Carb swap

In 2003 i changed the stock twin Zeniths on my Alpine for 2 x Holbay 40DCOE's. Early this year i managed to acquire a rare Alexander conversions setup from the UK, this consists of a manifold and twin SU carbs. They turned up on Friday with help from a UK Sunbeamer (thanks Tony T!)

Will be stripping and rebuilding them. Debating about what to do with the manifold, polish it, or perhaps ceramic satin chrome finish?.. should be interesting setup once done.

pics of current weber install and the new (for me) SU setup.

Michael, Please educate me a bit here. Not knowing any better, I thought that Webers were the "be all to end all" when it came to carbs. Are you saying the SU's are better, or perhaps is it something about the manifold that makes the combination better?

Gene

Hi Gene,

i would say that the 2 x DCOE is the "ultimate" setup.. look amazing, sound great and once set.. go very well. That's why i searched out the setup a decade ago.

That said... I just like to much around.. and have a bit of a fetish for period aftermarket parts.. so when i saw the setup come up and it was done specifically for the Alpines and Rapiers.. couldn't help myself.

The SU's should be a bit more fuel efficient than the webers.. and despite my motor being quite warm, it's actually a SI block.. so 1494 no even the 1592.. so the SU's might actually be a bit better in the lower rev range. It's all just to see how it goes.. bit of fun.

I had considered going to a DVG weber (single down draft) and even specially prepared a late model rootes manifold with the curved runners for the job.. hydro blasted it and then polished it, but just couldn't bring myself to go single carb (need to have 2 on a 4cyl 60's sports car )

Anyway.. so will rebuild.. clean up and see how we go...

Here are pics of the motor when on Zeniths, then after some clean-up, then on the first dcoe setup.. then more work.. the DGV manifold i did when i thought about the single carb setup..

Oh.. Gene, assume you got the newsletter the other night.. next month ironically i have a write-up on DCOE's on Rootes motors.. oh well!

The Webers look very cool, but I understand the period correct theme you are going for. Wish I had an Alpine I could put those on.

Kidz,

The DCOE's are period correct, they were offered by Jack Brabham, George Hartwell and Holbay in the UK and the factory Alpine's that ran at LM in '63 also used them.

The Alexander conversion is quite a bit rarer, you can still but DCOE manifolds from various suppliers in the Uk, USA and AU.. also i think the SU manifold just looks so cool. As a side note the casting on the Alexander manifold is REALLY nice.. so smooth in comparison to a Rootes, Redline or Edelbrock offering... and i love the detail of the recess on the "A" in the name badge... (i'm so shallow )

Despite I also love those period aftermarket kits I think better to just put the original Zenith's back in place. The reason is not much trust into all these CD carby technology. This conclusion is after many years of fiddling around with different spring rates, damper oil viscosities and needle shapes. Actually very hard to put them into perfect tune.

The Zeniths if In good shape are simply the best carb setup available for Alpines. This is also proven by many period Race successes. They can be also tuned to a certain degree. Runing a set with 30mm venturis and 150 mains on my series 1 and it goes like stink )

bernd,

I have to respectfully have to disagree.. the Zeniths were indeed the most powerful set of stock carbs on the Alpines (and probably the best looking) but they are a flawed carb setup in terms of staying in tune, leaking fuel and the throttle bodies ovaling out around the butterflys. I ran them for 6 years and while thy sounded good and went well when in tune.. they didn't stay that way as long as i would like. Also.. on the tunning front.. you say you have upped them.. hard to get parts for the Z's.. but i heard that running grose jets on them made them a bit better.

The twin DCOE;s once set are really good, better than the Zeniths and than a single DD.. the SU's, i really wont know till i get them set.. i am guessing they will behave much like the CD Strombegrs... but hopefully with a bit more grunt.

On the period race successes, remember that in production class you had to run the Zeniths.. in the high end comps (FIA international) even rootes went to DCOE's...

here is a pic of them in '63 at LM.

swap

Michael,
did you use the holbay intake with the twin webers?

michael-king said:

Oh.. Gene, assume you got the newsletter the other night.. next month ironically i have a write-up on DCOE's on Rootes motors.. oh well!

Click to expand...

Michael,

Thanks for the insights. And the news letter as well. It seems you have a lot of event options there, even in winter. Some nice reporting and pics. Thanks again.

Gene

It all depends what you want to achieve with the engine. Yes - for high revving race engines DCOE 's are certainly the best choice since they deliver plenty of power above 3000 rpm. That's why Rootes and many others used them for racing purposes. Holbay also had a hard time to get tem set up for proper street use. If you are looking for good low to middle end power the Zenith' s are rather good - but you are right there are some issues which should be cured to make them perform in the way intended ...

65beam said:

Michael,
did you use the holbay intake with the twin webers?

Click to expand...

No Bob, if you look at the pictures you can see that the manifold has the S shaped runners "gooseneck" style as Warnerford termed it. I had the holbay manifold but As i am not using the holbay head it would be limiting as it has smaller ports at the head side.

The manifold i used lifted the carbs higher up the guard allowing the extended auxiliary venturis and longer velocity stacks. Also longer runners help with lower end torque.

I also have a NOS TWM DCOE manifold.. short straight runners.. but means i would have to run shorter stacks, not be able to use the extended venturis and essentially loose more low end torque.

bernd_st said:

It all depends what you want to achieve with the engine. Yes - for high revving race engines DCOE 's are certainly the best choice since they deliver plenty of power above 3000 rpm. That's why Rootes and many others used them for racing purposes. Holbay also had a hard time to get tem set up for proper street use. If you are looking for good low to middle end power the Zenith' s are rather good - but you are right there are some issues which should be cured to make them perform in the way intended ...

Click to expand...

The Zeniths on my car didn't have much bellow 2800, I dont think the webers are any worse.. but i do have a decent length manifold whihc helps and the jetting was sorted.

The Zeniths are a good setup when in 100% condition.. problem was keeping them that way. Still have them sitting in a box.. AU Rootes parts store

swap

Michael,
I was wondering how you could get the holbay intake to fit a standard head. what car is the 2 bbl intake from or is it an aftermarket piece? it's not an original from a series 3 or 4. you say it's from a later rootes vehicle? what would that be? I also find the zeniths work quite well on the original engines in two of my lemans. if we could buy some fuel without ethanol our cars would probably run better.

You can fit the Holbay manifolds to a standard head, you simply cut a wedge out of them in the runner and weld it together again... the instructions are in the alpine guide, and is a common mod in the UK.. Apparently you can open up the ports a little too.. but as i had access to other manifolds that required no mods I used them. I sold the Holbay manifold and the airbox to a local guy who rallied a Hillman Hunter.

The 2BBL manifold pictured was on the scepters and vogues here and equivalent models in the UK. A better designed version of the S3/IV manifolds used on the alpines and rapiers. Think they appeared around '66. Conversion Tuning Centre manifolds made one that looks very similar.

That's cool Michael.

Tell you what I did have that I bought direct from Holbay in the 80's. An inlet manifold for the Alpine with the correct angle. Sold it on eBay after clearing out some old parts - wasn't surprised it went for good money. I recall the problem trying to cut an inlet manifold from a H120 or GLS and reweld for the correct shape to an Alpine.

Did see a few months ago an Alpine here in the UK, with the quad-carbs from a Suzuki GSXR 1100 motorbike, looked a real neat installation. Have a picture somewhere, I'll see if I can dig it out. Doubt the purists will like it