Need more top end (UPDATE)

What intake manifold are you using

If it's a sprint manifold with the coolant passage in it, throw it away and use an early stock intake manifold that has been opened up and modified to accept the DCNF car. I have run both and the difference is unbelievable. The sprint manifold has really small runners and kills the top end. With the 40-80 cam a big valve head and headers would be great. As tony says ignition timing is king. The cam timing will not make a large difference but will help especially if it is off a lot to start with.
Good luck
Charlie

I believe it is an Alquati it's hard to read the markings but I'll try to post some better pics soon.
So after my first drive of the day I think I need to recheck the Tach. when I checked the Tach last year with a digital Tach reader the readings were spot on. But I did this parked and in neutral. Is it possible for the Tach to be wrong under load? It pulls really strong until I hit 5,200 rpm then the tach just barely moves. It sure sounds like the car is reving higher but the damn muffler is so loud it's hard to tell. My but feels like it stops pulling at 5,200 but for all I know the Tach is just not reading right. I guess I need to try to hook up the Digital reader and run it up to the cabin and see the readings under load.
Anyway it's sure nice to get a her out again!

Here are some pics of the intake. As far as the air cleaner goes it's basicaly the same air cleaner Midwest Bayless used to offer back in the day. I do have a different one I used before which might let more air in but when I made the change I didn't notice any difference. The filter itself is basicaly just a metal screen.

weak valve springs?

New valves and springs about 1000 miles ago when head was machined.
Thanks for all the replies, this is why I follow this board almost daily. I think I need to verify my Tach is correct first and go from there. Check ignition timming, and purchase an Adjustable Cam Pulley. Maybe get some Dyno time to figure it all out.
Can anyone verify which Intake Manifold I have? Steave??

Oil Breather Hose

Just noticed you have your oil breather going to its own air filter element.While it is good that you have it filtered, you really should have a slight vacuum on the crankcase vent system. Something simple like a thin plate that fits on the side of the filter with a small pipe on it will do the trick. You'll never notice the power gain as things are now but you're engine will be doing better in a lot of ways with just that simple alteration. It will help to pull fuel vapor and combustion gas from the crankcase along with steam that results from the condensation within the engine on humid days. Big power engines have proven dyno benefits from crankcase vacuum and all engines benefit from the less contaminated oil.

phillips82 said:

That header is considered a 'shorty' and isn't designed for high end power. A long tube header with 2.5" pipe will help you move the power band up a bit.

The adjustable cam gear would be a good idea. You'll likely find you are currently several degrees off from true zero. Playing with cam timing will move your power band around by pretty noticeable amounts. Before you remove the current pulley, set up the degree wheel and dial indicator on the cam. Get a reference of where you are now so you can see just how far out you are.

You can also try adjusting your ignition timing. You've changed a lot of parts and you may find you can do with a bit more or less timing.

Click to expand...

I second the long tube header. Does wonders for this engine.

I agree that the adjustable cam gear really won't gain you any outright power... it'll most likely just move the torque/HP peak up or down a little bit.

With the milled head, you are most likely running the camshaft a little retarded from 'straight up'...

But from my understanding that running the camshaft retarded from 'straight up' should shift the torque peak up higher in the rpm range. Advancing the camshaft should move the torque peak lower in the rpm range.

Unless I've understood thing backwards for years...

I'd try to 'degree' the cam, to see exactly where it is in conjunction with the crank. And that would be just so you know what you have going on.

Then with a bunch of jets in hand, go spend $150 on a solid hour or two of dyno pulls... the accurate air fuel rations the dyno shows you will help with jetting decisions, and you can play with the timing and optimize what you have.

I'd do the adjustable cam pulley after you have a baseline.

Was the 40/80 cam ever setup properly?

You mentioned getting an "adjustable cam gear" Was the 40/80 cam ever setup properly? How was it dailed in?

Okay all good replies and questions. I feel I need to give you all a little background on this X. And my story.
So when I was 16 after driving a few cars my family had around I decided it was time to buy my own car. So after a few weeks of looking I came across this very cool and very Bright Green car that kinda looked like half Ferrari and half porsche 914. So knowing nothing about Fiats I bought it for $2,200. It was a 76 with the big ass double bars on the front. So I drove this Green X and learned a ton about fixing cars. After HS I got a great paying job and since I still lived at home with my parents I had plenty of cash to spend on toys.i ended up selling that X to girl up the street and moved up to a Porsche 924. From there it turned into a911 Turbo and a few other 911's after. Well as life goes I got married had kids and had to sell the 911 Turbo so we could build a house.
So fast forward to about five years ago maybe six and I started to remember how much fun that little green X was. Call it a mid life crisis or whatever, I had to find one. My father knew a guy who he thought still had one that he used to race in Hillclime races. We contacted him and yep he still had it. We pushed out of his garage and worked out a deal. Loaded it on the trailer and took her home. Took a few days to go over the motor change fluids and finally got it fired up, first time it was running in about 10 years. So we knew it had a motor that was modified but how much was unknown. We got as much info from him as we could but he was an older gentleman and couldn't remeber all the specifics. But he did give me all the racing info on the car with log books and all, it won many a race in his time. I have all the race badges fastened to the underside of the rear decklid. Anyway I really didn't know what was done to the car until I blew a head gasket and tore it down myself. Now I can tell you what Cam, electronic ignition, distributer and head it has. As for Pistons I belive them to be stock but I don't really know. So when you ask me if the cam has been setup properly I'm not sure what you mean. My father, who has been in the automotive industry his entire life, is my inspiration and always my main helper when it comes to projects like that was. What I can tell you is I have driven five different x19's and this one is by far the quickest one I have driven. That being said I'm sure there is more to gain from this setup. So I like to experiment with different things to see if I can gain anything. That being said I do not auto cross it is my weekend sunny day driver that always gets heads turning.
Sorry for the long post, I got carried away.
Today I verified all the timming marks are dead on. I now need to verify that the tach isn't playing games with me. I mean it sounds like it has to be turning 7,000 rpm's when it's only showing 5,200. I also removed the air filter and took it for good hard drive and had the same results. Don't get me wrong it runs great very smooth and quick throttle response with plenty of tourqe. I just feel, if the tach is correct, I should get more.
If you read this whole post you have more patients than me.

Manifold

Your right to check the Tach. If it is ok then and the engine maxes out at 5500 then the manifold, head valve size, porting are not your problem. It is either considerably retarded ignition timing, cam off by a bunch, maybe two teeth, valve springs defective, plugged exhaust, loss of fuel pressure or way off on the carb jetting. There aren't many thing that will stop the engine from going above 5500 RPM. Also you say you are using an electronic ignition. Is that a Bosch unit off a later X19? if so some of those units had RPM limiting electronics to stop over reving of the engine. PBS used to change the electronics in the Bosch black box to correct this problem. Use a timing light that shows degrees to check the advance curve of the distributor with the vacuum line disconnected.

Good luck
Charlie

MSD Ignition

box. If there was a limiter i dont think i could over rev the motor while parked correct? I plan on checking the Tach today after work. After that im going to purchase a good timming light with advance settings and see where im at. I need to find my jetting numbers i wrote down last year and post them here for some thoughts. I know i have 28mm chokes but i forget the rest. Or ill just pull the carb apart and write them down again. Thanks
Stay tunned for updates!

WHOA!!! What Rob said!

If you are sure of the cam and ignition timing... go to the carb next.

GOOD timing is NOT an answer, BTW... We need some specifics here like "30 degrees full advanced at 4000 rpm", or "Centrifugal advance ONLY, 17 degrees at 2000 rpm". Stuff like that.

Glad your tach is accurate!

Now... What rob said is so true about that aircleaner. Not much effect until WOT and the air tries to BEND 90 degrees down the throat. If you take the air cleaner off completely... you will definitely FEEL an deference... then add the velocity stack, then add the air cleaner.

MY BET is on the MOST performance with the Velocity Stack and NO air cleaner. A straight accelerated shot down the throat.

Air cleaners, scoops ans stuff can be played with later. As MX5 says, $150 bucks on a dyno will PROVE the point or a measures track and time will also. I think I would wait on the dyno until you get the adjustable gear though and kill a few birds with one stone.

HTH

right art

If it has a limiter it will work with no load on the engine as well as under load. Is it a 6al MSD? If so you are still using the distributor so checking the advance curve is critical. Also make sure that the timing marks are steady all the way up and not dancing around.

one other thing

I see in your post that the carb is a 42 DCNF but you say you have 28 chokes. If that is the case the chokes are too small. You should be around 32 to 34 chokes. In fact a 42 mm carb has an effective range limit of around 30 to 38 MM chokes. These numbers are not set in stone but 28 is getting really small for that carb. Weber's want choke sizes of .7 to .9 times the diameter of the throttle bore for best operation, .8 is ideal. You may be going really rich at the top end. With a choke size of 28 MM you will probably want a main jet size of around 1.55. With a 32 choke you will probably end up with a main jet size of around 175. These jet sizes are much larger than would be used for duel carbs because the intake manifold for a single carb really kills the signal to the carb. Also a single carb usually wants smaller chokes because it gives more carburetion to the engine than duel carbs. I bet that gets a response.

Charlie

All good advice. I'll need to get my hands on some larger chokes. But first I'll get those advance curve numbers. And yes it still has a distributer. Hopefully tomorrow I can verify the Tach is reading correctly. Had to work late today.
Thanks again.

Carb data

Okay I found my book with all the jetting for the carb.
Again it's a 42 DCNF
220 air Correctors
F24 emulsion tubes
160 Main
.50 pump jet
.55 idle jets
80 F7 Starter Jets
28mm chokes
I like the idea of going bigger on the chokes, I never tried that. Last year I did play around with the Main and Idlers but pretty much ended up back here where I started.
Like I said before the PO Hilclimed this car so It wouldn't be a surprise to find out it was set up for low end Tourque.

Tell us more...

Yah mon...a response.
Please share your insights about "killing signal to the carb".
And about "a single carb giving more carburetion".

Old Fiat Driver said:

These jet sizes are much larger than would be used for duel carbs because the intake manifold for a single carb really kills the signal to the carb. Also a single carb usually wants smaller chokes because it gives more carburetion to the engine than duel carbs. I bet that gets a response. Charlie

Click to expand...

Hi Orelscal

Think about it as if you were in the cylinder when the intake valve opens. This is for the single carb. What you see is the port, then a large plenum and then the 2 barrels of the carb. First there are three other cylinders sharing that same plenum. The pulses from all the cylinders tend to dampen all the other cylinder pulses. That's what a plenum does. It is called reversion where the intake breaths backwards into the port and then the plenum. This happens more at the lower RPM and idle making the idle and lower RPM more difficult especially with a hot cam. Therefore the signal to the carb is dampened and you need larger jets to feed the proper amount of fuel per a given choke size than an IR setup

Now the duel carbs. This time what you see from the cylinder is a port then a single carb barrel. Notice that there is no plenum that dampens the reversion signal to the carb. This is called an INDIVDUL RUNNER or IR system. The damping is really reduced because there are no other cylinders connected to it so the signal to the single carb barrel is much stronger and smaller main jets are required than a single carb on a plenum for the same size chokes on the carb. This is why duel carbs idle like a baby and have a stronger bottom end than the single carb, especially with a hot cam. The problem is that when you put duel carbs on the engine with the same size carb and chokes of a single carb you have just cut your carburation in half not doubled it because the cylinder only sees one carb barrel not 2.

That is why when you go to duel carbs you need to increase the size of the chokes to make up for the lost air flow that was provided from the single carb. The advantage is a much cleaner idle and lower end as well as mid range especially with a hot cam. However the single carb can provide equal to or better top end power as compared to duel carbs because as the RPM's increase reversion stops being a problem with the increased intake air speed and not all cylinders pull in air at the same time anyway. They pull in the air one after the other, sharing is fun. Keep in mind that Nascar engines produced over 850 HP from a 348 CI engine with a single 4 barrel on a open plenum. Production v8 engines typically used divided plenums to reduce the reversion at lower RPM's.

Cheers
Charlie

One other silly thing

Are you sure that the throttle is completely opening with the gas pedal??? I'm sue you have checked that, just saying.

Hope you find it Charlie