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Holbay Head and Webers
- Thread starter Nickodell
- Start date
alpine_64
Donation Time
and as the owber stated.. not much room left for a skim.. which is an issue for an alpine.. as they tend not to hold gaskets that long. I run the holbay webers but not the head.. i would have liked to.. but really you need the cam dizzy and pistons if you dont wan tto be re-jetting the carbs
S
SunbeamSam
Chaps,
I wouldn't get too excited about Holbay heads. Although they do have a better combustion chamber shape the smaller inlets ports are a real limiting factor (and opening them up to alpine size isn't really viable). A much better bet is to get a standard alpine head modified (just copy the combustion chamber shape to be similar to that on a Holbay head for a start). Actually I've got some pics i could post (if i could work out how) both of a Holbay head and of a Chirs Draycott fast road alpine head.
The cam in the holbay engine doesn't really have a great profile - there are much better ones out there that have oodles more torque at low speed and a more linear power delivery - I got one from Kent camshafts (UK), I know cat cams (UK) also do some profiles.
As for rejetting carbs, this is a fact of life if you are after performance increases. A trip to the rolling road is normally every penny. Even a stock motor (especially a 40 year old one) will normally see power gains from some gentle fettling.
I wouldn't get too excited about Holbay heads. Although they do have a better combustion chamber shape the smaller inlets ports are a real limiting factor (and opening them up to alpine size isn't really viable). A much better bet is to get a standard alpine head modified (just copy the combustion chamber shape to be similar to that on a Holbay head for a start). Actually I've got some pics i could post (if i could work out how) both of a Holbay head and of a Chirs Draycott fast road alpine head.
The cam in the holbay engine doesn't really have a great profile - there are much better ones out there that have oodles more torque at low speed and a more linear power delivery - I got one from Kent camshafts (UK), I know cat cams (UK) also do some profiles.
As for rejetting carbs, this is a fact of life if you are after performance increases. A trip to the rolling road is normally every penny. Even a stock motor (especially a 40 year old one) will normally see power gains from some gentle fettling.
64beam
Donation Time
Hi SunbeamSam,
You are probably not far from the truth. Going by the number of modified Alpines' owned by the forum members, there are only a handful who have the famous/infamous Holbay engine/head. The vizard or similar head mods seem to be the way to go (plus all the other engine mods - too many to speak of).
Regards, Robin.
J
Jeff Mannning
SunbeamSam, I just finished swapping out my Strombergs for a pair of Webers off an old Hunter. Not a simple task, but so far I like what I hear and feel.
I would be interested in learning more about your thoughts regarding modifications to a stock Alpine head vs a Holbay head. I'd be happy to help you with uploading/posting your images if it's simply a 'how-to' issue. If you'd prefer to send them to me directly,feel free to email me at: alpine@starus.org.
thanks in advance!
Jeff
I would be interested in learning more about your thoughts regarding modifications to a stock Alpine head vs a Holbay head. I'd be happy to help you with uploading/posting your images if it's simply a 'how-to' issue. If you'd prefer to send them to me directly,feel free to email me at: alpine@starus.org.
thanks in advance!
Jeff
64beam
Donation Time
I remember reading an article about the London to Sydney Hunter and if I remember correctly, it stated the the engine for that race was around the 150Hp mark. A tiny bit more than the H120/GLS. Someone may be able to confirm this for us.
Regards, Robin.
Wombat
Donation Time
Robin,
Somewhere in my boxes of old car magazines I have a Wheels mag in which they drove the Hunter (the column was called Cars, tasting not testing). The comment was somthing like "acceleration is devastating due to twin webers and a Holbay engine conversion". Somewhere else I read that they changed the head for a higher comprssion version on the ship from India to Australia. But then again rally cars were only losely related to the standard cars.
Somewhere in my boxes of old car magazines I have a Wheels mag in which they drove the Hunter (the column was called Cars, tasting not testing). The comment was somthing like "acceleration is devastating due to twin webers and a Holbay engine conversion". Somewhere else I read that they changed the head for a higher comprssion version on the ship from India to Australia. But then again rally cars were only losely related to the standard cars.
S
SunbeamSam
Almost there!
Current spec:
Engine rebuilt with +030 flat top pistons (needed to bump up CR with modified head - std hunter 1500cc pistons used from http://www.speedyspares.co.uk/
Lightened Flywheel: 8.5kg
Kent camshaft (rally spec)http://www.kentcams.com/
Fast road unleaded head: from sunbeam classic spares (Chris Draycott)
Quad motorbike carbs (yamaha R1) spaced by Bogg broshttp://www.boggbros.co.uk/
R1 fuel pump
Engine balanced
Gave 115bhp at 6000rpm with the bike carbs and 98bhp on strombergs.
but am only running 9.5:1 CR (unleaded fuel)
Still need to sort out air filter arrangement. More to follow when i get around to uploading some more photos (have worked out how to post them now).
S
SunbeamSam
I've had a few questions about head mods - i'll try get some photos together and posted over the next couple of weeks - i'll post them as a new thread when i do.
64beam
Donation Time
Almost there!
Current spec:
Engine rebuilt with +030 flat top pistons (needed to bump up CR with modified head - std hunter 1500cc pistons used from http://www.speedyspares.co.uk/
Lightened Flywheel: 8.5kg
Kent camshaft (rally spec)http://www.kentcams.com/
Fast road unleaded head: from sunbeam classic spares (Chris Draycott)
Quad motorbike carbs (yamaha R1) spaced by Bogg broshttp://www.boggbros.co.uk/
R1 fuel pump
Engine balanced
Gave 115bhp at 6000rpm with the bike carbs and 98bhp on strombergs.
but am only running 9.5:1 CR (unleaded fuel)
Still need to sort out air filter arrangement. More to follow when i get around to uploading some more photos (have worked out how to post them now).
Hi SunbeamSam,
What an impressive setup. I have never seen bike carbs on an Alpine. I assume you are in the UK, so why not try a pipercross filter setup. You can get them with a blank backing plate and drill them yourself (they look great as well). Did you considered Weber/Dellorto side Draughts? Are the bike carbs easy to synchronise?
Regards, Robin.
S
SunbeamSam
I was going to use webers - see my thread on holbay and modified heads for the preparatory work i did to the inner wing. But there where a number articles in 'Retro Car' and 'Practical Performance Car' magazines last year about the benefits of bike carbs. Essentially the argument goes that 1990s Japanese superbike technology going to beat 1950s /1960s British / Italian technology.
Cost is another issue – I’ve just sold my second-hand webers, pump, linkage and fuel regulator for around £450 – the same price it cost to get a complete bike carb setup from Bogg Bros. You can do it much cheaper, a set of Yamaha R1 carbs currently goes for around £100 on ebay, then all you need to do is make/buy/bastardise a manifold to fit them on.
The big advantage is that they’re supposed to stay in tune longer and be more fuel economic than webers (great if you cummute by alpine). I’ve only done 200 mile so far so we shall wait and see. Too bloody cold to go out at the moment!
As for filters, I have a set of pipercross socks – but I’ve been a bit daft – I had it rolling road set up without filters – main jets drilled out to 180 – runs perfectly… put the filters on and now it runs rich…
Guess I’ll have to revisit the rolling road when I’ve worked out my final filter arrangement – may use an airbox to keep inlet temperatures low… we’ll see.
If anyone else fancies doing this I would recommend getting the manifold to bolt straight to the head – mine bolts on to the weber manifold (carbs spaced) and hence my issues with space. Although you’re supposed to mount these carbs at 45 degrees there seem to be plenty of installations out there where this hasn’t caused a problem
Useful links:
http://www.teamswift.net/viewforum.php?f=8
http://www.ppcmag.co.uk/forum/
Cost is another issue – I’ve just sold my second-hand webers, pump, linkage and fuel regulator for around £450 – the same price it cost to get a complete bike carb setup from Bogg Bros. You can do it much cheaper, a set of Yamaha R1 carbs currently goes for around £100 on ebay, then all you need to do is make/buy/bastardise a manifold to fit them on.
The big advantage is that they’re supposed to stay in tune longer and be more fuel economic than webers (great if you cummute by alpine). I’ve only done 200 mile so far so we shall wait and see. Too bloody cold to go out at the moment!
As for filters, I have a set of pipercross socks – but I’ve been a bit daft – I had it rolling road set up without filters – main jets drilled out to 180 – runs perfectly… put the filters on and now it runs rich…
Guess I’ll have to revisit the rolling road when I’ve worked out my final filter arrangement – may use an airbox to keep inlet temperatures low… we’ll see.
If anyone else fancies doing this I would recommend getting the manifold to bolt straight to the head – mine bolts on to the weber manifold (carbs spaced) and hence my issues with space. Although you’re supposed to mount these carbs at 45 degrees there seem to be plenty of installations out there where this hasn’t caused a problem
Useful links:
http://www.teamswift.net/viewforum.php?f=8
http://www.ppcmag.co.uk/forum/
H One-Twenty
Donation Time
Hi,
Nice modifications SunbeamSam! Congrats on the Webers too Jeff!
Sorry in advance for this long post in defense of the Holbay!
The original development work carried out by Holbay for the Rapier H120 and Hunter GLS resulted in the 1725cc engine producing around 122bhp. In this state of tune it wasn't thought tractable enough at lower speeds for a production car. To fix this the inlet port sizes were reduced to roughly the same size as the exhaust ports. This, along with a milder camshaft improved torque and drivability. The final production spec was 105bhp with 120lbs/ft of torque.
For what it's worth (and I am of course biased) I think the power delivery, drivability and economy (as well as reliability) from the Holbay spec engine is excellent. I have an all original 133,000 mile Rapier H120 that has never had anything more than the valve clearances adjusted. I've never had to touch the Weber carbs at all; it seems to always stay in tune as long as you keep the points well adjusted. My Dad (who I can't remember ever being without a Rootesmobile) has had various H120s too and hasn't had serious trouble with any (if you can discount a broken rocker post!).
Anyway, my point is that the Holbay set up might not produce the ultimate power, but it does give a significant boost and makes the car a joy to drive, even in heavy traffic. The Webers make a wonderful sound and give great pick up. I'm hoping the Holbay head, cam, carbs, pistons and distributor I brought back with me from Scotland will be a nice (reliable) improvement on my standard (1725cc) SIV set up. I just need to get the inlet manifold sorted out. I'm guessing that the 'off the shelf' (left hand drive) Weber manifolds that are available are designed for the standard inlet port sizes, not the smaller Holbay ones. I may have to modify the standard Holbay manifold. Any ideas? What manifold did you use Jeff?
Nice modifications SunbeamSam! Congrats on the Webers too Jeff!
Sorry in advance for this long post in defense of the Holbay!
The original development work carried out by Holbay for the Rapier H120 and Hunter GLS resulted in the 1725cc engine producing around 122bhp. In this state of tune it wasn't thought tractable enough at lower speeds for a production car. To fix this the inlet port sizes were reduced to roughly the same size as the exhaust ports. This, along with a milder camshaft improved torque and drivability. The final production spec was 105bhp with 120lbs/ft of torque.
For what it's worth (and I am of course biased) I think the power delivery, drivability and economy (as well as reliability) from the Holbay spec engine is excellent. I have an all original 133,000 mile Rapier H120 that has never had anything more than the valve clearances adjusted. I've never had to touch the Weber carbs at all; it seems to always stay in tune as long as you keep the points well adjusted. My Dad (who I can't remember ever being without a Rootesmobile) has had various H120s too and hasn't had serious trouble with any (if you can discount a broken rocker post!).
Anyway, my point is that the Holbay set up might not produce the ultimate power, but it does give a significant boost and makes the car a joy to drive, even in heavy traffic. The Webers make a wonderful sound and give great pick up. I'm hoping the Holbay head, cam, carbs, pistons and distributor I brought back with me from Scotland will be a nice (reliable) improvement on my standard (1725cc) SIV set up. I just need to get the inlet manifold sorted out. I'm guessing that the 'off the shelf' (left hand drive) Weber manifolds that are available are designed for the standard inlet port sizes, not the smaller Holbay ones. I may have to modify the standard Holbay manifold. Any ideas? What manifold did you use Jeff?
64beam
Donation Time
Hi,
Nice modifications SunbeamSam! Congrats on the Webers too Jeff!
Sorry in advance for this long post in defense of the Holbay!
The original development work carried out by Holbay for the Rapier H120 and Hunter GLS resulted in the 1725cc engine producing around 122bhp. In this state of tune it wasn't thought tractable enough at lower speeds for a production car. To fix this the inlet port sizes were reduced to roughly the same size as the exhaust ports. This, along with a milder camshaft improved torque and drivability. The final production spec was 105bhp.
For what it's worth (and I am of course biased) I think the power delivery, drivability and economy (as well as reliability) from the Holbay spec engine is excellent. I have an all original 133,000 mile Rapier H120 that has never had anything more than the valve clearances adjusted. I've never had to touch the Weber carbs at all; it seems to always stay in tune as long as you keep the points well adjusted. My Dad (who I can't remember ever being without a Rootesmobile) has had various H120s too and hasn't had serious trouble with any (if you can discount a broken rocker post!).
Anyway, my point is that the Holbay set up might not produce the ultimate power, but it does give a significant boost and makes the car a joy to drive, even in heavy traffic. The Webers make a wonderful sound and give great pick up. I'm hoping the Holbay head, cam, carbs, pistons and distributor I brought back with me from Scotland will be a nice (reliable) improvement on my standard (1725cc) SIV set up. I just need to get the inlet manifold sorted out. I'm guessing that the 'off the shelf' (left hand drive) Weber manifolds that are available are designed for the standard inlet port sizes, not the smaller Holbay ones. I may have to modify the standard Holbay manifold. Any ideas? What manifold did you use Jeff?
Hi,
My current inlet manifold that I bought off Ebay UK was a Mangoletsi manifold. This manifold was suited for the Rapier/Hunter engine, so I had it modified to suit the series Alpine engine. This manifold used the smaller inlet ports to suit the Holbay head. I paid very little for my manifold (@ AUS$35 + postage), maybe you can source one as well.
Good luck,
Regards, Robin.
H One-Twenty
Donation Time
Hi Robin,
I didn't know Mangoletsi made a manifold for the Holbay engine! Do you know if it is any different than the standard one? I guess modifying the manifold for Alpine fitment is more straightforward with a right-hand drive car. My Alpine is left-hand drive and it looks like steering box clearence is going to be a big problem. I have read that you need an 's' shaped inlet manifold to overcome this. I just wonder if these manifolds (which are pretty expensive I hear) will all have been designed for the larger ports of the non-Holbay heads?
Cheers,
Stuart
I didn't know Mangoletsi made a manifold for the Holbay engine! Do you know if it is any different than the standard one? I guess modifying the manifold for Alpine fitment is more straightforward with a right-hand drive car. My Alpine is left-hand drive and it looks like steering box clearence is going to be a big problem. I have read that you need an 's' shaped inlet manifold to overcome this. I just wonder if these manifolds (which are pretty expensive I hear) will all have been designed for the larger ports of the non-Holbay heads?
Cheers,
Stuart
H One-Twenty
Donation Time
Thanks Micheal!
I never thought of the master cylinder being the issue (probably because I don't have one on my car at the moment!). If it's possible to use a straight manifold then I can probably get away with modifying the Holbay one that I have (as I have seen done back in the UK).
I'm now wondering how I can get round the master cylinder issue. I wonder if it is just the reservoir that fouls? If so perhaps I could use a remote reservoir?
-Stuart
I never thought of the master cylinder being the issue (probably because I don't have one on my car at the moment!). If it's possible to use a straight manifold then I can probably get away with modifying the Holbay one that I have (as I have seen done back in the UK).
I'm now wondering how I can get round the master cylinder issue. I wonder if it is just the reservoir that fouls? If so perhaps I could use a remote reservoir?
-Stuart
RootesRacer
Donation Time
The body of the master cyl tends to interfere, on the earlier cars (without the booster) there is a spacer between the firewall and the master cyl, which can help with clearances at the rear of the cyl to the rearmost carb.
I also had to grind some meat from the back of the master cyl to get that extra little bit of margin.