Why do we keep throwing rods? (Page 4 of 6)

Wow, out for my sons wedding and you guys are on it!     I have been at the Helm now for the Billy Beer Team, and yes $500 cars are #$%$# expensive.

Well, were do i start. We run 1 qt over, no accumulator, probably should widen the pan for more capacity, and cooling. the block was machined properly but the rods were not honed after ARP bolts installed and torqued. If that's what your saying, it does sound like that could be an issue. I must confess, this motor was tight at original start up.  I do have expensive tools, my torque wrench has been re calibrated about a year ago. The torque requirements on this motor are only 25 ft lbs if I remember correctly.

We get about 45 to 48psi on a cold start up and at race mode we get to a steady 35 psi on a mechanical gauge.

Woody is correct, that copper bearing was a 100K motor with a #5 rod out of the block. No scaulding or burn was noticed on the back of the bearings.

The Button Terrible Blow up last weekend was #6 rod, No teardown has taken place.  I blew up woodys motor and have been Known to make the "money down shift"  (i'm going to use that alot, the phrase not the action).   Like somebody said, we have no control, even a rev limiter wont work for that.....but I can energize the cool seat....Maybe....pain =longeveity

I did change oil after the 2 days of racing, it was fresh going into Button Terrible. I feel guilty about not changing after that first day on track.

Sometimes I think that if you make the little sewing machine push the semi truck around the track, that the sewing machine just might rebel. Go 460, and a ships anchor to slow us down on the corners.

35 PSI is at race revs.  and yes the torque could be inaccurate at the lower end, I should get a smaller torque wrench and possibly an inch/pound unit.  I re read my post, and I was referring to the rod bolts if I wasn't clear.   

I think Ive learned allot of valuable information from the previous Posts.
I'm voting to Run a box stock 200 at ThunderHill in September, probably the better Head, cam, improved oil capacity, and a large cooler with temp gauge.

I can't do a engine teardown until early August.  I will promise to post more pictures If all of you will send your expert advice. 

What am I saying????   Well send what you think you know.

No, the bearing would have melted.

Modern brakes are much better than the engines to slow the car down. If you have Disk brakes up front, you should be using the brakes 100% to slow the car and not the engine. The only reason people used to downshift is cause old drum brakes are not very good.

So Dave at the very least brand new oil pump (I honestly don't think we have ever bought a new one, unless you did on this motor). Either on the FordSix forums, or in the Falcon/Mustang book i would bet it says which pump delivers a higher pressure, or how to modify the spring for more pressure. Hopefully the cylinder head is okay, or can be cleaned up and reused. The cheapest non-smog motor cam we can get, which is likely to be a Comp Cams grind with a lot less duration than the Clay Smith options.

I always feel like e can splurge on a cam because when I built one of these the first time even the good bearings and internal parts were dirt cheap.

woody, the pump in this last motor was from the newest donor engine. the internals to the older unit looked tight but, the latest one looked better.  the pickup in the older unit had debris, but that could be from me driving it back to the trailer over 1.5 miles on 4 of 6 cylinders. 

I'm sure there is something I can do to shim up pressure. Volume and cooling of oil should help intensely.

I have always been a fan of more gauges. Give me a oil, (in the pan), rear head temp, transmission, rear end.  The freaking gauges will be busting my budget.

I need data logger to feed real time information back to the pits cause we don't get by just looking ahead, we gotta watch our mirrors while the rest of you are passing us.

One other procedure for oil pump prep is to lap the bottom plate, ideally on a surface plate.
Because the bottom plates are stamped they can get a bow in them and leave excessive clearance to the pump.
Usually, the pump clearance is checked without concern to the bottom plate.

Reusing an oil pump off of a blown motor can be a risky proposition.  As the motor is in the process of 'splodin the pump will pick up any bits of busted motor that may have made their way into the oil.  Unless you completely disassemble and clean out the pump/pickup, it's best to trash them after they've been in a blown motor.  You don't want those broken metal bits going into your new engine.

He's right. We did 2 motors and 3 turbos in one race, three times.

Woody, just printing our conversation last week-ish:

1. oiling is likely the culprit, yes.

2. an engine built with zero rod side clearance will have GOBS of oil pressure for the five minutes it runs before the rod bearings melt and mysteriously disappear
- rod side clearance (as long as you have good main and cam bearing clearance) is what predominately determines oil pressure for any given FLOW.
~note - oil pressure reading is just that latter, an indication the pump is holding flow rate for a given set of clearances~

3. Oil Flow is oil-cooling for: a) bearings b) pistons c) valve springs - designers importance mostly in that order.
- Oil flow is what you want in the rod bearing, for endurance/racing as long as the pump can maintain pressure (Too much flow in street cars scuffs the bearing or micro-abrades it like a water-jet cutter, so most OEM's are lower flow than we need for racing)

But 4. "Sliding" or "Hydraulic" bearings (most mains and rods) are "Dynamic" - to say that a thin film of oil separates the metal bits from directly touching, and in the rods this is a "captive pressure" system - so you DO need PRESSURE for the rod bearing to work as intended - this is where the ~10psi/1000rpm "wive's tale" comes from. There is SOME truth to it for a BUNCH of physics reasons. Modern cars use modern oils, so the math doesn't work the same, so we can't globally say that anymore... but for "old" design engines it's a pretty safe operating parameter (New cars work out between 2 and 10psi/1k, dependent upon myriad things, so...).
~So you are looking for goodappropriate flow AND proper (OEM Design) pressure~

5. I suspect that your rod clearances are too small.
    There's a formula for side-clearance vs bearing area vs pin-diameter/width plus intended rpm, but I have no idea what it is... My dad's old race-car guys, and the british-iron dudes' I know all tend to run about 2-3 thou more clearance than OEM/stock in order to get more oil flow - then they uprate the pump to meet the new needs of that more flow.
~I use the blow-it-up-and-change-it method, the Beetle has different needs than our iron inlines - the Mini likes to run 12-15 thou, 12 is OEM, 15 is high rpm race - with a cross-drilled crank (not all minis had x-drilled to start with) -- so there are parameters that your engine may have that I'm only second-guessing.
~~I think you need to open yours up from stock an additional 2-3 thou~~

6. If your engine is the longest stroke of the engine 'family' (I don't know Fords), then you may be suffering oil being centrifugally "pumped" out of the rods - this is an oil-galley inside the crank design problem for high-rpm engines. The cure has always been "Cross-Drill" the crank - it works. Many cranks have this done already. The alternate OEM/production-line cure is to tighten up the rod side-clearances, which results in lower flow, see about yadayada previously wanked about.

7. I could be wrong.
~as someone else said - check the inline-six drag racers groups or something - be always wary tho' - they don't go 7-9 hours straight~

As before, met me know what you find - hell, if it's even remotely an interesting drive I might be coerced into coming to see, in AUG when you get to tearing it apart.

~mike~

Let's look at this a different way. Say there is 0 oil pressure and the oil is all pushed out of the rod bearing. The bearing will wear away and open up the clearance in the big end of the rod. The bearing will spin or will wear away. Where is the rod throwing part? Where's the link? The rod end will make horrible noises before it destroys the rod from too much clearance.

I didn't do out the math for your engine but I'd guess it has very short rods and a poor rod ratio. I still say the rod are failing from too much rpm. I really don't see how low oil pressure throws rods.
The rods in your engine have an obvious to me weak spot where the rod nut is. I'd say that's where the failure starts but I'd blame it on low rod ratio/too high of rpm for what they can handle.

http://ftlracing.com/rsratio.htm

One machine shop I used to use would bore the engine with it hanging off its mounts because the big American iron (weight) would distort the block a lot. If you had the pistons too tight you should see a lot of scuffing in the bores.

If it was detonation from too much timing or compression you'd see signs of detonation and the piston usually fails before the rod.