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Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
3/29/23 11:01 p.m.
ShawnG said:

Boss and I both had a hand in exploding the fuel tank for a 1934 Packard Twelve.

Not an expensive mistake, but you reminded me.

Early 60s Chryslers sometimes had a vertical flow radiator with a giant top tank.  The tank was easily twice the thickness of the radiator itself, overhanging the fan.  I think it was supposed to be like a built in surge tank or something.

So there I was, working on a very clean, mostly original early 60s Chrysler product.  I would like to say it was a B-body, it definitely had a 426 wedge motor of particular enthusiast value: think crossram intake, twin AFBs, exhaust manifolds that wrapped over the valve covers, much rarer than the later Hemi stuff.  I was refilling the cooling system, using the airlift as per normal practice.  The airlift pulls the cooling system down to within a half inch/mercury of hard vacuum, then you switch hoses and the vacuum in the cooling system sucks the coolant in.  Can't have air pockets if there is no air to begin with.

About 20 inches of vacuum into this equation, the massive, overhung upper radiator tank sucks itself down with a very loud PONG!!!! sound.  Just... collapsed.

After the changing of the shorts, it looked like the only part that actually deformed was the bottom plate.  Top of the shell was curved, only the bottom was flat.  Installed the cooling system pressure tester to see if had any leaks. 

About 10psi into that equation, PONG!!! the tank straightened itself back out.  Didn't even chip any paint.

Added coolant the old fashioned way, and learned a lesson...

kb58 UltraDork
3/29/23 11:48 p.m.

Not me, but the buyer of my first car, Kimini. He added an electric water pump but plumbed it backwards by mistake. That had rather diabolical symptoms that masked the problem for a while. At idle or low speed, the electric pump won the "mass flow war", pushing coolant one way through the system. At freeway speeds, the mechanical pump won, pushing coolant the other way through the system. All was well... until they drove for a while at some middle speed, where the flow of one pump exactly matched the flow of the other. Net result, zero flow, and a destroyed engine.

octavious Dork
3/30/23 7:00 a.m.
matthewmcl said:

Does "buying a bunch of parts that you never actually use because you change your mind by the time you get there," count? Man I have a lot of those...

Or sell the car before you put the parts on?  Cause I've done that several times. 

ddavidv UltimaDork
3/30/23 7:08 a.m.

"Building" an engine with expensive machine shop work that wound up costing what the car was worth when I sold it. Lessons learned:

Don't bother rebuilding an engine that is known for lasting forever.

Just buy the faster car instead of trying to make a turd into something else.

Nathan JansenvanDoorn
Nathan JansenvanDoorn Dork
3/30/23 7:26 a.m.

Dropped a nut into a Porsche 3.6 bottom end while doing a top end. Couldn't fish it back out, ended up rebuilding the bottom end.

gsettle New Reader
3/30/23 8:46 a.m.

I didn't know about stock LS engine oiling limitations on a road course. 3 rods made made 2 holes on each side of the block heading into turn 5 at NCM.  Then, luckily, the escaping oil got on the headers and caught on fire. I was able to put out the fire (s) with my on board extinguiser though.

eastsideTim UltimaDork
3/30/23 8:47 a.m.

Not necessarily expensive in money, but in the amount of time it took to scavenge things at junkyards and in online sales.  Stored parts at a storage facility.  Fire started in the locker next to mine, and destroyed almost everything in my locker.  It may be years before I track down some pieces, as first gen S10s are thin in junkyards up here, and some of the parts I had weren't exactly overly common when they were new.

Tony Sestito
Tony Sestito UltimaDork
3/30/23 9:27 a.m.

My 20+ year 1979 Trans Am project car is essentially a dark void in my driveway that money disappears into. I rebuilt the original engine, even going as far as replacing the entire crankshaft, and it still found a way to blow up again. Then, I built another completely different engine, and while that runs well, it only has break-in miles on it due to the body needing extensive work. And thanks to that body work, water started leaking into the interior and destroyed much of that. Interior stuff for these cars is available, but it's VERY pricey and takes forever to get right now. 

So, I would say the mistake was not fixing the body first. When it was down for the count the 1st time, I should have saved up and had the bodywork completed, which could have saved me from doing the interior now, which will cost me more than rebuilding BOTH engines! 

David S. Wallens
David S. Wallens Editorial Director
3/30/23 9:39 a.m.

How about buying tires too early so they age out before it’s time or, simply, don’t fit the car’s final configuration?

Or waiting too long to buy tires and then you can’t get what you need when you need it? 

DirtyBird222 PowerDork
3/30/23 10:01 a.m.
Tom1200 said:

The D-sports racer ran hot because we used the stock Yamaha 1000 radiator.

A friend gave us a monstor aluminum radiator.

Two engines later we discovered that it was over cooling the car. Yamaha 1000 engines are clearanced such that if you run them hard below 140F they will loose oil pressure to the rods.

This problem was so aggravating that I ended up selling the car. It turned me dream car into a nightmare.

This. We windowed two H22 blocks because we had a monster twin core radiator on our Champcar Accord. It wasn't getting hot enough and the tune we had on it would run cylinder 3 super lean to try and get the temps up, which would eventually make a rod a member of the SpaceX launch family. I hate that it took us two motors to figure it out.

I've spent a ton of money trying to fix the ABS/Brake light issue on my Sequoia to no avail. New yaw sensor, new booster, new calipers/pads/rotors, new master cylinder, new wheel speed sensors, abs module, a ton of hours running through the fault and relearn sequence, to have the same four lights on my dash. 40k miles later, I'm still fine driving around with those lights and no ABS. 

With the S2000 build. I've bought aftermarket "performance" parts because the factory either doesn't make a replacement or requires the purchase of a much larger item to get the smaller thing (upper control arms and ball joints aren't separate pieces in the Honda parts catalog). Only to find out the aftermarket "performance" part is an absolute piece of poop that was likely just a resell of a RockAuto part for 10x the costs. 

And like others have said. I plan out a build. Buy a lot of parts. Then decide to go another direction. 

914Driver MegaDork
3/30/23 10:06 a.m.

Expense in my cred as a car guy, my ego and in frustration only.  But this is how we learn.

Peeled everything I needed off the donor car, running out of room in the garage so  had it scrapped.  Rats, there's a widget I need off the firewall (or something silly) so I run to the scrapyard and explain my plight.  Yeah, they remember me, go ahead.  I pull the part go back to thank the guy, "That'll be $18".


nlevine GRM+ Memberand Reader
3/30/23 10:32 a.m.

On my '71 BMW 2002 ITB race car - while re-installing a side window and chatting with folks hanging around the shop, I overtightened one of the nuts that held the window to the track and the window exploded in my hands. Then, when I finally got the thing on track 4 years after a "just over the winter" build, I stuffed the car into the wall exiting turn 10 at NHMS during my competition school, which wrote off the whole car. I had no crew that day, the car wasn't charging because in my preparation, I stripped-out most of the wiring harness (didn't read the GCR closely and relied on somebody else's bad information), had a leaking rear main seal, and a less-than-stellar cage installation (same somebody else's bad advice for a builder). Lots of time and $$ down the tubes on that one. Learned that I need to read rule books myself, and get more knowledgeable friends.

Many new, uninstalled parts went along with several other project cars that were bought high and sold low.

On the current Porsche, I've only broken one new $100 oil-pressure sender so far...


Ian F (Forum Supporter)
Ian F (Forum Supporter) MegaDork
3/30/23 10:37 a.m.

Somehow I read the title as "biggest mistake you've made on someone else's project"... Doh...

Biggest mistake - I definitely have many to choose from, but at the top is installing a 6" suspension lift on the 1978 F-150 4x4 I had 30+ years ago.  That was incredibly dumb.  I should have spent that money on bodywork and paint. 

Most expensive mistake - from the day I bought my Cummins 4x4 until the day I sold it was pretty much a constant hemorrhage of cash. I bought that truck for ~$9K... and spent over $10K trying to keep it running... and sold it for around $2000. 

nlevine GRM+ Memberand Reader
3/30/23 10:39 a.m.

In reply to David S. Wallens :

Yup! Bought a couple of sets of "closeout" track tires that I was planning to use both for racing (the ITA Z3 wasn't that competitive anyway, so they wouldn't have affected my finishing position that much) and HPDEs in the street car, just in time for me to hang up the race gloves with the kid's arrival and losing my "window" for track time in the DD while it sat in the body shop after an "oops". Ended up giving the tires away to somebody who didn't seem to care about date codes...

GameboyRMH GRM+ Memberand MegaDork
3/30/23 1:15 p.m.
Curtis73 (Forum Supporter) said:

I bought a GVOD unit (bloody expensive) for a TH400 without knowing that I had a pretty rare 13" long-tail version.  By the time I got around to the project I had missed the return window and GV wasn't sympathetic.  I had to order another tailshaft housing and coupler for big bucks.  I put the other parts on ebay and it took over a year of re-listing it before someone bit and they basically got it for half price.  In hindsight it would have been cheaper to buy a short-tail TH400, but the one I had was a fresh rebuild with some pretty serious money in it.

I also lost my shirt because [insert insurance company's name] denied a claim.  Many years ago, I bought a primo sweet W210 E300TD for the wife for $14k.  She got caught in a wicked hail storm and it turned every panel into a golf ball and broke the windshield, rear glass, and one side window.  Body shop said $10k to fix.  [insurance company name] denied the claim because I said the damage happened at 6:15pm and they said that NWS reported the hail didn't happen until 6:30.  I lawyered up, collected copies of all of my friends' claims that all said 6:15, and [insurance company] got a letter on Lawyer McLawyerson letterhead and their response was basically, "bring it."  Unfortunately [insurance company] was one of the ones that pays multiple actors in white aprons to make commercials that play during the superbowl, so Lawyer McLawyerson advised me to not pursue, citing [insurance company's] 80% success rate at beating litigation with their panel of about 100 big legal people.

During all of this, my project car was broken into.  They took the stereo and an ipod and left a broken window.  They denied the claim because I was at a friend's house and they couldn't reach the friend (who was now in rehab 6 states away) to corroborate the story.  Same deal.  Lawyered up, they said bring it, and it went nowhere.

Long story short, [insurance company] screwed me out of about $16k.  I had been with them for 6 years, insured up to 4 vehicles at a time, made two legit claims, and never got a cent.  I no longer insure my vehicles with companies that drown every commercial break with high-paid actors and mascots at the superbowl.  If they're that good at denying claims that they can afford that kind of marketing, they're not going to get my money.

Not a project car mistake but I've also lost a lot to insurance company ratberkeleyery in an accident, highlights include my car being given a non-negotiable before-accident value of $750 by the dealership - before that accident was just weeks after a guy was chasing me down in a parking lot begging me to take his $3500 for it, and that was just before I installed a new custom roll bar; and the other party's insurance company crookedly trying to contact me directly for a settlement payout at which point I lawyered up. I'll definitely remember the "this hailstorm started 15 minutes later in our books so the damage is not covered, must've been aliens" defense...

Datsun310Guy MegaDork
3/30/23 1:52 p.m.

In reply to Stampie :

Was it a custom 2-piece stick?

fearlesfil New Reader
3/30/23 4:51 p.m.

Rebuilding the engine, twice, instead of just picking up another at the U-Pull-It! The original engine had a warped timing cover causing radiator water to leak into the oil pan, and it's surprising how similar a little plain water looks like fresh synthetic oil. The rod bearings could readily tell the difference though. I finally figured it out, had the machine shop reface the timing cover and we were good to go again. The two races we missed cost my wife her Powder Puff championship. I won't say what it cost me!?!

bearmtnmartin (Forum Supporter)
bearmtnmartin (Forum Supporter) GRM+ Memberand UltraDork
3/30/23 5:43 p.m.

14 to 1 compression, pump gas and ear protection so I couldn't hear the pinging. But dang it was fast for a minute.

NermalSnert (Forum Supporter)
NermalSnert (Forum Supporter) HalfDork
3/30/23 6:34 p.m.

Not a project car but my '80 280zx daily driver. I couldn't find one of the wing nuts or the wing nut, I forget now, for the air cleaner. It made it all the way to #5- Broke the piston in half. The end.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
3/30/23 6:45 p.m.
NermalSnert (Forum Supporter) said:

Not a project car but my '80 280zx daily driver. I couldn't find one of the wing nuts or the wing nut, I forget now, for the air cleaner. It made it all the way to #5- Broke the piston in half. The end.

LQ9 engine. Analog methanol injection system's power transistor stuck on.  Low point in an LS6 intake manifold is under the #7 intake runner's inlet.  Engine hydrolocked on startup.

And people say powdered metal rods are weak.  This one bent in two places in this direction, and a little bit from the other angle too, but did not shatter.

This only cost one piston and rod, a head gasket and bolts, and 8 hours to R&R the rod.

marcucci New Reader
3/30/23 6:49 p.m.

I had worked on cars for nearly 30 years at the time, and after rebuilding my S2000 (F20C) with new crank and bearings as a result of hard track use without a cooler, forgot to top off the oil. But not just top it off... I out in half of a 5 quart jug I had left over, got interrupted, and failed to finish the fill or even check the oil level before running it. Hard. Ended up needing another new crank and bearings. That build at least lasted a few years before I wised up on needing a cooler (probably the most expensive mistake since I went theough a few motors on that car as a result) 

Stampie GRM+ Memberand MegaDork
3/30/23 7:06 p.m.
Datsun310Guy said:

In reply to Stampie :

Was it a custom 2-piece stick?

Yes.  I seem to remember it was a McDermott factory prototype for their sneaky pete.  I got it from a guy that worked for them.

jwagner (Forum Supporter)
jwagner (Forum Supporter) HalfDork
3/30/23 7:47 p.m.

These would be more humorous if they weren't so relatable to even dumber stuff I have done...

Was finishing up dropping a freshly built head on the Exocet, two days before the Memorial Day two day weekend.  Just had to lower the head on the block and bolt it all together.  The hex bit I was using to screw head bolts in dropped out of the screwdriver handle and I couldn't find it.  Anywhere.  After hours of searching that extended into the next day we decided it must have fallen down one of the little oil passage holes on top of the block.  Pulled the motor and damned if we didn't find it in the pan.  By the time it all was back together the weekend was lost - two days of paid for track time was most of the financial damages.

Ill skip the stories about the K20A2 with the 90 day warranty that I found had a bent rod on the 92nd day, the THM400 I bought for the Firebird and never bothered to install, etc.


Ranger50 MegaDork
3/30/23 8:51 p.m.

Using "free" E36 M3, just because I already have it....

If I have had to buy everything, it would have already been done. Twice.

kb58 UltraDork
3/30/23 9:51 p.m.
David S. Wallens said:

How about buying tires too early so they age out before it’s time..." 

Forgot about that. Designing and building a car from scratch means that every thing is built around the tires... so I bought tires first, then wheels, then hubs, and so on. Ten years later it was done, and yeah, rolling on 10-yr old "sticky" tires that weren't so much any more.

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