threw another #3 rod, how to prevent this from happening again. Options

[GregAmy]

(IMG:style_emoticons/default/agree.gif) check your connecting rod ratio to assist in cakculating you approximate RPM range. The long rods should allow for higher RPMs but the size of the Piston may be causing the inertia to jerk the bolts apart.

Did I miss something in this thread, or did the OP note that he ran the car despite a noticeable rod knock and low oil pressure?

Seems a pretty easy answer...no?

[crash914]

I did run it to failure. Before this last event there was no indication of potential problems. I also had a couple of runs that were normal. From first indication, it was a quick failure.

I think my rod ratio was good, but will review my that was one of the changes with this motor. I had shorter rods previously.

[Mark Henry]

To me 6800 rpm is really pushing the limits of a stroker T4.
You have a number of fail points that can be happening all at the same time, below I'm only addressing crank flex.

Crank flex the crank actually bending at/near the center main journal, as well the 2" "chevy" rod journals. Having 2 throws without support in between the rod journals is another weak point. the higher the RPM the more flex.
This flex is why a 1.7/1.8 case is a better choice over a 2.0 case, as the crank flexes even in a stock engine and it's hard on the center main case bearing saddle. VW knew this, basically stating a 2.0 couldn't be done reliably and it was Porsche that designed/modified the 2.0 crank for the '73 914. VW didn't use the 2.0 engine in the bus, till the 914 proved it was satisfactory reliable enough, for the 1976 model year.
With a longer stroke, in this case a 80mm, at high rpm you are amplifying all the bad, the crank flexes, causing bending stress on the rods, points of the bearings begin touching the crank journals, side loading, heat begins to spike, add into the mix events high RPM downshifting causing mechanical over rev, etc.
All of these stress points begin to cascade as RPM increases until the weakest point fails, in this case the rod.


I'd choose the 78mm crank with T1 rod journals just because the bigger T1 journal has more strength. I'd also lower my redline to no more than 6500rpm.

Hope this makes sense, I've got a L5 herniated disc back issues and I'm whacked out on pain meds.

[crash914]

Thanks Mark, I was hoping to get your insite.
Try whiskey? It helped with the pain of losing this engine.

Hope you get well soon..

[dirk2056]

When I had my heads reworked the machine shop closed/weld the breather vents is that a good or bad idea??

[crash914]

It sounds like it was a good idea.

[HAM Inc]

The NOLA "Jackie Stewart" commentary is gold! I have to ask, how did you handle the post race de-brief with the dive-bomber? Was a jack handle involved?

Oh, it did not go well AT ALL. The short version is I was tossing paper as I was climbing out of the meat wagon, and when the SOM decision went against him, he and his dad yelled and cursed at the stewards and flipped them the bird. Then started yelling at us, claiming we were damaging his chances for his future racing career. At the time it was kinda surprising; in hindsight it's freaking hilarious.

I DO NOT like thrashing at the track (or, really, at home). But I seem to surround myself with people that are all like, "dude, we're here, let's fix that s**t" and it makes for good stories. I need more less-motivated friends.

But last weekend at NJMP was nice: good weather, 914 ran all weekend without a hitch, boring video, pretty car goes back on trailer as pretty as it was when it arrived. Need more of those. (IMG:style_emoticons/default/wink.gif)

Now to decide what to do in 2020. I am becoming more attracted to that limited prep HProd 1.8L option...know anyone that could build a Micro/Megasquirt using the stock throttle body...?

Back to our regularly-scheduled "toss a rod" discussion. In that vein, here's what happened to me the weekend before the Lime Rock Historics 2019 (remember what I said about needing to be more boring...?)

Knitting. That's the ticket. Or crochet or quilting. Though they get pretty serious about that stuff...

Pretty funny the guy accused the racer he dumped of ruining his career. If he keeps driving like that he'll get more than paper thrown at him eventually.

I don't think you'll have too much trouble finding someone to build your MSquirt. What about DIY in Atl? I'll bet a post on the Sandbox would flesh out sources fast.

Greg your broken crank is kind of unusual for a stock crank. They're actually nice chilled forged German steel. I think case flex and or shuffling may have something to do with your failure. I have heard of them breaking in the center main before, but like I said it's not common.

I broke a 1.8 crank on the FP 914 at the #1 journal, just in front of the flywheel. But we had lightened the shit out of that crank and I was turning around 8k at W.O.T. in turn 9 at Roebling. Caused a momentary rear wheel lock up. It was exciting.

For our race engines I used to drill the 6 main bolt bores for 1/2" bolts. They fit snug in the case and that totally eliminated shuffling. I torqued them down good and that eliminated any separation of case halves. I line-bored the case with the new big bolts. This process was waaaaay cheaper and easier than installing shuffle pins and buying ARP case hardware.

I would spend in the neighborhood of a 100 hours prepping our dry sump race cases.

[Superhawk996]

I would spend in the neighborhood of a 100 hours prepping our dry sump race cases.

(IMG:style_emoticons/default/drooley.gif)

@HAM Inc

Love the fact that you're using the 1/2" bolts to effectively shuffle pin it without all the work and machining associated with shuffle pins. Colin Chapman would be proud.

“…simplicate, and add…lightness" has been attributed to Colin Chapman. To paraphrase his lightweight philosophy, each part should serve multiple functions. Your creative solution achieves that goal. Nice way to work smarter not harder.

Great job Len!

[GregAmy]

Dat's purdy work up there...if you're bored and want to do another one... (IMG:style_emoticons/default/wink.gif)

Not sure that I want to pursue the Limited Prep HProd route. I already have the chassis at LP (it's an ex-ITA/ITB car) but the induction regs require using the stock, unmodified throttle body. That's a lot of development that has to be done around that one piece.

[HAM Inc]

Colin Chapman was a genius. He would have gun drilled those bolts. I did at leat lop off the extra threads (IMG:style_emoticons/default/smash.gif) I considered using Jet Nuts to save some more weight, but didn't want to spend the money.

Greg, you ought to talk to Blake Meredith. He ran a ITB 914 and considered switching it over to HP. IMO it would be an expensive exercise in (IMG:style_emoticons/default/headbang.gif)

The case work was a labor of love. And it worked great. That bottom end never gave a minute of trouble and ran 11 double weekends plus test days. Oil samples always came back perfect and hot idle oil pressures never changed one bit from new.

When I sold the car that engine was in it. Kip sold it to a guy in CA. I'd love to be a fly on the wall when he tears into it.

[type2man]

One thing no one else has asked is how were the other rod bearings. If they all looked really worn, then you should have a lack of lubrication. If they all looked fine, then you have another issue.

[crash914]

Engine is out, I won't have a chance to split the case until the weekend. Lots of copper in the filter along with thin pieces of bearing.

[HAM Inc]

Herb, based on the picture of your crank I'd bet money your issue is oil starvation related.

You've probably had a lot of momentary oil starvation episodes that eroded the bearings over time till you suffered a seizure and failure.

[GregAmy]

FWIW, the prior owner of my car kept losing rod bearings due to oil starvation. It was an Improved Touring car, built in the late 90s. He said the problem began to manifest itself as Hoosier moved the (vastly improved) R3S03 tires...and ITx does not allow dry sump.

So he parked it in his basement garage with a spun rod bearing, built an ITS 944, and I bought the 914 from him 15 years later...

[crash914]

Oil starvation makes sense. More to come. The question will be how to address it without breaking the bank..damn, I was real strong this year. Keeping up with all the Caymans and gt's.

[GregAmy]

The question will be how to address it without breaking the bank...

Well, if one were to work on the baseline assumption that it is actually oil pickup starvation...

- Slightly Improved: Tuna can. Didn't see above if you're running one now.
- Better: Type 4 1.5qt oil sump. Watch for ground clearance, though.
- Best: dry sump. The CB Performance bolt-in dry sump pumps are not hatefully-priced, all you'd need to do is engineer a tank someplace in the chassis/engine compartment and plumb it. And it doesn't have to be 10-12 quarts, I'd suggest 4-5 should be more than enough...

[HAM Inc]

Herb are you running an accusump?

I'm of the opinion that an AX car doesn't need a dry sump system. A good tuna can and some mods to the windage tray are a big help.

Blocking the head vents will help keep oil from accumulating in the valve covers. That's a quart and half or more right there.

There are a bunch of little mods that can be done to improve the wet-sump function.

Properly engineering a dry-sump system is more complicated than just adding a dry sump tank and the plumbing. This is especially true if you are using a two stage pump, like the CB, which is a simple plug and play pump and adequate if proper prep is made, but not if you don't as the scavenge stage is not substantially larger than the pressure stage.

The mistake a lot of people make (I made it too) is to think that by adding the tank you can give short thrift to the scavenge aspect of the case prep. The reality is, you still have to prep the scavenge capabilities the same as if you were running a wet-sump system.

If you don't, when you corner and oil moves away from the pick-up you stop pumping oil out of the engine, but you don't stop pumping oil into the engine. This extra oil wraps around the crank and sloshes around in the case. With every significant corner you end up transferring oil from the tank into the crankcase.

At best this condition just robs power, but at worst it foams the oil so badly that even baffles in the tank can't de-aerate the oil fast enough. And if you vent the crankcase directly into a breather can and bypass the tank the oil that transfers from the tank to the crankcase will transfer out to the breather can.

The case mods I made to our dry-sump engines radically reduced the case-sump capacity with expoxied in place panels. The panels were arranged to direct oil to the pick-up which was down in my home made tuna can.

I also removed the goofy stud that runs through the pick up and cut off the restriction where the o-ring fits into the case. I welded a bung to the pick-up and sealed it to the case with a bead of silicon. The pick-up was secured to the bottom of the case with a bolt that went through from the bottom.

The stock by-pass circuit was sealed off with epoxy and an external regulator put in line.

[GregAmy]

Nice, Len!

I, too, have been thinking about that sloshing problem, coupled to the fact that the CB scavenge pump isn't very much bigger. I've noticed that even when I let the engine run without cornering, there's always a lot of oil left in the case before I do an oil change. This goes toward explaining why.

Thanks for sharing this stuff; it's giving me a lot of thoughts.

Edit: Just walked out to the gaage to measure the CB pump: the pressure gears are 20mm long and the scavenge side is 26mm.

[HAM Inc]

The CB pump is okay, but it has an internal cross over that can cavitate at high revs.

I used a Bugpack pump that came with 3 30mm gear sets and had the same cross over. I eliminated the cross over and one gear set. I did this by separating two gear sets with a hardened steel plate and shortening the shafts. This way the scavenged oil exited the engine through the cases original pressure circuit that originally lead to the stock oil filter.

With the external regulator I was able to dial in the pressure to a steady 50psi. That's not as much as most people run, but it's plenty of pressure. Observing the bypassed oil going back to the tank on the chassis dyno and comparing it to the scavenged oil returning to the tank I was able to estimate that ~ half of what was drawn from the tank was bypassed back, meaning that ~20mm of pressure side gear was plenty to generate a constant 50psi at 240* oil temps.

The modded Bugpack pump is on the left, the CB on the right. Once finished it fit behind the fan housing with only a slight bit of clearancing to a rib on the housing.

And yes, in case you're wondering, the old 10psi for every 1000rpm's is old school overkill. We ran 8300rpm's with 50psi for two years with zero issue. And on the dyno the difference between 60psi and 50psi was in the neighborhood of 5hp over 7Krpm's.

For a few years I circle tracked a 2.3 Ford mini-stock and ran over 8500rpms with 40psi and 275* oil temps. Never hurt a bearing though the oil temps did shorten valve spring life.

[HAM Inc]

Some more pics.
Opening the scavenge port in the case to port match it to the Bugpack pump.

A better angle of the modified pick-up and the channel opening to direct oil to the tuna can.