This post will cover the internal condition of the motor after tear down and inspection. The motor started life as a 587/1 in a early C carrera II coupe delivered in August 1963 (per Heinrichs Carrera book). It had an extensive rebuild in 2004 by Jacques LeFriant after its purchase by Stan Gold as a spare motor for his 904 (904-006) to use for vintage racing. The goal was to produce a 904 street spec motor. At that time the following was done:
- Crower billet crank, new bearings
- Pauter rods (CrMo), new bearings
- New valves, guides and seats. 50mm intake, 42mm exhaust. (904 valves are 50mm intake and
43 mm exhaust). Odd size stems ~ 8.5 mm intake and exhaust. Exhaust were bimetal.
- New carrera II cylinders
- New pistons machined by Wahl (ex Mahle employee who sold his own design pistons) on new
Mahle blanks – essentially 904 pistons with deeper valve pockets
- Heads X-rayed
- Solex P40 replaced with Weber 48 IDAs
- Dot 1 intake cams replaced with Dot 2 (higher lift)
- Carrera II flywheel replaced with 904 flywheel (lighter).
After rebuild the motor dynoed at 163 crank hp compared to a stock Carrera II at 130 hp.
- Original carrera II crank on left (with fixture to allow it to stand upright) and Crower billet crank from my motor on right.
- Pauter rods
- 904 flywheel, some of the valve drive shafts and the layshaft.
The motor then was used for vintage racing in Stan’s 904 for about 40 to 50 hours. The motor was torn down again in 2009 after something happened in the 1-2 cylinder intake valve train. It was bad enough to crack small parts of the cam enclosure part of the head in two places. This damage was repaired by welding. We theorize that an over rev may have allowed a drag lever to float enough for a lash cap to escape its home on a valve stem and wreck havoc. The valve drive “C” shaft pinion gear and its matching ring gear were pretty chewed up and were replaced. The damaged C shaft is shown below. Crank and rod bearings were replaced, but nothing else. The motor reassembled and dynoed again, yielding 164 crank hp.
- Damaged “C” valve drive shaft removed from motor in 2009. Note that new motors have a matched set of shafts with the same number on every shaft, preceded by a letter A thru F. In my motor all the original shafts were number 371. You can see C371 etched on the shaft.
- Valve drive ring gear from another motor. Note B443 etched on the gear. Every original shaft and gear in this motor would have had 443 on it. Note broken tooth and grinding. Gear was welded to the cam shaft and grinding was needed to get it off. This motor needed the B shaft replaced and what ever happened was bad enough to severely crank the head on that side.
The motor was then vintage raced in Stan’s 904 and RS60 for about another 40 hours prior to my purchase. I then put about 1000 road miles on it. Motor was running well prior to this tear down, with the exception of occasional plug fouling – which Jacques traced to too cold heat range spark plugs.
So at this tear down the motor had 90 to 100 vintage race hours and about 1000 road miles since the 2004 major rebuild. We found the following:
- Leak down 3% to 8%. Valve timing all within 3 degrees (factory spec is within 4 degrees) –
some closer than others. Intake valve lifts ~ 11.75 mm.
- Case main bore still standard, but a little tight (0.02mm) on the center main – likely due to a
little case shuffle. Rest of case in good shape. See Photo below.
- Crank mains near low limit but look good. Will need to closely measure mains and a bearing set
to decide if we polish and stay std or grind first under. Crank rod journals std and look very
good.
- Rod big ends still std. little end bushings slightly oval.
- Very little valve guide wear, but all valve stems slightly tapered – 0.01 to 0.02mm. 2 x intake
valve heads pretty pounded – knife edges. Rebuild justified on this alone. Exhaust valve heads
looked good. One chamber in one head had minor foreign object damage (small dings) – likely
something to do with the 2009 event? See photo of intake valve head with knife edge.
- All valve drive shaft splines not overly worn. Estimate 2 degrees rotation (problem over 4
degrees).
- All valve drive gears look good. Valve drive shaft bearing seats all worn 0.01 to 0.02 mm. Valve
drive shafts and gears good to reuse.
- We found the valve drive gears that are normally pressed onto the cam shafts had been brazed
to the shaft – likely preventative to keep them from spinning – but the sign of a turkey. See
photo below. OK to reuse, but if one of the gears is ever damaged, the cam shaft will probably
need to be sacrificed to save the gear. So a new cam shaft would be needed.
- Cam lobes looked good with no visible wear (they fit on cam shaft and can be changed out).
Reuse. Same for drag levers.
- Intermediate shaft gear looked good. Seat for 2 x valve drive gears was a little scored - like one
gear may have had a burr. Bearing seat worn 0.01 to 0.02 mm.
- Piston wear within acceptable limits to reuse. Rings need replaced.
- Cylinders worn oval enough to require recoating or replacement.
- Oil pump – very worn – likely never replaced.
- Foreign object damage in one chamber
- 50 mm intake and 42 mm exhaust valves. Note sharp edge on intake valve head indicative of valve being pounded into the seat.
- 509C3CAE-222A-49C4-8888-4E944DD2D1EB.jpeg (68.74 KiB) Viewed 9398 times
- Turkey modification- note gob of brazing at junction of cam shaft and valve drive gear on shaft. What appears to be a chip out of one of the ring gear teeth is some oil and the way the light hits it - not a piece missing.
So for those that say carrera motors are fragile, this one at least says different. Bill Doyle recommended rebuilding a 2 liter motor every 40K to 50K miles or every 40 racing hours (assuming it was built correctly in the first place). So here we have a motor with ~100 vintage race hours with only bearings replaced after 40 hours. And it is not in bad condition. Gregory Campbell has had similar experience with the 2 liter flat fan motor he races in his Elva.
We will do the following for this rebuild:
- Closely measure crank and a set of Std bearings to see if the main journals can stay Std or if we
need to grind them first under and renitride the crank. Polish rod journals.
- Replace rod little end bushings. May machine big ends to take Toyota clevite bearings – lots
cheaper than Porsche rod bearings.
- Ream valve guides to 9mm (currently ~8.5 mm). Purchase custom Ti valves with 50 mm intake
and 43mm exhaust heads. Install beryllium seats. (About $2,500 to $3,000 all in including
installing new seats). May clean up cylinder sealing surfaces in heads.
- Install oversize bearings machined to size for all valve drive shafts.
- Hard chrome intermediate shaft gear journal and machine to size. Install oversize bearing
machined to size.
- Replace rings
- New carrera II cylinders from Millennium (who make cylinders for L&N) – about $3500
- Purchase new oil pump (~ $4,000) or rebuild old one with new gears and center case that
Jacques has made (Parts + 3 days labor to match gears to new center case). Leaning toward
new while Euro is weak.
- Install a time sert in the one exhaust manifold stud that pulled from the head. Check all other
studs.
- New gaskets, stainless oil return tubes, replate fasteners and find some original fasteners for
more visible ones,
- Swap Weber 48 IDA for Weber 46 IDM. Found the Weber 46 IDM carbs several years ago and
had Pierce Manifolds in Arizona rebuild them.
- General cosmetic clean up.
- Install reproduction Speedco distributors with 123 electronic guts. Possibly also install a
Winterburn CD set up (like Jack Walther did on the Dean Jefferies Kustom Karrera). Have
original distributors rebuilt and keep on shelf.
The rough estimated cost for the rebuild, including parts and labor is $20,000 to $30,000. Which is about double a comprehensive pushrod motor rebuild needing the same kind of work. The main drivers for the higher cost compared to the pushrod rebuild are the custom valves & seats, new oil pump, more expensive bearings and more labor hours for machine work and reassembly. Shipping to/from Seattle adds another $1,500.
At this point I must thank Jacques for allowing me to work with him in his shop to disassemble the motor and for being so giving with his time to educate me. I asked a LOT of stupid questions. Olivier Auvray, a 4 cam mechanic from France, was also there and helped with the mentoring. Thank you Olivier.
Hopefully this thread will provide some hands on education about the 4 cam motors. My next few posts will cover various parts that have been purchased or fabricated over the last few years for the 904 chassis, suspension and body build.
Thanks for following along.