[Supras] Noisy injectors and piston slap

[berniek at technicaldevelop.com]

    Hope the following is helpful to others who may have concerns about 
engine noises. 


    In former postings I expressed concern about oil starvation based 
upon some really rambunctious driving and noises I was perhaps not aware 
of before when the modified JDM engine in my '91 had about 100 miles on 
it.  Also the stock gauge with a new sender read zero pressure at idle, 
covered in next paragraph.  Jeff Moller and Pat Golder were kind enough 
to write back to me allaying the starvation concerns, Jeff particularly 
in some detail.  I've had an instance before with a good cornering GM 
rear sump car where the oil climbed the side of the pan under hard 
cornering conditions, as evidenced by noisy hydraulic lifters.  Since 
the Supra is a bucket and shim engine, the first noise which would be 
heard under starvation conditions would probably be connecting rod 
bearings, a warning which would have come too late. 


    A couple of nights ago I measured oil pressure with a pressure gauge 
connected to a new oil filter casing (soldered in a section of 1/4" 
copper tubing to use with hose and a good gauge) and found that even 
with a new sender, the dashboard gauge still reads low by a constant 
20-25 PSI (differential pressure across the filter element is probably 
not in excess of 2 PSI at idle with hot 5W-40 oil, stating because the 
measurement is taken in the casing, upstream of the filter media).  That 
and other investigation is beginning to prove that noise produced by the 
engine does not emanate from the bottom end, although the first oil 
analysis after 400 miles showed 43 PPM lead.  The lab (Blackstone) does 
not analyze Antimony, important because lead based babbitt contains 15% 
of it for hardness.  The lead may be due to wearing of the soft coatings 
on the cam journals after tightening up the cap clearance as stated 
informer postings.


    After installing the regular oil filter again (Purolator Pure1), I 
again started the engine from cold (about 38F in the garage) without 
throttle, and listened yet more with a stethoscope, with both the 
diaphragm/rod and with just the open hose end during warmup.  
Conclusions are as follows:


    1.  There is no noise from the main or connecting rod bearings.  
There is no noise at all at the bottom flange of the block under any 
condition, including teasing the throttle when warmed up.  Ticking and 
minor rumbling noises may be heard at the front and rear segments of the 
pan, however.  I would not trust the stethoscope diaphragm/rod assembly 
to accurately reproduce low frequency sounds the way it is built.  Of 
course if you remove everything but the hose, you will hear every sound 
which is airborne.


    2.  During warmup, there is piston slap particularly on one front 
cylinder.  #1 was the first one I honed, and may have increased 
clearance a bit too much since the hone stones were new, and spring 
tension was apparently too high, although it was completely backed off.  
I used sufurized cutting oil with the stones at first, but then switched 
to machine oil.  I recall it did measure a couple of thou more than the 
others afterwards, but did not think much of it at the time.  Literally  
a couple of thou does not seem like much, especially when clearance 
ranges for stock pistons in the TSRM are considered.  During warmup the 
oil pressure is high, opening the piston squirters which probably keeps 
piston temperature low, as long as the oil pan feels lower in 
temperature than about 120F-130F, the hottest one can continuously 
touch.  The noise begins to disappear when the oil pan becomes too hot 
to hold my hand on, and is just about entirely gone when the radiator 
thermostat opens. 


    3.  Intake valve clearances, when last checked about 120 miles ago, 
were a bit on the high side.  One was .011", whereas .009" should be the 
maximum.  The exhausts were all OK below .012".  I did refinish all of 
the caps to get journal clearances down, but now the intake side has 
become a bit noisy.  During assembly the soft coating was gone from 90% 
of the exhaust cam but not from the intake.  Pushing the engine hard in 
back to back WOT runs may have removed the intake coating.  We will see 
what the next oil analysis shows, but I'm going to try to find a lab 
that does both Antimony and Gallium, Gallium being present in most soft 
alloys (softer than babbitt).  It is used in Wood's metal with Bismuth, 
used to make trick spoons that melt in hot coffee.  In any event, my 
belief now is that the soft coating is where the lead came from.  The 
next oil analysis will tell assuming I find a lab with comprehensive 
enough tests. 


    4.  Noisy injectors?  The stock injectors in the '90 made slight 
ticking sounds.  The NipponDenso 550cc low impedance items in the JDM 
are very noisy, almost like valves with twice the specified clearance.  
These injectors were purchased as Greddy items in sealed bags and were 
directly installed, since there was evidence of Stoddard solvent still 
on them (Usually used for test).  The engine idles beautifully, although 
that is not an ironclad guarantee of all injectors supplying the right 
amount of fuel.  That consideration not withstanding, one or two 
injectors are unusually noisy, determined by removing the diaphragm 
housing from the stethoscope and listening just with the hose for sounds 
in the air.  This is not a criticism of the injectors, just an 
observation to be understood. 


    5.  The father of all hellacious sounds in an engine is the 
crankcase.  The Supra is no different. 


          a.  With the stethoscope earpiece hose shoved into the 
dipstick tube, a subsonic sound at idle was persistent, which 
theoreticially should not exist since a straight 6 is in both primary 
and secondary balance.  In other words, there should be no change in 
crankcase volume like in inline 4 has, where a vertical shaking force 
and a hum from the crankcase are seen at twice the RPM, both due to 
connecting rod agularity.  The low pitched hum in the Supra was very 
intense and became deafening as the speed was raised.  There is a tiny 
amount of blowby, as evidenced at the topside oil filler from a sudden 
but short WOT condition from idle while unloaded, manifested as a couple 
of wisps of smoke.  It finally occurred to me that the hum might have 
been from a crankshaft counterweight windage nearest the dipstick tube.  
Otherwise, there is a great deal of clanking which is evident within the 
crankcase, decreasing in intensity with engine speed. 


       b.  Essentially the same sounds were heard at the oil fill port 
when threading the stethoscope hose into the hose behind the alternator 
which connects to the crankcase.  Again, the sounds, aside from the 
subsonic eardrum breaker, are believed to be from piston slap.  A 
borescope with a 90 degree mirror will be here shortly to get a real 
live view of what is going on inside.  I've wanted one as a toy for 
years.  Now is my excuse. 


    We just replaced the mule car I generally take to work with a 2003 
Maxima with the chain V6.  It is a very smooth and refined car(automatic 
for my wife) although it will accelerate and corner to a good extent.  
It has 55K miles, uses no oil, and no engine noises are evident when the 
hood is up.  But inserting the listening hose in the oil filler produced 
sounds almost the same as the Supra.  The subsonic component was there 
as well, but I'm not sure if the 60 degree VEE or some other even firing 
arrangement like split crankpins (a la GM) allows it to remain in 
secondary balance and hence, constant crankcase volume. 


    In conclusion, the sounds I was first concerned about regarding 
possible effects from oil starvation are probably not due to starvation, 
the high oil lead content notwithstanding. 


    As always, comments would be appreciated.  Thanks for the patience 
with my sometimes long-winded posts.


       BernieK