The Photography of Dr. Jeffrey P. Harper

My Friend John wrote:

Hi Jeff,

As promised: on your new dyno numbers, so 955 FtLbs and you say it was at 5500rpm. What’s your diff ratio and Nos shot?? What is the torque down too at 7500 RPM?  Anyway lets say your diff is a 3.7:1 and we have 20% drive train loss then (955/3.7)/0.8 = 322 Ftlbs at the flywheel so (322x5500)/5252 =  337  Flywheel HP or 270 Wheel HP.  So the dyno numbers (280WHP) are about right, or in the right ballpark.  Or your SMS figures with no nos 883ftlbs @5000 so (((883/3.7)/0.8)*5000)/5252 = 283/225 FHP/WHP.  Sounds like you using a 50 shot?  Your numbers do seem down a tad for having cams in, it but I notice you are only at 4.6PSI. Is that 4.6psi correct? Assuming it is then keep in mind a bone stock N/A 1uz auto has 240HP or 190 WHP, and in your case you are running 0.31Bar so you should expect around  315 FHP at this boost less supercharger drive loss so the no Nos 280 FHP mark is reasonable to expect.  I need to see more data and that dyno graph is vague but it sounds like torque might be dropping a little too much at the post peak torque rpm’s, you might be able to get that back through cam setting and a bit more tweaking. How does it respond to ignition timing advance increase steps?  Also when you run the car on the track, the trap speed will tell us HP quite accurately, so I wouldn’t be overly concerned about dyno numbers.

John

OOPS!

Cylinder #7 shows zero compression.  Something went away.

OOPS! Indeed

During the last dyno pull the engine would not rev to 5000 and there were strange noises.  Upon returning to the shop the number 7 cylinder was found to have zero compression.  Removing the head revealed the number 7 piston could be pushed down with one finger.  A broken rod! Rats!

This is what the broken looks like:

The bottom of the piston is also broken.  Hmmmmm . . . what happened?

I finally got around to getting a look at the busted rod.  Here are some better photos for the amateur metallurgists to sink their teeth into!

Yep, there's your problem!

There appears to be quite a variance in opinion, and experience, as to the strength, and horsepower limits, of the standard (large rod) 1UZ bottom end. Some compliment their own good tuning for the reliability of their high boost standard short block motors, while others claim bad luck for broken parts on well tuned standard 1UZs. And there have been some broken parts because of mistakes. I believe all groups. So, now I have to make a decision. I do not have unlimited funds for an 'ultimate strength' combination (Carrillo rods), but I have some petty cash. Here is what I am going to do now: I have found a good rebuild-able 2UZ (4.7L) bottom end (in "up country" Thailand). I will use my current intake, supercharger, heads (it is good, but needs two new valves, which I have), deep oil pan, camshafts/springs, and head studs with this 2UZ short block. Amazingly, I found and purchased a set of Lextreme steel rods and Calico bearings here in Bangkok. I will check (and correct, if needed) the 2UZ crankshaft and bore/hone the block .030 over (292cu.in), get ARP main studs, and order the appropriate forged pistons in a 10.5 or 11.0 compression - because I have taken the humps out of the combustion chambers and have only 5-8 pounds of boost on race gas. I will order another set of 1.3 Cometic steel head gaskets (I have sold the 1UZ set already). I was already at 85% duty cycle on my 565cc injectors with the dry NOS, so I will also get new 1000cc injectors (for MORE NOS!). For future use, I am also negotiating for one of those high flowing New Zealand single plane high rise manifolds converted to EFI . . . . . SO LOOK OUT! Wish me luck! I hope you haven't run out of it yet!