Harv's Repco HighPower crossflow head thread

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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

Mmmm.... funky Repco test car with cross-flow head..... 8)

http://primotipo.com/2015/06/26/repco-r ... ower-head/

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Re: Harv's Repco HighPower crossflow head thread

Post by GreyEJ »

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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

Photos below stolen from the Blacky's thread in the Whats Happening in WA area... putting them here so I don't lose them.
http://www.fbekholden.com/forum/viewtop ... 22&t=21408

Repco crossflow head in a private museum in Baldivis, WA:
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Harv
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

Some more articles featuring the Repco Highpower head (thanks Paul).
First one from Street Machine Hot Holdens number 3:
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The article below is from Wheels of May 1963:
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The next article is from the book Maybach to Holden: Repco, the cars people and engines by Malcolm Preston: Image Image Image Image Image Image

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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

Some stuff from John Brown's collection.

The photo below shows two views of John's Repco HighPower crossflow cylinder head, with twin SU carburettors.
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The photo below shows two views of a Repco HighPower crossflow piston to suit the Holden grey motor. Repco had a number of stages for the HighPower head. Stages 1, 2, 3, and 3a utilised the standard GMH flat topped piston to give 7.5:1 compression on an un-planed block. Stage 4 increased piston diameter to 3.125” using Repco part number HX0136 pistons. These had three rings, tee-slots (to retard heat transfer from the piston crown to the skirt) and 13/16” gudgeon pins and gave a compression ratio of 8.2:1. Stage 4a used the same bore, but lumpier pistons to give 9.1:1 compression. Stages 5 and 6 used the same bore, but with 9.5:1 compression. Repco had two other types of pistons, though the advertised compression ratios don’t exactly line up to the stages above. Part number HX0102 was a 3.125” piston, with three rings, a plain skirt and tapered ¾” gudgeon pins and gave a compression ratio of either 9.3:1 or 9.5:1 (depending on which part of the Recpo literature you read). Part number HX0122 was a larger 3.1875” piston, with three rings, a plain skirt and tapered ¾” gudgeon pins and gave a compression ratio of either 9.6:1 or 10:1. The absence of t-slots would indicate that John’s piston is either a HX0102 or a HX0122.
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

I was tidying up some old emails, and ran across one that Paul sent me a while ago... I've got a head like a sieve :oops: .

Magazine advert from Sports Car World of September 1962:
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Re: Harv's Repco HighPower crossflow head thread

Post by GreyEJ »

fb delivery wrote:COOL
How many crossflow head's were made ?
i was told 105 , i think it was more ?
i know of a few here in town
1 in a FX ute
1 in a FC sedan
1 in a lounge room on a motor, with a compete head under a bed { well know of , up here}
and 1 on a car in Dalby

Cheer's Rob

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Re: Harv's Repco HighPower crossflow head thread

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8)
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

Ladies and gents,

Some time ago, I posted some info regarding a set of Howarth low pressure fuel injection that I had purchased. The Howarth setup was installed on a set of Repco HighPower cross-flow head manifolds. I did some reverse engineering on the Howarth set-up here:
http://www.fbekholden.com/forum/viewtop ... th#p223746

As part of the same purchase, I obtained a set of two sidedraught carburettors, which I will discuss in the thread below.

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Like the injection set, the sidedraughts were mounted on (yet another) set of Repco HighPower cross-flow head manifolds. I had originally made a deal to purchase a HighPower head, though sadly the seller pulled out of the deal (great… now I’ve got two sets of fuel setup and no cylinder head to put them on :( ).

The history on both my Howarth injection and these sidedraught carburettors has been lost. The seller understood that both injection and carburettors were used on Repco heads (Holden grey motors), one in custom road circuit racer, and one in a dragster. The previous owner had the Repco heads stored in a building which burnt down, leaving only the injection/carburettors which had been stored separately. I have been able to tie-down the Howarth injection, but the carburettors are a mystery. There are no manufacturers markings, stamps or castings on the carburettors. As we will see below, the carburettors seem to take parts from a number of sources. I checked with Carburettor Service Company in Sydney, and they were of the view that the carburettors were custom cast. Having said that, the castings are very neat, with no obvious occlusions, flash or voids. The main body casting has a yellow dichromate finish. If these are home-cast, they were a very professional job. I’ve checked a number of other period sidedraught carburettors include the Carter YH and Zenith 11ADX12 (and more mentioned in the text below), though again they are very different from these carburettors. If anyone knows the manufacturer of my carburettors, I’d love to hear from you.

The mounting flange is a 3-bolt single barrel non-equidistant setup. It is similar to the 2-barrel Stromberg 3-bolt EE-model (“Stromberg 97”) flange, but not the same.

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Some Harleys ran 3-bolt non-equidistant flanges (for example on the Linkert carbs), though these carbs look nothing like any Harley I’ve been able to Google. The steel manifold studs are ¼-20/28 UNC/UNFx15/32”. Two of the three studs on each carb have been cast into the Repco manifolds, though it looks like this was done afterwards (drill an oversize hole, insert the stud, then pour in liquid aluminium) as the studs are not altogether horizontal, and the casting is porous around the studs.
The carburettors have a throttle bore of 1 7/16”, an air horn OD of 2¼” and a venturi diameter of 11/16”. The venturis are changeable, being constructed of an interference fit aluminium sleeve, partially pinned in place by the main discharge jet mitred tip.

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The throttle plate and shaft are both brass, held together by brass 6-32UNCx¼” raised countersink head screws. The screws are hollow point to allow them to be staked in place.

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The throttle shafts are fitted with brass collars on one side, and brass idle speed levers on the other.

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The idle speed levers are held in place with 10-32UNFx9/16” fillister head bolts, relying on the bolts to purchase onto the round throttle shaft. The idle speed levers act on a lug on the throttle body castings, and are adjusted with 10-32UNFx7/16” fillister head bolts, locked in place with a #6-32UNCx9/32” cross-screw.

The carburettors have a single float bowl, with the liquid level controlled by a Stromberg EE-type float and screwed hinge pin.

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The hinge pin drilling has been made all the way through both sides of the casting. One side of the drilling is threaded (to accept the hinge pin threads) whilst the other side has been blinded off by a lead plug. Whilst the floats are Stromberg, Stromberg however only made one type of sidedraught carburettor (the OH model), and this looks nothing like it (the OH for example had a round-shaped float). The needle and seat orifice, located inside the inlet banjo fittings, is 0.104”. This is considerably larger than a standard grey motor (0.070”), and closer to typical Holley (0.110”). The larger diameter needle and seat orifice would support methanol flow. The outlet of the banjo fittings is sized to -4AN, whilst the inlets are the funky 7/16¬”-24 thread used in Stromberg carburettor fuel inlet threads.

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The float bowl is 1 11/16” deep, and contains an integral-cast metering block. The drawings below show the float bowl in cross-section, with the float bowl lid shown in pink. The float bowl lid, fastened by three 10-32UNFx9/16” round-head bolts, has a single hole drilled through the casting to vent the float bowl. The hole is drilled at 0.070” diameter vertically, and then at 0.078” horizontally.

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The float bowl lid also has two brass inserts, probably made by drilling holes and inserting brass rod. The purpose of the inserts, pictured below, is unknown.
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The integral-cast metering block has four vertical passages, shown in the image and drawing below.

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The first passage, shown to the left of the image above, is an air-bleed inlet. Air passes through a brass mesh screen pressed into the side of the carburettor, which can be seen in the image below:

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The air flows through the brass mesh screen and upwards to fill the cavity between the metering block and float bowl lid. Note that the float bowl lid forms two separate compartments – a cavity above the float bowl, and a separate cavity above the metering block. From the metering block cavity, air is able to flow down each of the other three vertical passages, as shown by the red arrows in the image below:

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The second passage, shown second-to-left in the image above, is the main fuel discharge. An anti-siphon bleed is pressed into the top of the passage, as shown in yellow in the images above. The bottom of the passage is press-fitted with a mitred steel main discharge jet, which protrudes from the bottom of the metering block into the carburettor throat.

The third passage, shown third-to-left in the image above, is the main metering passage. The passage is connected to the fuel bowl by a cross-drilling located some 3/16” above the float bowl floor (shown by the black circle in the image above. The cross-drilling is fitted with a 0.0955” main metering jet. This is a rather large jet, being 3½ times the area of a typical grey motor Stromberg jet. This again points to the carburettors being set up for methanol. The main metering jets are Rochester, which are very similar to Holley. The difference is the threads – Rochester are ¼”-28UNF, whilst Holley are ¼”-32UNEF. Rochester made some sidedraught carburettors (the R and RC models), though these carburettors look nothing like them. The cross drilling is covered by a steel main metering jet plug, which are ½-20UNFx5/16” with an integral washer and 7/16”AF head. The top of the main metering passage is fitted with a screw-in main metering air-bleed, shown in pale green in the images above. The main metering air-bleed is 3/8-24UNFx3/8”, drilled to 0.039” diameter.

The fourth passage, shown to the right in the image above, is the idle passage. The bottom of the passage is press-fitted with a 0.093” internal diameter brass seat, shown in purple. The top of the passage is fitted with a screw-in idle air-bleed restriction, shown in dark green in the images above. The idle air-bleed restriction is 5/16-24UNFx1.05”. The idle air-bleed restriction is screwed into the idle passage, and bottoms out (seats) on the brass seat. The idle air-bleed (which controls the air flow) is drilled to 0.028” diameter. The idle emulsion-bleed is drilled to 0.033”. Whilst in theory this drilling should control the fuel flow, there is also a restriction where the air/fuel emulsion flows from the idle passage into the main carburettor throat. The carburettor throat has only been drilled to 0.038” diameter. Thus the combination of the 0.033” emulsion-bleed and 0.038” carburettor throat drilling will control fuel flow.

In addition, the four passages have been cross-drilled twice. The first cross-drilling, shown from the left of the images above at 11/32” below the top of the float bowl/metering block, connects the air-bleed inlet, main fuel discharge and main metering passages. However, the air-bleed inlet passage cross-drilling is blocked off with a brass sleeve, shown in orange in the images above. The second cross-drilling, shown from the right of the image above at 27/32” below the top of the float bowl/metering block, connects the main metering and idle passages. The first cross-drillings is sealed at the metering block edge with a drive plug, whilst the lower cross-drilling is sealed with a lead plug. The drive plug and lead plug are represented in blue in the images above.
Pictured below, from top to bottom, are the idle air-bleed, the main metering air-bleed and the main metering jet:

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When the engine is at idle, the throttle plates are near closed, as shown in the left-hand image below.

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A strong vacuum is formed downstream of the throttle plates, and air flows into the engine in the direction of the purple arrow. At the idle position the throttle plates are located such that the idle passage drilling is exposed to engine vacuum. The vacuum causes fuel (shown in red in the middle image above) to be drawn from the float bowl, through the main metering jet and up the main metering passage. The fuel flows through the cross drilling, and up the idle passage before passing through the idle emulsion-bleed.

The tip of the idle air-bleed tube is submerged in fuel, and air is drawn in through the air-bleed, forming an emulsion in the idle passage. The idle air bleed also acts as a vent to prevent siphoning of fuel from the idle system at high speeds or when the engine is shut off. The emulsified fuel flows through the brass seat, and out into the carburettor throat. Because the idle emulsion-bleed (and idle carburettor throat drilling) is much smaller than the main metering jet, the fuel flow is controlled (metered) by the idle fuel restriction (and idle carburettor throat drilling). To change the idle quality, the idle emulsion-bleed can be made larger (making more fuel flow) or the idle air-bleed can be made larger (causing more air to flow, leaning out and emulsifying the fuel). Note however that if increasing the idle emulsion-bleed much larger, the idle carburettor throat drilling will soon become the restriction controlling idle fuel flow, and will also need to be increased in size.
As the throttle is opened further (as shown in the right-hand image above), the vacuum behind the throttle plates increases. Fuel continues to be drawn into the idle circuit, but is also pulled higher up the main metering circuit. The fuel thus flows from the fuel bowl, through the main metering jet, up the main metering passage, through the cross-drilling and down the main discharge passage. The tip of the main metering air-bleed tube is submerged in fuel, and air is drawn in through the air-bleed, forming an emulsion in the main discharge passage. The emulsified fuel flows through the mitred main discharge jet and out into the carburettor throat. The fuel flowing out the main discharge jet is controlled (metered) by the main discharge jet. To change the engine fuel quality, the main discharge jet can be made larger (making more fuel flow) or the main discharge air-bleed can be made larger (causing more air to flow, leaning out and emulsifying the fuel).
Of note, the carburettor has no transition, power or accelerator circuits. If the carburettor is snapped wide open from idle, a lot of air flows through the throttle plates. The engine leans out, and will either pause or lean backfire. Equally, as the carburettor is moved slowly from idle to wide open the carburettor will initially run on the idle circuit. The fuel mixture will lean out as the throttle plate is opened, up until the point that the main metering circuit begins to flow. At this point, the mixture will rapidly become richer. This performance will give a noticeable effect on engine speed/power when accelerating. With no power circuit there is a risk of insufficient fuel (and either loss of performance or pinging) under load. This would be controlled by running a main metering jet of sufficient richness to cover the worst case load. Realistically, the carburettor has been designed to be in only two states – idle, and flat-out. This makes it useful for drag racing and speedway use, though less useful for street or circuit racing.
The float level is set similarly to an EE Stromberg, by bending the brass tab on the end of the float. Care needs to be taken in setting float level as the cross-drilling between the idle discharge and main metering passages is quite low in the float bowl (exactly the middle). This means that if the fuel level rises above the 50% mark, the float bowl will overflow through the idle circuit (as shown in red in the image below).

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I’ve gone through and stripped down, cleaned and rebuilt the carburettors. The next step will be to make up some aluminium adaptors to adapt the 3-bolt flanges back to the SU 4-bolt pattern. I’ll then give the sidedraughts a test run on the twin-SU manifold on my test mule grey motor (the same manifold I ran the Howarth injection on). Like the Howarth injection, it appears that the sidedraughts are set up for methanol, and will overfuel on petrol. Pretty fair chance I set the driveway on fire again :oops: :lol:

Cheers,
Harv
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Re: Harv's Repco HighPower crossflow head thread

Post by bootlegger »

Ill ask a mate what they are.
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

Thanks Dave.

The Repco literature indicates that for Stage 1, a pair of Holden Strommies gets used. This would have the same throat area as my sidedraughts. For Stages 2 through 5, a pair of 36mm downdraught Webers are used. This is a lot of carb... about 1.5 times the throat area of my sidedraughts. For all-out grunt, a pair of 40DOM Webers gets used (or 1 3/4" SUs). The name 40DOMs has "D" for Doppio (double-throat), "O" for Orizzontale (horizontal), no idea what the "M" stands for, and "40" for 40mm throats. A pair of 40DOMs would give a venturi area more than double that of my sidedraughts.

My guess is that whoever was using my sidedraughts on a Repco head was not chasing all-out grunt (they will flow better than Strommies, but not massively so), but may have been limited by bonnet/cowl clearance.

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Harv
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

I was recently looking at bellytank info on the HAMB forum, and run across the photos below:

SROS-110050-TANKERS-72-HR.JPG.jpg
SROS-110050-TANKERS-72-HR.JPG.jpg (54.37 KiB) Viewed 1783 times
SROS-110050-TANKERS-72-HR.JPG.jpg
SROS-110050-TANKERS-72-HR.JPG.jpg (54.37 KiB) Viewed 1783 times
bellytank.jpg
bellytank.jpg (53.11 KiB) Viewed 1783 times
Those carbs look to be identical to the sidedraughts I have been playing with in the thread above. Makes me wonder if they were made in the US, rather than custom cast in Australia. The bellytank has Riley rocker covers (it looks to be a Riley 4-banger in the bellytank), though my sidedraughts don't look like anything I can find on a Riley. At least it explains why there are brass inserts in my float bowl lids - they are leftover rivets for a nametag.

A quick check on the HAMB hasn't been able to identify the carbs either. Now I need to hunt down the owner of the bellytank to see if he knows what they are.

Cheers,
Harv
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

My search for a genuine Repco HighPower head has been unsuccessful, despite several years of chasing :( . I am now committed to a repro head, and have paid the deposit. In getting to this decision, I’ve done my homework, and will share the results below. Have tried to chase down the Chinese whispers, which has led to a lot of calls to some very interesting people (and managed to talk to the owner of two Normans that I did not previously know of). Talked to quite a few guys who either currently own, or have previously owned factory heads. The community is small, but very knowledgeable. Their time on the end of a phone has been appreciated.

Reproduction Repco HighPower heads have been made by Rod Scheffler in both aluminium and cast iron. Ballpark costs are $14k for an iron head, and slightly more for ally. This includes all the running gear (valves, rockers, rocker covers etc). Around 10 have been sold so far. I am going a cast iron head, as it "feels" more period correct, and will probably take a bit more abuse than the ally. This will be no show pony... I intend to make it earn its keep. Will probably have to sell on some other toys to make up the dollars.

The heads are supplied with ally roller rockers. No-one currently reproduces the factory type rockers. Terry King can supply rocker adjusters, posts and shafts. He made a run of 10 reproduction rocker arms, though no longer makes them. The factory Repco rockers have geometry issues (the exhaust valves unseat from the rocker tip at high revs), though can be successfully reworked by Ian Tait and survive up to 8,000rpm. However, the original factory rockers, based on Vincent parts, are rarer than rockinghorse poo. John Anderson made a run of 10 steel roller rockers, though no longer makes them. All up, the only currently available set of rockers (of any type) for a Repco head are the ally rolly rockers made by Rod.

It will be a few months before the head is ready. I still have quite a bit of work to do to get the bottom end of the meth monster together ready to receive it.

Cheers,
Harv
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Re: Harv's Repco HighPower crossflow head thread

Post by Harv »

For some years now I have been trying to identify the mystery sidedraught carbs that I bought in Sydney, described in the posts above. I’ve tried local experienced carb shops and various old Holden forums, but no luck. The search even led to a post on the HAMB (https://www.jalopyjournal.com/forum/thr ... t-12408685), but was not successful.

During my research, I stumbled across a thread about bellytankers ( https://www.jalopyjournal.com/forum/thr ... le.1052568), that had a beautiful red bellytanker, as seen in the post above. Whilst ogling the #253 bellytank, the carbs caught my eye – those are the same as my mystery sidedraughts! The article on the HAMB forum had been posted in the February 18, 2016 issue of STREET RODDER in the US. I did some digging, and managed to get connected through to one of the car clubs mentioned. Looks like the #253 bellytank was run by Baldwin and Sommerfield (B&S Garage, Hollywood, CA) with the Riley engine and mystery sidedraughts. Baldwin and Sommerfield were SCTA Season Champs in 1956 and 1958. The bellytank is now owned by Jim Lattin in the US, and the club is helping me contact him.

I was feeling pretty happy… then things got funky.

One of the contacts from the car club is a &*#@ 4-banger enthusiast. He recognised my carbs from an article written in the US F.A.S.T magazine Winfield articles. This lead to a discussion with the gentleman who wrote the aticle. Looks like my carbs are 1933/34 Winfield sidedraughts, from the second production run. Ed Winfield was one of the US’s master go-fast guys of the 1930s (https://www.mshf.com/hall-of-fame/induc ... field.html). His design, production and tuning of speed equipment, especially for early Fords is incredible. The Winfield rocker arm special one barrel carburetors were cast from patterns that were made by Gurz in Los Angeles at the same time the head patterns were built. They were used in 1930’s and 1940’s Indy cars, including the Lencki 1939 Indy car, which is now in the Speedway Speedway Motors Museum of American Speed in Lincoln, Nebraska. The Lencki engine has recently been reproduced by Coker (https://www.cokertire.com/blog/lencki-six-engine). According to the gentleman’s research, there are only about 18 of these carbs surviving.

So all up I’ve ended up with some pretty cool carbs, period correct for a 1930/40’s racer. Just how some hi-zoot US carbs ended up on a Repco grey motor head in Australia is a bit of a mystery… maybe through an Offy speedway engine at some stage.

Cheers,
Harv
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Re: Harv's Repco HighPower crossflow head thread

Post by Errol62 »

That’s fascinating Harv


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