1 (edited by AT-JeffT 2021-01-19 09:20 AM)

Topic: Successful Engine Rebuilding

Hello Everyone,

I have questions for those who have successfully rebuilt engines for Lemons use.  I realize the best strategy for reliable Lemons engines is to find relatively low mileage junkyard engines. These questions are mostly curiosity based. 

The recurring theme in Lemons seems to be that freshly rebuilt engines tend to blow up in short order.  For those who have successfully rebuilt engines that have survived Lemons races what do you consider to be the reason they last?

1)Are the rebuilt engines that fail, simply not broken in well enough?  Breaking in an engine in a non-street legal car is certainly a challenge.

2)Are tolerances an issue on freshly rebuilt engines?  I imagine most of us rebuilding engines will shoot for the tighter end of the tolerance spec.  Should endurance engines be built with tolerances on the looser side of things?

3)Is engine rebuilding inherently challenging and therefore many teams lack the time, resources, or attention to detail that is required.

4)Is lack of machine work the issue?  Do engines fail because parts are being reused when they are out of spec?

Let me know if your team has found any patterns with success or failure when dealing with engine rebuilds.

Re: Successful Engine Rebuilding

Two things...

Low mileage junk yard engine is the second best option but far, far below the best...running and driving parts car pull!  Depending on what you are racing this can often be a net positive purchase over a PnP engine and is almost always a net positive purchase over a "commercial" junkyard engine.  Example, our spare L67 Buick 3800 SC is from a $550 Bonneville SSEi that I drove 35 terrifying miles back home in a deluge thunderstorn with 3 of 4 gears working, 0 of 4 shocks working and 70% of the electricals not chasing angry pixies around.  I also drove it to and from work for two weeks and it had the best hot oil pressure of ANY GM product I had ever seen.  It also supplied a spare ECU, wiring harness, every sensor, supercharger, some accessories (our layout is bastardized to fit in a '47 Plymouth so it uses a combo of early and later accessories and mounts).

We used to refresh the Saturn 1.9L motors before installing in the car or on the spare subframe.  My car co-owner and I got to the point we could do one in about 5 hours working together.  This is crank and big end bearings, headgasket, timing set, and check oil pump, water pump, etc...plus of course all relavent seals.  None of them plew up because they were rebuilt (wait for note at the end) but two failed due to installation errors into the car.

That said, I helped another Saturn team do the same on their engine because they had lost their mechanically skilled team member and existing engine had a rod knock.  In this case, we indirectly cause the engine failure by rebuilding the junk yard motor verses just running it.  In short, on of the rod studs stretched on torqueing and that is the rod that fired tself through the side of the motor.  We knew it was questionable but had four days to race weekend so kinda had to run it.

Re: Successful Engine Rebuilding

It's an interesting question that I'm not sure if there's a definitive answer for it.  As someone who has some experience with blowing up motors I'd say mine were due to a single factor, trying to rebuild in the Lemons spirit.  For example, the Imp engines likely blew up because while race Imp engines exist, they are very expensive to build and they mostly are for short term races like hillclimbs.  A 3 main bearing crank turning high RPM in an aluminum block requires a fair bit of aftermarket help and I didn't use any of it nor is any of it available in the US.  The rotaries have always been down to rebuilding them in the least cost effective manner and that has been a losing effort.  You can rebuild them cheaply with used parts.  Doing them correctly is getting very expensive.  Probably $1500 in parts and machining so I cut corners.  And blew a lot of them up.

1990 RX7 "Mazdarita"  1964 Sunbeam Imp (IOE 2013 Sears Pointless) 2002 Jaguar x-type (Winner C-Class 2021 Sears Pointless)
Gone bye-bye
1994 Jaguar XJ12 (Winner C-Class 2013 Sears Pointless)  1980 Rover SD1 (I Got Screwed 2014 Return of Lemonites)

Re: Successful Engine Rebuilding

I have had crazy reliability from 2.2 and 2.4 Ecotec engines, both were around 120k miles from junkyard, the 2.2 did around 10 races then I sold it to a dirt track guy who won't he track championship the next weekend with it. I replaced timing chain and guides etc on both as these are easy when the engine is out and known weak points. Change oil with every race, nothing special just manufacturers spec.

Before the Ecotec we blew a few 20r Toyota engines then finally built one that lasted a while, that was new pistons, used slightly worn crank, for more spin, and a high volume, not high pressure, oil pump and a windage tray plus external oil cooler. It eventually dropped a valve but lasted a couple of years. The cost of building that engine again is what turned me onto the ecotecs, invest the time and effort to swap to a modern more reliable platform that is readily available in junkyards and weighs less, makes more HP and uses less gas.

Apocalyptic Racing - Occupy Pit Lane racing
Racing the "Toylet" Toyota Celica powered by Chevrolet Ecotec.
24x Loser with the Celica. 16x loser in other fine machines
Overall winner Gingerman 2019

Re: Successful Engine Rebuilding

My experience was with two different engines.  A Ford 2.3L OHC and a Mazda 1.8L out of a Ford Escort GT.   In both cases the owner wanted me to do only what needed to be done, such as bearings and rings. Also any head porting that could be done quickly.

The Ford got a better roller cam from a later model of this engine and the head was milled to raise compression some. I had to replace the pistons as one was on the verge of failure. I used the cheapest OEM replacement set ($100 for all 4.) That engine went on to run 3 full races without issues. Winning class B.  In the forth race the head gasket failed, but these engine are known for this if run hard. They replaced the head gasket and it won Class B again. After that Lemons deemed this a Class A car.

The Mazda was easier as all it got was bearings and rings. The engine won class B it's second time out but it did tend to use oil, about a quart per tank. I later modified the intake manifold to allow the use of a later 1.8L Madza Miata head. The intake ports were raised for better flow. It was still running strong when the owner sold the car to some other racers. He put it on a dyno  before he sold it and it put down  127 HP at the wheels!

Re: Successful Engine Rebuilding

Most engine rebuilds that fail, fail due to rebuild errors.

Break in has nothing to do with it. Engines break in takes only a few minutes with the possible exception of flat tapper cams

Too tight or too loose tolerances will cause failures, but keep it within factory specs and you’ll be fine.

Re: Successful Engine Rebuilding

For our 1st engine (1984 Trans AM) we just used the stock L69 305 w/ 149k on it. We did the basics, timing chain set, cam, valve springs, cleaned up the intake, rebuilt the carb, added an oil cooler and rolled. The engine ran great. We probably had 8 weekends of fun on that. It did spin a rod bearing. Engine #2 (1988 Formula Firebird) we did a rebuild. We went thru the entire thing. New rings, bearings (not cheap junk), cam, timing chain, ported the heads, unshrouded the valves, check all the seats/guides, put baffles in the oil pan (critical for a SBC). The thing runs killer,  it pulls hard to 5800-6k. SO my advice, if you rebuild it make sure you do it  right AND don't use cheap parts.

"get up and get your grandma outta here"

Re: Successful Engine Rebuilding

Thanks to those who have shared their experiences so far.  Seems like #3 is the most common failure mode. 

Glad to hear break in isn't a big deal. 

If others have more stories of success or failure, please share.

Re: Successful Engine Rebuilding

It's hard to answer for all teams. You can rebuild an engine correctly and destroy it in 1 stint with a driver that abuses it, or in 10 minutes when you forget to hook something up right. Or you can pull a 200k mile motor from a junkyard and have it run 20 races, and everything in between.


Rebuilding an engine isn't hard, it just takes some time to learn which parts require what knowledge to do correctly. But rebuilding it won't solve other issues that might be causing failure like insufficient cooling systems, wrong oil, overheating oil, revving too high, etc.


We used to rebuild the daytona engine every race. In that case rebuild means fresh bearings and gaskets. We should NOT have had to do that, but it took a while to beat our way though the learning curve and figure out what other things were going wrong, namely heat and oiling issues. We finally got a cooling system setup that was sufficient, a bigger oil pump and cooler, and then did a proper rebuild with some machine work to support it. Namely cylinders over-bored 1 step and honed to refresh worn cylinder walls, block decked, main journals checked for straightness. Head got decked, valves checked to make sure they were seating correctly. Then assemble with an MLS head gasket and good bearings and gaskets. No performance tweaks, no porting, no improved parts. That motor was a monster and ran a couple races before we dropped an oil cooler line and melted it down.

I'm getting ready to crack our 260k mile saab engine. Not because it's defiantly broken, but because I need to know the state of a few parts. Some of the hydraulic lifters are dead, exhaust gasket is done, so I have to do a few things anyway. Some of our oil analysis reports showed an increase in materials that come from bearings, so I want to look at 1 or 2 of them and gauge their life remaining. If they look ok I'll just bolt it back up and walk away. If the look like they're wearing I'll replace with OEM and send it.

20+ Time Loser FutilityMotorsport
Turbo Dodge Powered E36 Build
2008 Saab 9-5Aero Wagon
Retired - 1989 Dodge Daytona Shelby 2011-2015 "Lifetime Award for Lack of Achievement" IOE, 3X I got screwed, Organizer's Choice

Re: Successful Engine Rebuilding

cheseroo wrote:

It's an interesting question that I'm not sure if there's a definitive answer for it.  As someone who has some experience with blowing up motors I'd say mine were due to a single factor, trying to rebuild in the Lemons spirit.  For example, the Imp engines likely blew up because while race Imp engines exist, they are very expensive to build and they mostly are for short term races like hillclimbs.  A 3 main bearing crank turning high RPM in an aluminum block requires a fair bit of aftermarket help and I didn't use any of it nor is any of it available in the US.  The rotaries have always been down to rebuilding them in the least cost effective manner and that has been a losing effort.  You can rebuild them cheaply with used parts.  Doing them correctly is getting very expensive.  Probably $1500 in parts and machining so I cut corners.  And blew a lot of them up.

Yeah, I have a teammate who keeps thinking we should be rebuilding engines; it’s a similar thought process to the above, except that I don’t give in and start that process. Here’s why, in our case: the list price on a 5.0 DOHC Benz V8 long block is $35k. Not $3500, 35 thousand. No one ever buys one at list, but that gives some idea of the parts pricing. No, I buy either running cars or known good engines, and treat anything below the spark plugs and valve cover gaskets as a black box. So far, the most expensive motor donor was $1000 for a good running driving S500 with a blown AC evaporator. Have bought a few engines for 3-500 and have been given a complete car and a 4.2 motor we didn’t use. Yet.

#111 Tradewinds Tribesmen VW Passat Inde ‘20... shhh, the Benz is napping!
#888-Hong Kong Cavaliers Benz S500: formerly known as OMG Racing #140...
Judges Choice and Regional Award winner! Chuckwalla '12, Buttonwillow '13, BFE GP '15, Miller '14 & '15, Sonoma '13,'14,'15,'17, '18. Inde '16,'17,'18,’19. Other foolishness: Finisher of Hell on Wheels (Jaguar) IOE (Humber)

11 (edited by Guildenstern 2021-01-20 01:40 AM)

Re: Successful Engine Rebuilding

Most rebuilt engines that fail in Lemons are because they are rebuilt at the track on the dirt.

Keep it Clean, Get it onced over by an engine machine shop, Follow the torque specifications. Never trust a used Bering surface.

We rebuilt our 5.0 following a nasty head-gasket failure at the Corvette Museum. And I rebuilt our T-5 transmission and our rear end when I got them because they had been derelict and abused. It's easy as long as you follow the specs. I don't know about my team mates, but I had a great time rebuilding, it's fun if you stay organized.

Mistake By The Lake Racing (MBTL)
88 Thunderbird "THUNDERBIRDS ARE GO!", Ex Astris, Rubigo / Semper Fracti
A&D: 2014 Sebrings at Sebring (NSF), 2014 NJMP2 Jurassic Park (SpeedyCop), 2012 Summit Point J30 (PiNuts)
2018 Route Sucky-Suck Rally Miata, 2019 World Tour Of Texas 64 Newport

12 (edited by Team Infinniti 2021-01-20 06:17 AM)

Re: Successful Engine Rebuilding

Due to cost related of rebuilding a 32 valve v8 import engine vs replacing the entire unit, we do not believe in rebuilding, We start with a healthy engine, address oil leaks/tuneup/weak points (in our case, timing chain guides[not the chains]) and send it. 40+ races later we are on the 4th engine.

1st unit wore out, ignoring mains that looked like pounded copper pipe, changed 2 sets of rod bearings when the oil went glitter, finally the rings got weak, pulled/replaced while still running.
2nd was getting tired in the rings, I added something to the oil to help seal, instead wound up with a oil pressure relief valve stuck open, killing the crankshaft
3rd had a thermostat go bad, it did run all day but rings & springs were shot from heat
4th still running

Make sure the thing is oiled and cooled and they usually work as designed.

Homestead Chump 5th-Sebring 6th-PBIR Lemons 9th - Charlotte Chump  CrashnBurn 9th
Sebring 6th again -NOLA Chump 1st -PBIR Chump Trans Fail 16th
Daytona 11th - Sebring 6th - Atlanta Motor Speedway 2nd - Road Atlanta Trans Fail 61st-Road Atlanta 5th
Daytona 13th - Charlotte 9th - Sebring 2nd-Charlotte 25th broken brakes - Road Atlanta 14 10th-Daytona 14  58th- Humid TT 19th Judges' Choice!

13 (edited by Sir Thomas Crapper 2021-01-21 07:35 AM)

Re: Successful Engine Rebuilding

refreshed a 250K mile turbo 2.3 with crank and rod bearings and rings.  Ran it for a few years, then it blew a head gasket.  Put in a low mile replacement and had the alternator bearing fail, which threw the belt and by the time our guy realized there was a problem, seized the engine. 

Put in a 200K+ mile 5.0.  Never touched it.  Have about a dozen races on it, with oil changes and 2 sets of plugs....

Silent But Deadly Racing- Chief cook and bottle washer, Former Flyin Turd Race Team Captain 
Ricky Bobby's Laughing Clown Malt Liquor Thunderbird Turbo Coupe, Datsun 510, 87 Mustang (The Race Team Formerly Known as Prince), 72 Pinto Squire waggy, Parnelli Jones 67 Galaxie, Turbo Coupe Surf wagon.  (The Surfin Bird)
Besmirching race tracks in the Eastern US since 2001