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Keesjr

Original Poster:

57 posts

33 months

[news] 
Friday 23rd March 2012 quote quote all
Will it be possible to succesfully run a 1.6 8 valver with a weber 38 dgas carburettor and a Kent PT28 cam (race) 309/314 inlet/exhaust?
Anyone experience with a combination like this?
I have already fitted uprated valvesprings and spacers from puma.

Edited by Keesjr on Friday 20th April 19:15

packman10_4

213 posts

81 months

[news] 
Friday 23rd March 2012 quote quote all

Ask Puma then , by all accounts he has done a lot with these engines. I think there very fussy about cam profile as the factory ones are pretty good.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Friday 23rd March 2012 quote quote all
I hope puma reacts to this, he has very much experience with all kinds of engines. So he might know if this works.
Anyway i will be adjusting the valve-clearances and timing te camshaft tonight, and see what happens :-)

Keesjr

Original Poster:

57 posts

33 months

[news] 
Sunday 25th March 2012 quote quote all
Timed the cam and set the igntion timing, and it runs a bit lumpy as i expected already.
But put the pedal to the metal and it revs like crazy, see what happens on the rolling road in a couple of weeks.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Wednesday 11th April 2012 quote quote all
It has been on the rolling road today, 115 bhp and 150 nm at the wheels pulls from 2500 and revs to 7500 rpm.
I'm going to try bigger chokes in this carb and see if it brings more power.

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oakdale

662 posts

89 months

[news] 
Thursday 12th April 2012 quote quote all
Keesjr said:
It has been on the rolling road today, 115 bhp and 150 nm at the wheels pulls from 2500 and revs to 7500 rpm.
I'm going to try bigger chokes in this carb and see if it brings more power.
Bigger chokes?
You can't fit bigger chokes as these carbs don't have removeable chokes.
These carbs were designed specifically to be used on 6 cylinder engines and as a result of this it can be difficult to get the fueling right when used on a 4 cyl engine.
Was the jetting altered by the rolling road operater or has just been left as standard?
I have quite a lot of experience of using these on 4 cyliner engines and may be able to give you some advice if you tell me what jets and air correctors are fitted and what mods have been made to the carb.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Thursday 12th April 2012 quote quote all
Thanks! The main jets were 135's and now there are 148's in it, the air correction jets were left stock, the fuel curve is okay now, a bit rich at low revs but around 12,5 - 13,0 everywhere else.
The carburettor is a brand new one, with no modifications.
As the chokes cannot be changed i'm leaving them alone and see how it runs at the track!

Keesjr

Original Poster:

57 posts

33 months

[news] 
Wednesday 18th April 2012 quote quote all
It runs okay, just need more power.
I have thought to fit a 4-barrel Holley 390 cfm carburettor, has anyone tried this on a four-cylinder?
Or maybe a big old carb from an old straight six BMW or Opel.
The head and cam are not restricting the enginepower, it just that this carb flows not really enough air for this engine.
Pumaracing? Any idea's??

one eyed mick

864 posts

48 months

[news] 
Wednesday 18th April 2012 quote quote all
Throttle bodies and inj ,bike carbs , 45's take your choice, in my op a 4 barrel would kill it ,the dgas was fitted to 3 lt Capri's so you have your last posted option already, doyou have reg limit i.e. 1 carb ?

packman10_4

213 posts

81 months

[news] 
Friday 20th April 2012 quote quote all
It would run better with the 2ltr DGAV carb on there , would nice to see 120 + at the wheels cant see why with a good matched set up IE head and cam selection.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Friday 20th April 2012 quote quote all
What's the difference between a DGAS and a DGAV? In my last post i said that the A/F ratio was between 12 and 13, but it leans out to 13.7/1 at 7500 rpm, so i'm going to fit smaller air correction jets to bring the ratio to 12.5 - 13.0/1 at 7500.
At the moment 185 air jets are fitted, so i'm to fit 175's and see what happens at the rolling road, maybe pick up some more top-end power too.
I also have been thinking about trying a spacer between the carb and the intake manifold, it almost always works on V-8's so it has to work on a 4-cilinder too, a 3/4 inch thick spacer fits nicely and the bonnet does still fit without hiiting the air filter, so i'm going to try that too.
Just making one modification at once and see what happens, if it works --> great! If it doesn't --> it was already as good as possible ;-)

oakdale

662 posts

89 months

[news] 
Friday 20th April 2012 quote quote all
As I said previously, it can be difficult to get the fueling right with the dgas carb on a 4 cyl engine.

An unusual feature of these carbs is that fuel is pulled through the accelerator pump jets as part of the overall fuel metering of the carb, they are not just pump jets (a lot of "experts" don't realse this).

The carb was designed for the Ford v6 engine, which due to its very short inlet tract had a tendency to backfire back through the inlet manifold, so to reduce this tendency a lot of fuel was injected by the accel pump.

If you have 55 pump jets, remove the jet assembly and peen over one of the orifices, so that you are left with just one jet outlet, then try main jets in the 160/165 range with the 185 air correctors you already have.

This sort of setup produced serious power for me on a 2.1 Pinto with a bit less cam duration than you have.

ETA for some reason I was thinking this was a 1.9 (I should have realised it was a 1.6 due to the rpm stated) so I would say 160 main jets.

Edited by oakdale on Friday 20th April 23:03

Keesjr

Original Poster:

57 posts

33 months

[news] 
Friday 20th April 2012 quote quote all
Thanks Oakdale, my engine also has a short inlat tract, a 1.6 carb manifold with a new carburettor mounting pad welded to it to mount the dgas in the right position.
When i'm going to the rolling road again we'll try your suggestions.
Is it so that the fuel drawn through the pump jets richen the midrange fuelling but leaves the top-end relatively lean?
Let's get the fuelling spot on then, and then further experiment with the spacer and some other little things.
Thanks!

Keesjr

Original Poster:

57 posts

33 months

[news] 
Saturday 21st April 2012 quote quote all
When the carburettor and spacer are working good, i also want to try a tubular 4-2-1 or 4-1 manifold, but i also know that the stock cast iron manifold and downpipe are already very good parts, the manifold is already port matched to the head.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Sunday 22nd April 2012 quote quote all
So far i have blocked one of the accel jets and tried a couple of runs, but it hesitated because of not enough fuel, so both accel jets are back in place.
Got back to the 148 mains and 170 air jets instead of the 185 air jets, instead of starting to tail off at 6700/6800 it now pulls to 7200/7300 before tailing of, if needed it can be revved to 7800, then it seems to hit the wall and power stops immediately.
After that i fitted a 3/4" spacer between the manifold and carb, that also works, not much but it feel a little bit better from about 4000 onwards.
Can't wait to take it to the rolling road again to see the new power and torque curves.
I don't think the torque is much higher, but it feels like it's holding the torque till higher up in the revs, that's what is need a very long powerband!

Keesjr

Original Poster:

57 posts

33 months

[news] 
Tuesday 5th June 2012 quote quote all
Next friday it's a trip to the rolling road again, to see what the modifications have brought in torque and power, spacer under the carb, the jetting and filled inlet ports, just wait and see...

Keesjr

Original Poster:

57 posts

33 months

[news] 
Sunday 10th June 2012 quote quote all
The modifications worked, it needed smaller main jets, and some adjustment of the ignition. It produces 162 Nm of torque / 5000 and 125 bhp / 6600 @ the wheels, by 7000 power drops off, it can be revved to 7500 but what's the point of that?
What next? I would like to try a 4 into 1 exhaust manifold, but i don't want to loose power lower (under 3500).
So does anyone know some dimensions for the right pipe diameters and lengths, or is that really something to try and see what happens.
On Dave Baker's site (pumaracing) he says that the stock cast iron manifold is already very good, and i'm convinced that this is really true, but if it's possible to gain another 5 to 10% of power and torque it's definitely worth the trouble to me.
Supersprint have an 4-2-1 manifold in their program and Magnex did or does a nice 4-1 version although expensive.
I'm not afraid of doing some work on a d-i-y manifold and like to experiment with different manifolds.
A bit like the Saab where Dave was involved with getting more and more power and torque from.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Monday 11th June 2012 quote quote all
I'm going to weld up a manifold myself, in competition it always turns between 4000 and 7000 rpm, so my idea is that a 4-1 pipe should be okay and a little easier to bend and weld up, and also make more power, is there anyone who has experience with 4-1 and 4-2-1 pipes, because i don't want to loose torque at lower revs...

packman10_4

213 posts

81 months

[news] 
Tuesday 12th June 2012 quote quote all

Its good to see some good results with home brewed stuff , i was not far off in predicting ther power you should be seeing , also id try short trumpets out the top of the carb , i use to moddify DCOE ones to fit but in sure someone now does these.

Cant see why you cant pick up 2-4 hp and torque , it worked on pinto hot rod engines.

Keep the updates comming.

Keesjr

Original Poster:

57 posts

33 months

[news] 
Tuesday 12th June 2012 quote quote all
Thx for the tip to fit trumpets to my carb, i have some 45 mm ones on the workbench and they are short enough to fit under the air filter.
I'm also thinking to remove the cold-start choke valve, as i've never used it, it always starts with two strokes of the accelerator-pedal.
If the trumpets and removing the cold-start brings another couple of horsepower & torque i'm happier then ever :-)
So first see what the intake mods will do, then further with 4-1 or 4-2-1 pipes for even more power ;-)
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