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924RACR

Good news; I finally got the new (Porsche Classic) valve springs assembled in a head and measured, including with and without shims.

Without shim:
Lift (inches) Pressure (lbs)
0.050 65
0.140 92
0.224 120
0.336 155
0.438 192

With 0.050" shim:
Lift (inches) Pressure (lbs)
0.050 70
0.111 89
0.220 121
0.346 160
0.434 195

With 0.100" shim:
Lift (inches) Pressure (lbs)
0.052 92
0.121 115
0.235 147
0.352 184
0.432 208
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Mike9311 · Joined: 14 Dec 2004 Posts: 1798 Location: Chicago-ish

Good Data

I take it you will run the .1 inch shim with that low lift cam?
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

924RACR · Posted: Thu Aug 11, 2022 8:59 pm Post subject:

Exactly, I'll be running the 0.100" shim stack (doubled 0.050" shims).

Assembled it last night; last check of piston/valve clearance, then she goes together!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Mike9311 · Joined: 14 Dec 2004 Posts: 1798 Location: Chicago-ish

Awesome stuff. I am assuming the new cam has a more aggressive ramp and a more rounded crown?
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

924RACR · Posted: Thu Aug 11, 2022 11:34 pm Post subject:

I don't recall the specs, they're documented, but Hayes can probably speak better to it.

Unfortunately, I've confirmed that the new cam has I believe what's called a smaller base circle, by about 0.050" or so, so can't use it with stock lifters I believe. Will have to figure out another answer, but will have to have that wait for later, I'll just run the stock cam for now - down on power is fine.

Edit: as Chuck noted in the other (valve spring upgrade) thread, he got the 924 lifters from ACM in Sweden, along with both Manley 8mm 0.080" thick lash caps for the ACM lifters and Alfa 9mm lash caps of various sizes that fit on the valve stems to make it all fit; once together, it's been working well at the track, no issues.

So I'll clearly need to go down this route when ready to throw more money at this engine...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Mike9311 · Joined: 14 Dec 2004 Posts: 1798 Location: Chicago-ish

Cool. Those lifters will add a bit of usable spring force for you and get you a hair more rpm at the limit or a margin of safety anyway
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

924RACR · Posted: Fri Aug 12, 2022 5:38 am Post subject:

Yeah, honestly these motors just fall off so much above 6000 we don't really bother going past that anyway.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Fifty50Plus · Posted: Fri Aug 12, 2022 8:10 am Post subject:

What Vaughan said! So far I'm still running my 9.5:1 IT-B engine with the new Elgin cam. No problems but no big improvement. I can feel a bit of a gain in mid-range torque but nothing on the top end. This engine still runs out of steam above 6000 and lighter everything won't help that. Induction is the major issue. With this cam I'm consistently 1/2 second faster at "Summit Point than I was in the past. All mid range torque.
Hayes has 11:1 pistons in his engine and it makes a big difference. He can out drag me off every turn. I'm in the process of building a few 11:1 engines now that we have the pistons and rods and am looking forward to next year.
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

Mike9311 · Joined: 14 Dec 2004 Posts: 1798 Location: Chicago-ish

I like the mid range torque you are getting. Seems so much more useful
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

Fifty50Plus · Posted: Sat Aug 13, 2022 1:40 am Post subject:

Mike, yes the cam related torque is nice but Hayes gained over two seconds with the cam AND higher compression. Looking forward to the compression bump....
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

Mike9311 · Joined: 14 Dec 2004 Posts: 1798 Location: Chicago-ish

2 seconds is insane at that level (a good insane

)
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car