L47/Aurora 4.0L powered Fiero.


Fucking awesome!!! Ok-I see an oil in frame, front disc brakes, right hand shift, with 73 on style side covers. Is it a 74 Bonneville? Now that’s something I can get behind.
I thought you were saying I was the pot calling the kettle black as I said you should torch it when I have a Triumph, or 2. And 2 Nortons.
What does she Need? She looks to be complete-has it been sitting for a bit? If it disappears I didn’t do it…


Hah, yea. Bought it in December from my girlfriend’s dad. He was the second owner; for about the last 35 years or so. I believe it belonged to his brother-in-law during the former years.

She’s a ‘73. Or that’s what the title says. Shifter is indeed on the right. Goofy fuckin’ Brits. Torch the Pontiac, if you want. I just priced out a forged-everything rotating assembly for a fresh Northstar [the actual 4.6L] build. It was a lot. Just leave me the Triumph. I’m beginning to see why the smart guys around here don’t dick around with cars anymore.

As for what she needs, mostly some TLC. I have receipts from within the last 5 years or so of a complete engine overhaul with brand new +.040" pistons, rings and all gaskets and seals. Klispie apparently replaced all four valve guides, two seats and did a full valve job in addition to a bore and hone for the oversize pistons. I’m not sure why they went so far oversized. They’re available in 10 thou increments starting at +.010". I don’t have any reason to believe Lou rebuilt this engine before, so I wonder if there was cylinder wall damage. Guess it’s gone now? Receipts show Amal rebuild kits and a few other stuffs. Anyway, it’s leaking oil like a sieve, it smokes like a bitch, the tires are garbage and it probably needs brakes. Definitely going to tear into that one this winter.

Even came with the original owner’s manual:




.40 over isn’t that much, you can go to .60 over on those old twins but that is it. I can’t say why they didn’t go .20 over but I would imagine that it needed to be due to rings sticking to the bore. You can get new barrels for those from Low Bro if needed-I was going to go that route for my Bonneville but ended up having them bored as there was still a lot to work with. The shifter on the right is “normal” to me, anytime I ride the BMW I get goofed up and hit the brake at least once. And I have some bikes where it is 1 up 3 down and then some are 1 down 4 up, and then the lone left foot shifter that is completely wacky to me. And why the Brits ever had a right foot shift bike is beyond me-you would think they would have had a left shift as you shift a car in England with your left arm. If US bikes had a right foot shift, that I could see as it is how a US car is set up.
I had Empire do some work on the engine for my Bonneville and he is VERY reasonable, just an FYI. Those old Brit bikes HATE sitting for long periods of time and will proceed to leak more oil than the Exxon Valdez and the BP Gulf oil rig combined. My Norton that I haven’t done anything with in years-it looks like I punctured a 55 gallon drum of oil under it. They start to wet sump-lovely. You might want to kick it over here and there to prevent the rings from sticking to the bores again.

That is indeed a 73-if it was a left over 72 titled as a 73, which was VERY common back in the day, it would have different style side covers that were only on the 71-72 models. People will tell you that 70 is the most desired as it is the last year of the oil in tank and the values do reflect that. A basket case 70 will run more than a running decent 71-79 which is idiotic. The later ones, 73-on do look much better than the 71-72 as the side covers are different along with some other touches. It looks like it would turn around quite nicely and with not a ton of work. And a car thread has been successfully derailed to a bike discussion :bigtup:


I guessed that they went .040 over for a reason, just wasn’t sure what that reason was. Lou isn’t much of a mechanic himself, so I have a feeling there was somebody else calling the shots there. Good to know there’s a reasonable, reputable shop in the area for any future issues. I guess that’s good to know about the oil? Just something that happens with these old Brit twins? I’ll have to get in the habit of checking the oil before a ride.

The right shifter is definitely different. I’m taking the motorcycle safety course now and I keep getting yelled at for dropping my right foot first, because that’s where the brake is. Not on my bike.

Good to know some history on this thing. I knew a bit when I got into it, but I keep learning more every day.

Assuming the motor is actually okay and I can keep oil in it, all she really needs is a good once over to fix some wiring issues and replace some safety items like wearables. She really is in pretty good shape. Definitely can’t complain for what I paid for it.

I’m cool with bike discussion. I’ll start a new thread when I get started on it. Probably within a month or two.

EDIT: Just wasted an hour scrolling through parts and shit on LowBrow. Damn. They’ve got just about everything, eh?


Not a good update, but an update nonetheless.

I drove it tonight. The motor is fucked. The motor coughs and hesitates under load at temp and the noise it makes is crazy, mega loud. Much worse than before. I think the car scares my girlfriend normally, but today she was really terrified. It really did sound like it wanted to self destruct. I didn’t even drive it a full mile. I’m 99% sure it’s a rod knock, but I can’t be fully sure. No matter what, the motor has got to come apart. Look for a Triumph thread to start and finish before this comes back. I’m just going to build a motor for boost for this over the early spring months. Make it worth my while. Doesn’t take me long to R/R a motor in this stupid thing. Seriously. Like, a few hours each time.


Still riding season left…


FUCK! Hopefully it won’t cost a ton to repair.


Sucks to hear man, maybe it won’t be that bad a fix.


Gallon of gas~ $2.25
1000 Matches~ $1.99

Seems pretty cheap of a fix to me


First things first, I need to get the motor out and on the stand; then tear it down and find the culprit. If I did actually spin a bearing, I’ll need to have the journals shaved. I’ll also check the main journals while the crank is out and have those cleaned up if necessary. There are undersized main and rod bearings available, but rod bearings are only available .010" under. Mains are available up to .030" under, should there be huge issues there. If there is any damage deeper than a quarter millimeter in a rod journal, this crank is a fucking lamppost. There is a forged 4340 billet nitrided crank available for retarded power levels, but I’m not sure I even want to know what it costs and I don’t need it anyway. Forged Eagle rods are around $700, Ross forged pistons should be around $1,000 with rings, Clevite Tri-Metal bearings for everything will be around $250 and then whatever machining costs. Hoping the heads are okay. If that’s the case, they’ll drop right back on. All in all, I’ll spend $3,000+ on it this winter. After I finish the Triumph.

…but then it will really be ready for boost.




At this point I finally support @Quattro_Krant 's match and gas idea after being a staunch supporter of this car. I hope the engine issue isn’t too bad… frustrating though!


Just plan on doing it, this car is so cool.


If it’s just a rod journal you might just be able to turn the crank and replace the rod, but if it’s a main, I’d replace the crank and block. You might be able to score a used crank/block etc for less money than fixing the current one…

once you get it apart you’ll be able to tell wether it’s one bearing failure or if it’s oil pressure or contamination resulting in the failure…


Yea. There’s likely one of two things that happened. Oil starvation or lots of gasoline in the oil. I never did a compression test on this motor, so I don’t know if any of the rings were questionable. Could be that since it was running rich, a bunch of gas got into the oil and degreased the bearings. I dumped out the filter, but didn’t see any stripper glitter or smell any obvious gas. I won’t know for sure what the story is until it comes apart.

So. Just for the record, do not expect to pluck a Northstar out of the junkyard and run it with any reliability for any real length of time. Do a complete overhaul, or don’t fucking bother.


Can we just get an LS1 in this fucking thing or is it too cost prohibitive for what you want to do?


Believe it or not; I don’t really want one in there. I’ll [maybe] shove one in something cool one of these days, but that’s assuming I’ll even want a car project ever again. Hah.

Anyway, I’d have to cut apart and re-engineer basically everything in the engine compartment to get an LS in there and it would cost a bunch for the appropriate bellhousing adapter and the other ‘stuffs’ required to make the SBC bellhousing pattern work with the 60 degree V6 pattern of my transmission. Adapter is at least $400, so probably as much as the LS itself for the extra stuff would be my estimate.

I always felt that this car, given it’s goofy design and setup needed a small-ish displacement, high-tech, quick/high-revving motor; especially if we start talking about forced induction. That formula has always worked really well on F- and P-cars. I knew this car had to be a V8. Hundreds (maybe thousands?) of these have been built to 1,000HP+, and they share a few design features with the LS variants. Compare that number to the incredulous amount of 1,000HP+ LS motors that have been built and you’ll start to figure out that I just like being different/weird.

Having said all of that, if I did an LS originally; I’d have a functional car with 1,000+ miles on it and a huge smile on my face. C’est la vie.

Definitely doesn’t sound like an LS. 'Least I don’t think so.

I don’t mind joking around about burning it to the ground because it brings me to that point sometimes. But I love this car, and I can’t give up on it. I waited almost ten years to drive it again and it was worth it. I can’t even begin to explain what those 600 miles felt like. I drove it every single day for two weeks.

Next summer will be fun as fuck.


I feel your pain. My Honda G23 swapped fiero spun main bearings, its a bummer. I’m kicking myself for not replacing all of the bearings on the junkyard motor myself, especially after i found out that ACL race bearings were only $25. You’re 100% right that the way to do it is to buy a junkyard motor and completely go through it.



Of course it will be. You’ll be on your Triumph and this project will be all but a distant memory. Giving up on a cunty project car is so rewarding and satisfying.


Just wanted to subscribe to this thread, a little upset I have not been aware of it as this looks like an awesome project and obviously not one you’d normally come across.

Best wishes on getting this thing running right and hopefully for a longer duration than what I have been seeing. Props to you for not giving up! I’d probably have a bunch of broken tools from smashing them into the ground along with several dented panels from blasting my foot into the side of them.