250ci 24 Hours of Lemons Ranchero Update

[mad_science]

After getting some help scrambling to address a no spark issue and a head gasket sealing issue, figured I'd close the loop on how things went in Lemons last weekend.

The motor overall was a complete new build after the previous one sent the #1 rod through the side of the block. Freshly ground crank, hot-tanked and honed block, new bearings, 255 pistons, rings, honed bores, DIY deep sump pan, etc. I really wanted this motor to last.

On Friday the car was running well and we were out of problems to solve so we dyno'ed it at the on-track shop. (140hp @5k, 175 tq @ 2600 at the wheels). Absolutely terrifying to hear them slowly ramp up the engine inside a big metal building. Also, when the dyno coasts down it sounds exactly like a bottom end that's just self-destructed. I really need TUMS as a sponsor for this car...

After dyno we practiced, as I had 2 new drivers and needed them familiar with the car and track. Good thing, as the first one managed to spin twice in like 5 laps. Second driver got in and did like 1.5 laps then came in on the radio saying we had no oil pressure. FUUUUUUUUUUUU!!!

Here begins 36 hours of tail chasing and debugging...

We brought the car in and cranked it with no spark or fuel and it definitely sounded like a bad knock. We tore into it and main bearings were fine, but the #1-2-3 rod bearings were on their way out.



It was around this time it became clear my digital torque wrench wasn't to be trusted. Our previous head gasket issues matched being under-torqued, then the bottom end nuts came off way too easily Vs their torque specs. Also, the flywheel bolts were backing out and were basically finger tight. Allow me to not recommend the HF Quinn digital torque adapter thing.

Anyway, we still had no idea why 1-3 were eating themselves and no spare bearings, so we drew deeply from the "if it's stupid and it works..." well and re-arranged the best bearings into the tops spots along the length and put the worst ones back at 4-6 as they were apparently less stressed. We put it all back together but it was still making bad knocking/clacking noises.

Time to swap in the $80 craigslist backup motor. This thing was an untouched "swapping my Maverick to a V8" CL buy that I put a small-CC milled head onto. Didn't look at any bearings or swap the cam over from the other engine. We got it together and fired it Saturday morning about an hour after the green flag.


It sounded shockingly good and was holding oil pressure and temp so we sent out our first driver. Alas, like 1 lap later it was running 230s temps. That head ended its last race overheating with a suspected blown HG. I need to get it checked for cracks or warpage (apparently). In a moment of desperation, we added a bottle of Blue Devil Head gasket sealer stuff into the cooling system. It held in the garage, idling for the prescribed 50 minutes, but again overheated after like 2 laps on track.

At that point we gave up on the high-comp head, we then swapped the large CC head from the original race motor on. Probably gave us like...8.2 CR and 90hp with stock pistons and stock cam.

Alas, it wasn't holding temp on track either, but we were able to do just enough laps to finish out the day and take the Saturday checker with like 6 laps complete.

Saturday night we did some brainstorming/root cause analysis for what could look like a HG without being a HG. Remembering how bad the inside of the radiator looked when we added the Blue Devil, we went to the one available hose the flushed out the block and reverse-flushed/beat on/flushed again the radiator. An embarrassingly large pile of chunky rusty sand was removed.

Turns out a clogged up radiator will hold temp in the garage with no load and rapidly overheat when you start racing it. WHO KNEW?!

So Sunday comes around and the car holds temp fine (water low 200s, oil ~230-250) and drives well, if a bit down on power. We battled, then worked around a fuel delivery issue (the 22 gallon cell starts to starve for fuel when it's got 15 gallons in it) and a brake dragging issue, but ultimately got 4 drivers some good track time and basically did laps all day. We completed 95 laps and finished 61 of 90 registered cars. Not great, but not bad for essentially only running 1 day.

So at this point a few mysteries remain:

• Why did the rod bearings on 1-2-3 die? Was that a cause or effect of the zero oil pressure?
  • If we starved for oil or sucked some gunk up and spat it into them
  • Or were we under-torqued enough (again, faulty wrench) that they were loose enough to start eating themselves and that caused the intermittent oil pressure loss?
• Was our overheating with the high compression head due to the head or due to a combination of a clogged radiator and dragging front brakes?

 

[mad_science]

Also, unfortunately at this point I'm going to move away from the 250 for Lemons/endurance racing use.

For the money I spend to get the results we get, both in terms of reliability, fixability and power, it's just not a great option.

Our first 250 made it like 5 races with the original craigslist-sourced bottom end before it had a crack in the block and a knock on cold starts.

But since then we've gone through a motor per race. It seems like the more effort I put into making them good and durable the worse they do. At this point 3 different CL-sourced untouched bottom-end motors have raced fine, but efforts to put new bearings in them and clean them up have all resulted in infant mortality.

Yes, I'll admit that the common denominator on the failed motors is me (and my team) working on them. I'm not an expert or experienced engine builder and I'll probably look back on this era as a learning curve to be sure.

Still, for the money I've sunk into racing 150 hp 250s I could've nearly bought a build 300hp crate 302 and just run it.

 

[B RON CO]

Hi, my guess is you can blame the piece of crap torque wrench for everything. Get a mechanics quality torque wrench and every now and then compare it with another guys torque wrench. Good luck

 

[wme013]

I'll vote for the torque wrench and sand causing different problems.
I don't know about your fuel cell problems and FWIW in the old days I used wiffle balls as cheap baffles. They make baseball and golf ball sizes. Just fill up the tank with them.
The gas back then didn't bother the plastic, these days who knows about the gas and plastic.

 

[bubba22349]

mad_science said "So at this point a few mysteries remain:​

• Why did the rod bearings on 1-2-3 die? Was that a cause or effect of the zero oil pressure?
  • If we starved for oil or sucked some gunk up and spat it into them
  • Or were we under-torqued enough (again, faulty wrench) that they were loose enough to start eating themselves and that caused the intermittent oil pressure loss?
• Was our overheating with the high compression head due to the head or due to a combination of a clogged radiator and dragging front brakes?"

Sorry for all your troubles its really a shame, you got some very decent power to the wheels with that new 250 build even with using Larger Combustion Chamber size and a lower Compression Ratio. X3 I don't really think these are very much of a Mystery though. I do agree with the above comments by "B Ron Co" & "wme013" on the defective reading Torque Wrench, & the plugged up by having all the Sand in the Radiator so it won't flow very good. All of your other engine's overheating problems regardless of the head being used and the final engine failures are tied to that single Radiator being used. I will also add without seeing the engine and its parts that I can't answer the why part of the question on the lack of Oil Pressure, though I am sure there is going to be a easy to see reason for it. But as to the effect of having "No OiI Pressure" I can answer, it will only take 30 seconds or more of running an engine without any Oil Pressure to do some real damage to an engines Rotating Assembly and that is going to happen no mater what kind of engine your using. Yes the Over heating was all caused by that clogged up Radiator, as you even went to the extra effort of having this last builds 250 block cleaned out good with its Hot Tanking. Then of course having the Dragging Front Brakes would of compounded it adding to that problem. Many times we can learn much from a failure though. Best of luck

 

[Steve N Grace]

That's cool your getting to run the event. Its enjoyable to read about your trials and tribulations and a good reminder I have not calibrated my wrench in some time. Thanks for sharing.

 

[chad]

just think re: how good ur 4th and 5th year will B w/all this practice !

 

[wme013]

Did you ever see the Movie "Tin Cup" You can't quit now