Slant Six Forum

Turbo Dart @ MSR Lemons
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Author:  SpaceFrank [ Tue Nov 19, 2019 8:31 am ]
Post subject:  Turbo Dart @ MSR Lemons

I think I've had enough time to recover; time to write up our first "racing" experience with the Turbo Dart (sung to the tune of "Baby Shark"). And of course start collecting advice for how to remedy the ongoing issues. For background, we bought the turbo kit off Shawn Pohlman's truck late this summer and adapted it to fit on an early A-body for the Lemons race at MSR on November 9-10. We also had to put together a new engine, transmission, and rear axle assembly, as well as redo the entire instrument cluster to add gauges and make them more visible.

Build Summary
Engine: Stock 1973 (225) bottom end with a fresh ball hone job, cast iron rings gapped to .050", and fresh rod bearings. Main bearings and seals have 3 Lemons races on them and weren't touched. (We left the crank installed and wrapped the rod journals with tape while honing the cylinders.) This block (with a different head) has historically run hotter than our original engine: ~210° on the track vs. ~180° for our previous (1964) race engine. This may be indicative of problems in the cooling jacket, which we've never cleaned out. 1970 cylinder head, cleaned and magnafluxed, cut for 1.70/1.44 SI valves, bowl and mild port work done by me, shaved 0.080" for a calculated SCR of 8.6. Plain old Victor Reinz head gasket. Stock 1973 cam installed at ~107° ICL. This probably hurt our performance waiting for the turbo to spool up, but it was done to be conservative on boost. Dutra-blueprinted high-volume oil pump (1" rotor, hardened gear). EI distributor with brand new pickup and governor slots welded all the way up for locked-in timing, HEI ignition module. Heat range 7 NGK Iridium spark plugs, 0.028"ish gap. In order to fit our new electric radiator fan, we had to use a shallower big-block water pump pulley, press the shaft fitting down closer to the pump body, and cut about 1/2" inch off the shaft. Unfortunately the pulley was a little smaller in diameter, so we were slightly overdriving the pump, and also our belt was too long. The only shorter belt I could find on short notice was a little too short; it required a lot of brute force to get it mounted, and then the engine would throw it every time you revved above 2500 or so.

Transmission: Main case and L/R assembly from a 1965 B/C body A904, because it was the only one on hand with no cracks in the bell. Extension housing and guts from our previous 1964 A904, including a valve body that was mildly breathed upon by Circle D in Houston back when I had the original transmission on this car rebuilt in college. According to Bob, the final shaft end play was a little looser than the spec range; he didn't have time to source new thrust washers. We couldn't fit the trans cooler in the front of the car after the addition of an oil cooler and intercooler, so we ended up mounting it under the floor under the driver's seat. Our "customized" floor slopes downward here to provide some height adjustment when sliding the seat forward, so it has some exposure to oncoming air. (Probably needs an electric fan, or to be moved somewhere less stupid. For the first time in history we noticed our trans sump temperatures rising noticeably when the car idled.)

Rear Axle: Unknown year A-body 8-3/4" with standard wheel bearings (we actually re-used the old ones, since they felt good and we were short on time). 489 center section with fresh ($$$) clutch-type SG unit from Dr. Diff, new carrier and pinion bearings, and new 3.55 gears. 10" x 1.75" rear drums with old drums and shoes and mostly used hardware. I had our driveshaft shortened 0.66" (previously used an 8-1/4") and told the shop to install a conversion U-joint on the rear to go to a 7290. I should have looked closer at the yoke that came with the new rear, because it turned out to use an outer-locking 1350 U-joint, which is a hair shorter and has larger caps. Being so short on time, I made it work by removing the inner lock rings from the 7290 caps, grinding a hair off both ends, and installing them in the yoke with shims and U-bolts. There was also a slight grind from the right rear which, as far as I could tell, was due to the rusty drum rubbing on the backing plate. I figured it would self-clearance. (It didn't.)

Turbo (etc.) Setup: WH1C turbo (basically the same as an HX35). Way too much turbo for this engine. Integral wastegate control that I think Pohlman cobbled together himself. Dual Dutra Duals to 2" up-pipes to the turbo to a 3" side-exit exhaust. Big Damn Intercooler that required us to redesign the front of the Dart. Hilarious JDM-style BOV. 4-barrel Holley carb of unknown type (mechanical secondary but single pump), modified by Pohlman for boost, but only running on the primaries. Secondary throttle linkage removed, plates wired shut, no fuel supplied. Stock mechanical pump (later determined to be a bad idea) feeding 45 psi electric pump, feeding boost-referenced (from the hat, not the manifold) Aeromotive bypass fuel regulator. Ran a new -6 AN return line back to the cell. Ran a line off the back of the oil pump to the oil cooler, then the turbo, then a bung in the pan. Wideband O2 sensor/AFR gauge, vacuum/boost gauge, oil pressure, but no time to install an oil temp sensor. Inline fuel pressure gauge under the hood.

A picture from before we put the front of the car back together or finished the wiring:

Race Summary
It turns out we started this project about two weeks too late; even after spending an entire week working past midnight (while working full time jobs), Bob and I only got everything buttoned up on Friday evening. Friday at Lemons is normally spent getting your car inspected, and running the test and tune session if you're really fancy. We ended up getting to the track with the Dart around 10 PM. Its first drive with the turbo was to get onto the trailer.

In the meantime, Bob's wife Carrie towed the Oldsmobile (our even dumber racecar) to the track herself on Friday, got it unloaded with the help of some friends, and then came back for us and the Dart. We also had to source a new onboard fire system for the Oldsmobile at the last minute because we were so busy with the Dart that we forgot about the Lemons rule change this year. (The Dart has always had an integral fire system.) We got lucky and found one unused at a local racer's shop, which one of our friends from the Soviet Space Dart team not only picked up for us but then installed herself with help from another racer, all before Bob and I ever got to the track. I love Lemons sometimes.

Here's an underhood shot after we got to the track on Friday night:

We sacked out at the hotel after a few beers with wide-eyed friends and onlookers, then got up early to do some last minute work. Ran to the local NAPA to get various parts including an in-between "just right" sized belt for the Dart as well as a new belt to replace the one the Olds had chewed up. Got the belt mounted, mounted the trans cooler, wired up a couple remaining gauges, torqued the lug nuts, checked the tire pressure, etc. Finally got it ready, ran it through tech inspection a few hours after the race started, and sent Bob out first. I can't remember the exact sequence of events, but we spent most of Saturday chasing fuel problems. The car was running pretty lean on boost, and also pretty hot. First we removed the mechanical "lift pump" from the loop, realizing it may be a restriction for the electric pump at higher flow rates, but that didn't help much. We also discovered our "locked-in" distributor actually lost about 5° of timing at high RPM, so we set it to 20° initial and ~15° once the boost came on.

A decent view of the front of the car while Bob and I try in vain to find a good place up there to mount a trans cooler. (Note the cutouts on the front underside of the hood to clear the top of the intercooler; the car now uses hood pins.)

Meanwhile we put a new belt on the Olds, ran it through tech inspection first, sent out the first driver shortly after the green flag dropped, saw the car come back in two laps later with a destroyed belt, discovered a mismatch between the belt width and the alternator pulley, sent my girlfriend Hayley back to NAPA for another belt and a new alternator, hooked it all back up with a different pulley and a modified upper bracket, and then sent the driver back out. She was towed in 20 minutes later with the back half of the driveshaft missing and, even worse, one of the ears broken off the differential yoke. :shock: The Olds ran most of a full 24-hour race last year with horrible vibrations from the driveline when the utterly undamped rear suspension would bounce around every corner; I guess one race's worth of that was enough for the 77-year-old driveshaft. We briefly considered swapping in the Dart's recently removed 8-1/4" and finding a driveline shop that would cut and paste a shaft for us on a Saturday afternoon, but the Olds is a coil spring rear with trailing arms. No one wanted to reengineer that in the paddock while also dealing with Turbo Dart teething issues, so the Olds was retired for the race.

After the Saturday race session ended (and we watched two different cars get crushed with a tank), we dug into the fuel delivery system. The Aeromotive regulator had never actually been used (Shawn ran a mechanical pump with a threaded fitting in the air hole for boost reference), so it was our prime suspect. No matter how we adjusted it we couldn't get the fuel pressure on the outlet to come up. After several iterations of plumbing changes, regulator disassembly and reassembly, and looking up bad instructions on the internet, we finally found the problem. The pipe thread plugs and AN adapter fittings that Shawn had pre-installed on the regulator were too deep; they stopped the poppet from fully seating. So it was always bypassing most of its fuel to the return. We removed them, ground them all down with flapper wheels (far from the first freehand work I'd done with an angle grinder that week), and reinstalled everything. Voila, we had adjustable regulated fuel pressure.

The track was already cold, so Bob took the Dart out on the highway to test it under boost (it hasn't had the inspection renewed in 4 years, but it has plates). Bob learned three things on his test drive:
1. The fuel pressure now obviously kept up with the boost; the AFR was actually down around 12 at full tilt.
2. Bob had neglected to reconnect the headlights when he had rewired half the car earlier in the week in a sleep-deprived stupor.
3. When a car that has historically been underpowered suddenly sees several psi of boost on a dark country road with no headlights, the driver learns what he is made of. (He is made of meat.)
Bob managed to stay out of the ditch and bring the car back in, whereupon we threw up our hands in victory and looked forward to a full day of racing on Sunday. (Ha ha ha...)

Meanwhile, we had also signed up to host the official Lemons potluck party on Saturday night. Carrie and Hayley thankfully agreed to do most of the heavy lifting here, as Bob and I were consumed with wrenching prior to the race. It was a good time, with lots of food and even some hand-crafted beverages from various teams. Because Lemons turned 13 this year, we also decided it was about time to celebrate a Car Mitzvah. So after enough of the aforementioned beverages had been consumed, we performed such traditional rites as reading from The Book (of Haynes), lifting someone on a chair (with four floor jacks), poorly executed karaoke, and breaking a stack of (plastic) glasses by driving through them with a kids' ride-on electric car.

Jeez, this post is long enough already. I'll come back with the Sunday story later!

Author:  SpaceFrank [ Tue Nov 19, 2019 8:39 am ]
Post subject:  Re: Turbo Dart @ MSR Lemons

[I accidentally posted this in the Boost & Nitrous section yesterday, so I moved it to where it actually belongs.]

Author:  Rob Simmons [ Tue Nov 19, 2019 1:18 pm ]
Post subject:  Re: Turbo Dart @ MSR Lemons

Nice race report Frank! Thanks!! I miss Lemons... We'll get back at it soon,... I hope...

Author:  SpaceFrank [ Wed Nov 20, 2019 3:48 pm ]
Post subject:  Re: Turbo Dart @ MSR Lemons

I added more pictures to try and break up the impenetrable wall of text.

So... Sunday morning we awoke, nursed our hangovers, and belted Anton into the car. Anton is basically "The Stig" of Lemons. He has driven more Lemons races than any other person (by a long shot), and he has so much experience with so many different types of vehicles that he generally knows how to fix your car while also being able to drive it faster than you can. He's also one of the nicest guys on the planet. He signed up to race both of our crappy heaps with us at this race and had spent most of Saturday helping us diagnose Turbo Dart. Anton took the Dart out and came back in a few laps later with the following report:
1. It's pig rich all the time, like 9-10 AFR until the boost comes on, then maybe 10-11.
2. It's a total dog until the boost comes on (whereupon it becomes a rocketship), and
3. It overheats quickly.

This led to 4-5 iterations of us making changes to the car, sending Anton back out, and him coming back in saying "it took a little longer to overheat that time." Changes we made include the following, all of which seemed to help a tiny bit:
-Disconnecting the "pusher" fan on the oil cooler after discovering it was actually "pulling" the wrong way
-Checking our ignition timing and adding 5 degrees initial (for a total of 20°) after discovering that our "locked out" dizzy actually retards 5° at high RPM (for a total of 15° under boost) [I listed this on Saturday, but I now remember it was Sunday during the overheat-a-thon]
-Cutting more metal out of the valence panel to expose the bottom corners of the radiator, bending it down to make a crappy air scoop
-Adding a gutted thermostat (we'd previously run without one)
-Cutting a forward-facing flap in the hood behind the radiator and pushing it down to make an "extractor" scoop

Other stuff we did, not related to the cooling system:
-Shortening the kickdown mechanism after Anton reported the trans dropping from 3 to 2 with way too little pedal engagement
-Compression test to confirm head gasket integrity: results were 140-150 psi across the board (with the plugs out but the throttle plates closed, which I realize should have been open)
-Leaning out the idle mixture a bit to try to help the rich condition (and then putting it right back when it wouldn't idle right)
-Adjusting the wastegate again to try to limit boost (We'd done it the previous night, and it didn't help either time; the turbo would still put out 10 psi if you kept your foot in it)

After enough of the above airflow mods, the car got to the point that it would maintain ~230 °F as long as you babied it around the track. Anton said as soon as he started racing, the gauge would max out at 250, but easing off would eventually get it back down to 230ish. Overheating was strongly correlated with boost and/or high RPMs. More stuff we tried that didn't seem to change anything:
-Replacing the intercooler with a straight pipe, because it was blocking the upper 2/3rds of the radiator (this was a bad idea that we should have undone as soon as it proved fruitless, but we didn't)
-Flushing the engine and radiator with clean water (while running) until the (originally brown) water came out of the upper hose clean, whereupon we discovered that the water flow would actually stop if you revved the engine high enough.
-Pulling the water pump, not seeing any crud in the front of the water gallery, verifying integrity of the (8-blade) impeller, and then cutting off every other blade since we figured it was cavitating (it's now a 4-blade)

Here we are pulling the radiator so we can subsequently pull the water pump:

If you've actually read this whole mess of a race report, you'll remember I mentioned that this block (with this water pump, but a different head) always ran a little hotter than our original motor (210° under race conditions, NA and stock compression). At this point we decided we probably had one of the following issues:
1. A water pump impeller spinning on the shaft at high speed. We never heard a squeal, which rules out the belt slipping. To me, it also makes it unlikely that the external fitting (that we pressed down the shaft for fan clearance) was spinning on the shaft. It's hard for me to ignore the "flow test" result we saw when flushing the coolant, where water would stop coming out of the upper hose at high RPMs and take several seconds to recover. We didn't repeat the "flow test" after cutting off half the impeller blades, but it didn't make a lick of difference in the temperature behavior on track. So cavitation also seems less likely now, but it could still be a factor with us slightly over-driving the pump.
2. An internal problem with the engine's cooling jacket. The more I think about it, the less likely this seems. The only way this could explain the flow test results is if there's a moving clog that only closes off at high engine speed.
3. We also got comments from several people that we need to duct air into the front of the radiator better, which is true; there are some gaps on both sides of the core support after making room for the intercooler. But I doubt this is the root of the problem. I think all the airflow mods we made were band-aids on a mechanical problem.

We couldn't get a new water pump and modify it to fit our new engine bay in time to make the end of the race. We put a hard cutoff on our band-aiding efforts of 1 hour before the checkered flag, so that Matt and I (who hadn't driven the car yet) could get some seat time. I went out with an hour to go in the race. I experienced BOOST for the first time, which was awesome: after driving the car with a stock engine for the past year, it felt like the front wheels wanted to come off the ground when the magic snail finally spun up. But the car was severely hamstrung by its low to mid-RPM performance, and it still would max out the temp gauge after a lap of hard driving. I backed off for a couple laps, let it cool down to 230, and then went for another fast lap. I noticed something funny with the transmission under load, but I can't remember if it was an erratic 3-2 downshift or it just not wanting to upshift into 3rd under full throttle. Somewhere on the back straight, it dropped into 2nd under full boost and revved to about 6000. I slowed down and realized I no longer had 3rd gear at all. I babied it around the track for another lap, playing with the shifter buttons, but 3rd wouldn't come back. I pulled off and returned to our paddock spot.

One thing I've forgotten to mention until now: After the car gets hot, the pushbutton shifter will no longer engage Neutral or Reverse. After sitting for a while you could plunk it back into any setting, but it consistently would only engage D, 2, or 1 when hot. We got around this by jacking the back end of the car up when it came in to cool down (to allow the engine to run and keep circulating water), and clearing our head-on paddock space (where the Olds was sitting) to create a pull-through path. The car hasn't had a neutral safety switch for a while, because we've actually had this problem before, but I honestly can't remember how I fixed it last time. It probably has something to do with the cable adjustment, but I never had time to screw with it at the track. I didn't want to troubleshoot it with the car in gear on jackstands and everything hot to the touch, anyway. But that's another standing issue that may be related to the temporary loss of 3rd gear. (Did I say temporary? I did! Read on if you're still bored...)

With only two forward gears in the trans, our speed on track was limited to "dangerously slow," so we decided to stay off until the very end, when we would limp out to take the checker. Matt wasn't interested in getting in for a "victory lap," so I got belted back in and pulled onto the track with about 8 minutes left in the race. This was actually earlier than I intended (I hadn't wanted to be a rolling roadblock any longer than necessary), but I quickly discovered that I magically had 3rd gear again. After about a lap of babying the car and verifying that 3rd didn't drop out again, I decided "well, now's your chance to set a fast lap." When I got back to the start/finish line, I started giving her hell. I got all the way around to the back straight, started accelerating rapidly, and saw the boost gauge all the way at 10 psi again (we'd been trying to dial it down to 8).

I don't remember any loud bangs, but at that moment I experienced a sudden loss of power followed by the cab of the car filling up with smoke. I coasted along the side of the track trying to determine if I was on fire, and as the smoke started to clear up I realized the engine was still running. Giving it more than a little throttle caused the smoke to start building up again (I couldn't tell exactly from where), but I kept moving, had great oil pressure, and the coolant temp was actually starting to drop! I figured if the car was actually on fire I'd probably see a black flag, so I decided to keep driving until the checkered flag dropped... another two laps. (I made sure to put my boot in it when I came across the line to give the grandstands a good smoke show.)

Here's me driving the wounded car off track after the end of the race. (So far I haven't found any pictures of it actually on track.)

In the end, we did take home some hardware. There was another team that also wrenched on their car all weekend, and also contributed a lot to the party on Saturday night, so between "Most Heroic Fix" and "Life of the Paddock," the judges actually couldn't decide which trophy to give which team. So they awarded both of them to both of us and let us decide which one to bring home. (We already have two Heroic Fix trophies, so we took home Life of the Paddock.)

We've got a lot of work ahead of us before our next race in late March. Finish building the actual race engine that we didn't have time to finish (hopefully in a way that gives us better mid-range power), improve airflow some more, test our running temps with a new block (which has actually been cleaned inside) and new water pump, investigate the transmission issues, get the carb dialed in, figure out how to reliably limit boost to 7-8 psi, and fix whatever is grinding in the right rear brakes. I'll be asking a lot of questions on the forums in the next month.

Author:  emsvitil [ Wed Nov 20, 2019 7:28 pm ]
Post subject:  Re: Turbo Dart @ MSR Lemons

Is there a spring in the lower radiator hose?

My thought is the lower hose is collapsing

Author:  SpaceFrank [ Thu Nov 21, 2019 7:02 am ]
Post subject:  Re: Turbo Dart @ MSR Lemons

The lower hose is actually two pieces joined by a rigid union, in order to reach the outlet on our big Summit radiator without hitting the belt. I don't think it would collapse, but we weren't specifically looking at it during the "flow test." I'll add that to the list of things to look at.

Author:  Dart270 [ Thu Nov 21, 2019 8:29 pm ]
Post subject:  Re: Turbo Dart @ MSR Lemons

Man, that was (is) a journey! Thanks for the writeup. Could almost feel/smell the boost and wrenches on hot grease... Hope I can join this fray sometime soon.

I bet moving to another block/engine will help. Hard to see the radiator is not big enough or not getting enough flow.


Author:  Rob Simmons [ Fri Nov 22, 2019 5:39 am ]
Post subject:  Re: Turbo Dart @ MSR Lemons

Thanks Frank! I felt like I was there.

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