The Mighty 3.0 MFI Motor Has Finally Had It

[Mixed76]

Jeff,

Please show pictures of that piston failure from the side when you get it out.

Thanks,
Dan

Sent from my Pixel 7 using Tapatalk

[Jeff Higgins]

Originally Posted by Mixed76

Jeff,

Please show pictures of that piston failure from the side when you get it out.

Thanks,
Dan

Sent from my Pixel 7 using Tapatalk

OK. It will be a few days. I'm taking a break after a few days of heavy thrashing. I have to say, it was at least a 3:1 ratio of cleaning vs disassembly. A dozen cans of brake cleaner and a gallon of Super Clean already, and that's just getting everything clean enough to organize and put on a shelf for now. A vastly underrated aspect of an engine rebuild on one of these.

[Rosco_NZ]

I recall reading JE are now making 10:1 4032 90mm off the shelf pistons .. for my 2.7RS build, mine were custom request CR with 25cc dome volume .. ended up 10.3:1 after case decking, 1.25mm base sealing rings, 1mm deck height, fly cutting and skimming heads.

[Rosco_NZ]

How are the valves & guides?? Seems there are improved guide materials that last longer …

[Jeff Alton]

Originally Posted by Jeff Higgins

OK. It will be a few days. I'm taking a break after a few days of heavy thrashing. I have to say, it was at least a 3:1 ratio of cleaning vs disassembly. A dozen cans of brake cleaner and a gallon of Super Clean already, and that's just getting everything clean enough to organize and put on a shelf for now. A vastly underrated aspect of an engine rebuild on one of these.

^^^^ This! During disassembly, only parts needing final wipe prior to assembly hit the shelf. Takes lots of time. Anyone can take an engine apart quickly... Doing right, like this takes time. But makes everything else go smooth and allows for proper inspection early on in the process.

Cheers

[Jeff Higgins]

Originally Posted by Mixed76

Jeff,

Please show pictures of that piston failure from the side when you get it out.

Thanks,
Dan

Sent from my Pixel 7 using Tapatalk

Here you go, Dan. First pic is the failed piston, second is typical for every other piston.






I was able to remove the upper and second rings from the failed piston, although they were pretty tight in their grooves. The oil ring wouldn't budge, wouldn't even rotate. All of the other rings in the other pistons were as installed, no tighter nor any more loose.

Notice too that the carbon buildup on the failed piston is significantly increased over that on the intact piston. I don't think this could have possibly happened on the way home from the track (about 70 miles).

My friend John Walker rebuilt the heads for me (thanks again, John). He noted that several valve guide seals had failed or were failing. The guides themselves looked brand new. So, I'm thinking that the oil getting past the seals, building up carbon on the dome and in the combustion chamber, may have contributed to this failure. Not surprising, I guess, considering the use to which I subjected this poor thing.

Even scarier was one of the valve stems that John showed me - it was all but missing the grooves into which the keepers seat. It was essentially ready to drop a valve. I think I really "dodged a bullet" on this one. In the end, this was probably my motor's least damaging, most easily repaired way of simply running up the white flag. It had had enough, and was crying for attention. Pretty good lesson in just where the limits might lie in a street/DE motor. I was there. The next level up would have been far more disappointing.

Oh, and all of the rod bearings looked essentially brand new, even on #5, the one that was so clearly detonating.

[Jonny042]

More likely if that oil ring was stuck, it was allowing oil by. Oil lowers the detonation resistance as though you've lowered the octane considerably. (EDIT - as a contributing factor, especially on something that's maybe pretty close to the edge already). Have you considered going 98mm while you're in there?

[al lkosmal]

Yep....#5 looks well done/toasty. You did luck out if that missing chunk didn't do further damage.....

regards,
al

[Jeff Higgins]

Not sure if the oil ring was stuck, leading to oil in the combustion chamber and leading to detonation, or if it got stuck as a result of detonation. The oil may have gotten in there past one of the failed guide seals as well. I guess I'll never know.

And yes, this thing was certainly on the edge. Going forward, just for peace of mind, I'm dropping compression via a set of 9.5:1 JE 95mm pistons that Al (posting above) was kind enough to source for me.

So, no 3.2 short stroke, at least for now. I do have a set of freshly reconditioned 41mm throttle bodies and stacks from Eurometrix meant for that sort of a project, but to make it all work together I would be looking at either porting my existing heads or sourcing maybe a set of 3.2 heads or something. Then there would be exhaust (I'm running SSI's, which simply wouldn't be big enough). It would kind of snowball. For now, I just want to get it back on the road (and track) before our rainy fall and winter arrives. Besides, I never really felt like it was lacking for power.

[john walker's workshop]

Originally Posted by Rosco_NZ

How are the valves & guides?? Seems there are improved guide materials that last longer …

It had manganese bronze guides, which are pretty tough, more so than phosphorus bronze. My machinist buddy says it's a bittch to machine.

[MST0118]

You might consider staying with your SC heads if still running MFI or get another set of same type.

The 3.2 heads flow well but are shorter on the intake length and have longer studs. You could make them work but would probably need MFI injector blocks and only a couple places sell them like Retrosport and Zuffenhaus. It could be another $600-$800 for blocks. You can make 3.0 heads flow well if looking for more power!

[Jeff Higgins]

Que the Willie Nelson... "on the road again"...

After an 11 day USPS imposed delay (they delayed shipment of the last little part I needed, an MFI drive seal ), the mighty 3.0 is singing her sweet music once again. Took her on about a 50 mile test loop today, ran like a champ.

Big thanks to my friends John Walker (for rebuilding my heads) and Al Kosmal (X Factory, for sourcing pistons when they were out of stock everywhere else). Oh, and Henry at Supertec, for digging through the archives and finding a part number for that seal (I have updated one of my old threads on the Engine Building forum, where we were discussing all of this years ago, to include that part number for future reference).

Couldn't have done it without you guys.

[rwest]

Great job!

And your speed is embarrassing to most of the rest of us...

[Danimal16]

Awesome, the kind of people and projects that made this site what it is!!!!

[evan9eleven]

Originally Posted by Jeff Higgins

*Sigh*. Only 125,000 miles on this build, completed 18 years ago. Only about 80 track days as well. I can't believe such a pampered little cream puff has failed already...

I laughed out loud when I read this. Quote of the day! Glad you got it sorted.

[chrismorse]

Hi Jeff,
Amazed at your speed, I've been at it 12 years, doing my dad's entire car.

Just for Grins, I was thinking it might be worth while to check the MFI, including the injectors. This "Opportunity" might give you a bit more peace of mind.

Chris
( 74 2.7, upped to 2.8, with X factory PMO/MS2, JE 10.5, Twin Edis ign, SSI, Scart Riva, Carrera oil pump & case mods, RSR 6.5 flywheel & KEP all alum PP, Guard LSD, full suspension upgrade and a bit of rust work, sport seats recovered, ect.
Lots of help from Al Kosmal - thanks

[Jeff Higgins]

Originally Posted by chrismorse

Hi Jeff,
Amazed at your speed, I've been at it 12 years, doing my dad's entire car.

Just for Grins, I was thinking it might be worth while to check the MFI, including the injectors. This "Opportunity" might give you a bit more peace of mind.

Chris
( 74 2.7, upped to 2.8, with X factory PMO/MS2, JE 10.5, Twin Edis ign, SSI, Scart Riva, Carrera oil pump & case mods, RSR 6.5 flywheel & KEP all alum PP, Guard LSD, full suspension upgrade and a bit of rust work, sport seats recovered, ect.
Lots of help from Al Kosmal - thanks

Oh yeah, I went through all of that (and more) during the 11 days I was waiting for the seal that the USPS misrouted.

I have a pretty cool little injector tester that Al (X-Factory) ginned up a few years ago (actually way more than "a few") that I used to check all of the injectors. They all passed with flying colors.

I also removed all of the covers from the pump itself and gave it cursory inspection. It all looked brand new.

I even went as far as to crawl under the dash and check all of the bushings in the pedal cluster. Glad I did - the clutch lever bushing was gone. Missing. Absent. As a result, the clevis pin took on the role of the "wear item", rubbing up against the obviously harder pivot arm. It was worn halfway through, on its way to imminent failure. Put a new bronze bushing in, good as new.

The throttle bellcrank on the tranny was also pretty sloppy, its bushing pretty worn. Made up a new aluminum bushing to replace the plastic, greased the hell outa it, also good as new.

There were other little things, but that kind of captures it. In the end, I was actually happy that the USPS delayed my shipment. It gave me the time and inclination to look at and address a few things in need of some TLC. It never ends with these cars, especially if you drive them. But it's worth it.

[Steve W]

Originally Posted by Jeff Higgins

The timing was at 28 degrees total when this happened. That does not seem excessive, but could that have been it?

This is likely what did you in. 11:1 CR, twin plug at 28 degrees at full throttle you'd need race gas. I don't know the details of your engine build, but if you were running 91 octane pump gas, it should have been no more than 20 degrees, or at best 22 degrees with 93 octane.

[Jeff Higgins]

Originally Posted by Steve W

This is likely what did you in. 11:1 CR, twin plug at 28 degrees at full throttle you'd need race gas. I don't know the details of your engine build, but if you were running 91 octane pump gas, it should have been no more than 20 degrees, or at best 22 degrees with 93 octane.

Yup. I had been running 24 degrees total for the last 18 years with success. It has always run hot, however. Sometimes lazy timing will do that, so I thought I would start bumping it up, listening intently for any signs of detonation. Silly me. We cannot, of course, hear high rpm detonation. It's the "silent killer". So, yes, I had it coming, with this ill-advised experiment.

But, then again, this failure saved me from a much costlier failure. When my friend John Walker rebuilt my heads, he discovered a valve stem that was all but missing the retention grooves for the valve keepers. It was going to drop a valve, and soon. So, in a very big way, I feel I came out way ahead on this one.

[icarp]

Jeff, over the years of fun and excitement, did you ever get a chance to run the car on a dyno?

Any estimates on hp for the years of romping?

I glad you got things back together , well done .

Ian