mad_science
Well-known member
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:
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?
Last edited: