Engine bay work continues today with the removal, cleaning, polishing and painting of the Mk1 Austin-Healey Bugeye Sprite. I've previously removed most of the engine accessories on the left side of the engine and the radiator. Having the radiator out of the way makes the removal process very easy.
The Mk 1 Austin-Healey Sprite has a cable driven tachometer powered by a "gearbox" on the end of the generator. Loosening the large brass nut allows the drive cable to easily slip off.
Disassembly of a Lucas generator is relatively simple. Two long thin bolts fasten the two end plates to the central generator body. Care was taken to photo how it all came apart, taking special note of wire connections and the condition of the brushes. All of the metal parts were dipped, dunked and polished. The body was sanded and given a coat of paint.
One of the interesting components of this model of generator is the self-lubricating rear bearing feature. The brass tube at the rear of the generator contains a spring loaded felt that is impregnated with high-temp grease. This should be serviced every 12,000 miles.
Here's the final product. As will be a continuing theme in my engine bay clean-up, I've elected not to paint the aluminum components. I've also not painted the pully and fan. I've seen this done both ways (painted / bare metal). I think this adds a bit of "bling" without adding additional chrome, etc. The clutch/brake pedal box and generator are now ready to be placed into short-term storage as I move on to removing the oil filter mount/adapter and the starter.
The Econobox Garage YouTube channel has put together a very nice video on How to assemble a Lucas generator as used in an Austin Healey Sprite MK1. Bugeye Build Episode https://youtu.be/Sk3dOYhdSpw
Ms. Scarlet, the 1959 Mk 1 Austin-Healey Sprite, came home with a number of issues that needed to be addressed before she could hit the road. The seller had disclosed that the right rear brake cylinder was leaking and would need to be replaced. Once I got her home, I pulled ALL of the brake drums to give them a quick look-see. As it turns out, there were leaks at both of the rear brakes, but the front brakes looked leak free. The decision was made to replace ALL of the Bugeye's hydraulics including the master cylinder, lines and slave cylinders. The first step in this process is to remove the brake/clutch pedal box assembly, complete with the master cylinder and pedals.
The first step in the process was to dismantle the various parts (lines, pedals, master cylinder and pushrods. Once removed, everything got a dip in a parts cleaner bucket and then Evapo-Rust to soak off all of the surface rust before further, more aggressive, cleaning with the Dremel and brass wire wheels. With all of the clean-up complete, the next step was to remove the paint from the pedal box.
With the clean-up and paint stripping complete, it was time to move on to the fun part . . . painting! Etching primer for the bare metal, then filler primer for filling in the pitting and sanding lines and finally the topcoat of black paint.
I made the decision replace the original Lockheed master cylinder with a new one from Bugeyeguys. Rebuild kits were ordered to rebuild the original master cylinder as a winter project. Before installing the master cylinder, it was bench bled in an effort to minimize (as much as possible) adding air into the system.
Econobox Garage has done a nice job of showing many of the parts and steps involved in putting the brake/clutch pedal box back together. One of the interesting things about his videos is that he shows many of his mistakes as well as his tips. #wdydtyst #whenifixsomething #DIYCarMaintenance #bugeyesprite #msscarlet
Our first 1959 Bugeye Sprite (Wally) came with numerous spare parts, including a spare 1098 cylinder head. Wally's previous owners had upgraded much of his engine and drivetrain with later-model MG Midget components like disk brakes, 1098 cc engine, ribbed case transmission and a 3.9 final drive. Barring any disasters I didn't anticipate needing to ever use the spare head.
Fast forward to 2023! This Summer we purchased a second 1959 Austin-Healey Mk1 Sprite. The big difference is that Ms. Scarlet has, for the most part, remained intact with its 948 engine, smooth case transmission and drum brakes all-round. So why the interest in that spare cylinder head now?
The cylinder head in question is a 12G295 MOWOG head purchased on ebay in 2015. It was described as a MG Midget 1100 Rebuilt Cylinder Head and sold for $355.00. The seller listed the following specifics: Magnafluxed, new guides, oil seals, resurfaced, valves ground and the spring pressures set. Casting fitted for larger intake valves. Should I consider using it on Ms. Scarlet?
What are the differences between a 948 cylinder head and a 1098 cylinder? Can a 1098 head be fitted to a 948, and if so, is there any benefit? It seems that the 1098 head can be used on the 948 block and has better (larger) inlet ports and valves.
What about the head gasket? Conventional wisdom is to use a head gasket that matches the larger 1098 head. The 1098 and 948 gaskets may even be the same part/size.
What about skimming the head? The 1098 head has larger combustion chambers and must be skimmed ~ 60 thou if used on a 948 engine in order to bring the compression ratio up. It's recommended to check if it's been skimmed already. Measure the thickness of the head - they ALL start life at 2.750" . Any less then that is what's already been skimmed off.
In doing my due diligence on this topic, I came across a fantastic article in the Mini Spares website "Articles" section - Cylinder Head 2022. This very detailed article lists casting specs, history, cylinder head identification, and descriptions and photos of each head.
Specific to this post, here's a sample excerpt from the 12G295 description:
"Keith Calver says- The 12G295 invariably has bigger intake ports and very shallow short side radius. For most road applications the ports are too big as standard – It does not need port work doing, just sorting out the valve seat shape and valve throat area. The inlet valve throats often have very, very thin seats so the valves seem to be barely hanging on. Also generally the throat has what appears to be an insert fitted because the underside is square stepped in shape like a shallow insert, they are cast like this. The 295 was produced for Group 1 race/rally homologation in mind at a time where big was beautiful. Keith Calver is still amazed at some of the valve sizes they crammed into them. The 206 is a much better head for road use – including those with a sporty camshaft. Far less prone to cracking as well.
Often described with the wrong description and wrong inlet valve sizes as an alternative to 12G295. Even our catalogue had inlet valve size wrong with a typing error from the late 90’s on hard copy which many have copied without research but I can confirm the following. The Inlet valves were original 1098cc size at 1.156?. Cast with MOWOG above 12G206 between 2&3 rocker posts, it has a recessed back and Wellingborough symbol between 3&4 rocker posts. Has square inlet ports and no locating ring recess and same 12G202 inlet valve size but often increased by .060” to the 1.218 inlet for either valve seat repairs or performance. The better flowing combustion chamber shape is 28.4cc but smaller and deeper at around 0.450” whereas the 12G295 is larger and shallower at around 0.430”deep, usually 20-25 thou difference. Although listed as part number 28G191 by BMC in AKD3509 parts list for very early 998 Cooper with low 8.3 CR, and a few 9-1CR- (I can only ever remember seeing the raised D shape pistons for 9-1 CR with 12G295 castings back in the 60’s}. Mainly fitted to inline 1098cc 10CG engine Sprite/Midget 1962-4, pre 12G295 fitment, plus a few found on A40, Morris Minor with 1098 engines but probably had Compression Ratio modified aftermarket.
Note 11. 12G295 1.218? inlet valve 1963on"
The FIRST of my eBay purchased H1 carburetor sets has arrived and, as described, is in poor condition. I'll document the "As Received" condition in pictures below. This set was purchased for $60 solely for parts that are missing on the second set of H1's that are arriving soon. A new heat shield alone would exceed the expense. Parts that I hope to refurbish include the heat shield, air filters, some metal tubing and minor linkage bits.
The first step today is to drop the entire setup into a tub of Evaporust to see what can be cleaned up before I begin to dismantle the manifold, heat shield and carb bodies. Below is an excerpt from the AH Experience Forum port "H1 SU Carbs" by Mike P:
"The BE's H1 carbs were among the last of the 'H' carb series. The 'H' series had a lot of parts, meaning more possible failure points. The later 'HS' series simplified the jet/jet bearing assembly, making carb adjustment and balancing much easier.
Brooklands Books publishes 'SU Carburetters Tuning Tips and Techniques.' This compact manual provides good information, beginning in Chapter 7 on dismantling, reassembly, and tuning. Remember, this is an 'H' type, as this (and all other manuals) jump around a bit, so follow the text about H-type tuning.
Other important tips: The H type is adjusted mostly through the jet adjusting nut. Up and down (left and right turns) leans or enriches the fuel flow. The jet adjusting nut is a Whitworth size, so it doesn't have an ASE or metric equivalent. All suppliers will offer a single adjustment wrench - consider getting one.
The carburetor air flow meter sold through the various suppliers is great for balancing carbs, but is too big for the H1. The carburetor synchronizer tool can work, but is designed for later carbs. Your H1 has a 1 1/8th inch diameter air passage. Later HS versions had the wider 1 1/4 diameter passage. The air flow meter can be used with 1 1/4 inch and wider carbs.
John Twist at University Motors on Youtube has instructive videos on H-type carb adjustments.
Successful H-type carb adjustment is dependent on proper jet centering. If the jet isn't centered then the needle doesn't move freely. Look to John Twist for the best video on H-type et centering. Even then, it is much, much more art than science. H-type adjustment instructions are based listening and feelings.
The H type carbs has several cork parts that eventually dry and crack - creating air leaks that make proper adjustment difficult. The H-type jet bearing assembly contains three (maybe two?) cork parts. There are failure points.
The final prominent H-type issue is air leaks at the throttle shafts. The soft metal brass shafts are brass and do wear. The softer metal housing on the throttle body can wear (even though not as much as many casual observers believe) requiring the throttle body's "re-sleeving." Air can leak in through the gaps worn between the throttle shafts and throttle body. Replacing worn throttle shafts (with similar-sized replacement shafts) is often sufficient to address the problem. "Re-sleeving" with new shaft bushings is often recommended. This service costs a minimum of $50 per throttle body - plus shipping.
Bottom line: Effective H-type adjustment depends on eliminating air leaks (from shafts, throttle bodies, and cork pieces in the jet bearings) and properly centering the jet. Eliminate these issues then you can move on to jet and choke adjustment (mostly jet adjustment). Common adjustment tools (air flow meter and carb synchronizer) have very limited use with H1s because the tools are too large for the H1's 1 1/8th air flow opening. The guys I've assessed as most effective (and I've seen in action), can "feel" when the carbs are in adjustment. On H's that will be the best one can ever effect."
In my pre-retirement profession we would call these two eBay finds a "Matched Pair". They're highly similar and the price reflects the condition and amenities.
Scarlet, the 1959 Austin-Healy Mk1 Sprite has its original 948cc motor but at some point in her life was updated with a pair of later model HS2, 1 1/4" carburetors. These are great and were worthy of rebuilding and polishing. The thing is, the more I dig into Scarlet the more I find out about her originality. Does she deserve a set of original "period" carbs? I think so! As it happens, there were two sets of complimentary HS1's available on eBay. Between the two, I could build one complete set. Below are what I bought . . .
This twin SU H1 carburetor (Gray Background) was listed for sale on eBay as a used SU carburetor setup, part #AUC863. These 1 1/8” carbs are from a 1958-61 Bugeye Sprite. They appear to be in good condition but missing the heatshield. After years on the shelf they will definitely need a rebuild. What's cool about this pair? They are a relatively clean set of carbs that include the original brass oil damper assemblies and float overflow pipes.
The Austin Healey Sprite Twin SU H1 Carburetors 1 1/8 With intake (Yellow Background) were described as being in storage and need rebuilding. What was of interest in this pair of carbs was that it included the original air cleaners with snorkel in the first carb, heat shield, copper heater return pipe, float bowl tags and intake manifold.