MGB carb circle-back

So yeah.. it has been a long time since I've posted much. Life has been full. Today, I will just close the loop on the carb deep cleaning and re-gasketing. I will try to get back here relatively soon with some other goings on. I thought I posted this update last Fall when it happened, but I clearly didn't.

Just a reminder, Oliver (1978 MGB) has a SK Racing or OER Racing side-draft carburetor. These look very much like the DCOE Weber and even can use some of the jets from a Weber. The accelerator pump and float level can be adjusted from the outside and the main jets can be accessed through a cover on the top. So, very few of the changes one usually makes to a carb requires the carb to be removed from the engine. The inlet pattern matches the Weber DCOE, so you can use a more readily available intake from Weber. Even the 4 bolts on the bottom are the same so you can use a Weber-intended heat shield like I did. Curious about getting one? Here is a source in Japan (these are a go-to carb among Nissan/Datsun enthusiasts I am told). Those who have them rave about them. Except me, so far. I hope to be among the celebrating majority soon.

Almost a Test Start

Setting the stage, I had a crisp fall day to take a look at Oliver, the 1978 MGB. I wanted to see if the carb work was the winner for his bogging down when I hit the accelerator pedal. I pulled his cover off, hooked up the battery and added some fresh fuel. I had pumped the tank dry when I removed the carb; not sure if I mentioned that last time. Anyway, I turned the key to run. I got the satisfying sound of the fuel pump running and then that not-so-satisfying gasoline smell. I went around to the right fender and could see fuel shooting out towards the radiator. Eeek. I turned off the key and then spotted a failing fuel hose. After a brief rummage through some boxes in the "tool shed" I found some suitable hose and had the system buttoned back up relatively quickly. This is as good a time as any to remind all my fellow old-car owners to replace your fuel hoses.

Actual Test Start

With the new hose in place, I returned to the driver seat, turned the key to run and waited for the fuel pump sound to change, letting me know that it had established pressure. With the earlier fuel line failure, the smell of gas was still present, so I walked around to the front to inspect for leaks. Nope. So, I turned the key to run and he started pretty fast. It was rough, but I could keep him idling at the carb by pulling on the accelerator cable.

Fiddling with it

I focused first on getting the idle jets set. I followed the basic set-up rule of turn all the way in, then back out 2 turns when I did the reassemble. In theory, you should be close at that point. I did not notice much difference when I moved the screws in and out more than 1/2 a turn. I think I eventually settled on them being out just past 2 turns. I expect when fully warmed up and in an expert tuner's hands a different setting will be found.

Then I shifted to the idle speed screw. Doing this on your own without a hand-held tach is kind of comical. You walk to the driver door and look at the tach. Note the speed and if it needs to be faster, go to the carb and adjust. Then walk back and see if you hit your target. If not, wash-rinse-repeat. I am sure there are much more experienced mechs out there who can hear the right speed or have a hand-held tool so you aren't getting your day's steps in 2 steps at a time like that.

Last, I wanted to see if I had solved the bog-on-accelerate. So, I yanked on the accelerator cable at the carb and.. bog. Sadness. In my time during the rebuild, I spent more time looking at the exploded diagram than I had before. I remembered there was an accelerator circuit, and located the screw on the top of the carb. In the image on the left, here, the screw is the big one on the furthest left, near the intake-side of the carb.

When I dismantled the carb, that screw was nutted all the way down snug. So, either the prior owner had torqued it down or I did at a time I don't remember. Regardless, I started loosening that screw (lefty-loosey) while I rev'd the engine. And the bog started to fall away. I was able to rev it fairly quickly without the engine starting to die on me. I stopped loosening it before I was able to yank on the cable as if I was going from foot-off-pedal to pedal-on-floor. I believe what had been happening was that the accelerator circuit had been flooding the engine with too much fuel when I pushed on it. Now, it was getting the right amount of fuel to account for the big burst of air from the opening of the butterfly without overcompensating. Looking back, this has probably been the issue all along and the cleaning/resealing may not have been necessary. In the end, I don't care, and cleaning the carb will only pay more dividends anyway.

Wrap Up

So, did I go for a test drive? No. Why? The brake bleed attempts that I have done since I replaced the master cylinder have not gotten the brake pedal predictable. Rather than have a spirited drive to celebrate, I waited for the tailpipe to cool down and put Oliver's cover back on (queue the sad trombone). One of the first things I will be doing this spring is another brake-bleed attempt. I may just hobble over to the local Firestone and have them do it. I just want to drive this guy now and his spongey brakes have been a blocker for too long.

Also on the list are changing the 12V source for the voltage gauge from the purple circuit which used to power the clock to the switched and fused green circuit. I have a few other odds and ends I need to complete before Oliver is "finished", the largest of which is replacing the body-to-windshield seal so he can be driven in rainy weather. There is always something with these old cars and I really wouldn't want it any other way.... so long as the something doesn't leave me stranded on the side of the road outside cell range.

Well, that's it for this time. Sorry it has been so long. Life gets busy and I have not been able to play with my cars much. I am working through the permitting process to get a garage built so there will be posts about that, and then playing on cars (and blogging about it) can return to a year-round sport. Thanks for tuning back in, and I hope to be more frequent in 2025-

MGB - Side Draft Carb fun

Today, I return to the little British car: our 1978 MGB, Oliver. Oliver has sat unused for too long. I had been having considerable and increasing trouble just getting him to start and run. So, earlier this year, I removed his carburetor for dis-assembly, cleaning and re-assembly. I did the removal and tear down what feels like months ago, and just completed the re-assembly. So, while this post may feel like a couple of consecutive weeks of fun, it's really a little from March, a little from June and a little from last weekend.

Removal and Tear Down

re-assembled

As is the case with most things on a small car, removing parts requires some flexibility not needed for larger cars of this vintage. Still, removing a carb is not complicated, but I encourage you to take pictures. If your life is anything like mine, you may intend to be back to this in a few days, but days can become months really fast. Anyway, remove the air cleaner. Remove the fuel line (pinch it off first and then plug it). Disconnect the throttle and choke cables. Then remove the carb from the intake. With the side-draft weber (DCOE) and this SK Racing/OER carb, it is held to the intake with 4 nuts threaded onto studs emerging from the intake. The DCOE and SKRacing carbs use the same intake, by the way. Once removed, I stuffed rags into the intake to prevent critters from climbing into my engine, closed the hood and re-covered him. I took the carb over to a bench in the back of the little garage attached to the farmhouse.

At the work table, I started with the most obvious things and worked my way inward. First, the inspection cover and top half of the carb was separated from the main body. I removed every slotted bolt and whatever lay beneath, taking pictures as I went. Last from the top were the air correction jets and then I removed the set screws that held the venturi to the main body. The main body was effectively disassembled, so I shifted to the top half, removing the float, the fuel inlet bits and the choke bits. Last, I pulled the little cover or plate that faces the intake when installed. I am sure someone who does this often would have done it faster, but I needed to chronicle it so I could re-assemble later.

Carb Cleaning

remove from car day

I started like most folks probably do: shooting the carb with rattle can carb cleaner and gently scrubbing it with a toothbrush. I focused mostly on the exterior with the brush and let the carb cleaner do it's magic on the little holes without brushing. Satisfied that I got the worst of it, I pulled out a razor blade and removed all of the gasket bits and rubber seals. Then, put together a ultrasonic cleaner soaking tank with solution designed for carbs. I had read online that some folks will use Simple Green or other things, but I figured the correct solution was far less expensive than a replacement carb in the event those advisers were wrong.

The cleaners, well, the one that I got, but from what I read, many of them have a setting to warm up the solution while doing the ultrasonic. From what I read, there was some level of concern about how well they actually maintain temperature and that sometimes they can run the solution too hot. Since the solution is concentrated (read: need to add water), I decided to use boiling water and when poured into a room temperature solution, the overall temperature would be sufficient. I ran the carb body and all of it's pieces in the ultrasonic cleaner for multiple 20 minute cycles. Once I was satisfied that the carb was as clean as it was going to be, I moved it and the parts into a bucket and rinsed them with water. I then set everything out in the sun to dry.

Rebuild Kit

great kit

Unlike a Weber DCOE, the SK Racing/OER carb is not exactly common in the US. It is not generally sold here; it is much more popular in Japan. So, finding a rebuild kit for an obscure, foreign and old (time is relative) car part was time consuming on it's own. I was able to find a single supplier of a kit, a person in Japan with a storefront on eBay (Bprojects Japan). While I have a healthy skepticism of eBay sellers, deals and parts, I really had no other choice. The kit I received was incredibly well set. It included the major gaskets, replacement air correction jets and springs, new crush seals for the pump jets, a pair of ball bearings for the "pump non-return", a pair of copper crush seals for the fuel inlet and a big collection of rubber o-rings. It really had everything except a manifest indicating what part number each bit was for and the gasket for the jet inspection cover was missing. At this point I realized that I took pictures of the disassembly, but failed to take pictures of the rubber seals as I cut them off.

Re-Assembly

view from firewall

With my laptop open to the SK Racing carb manual, and my phone open to both the pictures I took and a blurry exploded view drawing of the carb, I started putting it back together. I started with the last picture I took and worked by way backwards through them. The only step I took that I had to undo and do again was the placement of the gasket between the top half and the main body. I had assembled the float, but the gasket needs to set above the float, which had I thought about that for a second, it would have been obvious. The float did not fit in the opening in the gasket, nor does it ever need to along its travel path. Also confusing was where the pair of ball bearings and small rectangular rods went. Process of elimination worked well here, choosing to do other things until it was apparent what hole those dropped into.

I used liquid gasket-maker for the jet inspection cover. That stuff makes a dark sticky mess. The instructions on the bottle say to let it dry "for a few minutes" before putting the 2 pieces together which need a gasket in between. I let that sit for well past the recommended few minutes and it was still very wet.. and even after letting it sit in the sun the stuff didn't dry very much. So, I did everything else install-wise and add the inspection cover dead last.

While I had the carb in hand, I decided to add a heat shield to the underside. The header that I installed has a thermo-barrier powder coating on it, but I know from having the hood open after driving it that a ton of heat is still getting into the engine bay. I suspect the source is the header (or the radiator), and the best thing I could do for the carb is to help prevent heat from getting to it. So, I got a DCOE carb heat shield from Pierce Manifolds. The mounting bolt pattern is designed for a Weber DCOE, but the SK Racing/OER is exactly the same in this area. The venturi maintenance holes line up, the cut-outs for the intakes, etc. it all just lines up. The heat shield is heavier and thicker than I expected, but I expect it will do exactly what it is intended to do: block and route-away heat rising from the exhaust.

Install

re-install day

As easy as the carb was to remove, installs always take longer. This bugger was no different. First, the carb mates to the intake with these thin (maybe 6mm thick?) plastic isolator bits between the carb and intake. On each side of the isolator resides a rubber O-ring that is set inside a groove. So, you are managing a carb, 2 isolators and 4 O-rings at one time. That required some dexterity.

I discovered that the heat shield has a small tab on the intake side that would hit the center header pipe. Recall, the MGB has a Siamese head, so the middle 2 cylinders share an exhaust. The PO had a home made exhaust manifold with a center pipe effectively pointed straight down. The header has a more typical curve. So, the heat shield came off and I adjusted that tab to point angled upwards so it did not hit the header pipe, but actually will shield the top-most end of it. Then, I realized that I could not address the lower mounting studs with heat shield installed so I removed it again, re-installing after the carb was nutted down into the intake.

From there, the install was about what you would expect, complete with a dropped bolt under the car. I had to reverse the spring-return arm on the carb as well as flip the fuel inlet. Still, it was relatively smooth, hooking up the fuel line, control cables and air filter.

No Test Fire

By this time, I had sweated my way through most of a summer afternoon and cleaned liquid gasket maker off my hands more times than I'd like to count. As much as I wanted to enjoy the sound of the engine running, I chose instead to take the limited win: Oliver was in one piece. Boo and I went to the county fair instead of test-firing Oliver's engine. Now, Oliver is covered back up, again waiting for me to have a few hours to test fire his engine and fiddle with settings. I sincerely hope the tear down / deep cleaning was what he needed. I'll post an update when I have one.

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That's it for today. Thanks, as always, for following along-

Door Cards

Today I will be picking up where I left off regarding the doors. As I described in my last post, the front doors now open, close and lock like a real car. No slamming, not funny jiggling of the handle, etc. Just open, close and lock. Well, the passenger door lock is different from the driver, but I'll swap that out once I find all my parts. Anyway, since I had to remove the cards to fix the doors, I thought I would take the opportunity to improve them.

Door Cards As-Was

foamed card installed

With operational doors, I got to thinking about how to get the door cards to hold to their respective doors. The Arizona gentleman who ran the business creating and selling these ABS door cards was looking to sell off the business a couple of years ago, so I imagine that has happened by now. He had a mixture of molly-based fasteners delivered with the cards. Either the fastener was a screw that dug into the molly which was pushed through the card into the original mounting hole or it was a push-to-hold plastic bit. Regardless, the molly's did not hold in all of the original mounting holes on my bus (YMMV). This could have been poor implementation on my part, something particular about Hapy or just less-than-ideal engineering on the fasteners. It doesn't really matter; for Hapy, they did not work. When combined with the slamming doors, the door cards would rattle and Hapy had a very junky vibe. Now that the doors no longer need to slam shut, improving the cards adherence to the doors will help un-jalopy Hapy that little bit more.

Door Cards, Mounting Upgrade

broken M4 riv-nut bit

To remedy the floppy door cards, I tried a more permanent solution: Riv-nuts and bolts. The plan: into each original mounting hole in the door, I attach a riv-nut (it's a nut that is applied with a rivet gun, basically), and then send a bolt through a washer and then the card, into the riv-nut. Such a simple plan, and while a little time-consuming, it was easy to do. Of course, I found that not all of the original holes were the same size. To fix, I used some as large as an M6 or as small as an M4. I think this is why the supplied molly-based fasteners did not work as well: the M6-sized holes were simply too big for the molly and they fell out. As shown in the picture here, too much pressure with the riveting tool and you can break it. Once I had all of the riv-nuts set, I shifted to the cards themselves.

Noise Abatement Revisit

setting riv-nut

While I had the door cards out of the bus for repairs, I applied a thin noise-absorbing closed-cell foam to the 3 cards. This material was among the things I got a few years ago when I did the sound deadening effort, and it's application to the door cards was part of that plan. At the time, the research I did (See Hapy Noises - Part 2) indicated that multiple attack vectors would bring the best result: Constrained Layered Dampener, an open cell sound deadener like Jute Thermal and then Mass Loaded Vinyl. These all really address reducing the impact of external (and mechanical) noises transferring into the cabin. Any noises or sound that make it into the cabin which are not absorbed by the seats are prone to bouncing around. I placed some larger acoustic panels (these) under the upper bunk, in the slot where the original sunroof used to go. I believe they are helping absorb some ambient sound. I also covered the ceiling with Mega Zorbe to address the sound reflection and ambient sound absorption. In the picture on the right, here, you can see the MegaZorbe applied to the inside of the outer door skin. 

Based on the tests I did at the end of the effort, the only real gains as-measured were in the "around town" (under 40mph) zone. Decibels at idle or on the highway appeared about the same. In practice, however, using a less complex "measure" like how loud we have to run the stereo to hear it on the highway, it is definitely quieter. An even less precise indicator is how loud we need to speak to each other to have a conversation: barely louder than we talk at home, which is quiet (no yelling house) where we used to have to almost yell without the stereo on. So, I am setting aside the scientific evidence and embracing the anecdotal: this implementation of the sound abatement absolutely and significantly improved our road tripping experience. I may take more readings because the numbers I took before continue to bother me.

Door Cards, Reflective Sound Absorption Added

applying the foam

So, with all that context, I decided to press forward on my original plan to apply the thin foam sheets to the hard plastic cards. I started with the cards along the sleeping deck, running from the rear hatch forward along both sides under the windows to the rear of the rock-n-roll bed (1 foot tall by about 4 feet long). I started here for 2 reasons: it was very easy and the plastic cards were jarring-cold when bare skin pressed against them while sleeping. The foam definitely improved that.

For the slider and front doors, I simply traced the door shape on the peel-off paper side of the peel-n-stick foam and cut along the line with scissors. I aligned the cut along the card and peel-stuck them down, working from one corner, down along one side and then across. I will be applying carpet later, but felt that the foam might help reduce the reflected sound while also providing a cushion under the carpet.

With the foam applied to the cards, I considered the game of "which bolt fits" for each mounting point. I could have just started trying bolts, but that felt like an exercise in frustration. So, instead, I grabbed some painters tape and marked to the outside of each hole (where the card would not cover) which bolt size to use. I set the front door cards in place using the door pull to hold the card in the right spot. Then, I simply sent bolts through a black vinyl washer and then the card into the door. Once mounted, I removed the tape. Easy-peasy. If you do this, I suggest that you do the corners first, and only threaded enough to hold. Then, skip around the card, and have all of them like that before you start tightening. Then, again, start with the corners and pay close attention to the bottom edge near the vent. These ABS cards fit perfectly, but the one hole near the bottom align the trailing edge of the door did not line up for me and I had to skip it. YMMV, of course.

slider door foamed

The door card kit included panels for the wall under the driver-side jealous window and for the partitions behind the front seats. I have yet to do those cards, but I am holding off on doing those until I am ready to fast-follow with carpet. The foam is not as scratch-resilient as the hard plastic, and those cards take the brunt of the abuse when camping or music gear is loaded, unloaded and in-motion. So, I will apply the foam and the carpet at the same time. All of that will happen at some point in the future. As it is right now, there is that little bit less noise reflection happening and when bare skin touches the side of the sleeping area, it no longer triggers a shuddering wake up. We are taking the win.

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That's it for today. Thanks, as always, for following along-