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Sunbeam Alpine (1956-1967) 1725 Holbay cylinder Head AM3 71981232 world wide shipping

alpine_64

alpine_64

Donation Time
Alpine Addict said:
What is the difference between this head and the stock head?
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Holbay head has smaller intake runners, larger reshaped combustion chambers with sodium filled valves and different valve springs... the head was on the holbay motor which had flat top hepolite pistons, different cam, distributor, alloy sump and ran 2 x 40 dcoe webers. It was used in the H120 rapier and hunter GLS
 
65beam

65beam

Donation Time
head

the question I've always asked that no one seems to answer is how good would the head be with the dual weber set up for a series alpine if the intake ports and the manifold don't match. it would be tough to use the holbay intake without modification in a series alpine. the holbay intake would be angled down since the fastback engine sets at an angle.
 
RootesRich

RootesRich

Donation Time
65beam said:
the question I've always asked that no one seems to answer is how good would the head be with the dual weber set up for a series alpine if the intake ports and the manifold don't match. it would be tough to use the holbay intake without modification in a series alpine. the holbay intake would be angled down since the fastback engine sets at an angle.
Click to expand...

You can't run an H120 manifold on a Series Alpine as the DCOEs would set at an angle approx 10 degrees. I know a couple of Truimphs running DCOEs and the maximum slope of their carbs can't be more than 6 deg otherwise the floats start getting fouled up.

As far as how DCOEs would perform with larger intake runners mounted to smaller Holbay head intake ports, it could run, but obviously not as efficient as if the ports were matched. I'm sure Jarrid would be able to state for certain.

I can tell you that our pre-production SV was delivered to the dealership in the UK from the factory with a stock Holbay head, stock SV manifold and Stoms fitted with 5C needles rather than the stock 5Ms. I only discovered the cylinder head was a stock Holbay a few months ago while cataloging our spares. The engine performed well despite the difference in intake runner and intake port diameters.
 
alpine_64

alpine_64

Donation Time
65beam said:
the question I've always asked that no one seems to answer is how good would the head be with the dual weber set up for a series alpine if the intake ports and the manifold don't match. it would be tough to use the holbay intake without modification in a series alpine. the holbay intake would be angled down since the fastback engine sets at an angle.
Click to expand...

Not sure why you haven't read the answer to your question, it's been answered many times on the forum over the years. You cant use the stock holbay manifold on an alpine, you have to cut a wedge @ 10deg and reweld it so that it sits level for the carbs.. or more to let them sit slightly up. This is covered in the alpine guide and is a very popular mod in the UK. Holbay also made a manifold for alpines.. but its hard to find.

The other option is to open the ports on the head to match a TWM, wanerford etc manifold and mount webers.. it changes the low end torque character of a holbay setup.. there is the issue you cant bolt a holbay head on a stock alpine motor as compression would be to low.. so you either get a full setup.. or modify an engine to suit.
 
65beam

65beam

Donation Time
head

another thing to keep in mind is that the weber set up for the H120 would not fit the fastbacks sold here without a lot of work such as a special built exhaust. you can not fit the weber intake without this mod. I know because I have a nice paper weight in the garage. since my GT runs so well it just isn't worth the time and effort to do the changes. the Stromberg intake from a series 5 alpine won't fit either without changing to a custom made exhaust and carb mods. someone may have given an explanation last year or 5 years ago but with a job, a business, a few houses to worry with and family along with other things I tend to forget things that aren't of importance since I'm not obsessed with having every sunbeam detail stored away. if I need a detail and can't remember it I ask one of the many old guys I know. usually they can't remember either. we call it "old timers disease". I have checked into buying an H120 and bringing it to the states. since we don't drive the cars much it just wouldn't be worth it. the handling of the fastback is bad as it is. the extra power of the H120 would probably be scary.
 
R

RootesRacer

Donation Time
RootesRich said:
As far as how DCOEs would perform with larger intake runners mounted to smaller Holbay head intake ports, it could run, but obviously not as efficient as if the ports were matched. I'm sure Jarrid would be able to state for certain.
Click to expand...

Well you have one of three choices:

1) Embrace the suck of having a large step in the intake flow of your runners.

2) Hog out the pristine H120 runners in the head and alter the course of history for that head.

3) Team up with team JB weld and make the intake runners match with the smaller holes in the head.


I'm all about horsepower over torque so I myself would go with door number 2.
If you want the H120 experience you should choose door number 3.
Door number 1 is for idiots with more money than common sense.;)
 
B

Bill Blue

Platinum Level Sponsor
DanR said:
JB Weld? What's that to an Alpine owner;)
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Expensive!

When I built the trombone intake, I shaped it to match the ports using a product called Lab Metal. The 2.5 intake ports are much larger, so I had to remove the Lab Metal this last winter and it put up a good fight. Don't know if it will work on the variety of applications that JB will, but for smoothing/reshaping an intake passage, it is just fine.

The price of admission when using Lab Metal is sort of high, I think the smallest size is either a pint or quart.

Bill
 
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