Dual Carb Ideas

different cranks can be swapped around between engines... to give different swept capacities.

1603cc (87 x 67.4)is a popular one as it fits inside a stock 1500 block,
a quick search of 1599 sohc, 1600 sohc and 1603 sohc bought up these (and more)

http://xwebforums.com/forum/index.php?threads/22458/
http://xwebforums.com/forum/index.php?threads/25589/
http://xwebforums.com/forum/index.php?threads/22058/
http://xwebforums.com/forum/index.php?posts/194236/

67.4 crank is found in sohc's from 1372 (80.5 X 67.4) all the way to 1581 (86.4 X 67.4) ... in blocks that are the same overall height as the X19 1500 block height

any longer stoke cranks (stock Fiat and most aftermarket) will require a "tipo" style block, which has more crankcase room to accommodate the longer stroke options...

The plethora of aftermarket parts hasn't been spawned by demand from the USA... more so from yugoslavia, croatia , serbia, and greece,,,,where one make race series in Yugo's has kept demand and supply strong.

1500 can be built quite strong on a budget... here's another example.
http://www.xwebforums.com/forum/index.php?posts/189012&highlight=R.P.F.C.C.+engine+build#post189012

SteveC
 
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What kind of performance gains can be expected with a 1581? Also not too sure of the costs involved?

One final question to round things off: Where do you source parts such as uprated pistons, rods, camshafts etc?

Thanks
James
 
The conrod for 1372,1495 and 1581 engines is the same C to C length and journal sizing. SCAT makes an acceptable 4340 CrMo H bean rod with ARP bolts..search this for you will find PLENTY of reference to them. Can be found around $300/350us for a set of 4...sometimes on ebay.

Pistons.... how big is your piggy bank?

Custom forged can be around $650/750 us plus rings plus waiting time....
lots of people in the UK and USA that will make custom pistons... and in croatia, argentina, italy ... if you can overcome the language barrier.

Cams...in the UK you have Kent and Piper that both make new cams and vernier cam gears for Fiat sohc ....there are also a few retailers in croatia/serbia/greece etc that might have what your after?

It all depends what your plan is?

It all depends where your starting from??
(your engines current mileage/ condition/configuration)

if your starting with a 1500 euro spec 85hp engine there is little you can improve with "add on" external parts. ...

the standard cam is already quite performance oriented (24/68)
the standard cast iron twin out exhaust manifold and twin front pipe is 'as good as' -or better- than a lot of the aftermarket extractor systems out there
The standard head is one of the better flowing 1500 (36/33.4) with the biggest valve seat throats of the x19 heads
The standard head/piston configuration is already at 9.2:1
The standard intake manifold ports and carb is the largest supplied stock on an x19


so what do you want to improve??
(for a 300 GBP budget)

SteveC
 
Thanks for the info Steve.

It's got about 60k miles on it, but the interior and paintwork is awful. The engine also only runs on two cylinders at idle (1-1.5k revs) then fires on all 4 past about 2k.

As I've mentioned previously, I'm going to do a complete restoration on the car, just thought it would be a good opportunity whilst the engine will be in pieces to spruce it up a bit.

Thanks
James
 
YES... the choice is yours! DCOE's will require...

some intrusion into the rear trunk area... DCNF's won't. A straight shot using DCOE's will certainly have a somewhat better hp gain if all else is the same.

Have fun... spend lots!
 
As long as your block is in good condition with minimal bore wear, with your £300 you could have my Punto Sporting crank and pistons to give you 1581 cc, a Piper fast road cam and a carb rejet. That should get you up to something like 105 bhp.

Some might say it's a bit "ghetto" to just put some used pistons and rings in your block but as long as the engines concerned are low mileage you should be ok. I can say the Punto block I'm using has minimal bore wear.
 
rachaeljf said:
Some might say it's a bit "ghetto" to just put some used pistons and rings in your block
Click to expand...

Not me! It's the best way to go I think!

Thanks for the offer, I'm away at the moment but when I'm back I'll look over things and get back to you.

Thanks
James
 
124868.jpg

Dual DCNF's.

HEc4xN.jpg


OKTSyE.jpg

Dual DCOE's.
 
Shave the head 60 thou (head face and cam towers) and try a single dcnf 36mm for 1300 or 40mm for a 1500 and a 40-80 cam. The trouble is finding an intake manifold. The carb barrels needs to be parallel with firewall. That"s one way to get HP, my old orange car rocked with that setup, (a lot of porting and large valves) it really didn't feel like a X anymore! (I sleeved the tensioner bearing to work with a 1500 stock belt)

Chris
Oakland, ca.
 
karhawk said:
Shave the head 60 thou (head face and cam towers)
Click to expand...

Chris,

that's not going to work for James, he's in the UK and has a euro spec carb 1500, the head face is already flat (no 60 thou full circular USA decompression recess)

The single dcnf style carb idea works well and is a great compromise. A single 36/40 dcnf style carb setup is up around 90% of output of twin carbs, but much less expense and far easier to set up.

SteveC
 
That sounds an idea, thanks Steve.

Got the engine out, two mounting points were broken, one on the gearbox and one on the engine. Looks like I'll have to tackle these first before anything else.

Thanks
James


 
rachaeljf said:
As long as your block is in good condition with minimal bore wear, with your £300 you could have my Punto Sporting crank and pistons to give you 1581 cc, a Piper fast road cam and a carb rejet. That should get you up to something like 105 hp
Click to expand...

all that would give you is a 9.2:1 1581 cc engine... which when it has the larger intake valve head fitted (and a pretty ordinary camshaft) is rated at 90hp...

But you're not talking about including the larger valved / port late tipo style head, so the output will be reduced. Add a better camshaft (I would tend to use the euro spec 1500 cam as that you already have) and output will increase.

A single dcnf /dcnva style carb will require a different manifold or welding/cutting on your existing manifolding. I have these modified by a friend of mine who is a good machinist and tig welder.

http://xwebforums.com/forum/index.php?threads/9564/

SteveC
 
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Fuel droplets and air molecules have mass, which is affected by gravity.

overall runner length and volume have a big effect on throttle response and air speed.

One back to back test I did (about 30 years ago) on my 128 was dcnf vs dcoe, and the dcnf's definitely made more torque, all other things (jetting / chokes) being the same...but manifold volume and length was longer/larger with the dcnf's

Compare the insides of a 40dcoe and a 40dcnf and you will be surprised at how restrictive the dcoe is, especially in the area of the primary diffuser. The 40 dcoe has a full circular ring that reduces the cross section considerably, dcnf's dont. 45's are made differently in the primary diffuser area.

I plan on flow testing dcnf vs dcoe (one day) for a definitive answer, but when time permits (and someone loans me a dcoe to test)

I believe the "more hp with side drafts" is yet another example of mythical anecdotal "evidence" which has no basis in fact.
 
That's more great info, thanks Steve. Would be interested to see those results, wondered if the DCNFs suffer because the air/fuel has to change direction compared with a DCOE?

I think in the end, it'll boil down to what's available and intake manifolds (where do you get them from??)

Thanks again
James
 
Bradders said:
wondered if the DCNFs suffer because the air/fuel has to change direction compared with a DCOE?
Click to expand...

Black-Tooth said:
A straight shot using DCOE's will certainly have a somewhat better hp gain if all else is the same.
Click to expand...

And these are precisely the myths I'm talking about.

dcoes do still force the air to change directions, in fact more so than the dcnf setup, and could someone please explain to me why dcoe's apparently make more power...

with dcoe's the air is forced left/right and then down into the cylinder, three changes of direction... and remember that the air as it enters the carb mouth isn't moving in a linear fashion, if flow is best, the air actually spirals in a vortex into the carb mouth, that's why we have full rollbacks on our bellmouths etc, to assist the air in spiralling inwards thru the bellmouths as this increases the flow rate.

I like to think of the air column in a way replicating the movements of a tailshaft... and the smoothest tailshafts have precisely the same angles imposed at both universal joints, and three universal joints just does not work. I believe this is a direct analogy for what is happening in the inlet tract of an individual runner system in the real world...

So what does the dcoe "tailshaft" look like... absolutely wrong.

Now consider the dcnf setup. Air enters the carb, past the throttle blades and bends forward, along the port and then bends precisely the same angle downwards into the cylinder... just like a tailshaft with two universals that have the same running angle.

Now if this sounds like smoke and mirrors, I can come up with some real world examples that follow with what I'm saying. As my day job I design and install and maintain pumping systems for the underground mining industry. I spend my weeks at work measuring and improving water flow thru pipework (just like I spend my weeks at home measuring and improving AIR flow thru pipework)

Big pump station underground (we are talking multi million dollar installations) designed by an engineer who is a very clever guy...but he specified the discharge pipework had a series of three bends (2 x 90 and one 45) as the manifolding headed upwards and disappeared into the rock... damn thing would shake itself to pieces as the design had introduced a very unwelcome harmonic. I suggested that the 45 bend was the issue and was met with some very quizzical looks... explained my analogy of the tailshaft and universal joints ... and after lengthy discussion the company (after trying many other solutions the engineers thought would work i.e. several hundred thousand dollars later) as the issue still persisted decided to give my idea a go... 45 bend removed, harmonic disappeared and pipework shake vanished.

Airflow is a lot about harmonics.

SteveC
 
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