7 Links

Other S4

1970 Lotus 7 Series 4

Group 1 Lineup, TWS
53 (pictures are clickable)

Raced in classes varying from "all British" to big block American Iron, the Yellow Brick has been extremely successful, winning the Super 7 Challenge Series, class B.  The Brick exemplifies Lotus' handling superiority when running with the V8's, beating cars many times more powerful (example.: 11/2004 results .pdf)

being chased
Engine:  1558cc twin cam with Webers, Custom cams

Chassis: Lowered, stiffened and slightly streamlined

TWS times:  
          1min 58.13sec  long course (class record)
          1min 19.70sec
short course
MSR times:
          1min 24.628 seconds 1.7 mile course

Race Results

Seven Challenge Series
 (click for details)
7 interactive model (actually a rough sketch for trailer sizing purposes)

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Purchased in 1977 from Ft Worth, TX.  Had been used as an ocasional street car and autocrosser.  In 1994 converted to a vintage racer. 
Technical Details
work in progress 9/2006

notes spreadsheet  in MSExcel, not updated anymore- not for competitors eyes!

Lotus Twin Cam head over ford 1588cc bottom end
compression 11:1
+20 overbore,
Big valve head (1.56/1.32 dia),
Carbs:  Twin DCOE40 with 34mm chokes,
Cam  .0.438 lift, 258 duration
Headers - 1.5dia primary 4-2-1,
       had made at Kirk Racing for $475 - should be cheaper now that they have a jig, ask for invoice # 23926

Distributor Lucas non-vacuum, modified advance curve
full advance ~39deg
ignitor unit
rotor NAPA EP41/Oreily D570, Cap NAPA EP40/
Oreily c532

8.5" disc, standard pressure plate
difference in flat face and round nose bearings
 fork - non bent i hope!
flat style throw-out bearing  FKC 6/W 1-3/8


front bearing SKF 6206 NRJEM,rear bearing NSK 6206 NRC3,  input seal 045F7052 (bean number), tailshaft bush Ford 71WG 7041 BA 1499297,

Rack - Burman unit, used in capri/ MkI escorts, photos of innards, with description
             can't find a source for the pinion bearings, but can replace the balls.  Inner rod end rebuild kit
             still available.
Tie Rod End - marked PN01A   62,  3/8"dia pin, 1/2" male, taper 0.45" to ~ 0.5"

Rear Suspension

Live axle
Limited Slip Differential (not sure what type - previous owner installed)
Two trailing links, two leading links.  One of the trailing links has a triangulation arm that mounts to the center of the chassis below the diveshaft for axle lateral location. 

This mount has cracked many times at the junction of the fabricated sheet metal mount and transverse chassis tube, on the "tension" side of the mount.  Beefed up with gusset plates welded in. 

Looking at photos (example - that tire should be about 1/4" within the fender, not 1 inch out!), lateral axle movement was apparent.  Made polyurethane (shore 95) bushes for the two split bushes, and added a transverse tube in suspension arm to beef things up and for peace of mind -

Split Bushings -
Harrisflex TP 8549  also used on early Lotus 51
1/2" ID  Dave Bean

Shocks - AVO

Springs - stock, cut some

standard 7 S4 radiator recored 3 row, interior nose ducting
11 row oil cooler with thermostat

Seven Links


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