Wrote:
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> So the HD does have more spring pressure?

Clark's offers 1200 lb, 1500 lb, and 1800 lb diaphrams

Page 111 in their catalog

Jim, the difference between the standard and heavy duty is 100-200 lbs of force are shown on the specification sheet.

Crawford

C.A. Rose
Metairie, LA
1962 Spyders



Edited 1 time(s). Last edit at 03/11/2023 01:50AM by caroseiii.

caroseiii Wrote:
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> Jim, the difference between the standard and heavy duty is 100-200 lbs of force are shown on the specification sheet.
>
> Crawford

Your spec sheet is a bit misleading - only for 1962 based on what I read.

Does not include the differences in the LM pressure plate?

For the LM bent finger it is not much of a difference. The HD is the nodular iron in the chart.

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
62' Wagon rebuild MY Build Thread
65' Monza MY Build Thread
73' NovaSS 454 Big block (Sold)
86' BMW 325es
67' UltraVan 211 "Violet"
NFCC, UMCC
Grand Island, NY

So in the stock LM bent finger pressure plates, the difference in spring pressure between regular and HD is probably slight but the difference between nodular cast iron and cast iron is advantageous. That would be the reason for going to the trouble of machining the extra weight off?
I have a lightened pressure plate and ceramic puck disc in my road racing car but it's been a long time since I purchased them.
At this point in time I'm just refurbishing parts on hand for customer jobs, some more high performance than others. I'm just trying to determine the best use of parts on hand and not buying new diaphragms or anything.
I might consider having the weight machined off a HD for one job in particular, a 180 progressive Weber. I've contacted the owner for input on what's more important to him. I put the Weber in there for him and it worked so good the clutch started slipping.

It seems like a VD 102 FC Van probably would have wanted a heavier pressure plate to help it get underway, although it did have a 3.89 differential. It was an interesting vehicle. 3813516 102 heads but with valve rotators. Also 64 style shifter. I sold it back to the people I bought it from after I got it running and enjoyed it for a year.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Nodular cast iron is tougher than cast iron, and can take more abuse.

The lightened nodular flywheel on the 180 should allow it to spool faster.

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
62' Wagon rebuild MY Build Thread
65' Monza MY Build Thread
73' NovaSS 454 Big block (Sold)
86' BMW 325es
67' UltraVan 211 "Violet"
NFCC, UMCC
Grand Island, NY

The thickness of the diaphram spring can be measured and correlated to the pressure rating.
The range, IIRC, is .09x to .107.
Obviously the thickest if the HD one in the chart above.
The gap for the disc also makes a difference.
And can be closed up a little to increase the clamping force.
IMHO, no need to machine the weights off the PP ring except for faster gear changes in Road Racing.
And maybe autocross in prepared classes where it is legal.

Bob C aka Dryenko
Dobson, NC 27017

Normally I like the lightest Clutch assembly possible but on my Spyder I like the heavy set up ,it seems to not loose much rpm between shifts and actually makes the shift’s smoother under boost. Maybe it helps starting off with the 3.08 gear

1964 Bill Thomas Monza Replica Racer
1964 Spyder Street Car
1998 Honda Prelude Dirt track car
1967 Crown V8 under construction
Mike Levine
Cumming Georgia
North of Atlanta

Back when I drove my car very aggressively (no longer do that) I had a large boost gauge. I would flat shift it at full throttle. The energy stored in the flywheel and turbo would cause the boost to jump up a pound or more when I hit the next gear.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2023 KIA K5 GT/GT1 turbo-AKA ZIPPY II (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa