Going dual carbs on the manx!

[Lee.C]

well I have been thinking about it for a while now and I have all the bits I need (except the linkage) 

I have the following:

- x1 Pair of Race Trim DCN manifolds - unported
- x1 Pair of Weber 40dcn14's
- And various venturis

I know which linkage to get so no worries on that score - What I am wondering is - shell I do some head work while I'm at it 

I don't want to go toooooo mad as this engine is staying in the manx and will be driven all over Europe in 2008 plus I only have an engle 100 in there  I just find that with the Single dcn set up on that DDS manifold I use ALOT of fuel and I just know that duals will be alot more efficent (I hope )

My plan is to get all this lot fitted and checked on the bench and then get it Dyno'd - Can anyone recomend anyone GOOD in the uk 

Anyway let me know your thoughts guys 

[louisb]

Check out the How to Hot Rod VW engines. It has some mild porting in it you can do at home. You might consider flycutting the heads a bit to get the compression up to around 8.  A three angle valve job would be good too. HD springs maybe. Maybe some 1.25 rockers.

--louis

[Zach Gomulka]

Cool!! You should get better mileage... that is if you can keep your foot out of it
What are the specs on the motor now?

[Lee.C]

Hey Guys sorry for the delay in replying  Here's the spec's of my little 1641 so far:

AS21 case - full flow oiling
69mm counterweighted crank with lightened and balanced rods
87mm barrells and pistons
Engle 100 cam
Stock dual port heads 040's with stock valves (slightly ported to remove all the sharp corners)
32mm oil pump (race trim)
deep sump (race trim)
Boosh 009 dizzy with electronic ignition kit
Power pulley (smaller 356 diameter)
Lightened and balanced and 8 dowelled 200mm flywheel
"Bolt up" rocker sharfts with swivel feet adjusters
Cromoloy pushrods
Straight cut timing gears
DDS center mount "RAM" type manifold with a single Weber40dcn14 Carb (with 24mm venturi's) the two end piece's of the manifold although stock have been heavily ported,

and all this little lot revs to about 5500rpm 

I have also been thinking it might be a good idea to check mt "timing" you see my power pulley has NO markings on it  and I have only ever done my timing by "Ear"

So let me know what you think guys 

[Diederick/DVK]

too bad for the looks, but i'm sure it will turn out for the best once you run dual carbs!

and nope, it's not very fuel efficient.
i can vouch for that after our ride 

[Bewitched666]

To bad you already have the 40 carbs otherwise you could have looked for some 36 carbs.
The dual setup can run very economic and yes it also depends on the heavyness of your foot.

If you setup the carb correctly it can run great without very high costs of fuel

[Rick Meredith]

So Monkiboy, did ya go with the duals?

[Lee.C]

Funny you ask actually cos I decided yesterday NOT to go ahead with this little project cos it runs and drives SOOOOOOOO well at the moment it just seems a shame to mess about with it - I will be getting it dyno'd though 

I doing alot of other work on the Manx over the winter including moving the oil cooler and filter and breather box and fitting a rear seat and roll hoop - I will post some pic's asap 

[Diederick/DVK]

I doing alot of other work on the Manx over the winter including moving the oil cooler and filter and breather box and fitting a rear seat and roll hoop - I will post some pic's asap 

dude! sounds cool, but where are you putting the cooler etc?
p.s. should you not be working on another project 

[Lee.C]

I doing alot of other work on the Manx over the winter including moving the oil cooler and filter and breather box and fitting a rear seat and roll hoop - I will post some pic's asap 

dude! sounds cool, but where are you putting the cooler etc?
p.s. should you not be working on another project 

You'll have to wait and see dude  its all nicely hidden though - it was a MISSION I can tel you

As for that "other project" I need to save some serious cash first BUT the body is fully ready to be lifted off 

[Lee.C]

Well guys I have been thinking about doing this again - so any hints and tips guys

Here's what I have:

x1 Pair of Race Trim DCN manifolds - unported and they will also be shortened to fit under the back of the manx
- x1 Pair of Weber 40dcn14's
- And various venturis

[Zach Gomulka]

Do they have to be shortened? Shame if they do

My suggestion is to bolt them up and tell us what happens What size venturis do you have at your disposal??
Good luck!

[Lee.C]

Hey buddy - I am not too bothered about the whole shortening thing as the top plates have been drilled about 3million times for different carbs over the years - plus it will make everything ALOT easier to fit in (including airfilters)

I am planning on just getting hold of some 1/4 inch ali sheet and making some new top plates - shouldn't be too hard

I have 24 or 32 venturi's - I was thinkin 32's for this set up 

[Jim Ratto]

Hey buddy - I am not too bothered about the whole shortening thing as the top plates have been drilled about 3million times for different carbs over the years - plus it will make everything ALOT easier to fit in (including airfilters)

I am planning on just getting hold of some 1/4 inch ali sheet and making some new top plates - shouldn't be too hard

I have 24 or 32 venturi's - I was thinkin 32's for this set up 

yeah I think with your past experience, like on the Ferrari restorations, and the mirror you had talked about polishing, you could make the manifolds work. How much do they have to be shortened?

Did you make a decision on head work? I don't think the effort in doing much to the heads would be worth it in the end, for one because it isn't a really big motor where the pull thru the intake is that hard. Sounds like you've already cleaned up the ports a little anyway. I think just by eliminating the restrictive VW dual port end castings will free up a bunch of flow (going to dual 2bbl carbs). I think the 1.25's would be good move though, it will hold valves open at higher lift, longer, increasing time the valves can flow.
I think your light buggy will benefit from the 32mm vents as well. If your motor was in a Beetle or Ghia, I'd say 28mm. But since you have much less weight to get moving the 32's will work. There is a formula I can send you if you want to determine venturi diam vs. engine cc vs. rpm.
I bet anything the dual Webers are going to give you much better mileage than the DDS/single.... especially in cold weather, I am sure that manifold ices up and fuel pools up and.....

cool deal.... go for it

[Lee.C]

Hey buddy - I am not too bothered about the whole shortening thing as the top plates have been drilled about 3million times for different carbs over the years - plus it will make everything ALOT easier to fit in (including airfilters)

I am planning on just getting hold of some 1/4 inch ali sheet and making some new top plates - shouldn't be too hard

I have 24 or 32 venturi's - I was thinkin 32's for this set up 

yeah I think with your past experience, like on the Ferrari restorations, and the mirror you had talked about polishing, you could make the manifolds work. How much do they have to be shortened?

Did you make a decision on head work? I don't think the effort in doing much to the heads would be worth it in the end, for one because it isn't a really big motor where the pull thru the intake is that hard. Sounds like you've already cleaned up the ports a little anyway. I think just by eliminating the restrictive VW dual port end castings will free up a bunch of flow (going to dual 2bbl carbs). I think the 1.25's would be good move though, it will hold valves open at higher lift, longer, increasing time the valves can flow.
I think your light buggy will benefit from the 32mm vents as well. If your motor was in a Beetle or Ghia, I'd say 28mm. But since you have much less weight to get moving the 32's will work. There is a formula I can send you if you want to determine venturi diam vs. engine cc vs. rpm.
I bet anything the dual Webers are going to give you much better mileage than the DDS/single.... especially in cold weather, I am sure that manifold ices up and fuel pools up and.....

cool deal.... go for it

Thanks for droppin in Jim - They don't actually haveto be shortened it will just make EVERYTHING easier - I will probably chop off between 30 - 40mm - not too sure yet  What height are type manifolds 

You are also right about the heads - I won't be taking them off (no need) I am very interested in 1.25's   
I already have chromoloy pushrods BUT will I have to adjust their length if I fit 1.25's 

You are also right about the "icing up" it doesn't seem to effect the running too much but it looks like an ice lolly thats just out of the cooler 

Oh yeah I will also be fitting a proper header with a single quiet pack so that should give me abit more "Flow"

Also got any rough ideas for jetting Jim 

[Diederick/DVK]

cool idea lee.
looks like you've pulled an all-nighter just thinking out your plan! hehe.

theoretically, it should do your engine a lot of good. but i hope you can cover up the cutout you made for the single carb...

[Jim Ratto]

Hey buddy - I am not too bothered about the whole shortening thing as the top plates have been drilled about 3million times for different carbs over the years - plus it will make everything ALOT easier to fit in (including airfilters)

I am planning on just getting hold of some 1/4 inch ali sheet and making some new top plates - shouldn't be too hard

I have 24 or 32 venturi's - I was thinkin 32's for this set up 

yeah I think with your past experience, like on the Ferrari restorations, and the mirror you had talked about polishing, you could make the manifolds work. How much do they have to be shortened?

Did you make a decision on head work? I don't think the effort in doing much to the heads would be worth it in the end, for one because it isn't a really big motor where the pull thru the intake is that hard. Sounds like you've already cleaned up the ports a little anyway. I think just by eliminating the restrictive VW dual port end castings will free up a bunch of flow (going to dual 2bbl carbs). I think the 1.25's would be good move though, it will hold valves open at higher lift, longer, increasing time the valves can flow.
I think your light buggy will benefit from the 32mm vents as well. If your motor was in a Beetle or Ghia, I'd say 28mm. But since you have much less weight to get moving the 32's will work. There is a formula I can send you if you want to determine venturi diam vs. engine cc vs. rpm.
I bet anything the dual Webers are going to give you much better mileage than the DDS/single.... especially in cold weather, I am sure that manifold ices up and fuel pools up and.....

cool deal.... go for it

Thanks for droppin in Jim - They don't actually haveto be shortened it will just make EVERYTHING easier - I will probably chop off between 30 - 40mm - not too sure yet  What height are type manifolds 

You are also right about the heads - I won't be taking them off (no need) I am very interested in 1.25's   
I already have chromoloy pushrods BUT will I have to adjust their length if I fit 1.25's 

You are also right about the "icing up" it doesn't seem to effect the running too much but it looks like an ice lolly thats just out of the cooler 

Oh yeah I will also be fitting a proper header with a single quiet pack so that should give me abit more "Flow"

Also got any rough ideas for jetting Jim 

Lee,
You will have to look at the geometry of the rockers at zero, half- and full lift to determine what to do about length. Are they rockers with adjusting screw at valve end or pushrod end?

If pushod end:
install rockers with your current length pushrods, then adjust valve lash (I assume you're setting lash at "zero" cold?), if possible. You may find that you cannot get lash and vlaves get held open. You'll notice that screws will be backed all the way into the rockers and you will not be able to "spin" pushrods with your fingers. If that happens, you may need to shorten pushrods. Here is how you can determine.... how many threads are "out" beyond lock nut on adjusting screws... you should have 2-3 threads showing, and check that cup (for pushrod) isn't backed all the way into rocker. If you can get this setting by using the rocker pad shims, then you can use your current pushrods as they are. If not, then you'll need to shorten them. Do you have an adjustable pushrod tool? If not you can make one easily from a stock pushrod. The sure fire way to check this and you can do it in the car (since it is a Buggy  ) is to mount a sutiable dial indicator on head and measure valve travel. At 50% (half) lift the rocker pad should be "centered" on the valve lash cap (if you have pad rockers you'll need lash caps, and those will require shorter pushrods almost for sure! They increase length of valve, basically) meaning the curve of the rocker pad should be at the peak at 50% lift. Hard to describe without pics.

If the adjuster is at vlave end... get ahold of Diederick. I taught him how to do this with some emails and pics of his geometry on his motor befor ei shipped it. Or let me know... 

Jetting? I've never jetted those Webers, but assuming 32mm vents I would say 130 or 135 mains and 50 or 55 idles and 185 air correctors. I have no idea which emulsion tubes though.

have fun

[Diederick/DVK]

yup, i've got a 5-page how to set your geometry guide by jim 

[Jim Ratto]

yup, i've got a 5-page how to set your geometry guide by jim 

8 pages? 

what font size did I Use?

[Diederick/DVK]

sorry i just checked and it's 5 page without the pics.
i copied and pasted

what font size did I Use?

that would be courier 13

[Lee.C]

Thanks for the tips Jim - I think this should be a fun little project for the winter 

Those jet sizes sound about right from what little I do know - By the way my adjusters are at the VALVE END

So over to you dieds 

[Jim Ratto]

Thanks for the tips Jim - I think this should be a fun little project for the winter 

Those jet sizes sound about right from what little I do know - By the way my adjusters are at the VALVE END

So over to you dieds 

it's not complicated... you'll see. Let me know if you need some help 

[Jim Ratto]

oh by the way... you may be able to increase your total timing once you get the Webers on, further helping performance and mpg.

[Lee.C]

my timing is actually around 28/29 degs at 3000rpm - So I could move up to 32 degs then 

[Zach Gomulka]

The more the merrier! I run 35 total on my car, but it is a stockish engine with factory CR...

[Jim Ratto]

my timing is actually around 28/29 degs at 3000rpm - So I could move up to 32 degs then 

did you get degrees on your pulley?

Lee, I can't tell you what your motor will tolerate... you have to tune it and see. But since your car is light, and since you have small bore and are going two 2bbl carbs, I would say depedning on ambient temp and fuel you could start @ 30 and listen carefully for pinging.
Also, you can watch the plugs! Your buggy probably has a loud exhaust, right? So hearing the pinging my be tough
Go drive car thru thru the gears, fairly hard, then do a cut clean. Pull plugs and with a magnifying loop, look at insulator nose of plug.... if you see speckels or "pepper" (pin sized dots) on porcelain... you can bet it is detonating... those are flecks of alumimun on the plug.
Also you can look at heating signs on threads of plugs... if they are blued all the way up....trouble.... 
And watch rocker chambers in heads.... if you see that they turn "gold" then the heads are getting too hot and frying the engine oil.

[Lee.C]

Yeah I got a "marked" pulley now (at last) plus I will have a proper header on there next season with a single quiet pack so I should be able to hear any pinging or as we say over here - PINKING

[Jim Ratto]

Yeah I got a "marked" pulley now (at last) plus I will have a proper header on there next season with a single quiet pack so I should be able to hear any pinging or as we say over here - PINKING

ah yes "pinking" maybe because mixture is "weak"
spanner
wings
windscreen
carburettors
whilst

I have read my fair share of Haynes manuals

I think Dieds has the pics and write up I sent him to do his 1915 when I finish his heads and ship 'em.

[Lee.C]

Well guys I went to a local machine shop today and they are going to make up a couple of new top plate for my race trim manifolds and they are gonna shorten them for me to - they will cut across this line 

[Lee.C]

Well I went to the machine shop today - they are still having a little trouble working out how to shorten the manifolds properly - I think we have it sorted now - But they have finished these new top plates for me