New exhaust

You may have noticed a bit of a lope in the idle previously… that was just a bad spark plug. Naughty spark plug! It went to time out and was replaced with a new one. Now she idles a lot more smoothly.

A legendary mate of mine Marty expertly cut and TIG welded up a full 3 inch stainless steel exhaust in the garage. It starts with a 6 into 2 header by AS Watanabe (manufactured by Fujitsubo, I think) then into a 2-1 collector. The header runners are 48mm diameter, the two outlets are 65mm each, and the 2-1 collector meets the 3″ pipe just after the firewall. the system includes a very effective straight through Adrenalin R resonator and travels back to a straight through can at the rear.

The sound is fantastic and possible due to less resistance, the engine itself sounds better on deceleration.

Watch it run

The moment of truth – will it bash valves? Will the modified torque values cause something to strip? Will the camshaft bind and gall in the towers? Will a bit of metal from the rebuild cause damage to a bearing?

These and other potential catastrophes cross my mind before I turn the key and fire the L31 up for the first time.

First fire up

Due to some conflicting, or even completely missing information about timing the distributor drive spindle I realise it is installed a tooth out. So after a lot of mucking around with modifying the distributor’s mount plate, backfires, jets of fuel spurting from plug holes et al, it fires up and rumbles, just like that.

Feeding the beast

A Carter high volume pump goes in, mounted by the fuel tank and right rear wheel. It’s not the quietest pump around, but it gets the job done – I think it feeds over 180L/hr. New filters at each end, a restrictor on the return pipe from the carbs, an educated guess at jet sizes and this setup is ready to rock!

Mounted underneath

Those fossils aren’t going to burn themselves, are they?

SK OER 50mm carb and jets

In she goes

With a mate’s garage rafters, some luck, beer and other helpers the old engine comes out and the new beast slots in.

240z loses an engine

Then gains another! They look pretty much identical apart from the bolt-ons

Completion!

Polished head cover, SK / OER 50mm triple carbs, OER manifold complete it.

I had to make the linkage rods myself, from some 1993 Honda Dio 50cc scooter cylinder studs and spherical bearing rod ends from a local supplier (cheers Auckland Bearing Distributors). The bolts were 5mm at one end an 6mm at the other so it involved drilling and retapping the three 5mm rod ends.

Hand drill the smaller rod ends

Then hand tap ’em!

If you can’t buy ’em, then make ’em

Carb linkage rods for OER /SK 50mm

Complete engine

Everything in life needs balance

Fidanza flywheel for LD28 crank in L31 / 240z

Alloy flywheel for 240z

replaceable friction face

250mm clutch disc

centering flywheel on the crank

Never truer than for spinning steel. The Fidanza flywheel is listed for an RB20DET and weighs 4.5kg or so. The ring gear and friction faces are replaceable. It happens to bolt straight on to the L28 with only a minor redrill (by hand seemed to be fine) to match the LD28 crank’s dowel. The RB’s recess is 1mm bigger in diameter than the LD28 crank’s snout. I decided to ignore that.

I used turbo engine flywheel bolts, torqued them to the higher Kameari spec and loctited them. The clutch pressure plate is a RB30ET item, and the disc is a monster 250mm item from a 350z. I had the whole rotating assembly balanced.

Using the highly advanced method of wrapping a hammer with a bicycle inner tube and tapping the flywheel side to side with the bolts just nipped up, I managed to get the flywheel to below 1/100th of a millimetre runout. That means nothing if the balancing shop didn’t achieve the same accuracy when centering the assembly on their machine, but it still makes me feel good.

Head work

So peaceful right now

I can’t believe I’ve got this far without bragging about the head work. Let me catch up below:

Argon welded, combustion chambers reshaped, 37cc each
Short valve guides
Big diameter stainless steel valves 46mm inlet, 38mm exh
Lapped valves
AS Watanabe valve spring shims 0.5mm, 0.8mm and OEM 1.0mm used to match spring installed heights to 43.8mm +/- 0.15mm
AS Watanabe performance 10,000rpm valve springs, height matched
AS Watanabe performance chrome moly retainers
AS Watanabe performance chrome moly valve collets (locks)
AS Watanabe performance 4.0mm valve rocker guides
OEM rockers, all resurfaced and height, weight matched in 6’s for inlet/exhaust
Valve lifts 13.4mm +/- 0.1mm
Valve lash clearance 0.2mm
AS Watanabe 75R KAI camshaft 9.8mm cam lift 102 deg Tuf-tride treated
Kameari adjustable vernier cam sprocket
All cam towers checked, bases oil stoned. Hand ground clearances for higher springs/retainers
AS Watanabe 1.2mm cam tower shims and longer allen head chrome moly long bolts

Timing gear and head gallery

The L31 bottom end, assembled

Big port P90 head, AS-Watanabe composite head gasket

The timing kit, too much chain slack

Acceptable chain slack after slotting

Kameari vernier adjustable cam sprocket

After choosing the piston order depending on the flycuts (of course) and 0.001mm clearance differences (anal), final torques are applied and I bolt on the timing kit. I drill out the oil gallery feeding the head to 2.3mm.

Head goes on next. With the huge 4.5mm shave done on the head, one of the consequences is a slack chain.

I space out the cam towers with 1.2mm shims and longer cro-moly bolts and slot the chain guide mount holes to tighten up the chain. I drill and tap the chain guide mount holes to M8 (up from M6) to improve reliability under high stress. The tensioner is a clever design, ported to the oil gallery to react to oil pressure.

The crank’s oil thrower can be discarded.

I time the cam to the recommended spec from Kameari and torque the eight fixing bolts in the sprocket. Kameari specify new torque values for every important nut and bolt on the engine, regardless of whether it is an OEM or aftermarket fastener.

The L31 bottom end materialises

Stuffed full of goodies, like you wish your Chistmas stockings were.

Essential for determining head gasket thickness