243 replies to this topic

[Brian Pascoe]

Hi James. Below is a email I sent Keith in regards to my engine. He thinks I might need another progression hole on my 13's, what do you think.

Edited by Brian Pascoe, 05 February 2018 - 12:06 PM.

[Brian Pascoe]

Hi James , Disregard the above, I stuffed up.I sent Keith an email in regards to purchasing EVF's and idle jets that you have,but he mentioned that I might have to drill another progression hole in my 13's. What is your opinion as I don't want to go down that path just yet.

Brian

[jd lj]

I agree that it may be something that you would benefit from. You could try using the EVF tubes and "W" idle jets and see how you go I guess. Don't be too afraid of the idea of drilling a third progression as Keith has a mechanism available for doing just that and he'll guide you through the process as much as possible. Others on Sidedraft Central have done this with good results. Don't attempt it without some guidance though unless you're experienced in this type of engineering work, but even then you must understand the positioning requirements. The idea behind doing this is to extend the duration of the progression circuit so that it overlaps more smoothly with the start of the main circuit. For your piece of mind I would happily recommend 45dcoe13's for use on a Holden red motor due to the fact that the first progression hole is ideally located to suit the position of the throttle plates at idle. This fact is one of the most crucial factors in tuning dcoe's. However if I was to use 45dcoe13's myself in the future I'd drill the third progression hole (but this must be done correctly).

You can confidently put your trust in Keith's advice as he's left no stone unturned in his quest to reverse engineer these carbs and I have no doubt that he could teach Eduardo Weber a thing or two about his own carbs if he was still around.

James

[Brian Pascoe]

Hi James,Is there any engineering drawings out there in regards to adding progression holes to DCOE 13's to suit my 186. I would like to make a jig to do the job.

Brian

[jd lj]

I don't know of any engineering drawings for the above task.

If you wanted to make a jig to do so you could design something that screws into the idle mixture screw holes (m5 thread) and the progression hole port (M8 thread on early model and m9 thread on later models) that can then be flipped over from left to right to mirror the location of the holes for each side of the carb. You could use the overlap of the existing two holes as a reference for working out a suitable position for the third hole and use a similar diameter to the existing ones or start smaller and gradually increase the diameter as needed to achieve a suitable result. With such a jig this could be carried out without needing to remove the carbs. Perhaps bring this up on Sidedraft Central for a higher level of knowledge than I can offer as I haven't ever performed this task myself but the information in this post is how I'd expect to approach it.

[jd lj]

Actually, you couldn't use the thread off the progression hole ports as you need to drill through there but you could use a tube attached to the jig that fits in the progression hole port to help locate the jig in position and have the hole in the jig to drill through.

Or if your set up with some type of milling machine your could set something up with that I assume.

[LC-GTR-1969]

For what its worth, my thoughts on the matter are; making the jig for repeatable accuracy with holes should be relatively easy (with a bit of know how and fabrication). 

 

However, my concern would be placement of the holes and size- this would need a fair bit more thought. James- I remember you sending me pics of various progression holes from various DCOE models- perhaps Brian can use these to help guide him to hole placement and size. You could index the existing hole sizes against the pics to help identify where and what size the new holes should be. However, there is still going to be a fair bit of estimation involved-- unless you can find someone who has drilled extra holes in your specific model before, and who can give you some guidance. 

[Brian Pascoe]

Hi James,I am having problems with yahoo so i'll post it here.I put 45F8 idle jets in and took the car for a run.My AFR was 12 to 12.5 cruising in any gear 1000 to 2000 rpm,but the AFR leaned out more (18 to 20 ) compared to the 50F8 jets.Does that help any with problem I have. Brian

[jd lj]

Hi Brian,
Are you still referring to the off idle stumble or is it going lean at a different rpm? You need to make sure that you always specify the rpm's where the problem occurs if any diagnosis is to be offered.

James

[LC-GTR-1969]

Hi James,I am having problems with yahoo so i'll post it here.I put 45F8 idle jets in and took the car for a run.My AFR was 12 to 12.5 cruising in any gear 1000 to 2000 rpm,but the AFR leaned out more (18 to 20 ) compared to the 50F8 jets.Does that help any with problem I have. Brian

 

For what its worth- I generally aim for lean cruise like 13.8:1 or 14:1 for cruise, limited load state. This works for me and my engine- but my current cam has a lot of overlap- so my AFR can appear slightly leaner than reality due to some over scavenging (read unburnt fuel out the exhaust reads as lean) when the cam is not on the boil. 12 to 12.5 AFR for what I call cruise is quite rich- but with your fewer progression holes this may always be a compromise- ie it may be a challenge to achieve a clean lean cruise with only 2 progression holes. 

Edited by LC-GTR-1969, 20 February 2018 - 01:12 PM.

[Brian Pascoe]

Yes James,  Same small off idle stumble but leaner

[jd lj]

Since you've got access to a lathe drill out a set of idle jets to give them a 3mm internal bore and test again. You could also drill new air bleed holes in them a few millimetres closer to the bottom and plug up the original air bleed holes. This will work similar to the "W" idle jets by providing a bigger mixing area for the air and the fuel, obviously this won't give you the luxury of an adjustable air bleed like the "W" idle jets have.

As I've previously mentioned I'd suggest trying a lighter pump rod spring too, contact me if you'd like to borrow a set to do so.

James

[Brian Pascoe]

Do you suggest I do the mod on the 45F8's.I will probably buy a set of light springs,but thanks for the offer.

Brian

[jd lj]

You might as well try it on the 45f8's and if they need more fuel just drill those ones out to 50f8's. They'll behave differently to your existing 50f8's due to the larger internal bore size.

No worries in regards to borrowing the springs. If you want you can borrow them, test and if you like them you can purchase them from me and if not just send them back and all that it'll have cost you will be the postage cost.

I have access to just about any dcoe part required if anyone else needs anything or even will restore or rekit peoples existing carbs to meet their requirements.

James D

[Brian Pascoe]

Hi James,

Keith asked me to email him on his personal one a photo of my progression holes, but all he gave me was kdfranck@ 

Can you help me out.

Brian

[jd lj]

No worries, I have a photo of the progression holes on a 45dcoe13 handy that I'll send him on your behalf. Yahoo Groups has been playing up recently.

[Brian Pascoe]

Thanks James

[Brian Pascoe]

just ordered light pump springs,I will let you know the outcome.I will also do the jets next.

Brian

[Brian Pascoe]

hi james put light acc springs in. it went to 19-20afr on them compared with 16afr with the original heavy springs with 45F8 idle jets. i am going to try 50F8 when I get a chance

Brian

[jd lj]

I'd expect that the 45f8's would be too lean for you, but once you drill the internal bore to 3mm etc as described above then they will behave differently and may work and if not then drill the fuel orifice to 0.5mm which will make them a 50f8 with the internal bore modifications. This way if it turns out that the original 50f8's were more suitable then you still have those untouched and ready to reinstall.

That's interesting about how the change of pump rod springs reacted. I've found that the lighter springs can have the opposite effect to what you experienced but I believe that that's more about the amount of leverage being utilised in the linkage set up.

James D

[Brian Pascoe]

Hi James,

I drilled out my 45F8 with a 3mm drill and took the jet out to .5 mm.But I haven't moved the F8 hole as yet.Took it for a road test and noticed a great improvement with the off idle lag.(hardly any) When I accelerated in top gear at 2000 rpm the afr went to 17/19 for a moment.It looks like we are slowly get it sorted.

Brian

[jd lj]

That's good to hear Brian. Is that lean spike you mentioned any different to what you experienced before you modified the idle jets? What's the AFR reading during the rest of the progression circuit, perhaps you could drill out the fuel inlet in the idle jets further to 0.55mm, tbc.

James D

[jd lj]

Well we've all heard that you need to use softmounts when you have dcoe webers. We've all been told that if you don't then the vibrations make the fuel froth which alters the fuel level which in turn richens up the mixture.

I had my doubts about this and decided to test the theory. After making a cam lobe to fit to a drill I filled a spare carb with fuel and let the drill shake the carb at various rpm's. I was unable to induce any frothing whatsoever and found that as the rpm's rise the movement of the fuel actually smoothes out. At the drills lower rpm's the fuel is shaking around but not frothing, this condition is still present even with softmounts fitted, to see this for yourself remove an emulsion tube and look down the e tube well whilst the engine is idling (just don't rev it past 2500 rpm's with the e tubes out (the emulsion tubes aren't required at low rpm's).

Based on the above experiment I decided to try running my carbs without softmounts and made my own bakerlite dcoe spacers on the cnc at work. I've been using these for several weeks now with no negative effects or noticeable changes in the mixture strength.

I've read in the past that an engine with its number of cylinders being a multiple of three has different vibration characteristics than an engine whose cylinders are a multiple of two. The multiple of three is meant to be smoother. So a 6 cylinder should be smoother than a 4 cylinder.

RT Charger's which were originally fitted with triple dcoe's from the factory were never fitted with softmounts along with various other exotic European cars that were fitted with dcoe's.

Obviously this testing is still in its early stages and only a sample size of one, your own application may differ to mine, but it'll be good to not have to worry about the headache that softmounts can provide for various reasons.

https://www.flickr.c...2478@N02/uMcAS0

https://www.flickr.c...2478@N02/uMcAS0

James D

[jd lj]

Hi James,
I drilled out my 45F8 with a 3mm drill and took the jet out to .5 mm.But I haven't moved the F8 hole as yet.Took it for a road test and noticed a great improvement with the off idle lag.(hardly any) When I accelerated in top gear at 2000 rpm the afr went to 17/19 for a moment.It looks like we are slowly get it sorted.
Brian

I should have mentioned this earlier but now that you've modified the idle jets they will now work like a venturi vacuum pump. So just like a spray painting gun where you pull the trigger and more air flows through and this in turn draws more liquid along with it, if you increase the size of the air bleed hole or number of holes you'll be drawing more fuel through the jets as the rpm's rise.

So with these modified jets a larger air bleed hole will lean out the lower rpm's of the progression circuit but will also richen the upper end of the progression circuit and the opposite applies if you have a smaller air bleed hole in the modified idle jets.

If the mixture is too rich or lean throughout the entire range of the progression circuit then the fuel inlet hole needs to be altered.

Regardless of these changes the idle mixture is adjusted with the idle mixture screws.

The same theory applies to Keith Franck's "hypojets" and "W" idle jets, however these have the great addition of a split collar which you rotate to open or close the amount of air bleed holes that you require.

James D

[jd lj]

Brian,
It sounds like you're getting close but still have a little bit of work to do. How does the drivability etc currently compare to when you started this thread?

James D