Pete,
Real sorry to hear of all your troubles.
I went back to the archives:
<http://www.listquest.com/lq/search.html?ln=datsunroadsters> and searched
for some posts I knew I had written on this very subject when I had the
problem. These were in response to a Sam Turner, who was suffering the same
as I had been and you are now. I have since sold the car (and engine) which
was the focus of these posts....still running strong. Don't know what
became of Sam and his car.
For some reason the message won't post (perhaps too long) after I cut and
pasted three responses together. So here's the best I can do which is to
post each one of three individually. Sorry for the added bandwidth.
> Date: 29-Jan-1998 02:48:48
> From:
> Subject: Re: R16 race engines
>
> Dear Sam,
>
> I had to reply to you (I wonder if you've gotten any
>other help) 'cause
> I've had the same problems with my race engines. And
>I'm still trying to
> get it right so I'd be interested to get copies of any
>replies you've got.
> But here's what I've learned so far...(from one full
>season of racing).
>
> Now what I'm going to say only applies to R-16 race
>engines; engines that
> spend all their time between 5500-7500 rpm. I've
>autocrossed (solo I (track
> events) and II (parking lots)) and driven a stock 1600
>for seven years
> without ever even checking the bearings. I still drive
>the car when weather
> permits (but no longer competitively). With a stock
>rear end, street cars
> rarely spend much time above 6000. You can run a
>street engine hard and
> don't need to worry.
>
> But, put that same engine in a car with a 5.13 or 4.86
>rear and turn some
> laps and you'll get two-four events...then BOOM.
>
> The problem is the design of the bottom end-that the
>center main feeds both
> #2 and #3 rod. At sustained high rpm's, either #2 or
>#3 starve, spin and
> let go. Take your pick, but it'll be one of those two
>rods. I've blown up
> three bottom ends (all stock, two rather spectacularly
>;-) the last one I
> saved but the bore was scuffed and the crank blued)
>
> So, what do you do? Well, here's what I am currently
>doing. Start with
> carefull engine assembly. Clearances should be checked
>with a dial bore
> gauge, not plastic. I run 2-3/1000th on both the rods
>and the mains. The
> rods should be closer to 2, mains can be slightly
>looser. Remember that
> the specs (rod and main journal diameters, and hence,
>bearings) for a
> 5-main R-16 crank are the same as the U-20. NO
>runout!-you want it staight
> as an arrow.
>
> I cross-drill and chamfer the rod journals and #1, 3
>and 5 main. Lastly,
> I've opened the hole in the block that feeds the
>center main ~30% bigger
> (and the hole in the bearing shell). This hint is
>derived from a book on
> the four cylinder L-series motors which fed the rods
>off the #2 and #4 main
> (Frank Honsowetz, How to Modify Your Nissan/Datsun
>OHC Engine).
>
> I use ARP rod bolts to a Chevy big block 3/8"
>(ARP-135-6002) and torque
> rods and main caps to U-20 specs.
>
> I still use the stock oil tube to the distributor tach
>drive (even though
> I've got an electric tach). I've also got a pressure
>gauge (1/8"th tube)
> plumbed in the hole in the stock location. I use a
>stock 2L oil pump. On
> the track the pressure stays between 55-65lbs. The oil
>filter (Fram PH-8)
> and cooler are remote, but plumbed with 1/2" braided
>hose and Aeroquip
> fittings (no tortorous bends or long runs, cooler
>mounted behind the
> headlight scoop in the engine compartment).
>
> This is what I'm trying, but like you I'm still
>searching for reliability
> (the last engine I had built, the shop installed the
>cam bearings
> incorrectly (I gotta do this stuff myself, I quess),
>so I've not been able
> to test the bottom end).
>
> Now, destroying a piston is a carb too lean, over
>advanced ignition, etc.
> problem (if it melted) as Tom suggested. However, if
>it cocked and broke in
> the bore, then again it's probably bottom end (spun
>bearing, scuffed bore,
> broken piston). If it broke with no bottom end damage
>(and didn't melt),
> then it probably tightened on the pin (need
>~0.7-1/1000th) for some forged
> alloy pistons because they grow with heat (that's why
>they need more piston
> to wall clearance ~4-7/1000th as opposed to 2-5/1000th
>stock cast).
>
> Now, the U-20 cranks feed the rods from each main, so
>it is not prone to
> this problem (although there is a tip to drill #2 and
>#4 main passage out
> to equalize the flow that I've seen...but that's
>another story.
>
> Any other GP/vintage 1600 racers care to comment?
Bill Wessel
Madison, WI
'68 1600 and
GP race car
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