Diagnosing Low Max RPM: Margaret Thatcher Needs her Coffee!

During the practice day for the 2013 LeMons Capitol Offense race, it was hard to NOT notice our MGB GT had somehow dwindled to an upper limit of 4500 RPMs, which means the very important upper 20% is missing, right in the power band. The poor girl is weak already, and a limit of 4500 would literally (and figuratively) knock us out of the race.

Sigh.

We check the pedal linkage, it was OK.

The accelerator cable was making grinding noise; we sprayed into the cable all we could with silicone spray, to some-but-little effect.

Scot noticed the butterfly gears on the Weber DGV Downdraft Carb were not articulated 100%, so we bent and adjusted the cable bracket all we dared to extend the motion, and then greased the hell out of it. To no effect.

We were getting driver stints in between tweaks, and by the time we fixed the butterfly gears it was time for LeMons Tech Inspection, which we failed, so we dropped the whole "Upper 20% power missing" because Tech had rendered us with a "Upper 100% power missing" situation.


After the sobbing subsided (2 weeks later) I finally got back to diagnosing the issue.

First up: Fuel Delivery.

We had previously had mega-carberator problems with gunk at Summit Point 2011, so that was a thing.

Remembering the Jet Ski in-tank fuel filter I had added 2 years prior, I decided to make sure the carbs were getting enough coffee fuel.

1) get a glass jar, clean it out, drill a 3/4 inch hole in cap (or whatever size your fuel hose is, 'natch)



Guinness does not come in clear bottles, so you'll have to resort to 9 oz poison bottles.

2) disconnect fuel line from carb.

Might want to make sure fuel pump power is OFF before doing this, dumbass.



 3) stuff this thing in that thing:

Probably illegal in New Jersey.

 

4) apply power to fuel pump, count how many seconds it takes to fill up bottle (6 or so seconds). Do not drink, though it would be healthier than what originally came in the bottle. I messed up timing this, in that (1) I didn't run the car first to purge the air, and (2) I didn't use a timer, but counted one-mississippi.

Pretend this pic is rotated 90 degrees counter clockwise.

5) now, don your best Saran Wrap Fetish Gear, and give your Fuel Cell a proctal exam:

Definitely illegal in New Jersey!

6) wave to neighbors, note which ones wink, reach into fuel cell and fish around for fuel pickup and in-tank filter:

This may feel uncomfortable...

7) remove said filter (and small connecting hose):

Possibly clogged filter removed, immediately wash arm with 30 gallons of soap

 

 8) change crappy-ass "Fuel Pressure Regulator" which is actually just a friggin fuel restrictor from 4.5 PSI to 6 PSI; retest fuel flow, receive same damn 6 second time.

Crappy ass.

 9) Be sure to leave bottle cap in fuel line so that you look like the complete tool that you are, buttclown.

Honest, it's a heat shield!

10) test drive that bad boy - 5500 RPM, bitch!!!!!   Dunno if it was the pressure regulator (probably), clogged fuel filter (probably), or the need for a saran wrap proctologist exam (probably)... but whatever - I'm happy.

Last check I need to do it run it HOT, and see if 5500 is still reachable; not too worried since the 4500 limit was all day, even once cooled. Sounds fun.

Rev Limiter for MGB Survival

We surmised that we over-revved the MGB engine in the first race of 2012, because:

    1) there was no tachometer

    2) there was no speedometer

    3) the engine is underpowered, causing drivers to floor it all the time, for the entire 14 hours

    4) the 4 speed manual transmission really really needs a 5th and 6th gear, causing drivers to floor it all the time, for the entire 14 hours

So we installed a tachometer from another MGB and rotated it so that 5250 is pointing straight up - she really could use a "shift now" light for gears 1, 2, and 3 and a "sit back - you're just along for the ride at this point" light for 4th gear. Some day.

We installed a Rev Limiter instead since our driver pool is often hungover and barely focusing on the road ahead much less the little numbers on the tach.

The Rev Limiter we ended up with was the Procomp Single Stage Rev Limiter PC2031, and it did just fine as far as well could tell. 

1-800-Dial-a-Prayer!

Also on the menu was a new fuel pressure regulator, the Holly Fuel Pressure Regulator had died after a failed attempt at rebuilding the internals with new rubber and filter element. Oops.

All those pretty blue AN fittings were a real pain to match up, but they sure mate nicely and are clean etc etc. Soooo un-MGB like.

MGB Fuel Pressure to Weber Carb should be about 4.5 psi and very shiny.

Race Report: 2012 Capitol Offense - The 24 Hours of LeMons

Race Report: 2012 Capitol Offense - The 24 Hours of LeMons at Summit Point Motorsports Park's Shenandoah Circuit in West Virginia

The Mighty Shenandoah - an MGB Friendly track if there ever was one... 22 turns, no waiting!

Never Mind the Bullocks Here's Gormless Racing MGB!

We had over-revved the engine at the last race and grenaded the engine, and so for this race we had installed not only a tachometer but a Rev Limiter as well, set to 5000 RPM - the suggested point at which cylinder 3 bearing starves for oil, melts down and goes all shambolic.

It worked great as far as we knew - engine didn't blow in any event. We sailed though Tech Inspection.

50 Years, 50 Horsepower, whatever

In the first 40 minutes of the race the accelerator cable popped out of the trunnion and left Driver Carl idling around the remaining 80% of the track, until pulling into the paddock. Remarkably no other teams noticed the speed difference. The FAIL was poetic justice, as Carl was the culprit that had gerry rigged the connection in the first place.

"I have NO IDEA why that trunnion would fail. Weird. Why do you ask?"

Dave and Scot hacked in an emergency repair and it lasted the rest of the race. About an hour total was lost.

"Ah HA! Here's the problem - Hamster wheel came off it's axle."

SEEMS LEGIT

We had also noted a half quart of oil "missing". No one would admit to taking it, but our sister BMW team was in the paddock beside us, and something about Germans stealing English oil rings true - they would not confess however.

2 hours and 15 minutes into the race, Scot driving... the entire pedal assembly holding the brake pedal and the clutch pedal fell off! oops. Scot was nonplussed however - explaining that one bolt was still sort of hanging on, and if he tilted the assembly correctly he could EITHER shift OR brake, but not at the same time - which was fine by him, as he swore to never use the brakes anyway. We noted another barrel of missing oil, so we tightened up the oil cooler lines at the engine and adjusted the connection angle.

"Look MA! I made it all the way to Turn 17!"

The rest of day one was only fun fun fun for us, cranking out the laps - slow yes - but laps none-the-less. Added 1/2 quart oil here and there, while wrapping various oil lines (there seemed to be a 'mist' around the distributor side).

Our poor sister team was pulled into a mashup, and smashed up their front end, enough to moved the drive train an estimated 3 inches forward!! They spent the rest of the evening replacing engine mounts, radiator, and trying to get old Ali running again for the next day. Quite a crowd gathered to help out, late into the night.

:-(

The only 'event' we had Sunday was Dave was attacked through the Esses and the gang of cars sheared off the passenger side mirror!

Saturday Night's Race to the Emergency Room: note inebriated skateboarder hanging onto the moving Boat-Mobile... which would later hit a newish expensive car when doing donuts in the parking lot...

Barely any water loss, so maybe head gasket ok. Oil consumption may be valves, rings, leaky oil pan, or leaky oil cooler hose... or all four. Probably all four.

It wasn't raining, and so "Queenie" was mounted to the windshield wiper post and continued to disapprove of our driving the entire race:

No matter what you asked the old girl, it just wasn't good enough

The home-made Cool Shirt cooler & pump worked spectacularly; highly recommended.

All in all: we finished 64th out of 117 starters... pretty damn good for taking our time swapping drivers, having the pedal assembly succeed from the kingdom, and having only 50 horse power.

Race Report: 2012 The Real Hoopties of New Jersey - 24 Hours of LeMons

The MGB was all ready and rarin' to go for the 24 Hours of LeMons race The Real Hoopties of New Jersey at New Jersey Motorsports Park on April 14 & 15 2012.

Sometimes it takes 12 wheels to get a tiny 1500 lbs car to a race.

Nice open pit area, front row. So front row that the LeMons crew came over to inspect us early so we didn't have to wait in line! Classy! 

Those big gold "50" balloons later detached in the gusty wind and floated up into the next-door airports airspace... oops - sorry NORAD.

Safety Inspection found a few items, which we fixed pronto:

1. Some of the seat bolts were a bit loose which allowed them to move it a bit side to side, so we tightened them all up and added bolts to the back bottom of the seat for extra stability.
2. Bolts holding the seat back support to the seat itself needed spreader washers (the seat is aluminum and would tear easily).
3. Seat harness bolts needed tightening.

Since we had plenty of spare time, Bob & Scot replaced the Weber DGV Carburetor Accelerator Pump Diaphragm:

Blue engine bay, blue roll bar, blue engine, blue hands, blue shirt... gee, no wonder we blew the engine.

Poor Queenie the Solar powered forever waving monarch fell off the MGB 50th Anniversary Cake and had a bit of a mash up - we didn't recognize the portent for what it was until too late.

"I Shall Forever Wave No More Forever"

Having fun while it lasted:

Now that's what I'm talking about!

 My bad, turn 1, ran out of talent:

The tire mark is only halfway up the MGB fender - what's the problem?

Scot's first stint - came in and reported the drivers side front suspension "wobbles" at high speed. We told him to keep his elbow INSIDE the window, but to appease him we checked it out anyway... sure enough, the bolt that sealed the oil in the shock / dampener had vibrated a bit loose and was leaking oil. Yes, MGBs have dipsticks on the shock absorbers. We filled it back up and out she went, ready to rumble:

"Knock yourself out, buttplug!"

Scot was just happy that, since it was indeed the dampener, he could return to hanging his elbow out the window:

She wobbles at high speed, just like the Queen!

At the end of day 1, the car seemed a bit underpowered but was running good enough as far as we cared to admit, so we offered Steve - who had just come down to pit crew and see what was up with endurance racing - some seat time.

Unbeknownst to Steve, he prepares for the worst.

Remember that whole "If someone offers you something for free it's probably worth every penny" parable? Yeah, that... Engine Grenade in 3...2....1.... I think he only got 4 laps or less!!! Sorry about that.

The old MGB cylinder 3"Bearing Blender" maneuver.

Hey! You can't park there Steve!    Wait... why aren't you out on the track!?!

Manly tractor engines can cry too, you know.

The full extent of damage in the blown engine may be found in this post: Engine Done Blowed Up Real Good!

The other four drivers - notice the correlation between the still-running engine before the race and the smiles - 100%!

The MG is thinking: "Uh huh - put your asses on ME will you?!!? I'll show you bastages in about 7 hours!!

New Throttle Cable, Finally

Our throttle cable has always been a mess; not sure how it lasted endurance 3 races.

I tried to Tap-and-Dye the end of the new throttle cable so i could positively hold it in the Weber DGV Carb attachment bracket, but I positively failed to thread it. I reek with a tap and dye set, leaving a swath of destruction in my wake whenever I attempt it. I decided to quit while I still had a functioning cable and purchase (with actual money!) a proper cable end/attach/adjuster bit.

Both bike shops in Mt. Airy were closed on Sunday, so I resorted to raiding my backyard stash of old Ten-Speed bikes I had been stockpiling to make my Baltimore Kinetic Sculpture Race vehicle. Below is the victim, and the two pieces it donated:

The Cable Adjuster needed to be drilled out a bit so the new throttle cable end would fit, here you can see the nice shiny newly drilled inside, and below that the end of the new throttle cable:

Here is the final setup, with much improved throttle feel, less cable wear, less cable-falling-out-of-bracket-and-getting-throttle-stuck-at-wide-open-SCOT!, less badness overall.

Yeah us. Maybe we'll finish a few damn laps this year.

Bogging Down Exiting Corners - Weber DGV Accel Pump?

During our last few races (ok, all of our races), I've noticed the ol' chap tends to hesitate when exiting corners. Up till now I've assumed that's just the carb being slightly dirty or temporarily starved when stomping on the gas (right after holding your breath through the tight corners).

It's been nagging me for a year now; something's wrong, but not sure how to troubleshoot it without having someone hang on the hood while we drive around the track?

Then I stumble across this little gem of a description from the Pegasus Auto Racing Supplies catalog:

Accelerator Pump Diaphragm Assembly, Weber 32/36 DGV

 
If your car bogs down exiting corners, your accelerator pump may not be pumping! When the throttle is opened all the way from idle, the accelerator pump should deliver a shot of fuel directly into the carburetor throat. If this shot is not visible (with the engine off), the diaphragm may be ruptured.






You know what today is? DAY I GOT COOKIE!!!

Problem may still be elsewhere, but boy does that description fit! With all the crap and junk and dirt and bits and crud and grime and filth and rubbish and mud and garbage we pulled out of the tank and carb and filters at 24 Hours of LeMons Summit Point Capitol Offense 2010, it is very possible this contraption is hobbled.

Thanks Pegasus for the schoolin'. Order placed.

[UPDATE 2012-04-08] Either we don't have a Weber DGV, or Pegasus sent us the wrong part... either way, it don't fit no way no how. We need the part shown in photo above; the part we received was not 'square' and the brass pin in the middle was mush skinnier and was not spring loaded.

Bob found and took out the old part, and it looks like there could be a little leakage around the circular shape of the rubber is.

We put the original piece back in until we get our hands on the unobtanium accel pump...

Timing - Vacuum Advance System

Still in the works: Spent some time getting the proper size vacuum tubing and researching the aftermarket carburetor presently on the MG (it’s a Weber DGV). Hooked up the Vacuum Advance system on the distributor to the carb and it felt a bit worse, and was hard to start after stopping for gas at Exxon during test drive (probably an air leak). I used the handy-dandy MiteyVac (brake bleed system) that has a vacuum gauge on it to measure the vacuum on the carb – it is giving about 3 to 5 psi at the carb pip… but the distributor advance needed about 20 to 25 psi before it started ‘sounding like’ it was having an effect on the timing. So, more research needed; there is some contention on the web weather you hook the vacuum line to the manifold or to the carb for that model. I couldn’t find the right manifold adapter so there some hope of improvement yet.