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AngleT

AngleT

Always more tuning to do
Now that I have an exhaust, I just came back from having an alignment done and the car didn't run very well. It doesn't have any go above 2500 - 3000 RPM. I just got a fuel pump and pressure regulator and will install it tomorrow. It might be that the fuel pump isn't keeping up with the volume needed at higher RPMs.

On the highway in 5th any more than 1/4 throttle made very little acceleration difference.

If the fuel pump doesn't fix the issue, I'm looking at the cam timing being the culprit. It seems to have plenty of power when taking off but will not rev under load. It doesn't fall on its face, but more like someone gradually pulled on the e-brake or I'm dragging a piano.

I have the Project X1/9 book from PBS and will be studying the cam timing sections more closely if the problem persists. I'm just hoping the fuel pump fixes the issue but would love some advice from you guys with race engines on the best cam timing to use with a PBS S2 cam.

Thanks
 
Hey Tom, your posts are great. I really dig the exhaust and will adapt your upper engine torque rod idea too. I don't remember but what are your jet and emulsion tube sizes - (check each port)? Did you recheck your ignition timing too? When it revs up and peters out it usually is a main jet problem. I suspect your old fuel pump, although not optimal, was not that bad. Please keep us posted. If you are not successful in your "bench tests" you may consider a trip to the local dyno to get a hp/torque and Air/Fuel curve. The $110 (or whatever it is locally) can really reveal quite a bit. From what you describe it does sound like lack of fuel. Hopefully the new pump will resolve the issue.
 
Jet sizes

I checked all these jets to be sure they matched

Air Corrector Jet (#11) 200
Emulsion Tube (#16) F-24
Main Jet (#24) 130
Idle Jet (#25) 50

I also adjusted the Idle Mixture Screw according to the Weber Tuning Manual (started at 2 turns and peak idle was at 2 1/2 turns adjusting in 1/4 turn increments) and it was running very rich. (flames out the exhaust! :eek:) It also had no power at any RPM and really wouldn't get out of its own way. (this was the unpleasant trip to the exhaust shop) I adjusted it to 1 1/2 turns, only because it was where it revved the smoothest and no black smoke or flames. I wasn't able to take it for a test drive at 2 turns last night, (wanted to get it to the alignment shop before they closed) but a test drive could be the first thing on my list this morning before tearing into the fuel pump.

The ignition timing I adjusted on the fly while I was driving for the best seat of your pants pull at full throtle.

The car used to run really well before the rebuild, so if anything there is a lean issue associated with the (slightly) higher compression. Higher compression from decking the block an addional 0.010 and total seal rings. Total block decking is 0.018. I'm not sure exactly how much was taken off the head, but when I got it back from PBS it had marks on it that looked like it had been shaved. This with my 9.2:1 pistions should make a good pump gas compression.
 
jets

Hi Tom,

Idle jet settings have no bearing on driveability,and a lean condition usually goes with misfires and spitting. I suspect your cam timing is off.

Also I would invest in dial type timing light. Then you can set the distributor for your preferred maximum advance instead of having to calculate back to what it translates to at idle. Steve posted he likes to set ignition at 36 deg BTDC, I find that my car doesn't quite handle that much, and it's more like 32 for me. Set ignition and cam timing before you mess with the carbs.

Good luck.
 
That all looks reasonable. I agree with your thought, double check the cam timing and set the ignition with a timing light. Hopefully that will resolve it. I would do the ignition timing first, it is certainly the easier of the two. Good luck. Just for grins visually verify you are sparking on the #1 cyl during the compression stroke (TDC). Rotate the engine until the valves are closed and see that the distributor rotor is pointing at the #1 cyl - just another quick check.
 
timing timing timing

Just came back from a test drive with the Idle mixture screw at 2 turns and it ran better but still not great. It jumps out of the hole with a lot of zest and then slacks off at higher RPMs. I'm going to go ahead and change out the fuel pump and add the pressure regulator and try that before messing with the cam timing.

I used the dead stop method to find TDC and then set the cam at an even split overlap. The only thing I could do is advance or retard the cam. Which way should I try first? PBS book says to only use a max of 4 degrees of advance or retard.

Quote from book
The cam can be advanced slightly (up to 4 degrees crank) to enhance mid-range torque with some loss in top end power. Or it can be retarded slightly to give a small increase in top end power with a significant loss in mid-range torque.

With no vacumme advance on the distributor and only 0 5 10 degree indicators to check on the crank, how do you set the ignition timeing to achieve 32 degrees max timing advance? Factory timing at idle is 8 degrees (if memory serves me right) and with no vacuume advance would not achieve even max factory advance. Do you place a degree wheel behind the crank pulley?

FYI... I have checked to see that the distributor is advancing and it seems to be working fine.

Thanks for the help,
 
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This is dual 40 DCNF, right?

[Disclaimer - I know just enough to be dangerous]

At low RPM operation, those carbs will be running mostly on the idle/progression circuits. So if everything goes bad above 2500 RPM and one-quarter throttle opening, I'd really distrust the main circuit. Even if the jetting looks reasonable, you could have blocked passages, crud in a jet, or other main circuit problems. And only one of the carbs has to be sick to make the whole engine sick.... when everything looks right and the engine still runs like crap, it's the carbs more often than not.

Another possibility is the centrifugal advance in the dizzy. You can set the static timing by ear, but you'll need a timing light to verify the mechanical advance... rev the engine while watching with the timing light, and see how much it advances. If it's not advancing, that would explain why you're running badly at revs. Also, with a timing light you'll be able to see what static timing you got with the by-ear adjustment... if it's not something reasonable, say between 0 and 10 BTDC, you'll know that the static timing has been masking some other problem.

Pull the plugs. Replace them if there's any doubt at all. They're cheap and you've already put them through one episode of way-rich operation. And one of the fun things about dual-carb setups is that each cylinder can be out of tune in its own unique way.

Split overlap may not be the best possible cam timing for this engine/carb/cam combo (as I said above, I know just enough to be dangerous) but it's hard to imagine that split overlap is far enough from ideal to explain what you're seeing. If you're sure you're at split overlap, I'd be inclined to leave it there until you have everything else sorted out.

(I'm assuming you're already confident about the basics: decent compression, stable vacuum gauge readings, sensible valve clearances, ...)
 
up date

I don't run a PBS cam but here is how I set my 38/78 (delta) cam up in the race engine.

The correct amount of advance is for the cam pully to be about foward of the timing mark by a 1/2 of a tooth or 3 to 5 degrees. You will need an adjustable pully to get this. With the ajustable you will require a degree wheel/dial indicator or adjust it on a dino untill you get the best results, about 3 or 4 pulls should do it.

I am still working on getting that MSD system into the X and I"ll let you krow what's cookin' when it's finished.
 
No High load RPM

Your jet setting look good, maybe even a bit rich. But you have not stated the Venturi size you are using. The chances of 4 emulsion tubes being plugged is a long shot.

I suspect the cam is really retarded. Your idle should be loppy at 800 or so and rich as the amount of overlap will be dragging a lot of clean fuel into the exhaust system. The Rpm should under load at about 3000 and in 3rd should be a good combination for torque and really want to pull right up to 6000 or more rpm. In rare cases I have seen a faulty pick up coil in the Bosch Dizzy cause a miss or limit the rpm from climbing under load.

You may have to check cam timing with a degree wheel to the camshaft lobe.

I would not worry too much about the small amount you have decked the head. I shaved .120" off of my head and another .040" off of the cam box. Currenlty I am running the cam just a bit retarded by about a tooth for better idle but the power is there at higher rpm. I had to sleeve the timing belt idler to make it bigger to take up the slack in the belt.

Have pictures if interested.

TonyK.

Grimsby Ontario Canada.
 
Check your ignition timing, get that one off the table. Verify your distributor too, it seems to me there are different centrifugal advance values for different distributors (28deg and maybe 18deg). I have a 79 Bosch distributor with 28deg centrifugal. So

8deg static + 28deg cent = 36deg tot

I can't say this for certainty for all models and all years but I am pretty sure all use the vacuum advance for better drivability at part throttle, like a 10deg advance. At idle and high rpm the distributor is in centrifugal "mode".

I don't use vacuum and have plotted my timing using a variable timing light and it runs right at 36deg total. Use a standard light and put a little paint on the crank pulley timing mark to see it easier. Eyeball the timing between the 5 and 10deg marks on a warmed up engine at 850-1000 rpm.
 
Mounting the fuel pump and pressure regulator is taking a little longer than I expected. My obsession with trying to make it function properly and look like it was installed by a professional (of which I am not) just adds time to the installation process. Not to mention the restriction of cash flow from the local banker (aka My Wife).

The distributer timing has always seemed to be an issue with the X's I've owned. It all started when I was 19yrs old and just figuring out that the TCD timing marks don't line up with the number one spark plug (as the book said) but line up with #4 (180 from compression stroke) was only the first issue. Frozen weights, magnetic pickup issues, etc and now I'm 35yrs old dealing with no vacuum advance. Wow! How time flies!

After I get the pump hooked up I'll have to try static timing it to 8 degrees and see how it does.

All this knowledge is starting to make me question my shadetree ways!
 
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PU coil and venturi

The pickup coil ohm'ed out OK. I did have one on it when I was first tried to start the engine that was bad. If they're cheap enough, a new one might be in order just to be safe. It does sputter a little bit every now and then, but I was saving that concern for after I get some of the other major questions answered.

I'm running a 32 venturi and a 4.5 aux venturi. It does lope at 800 RPM but I have the idle turned up to about 950 - 1000 RPM to run a little smoother. I have checked the emulsion tubes and all were clear.

I wasn't fully trusting of the Mr. Gasket fuel pressure gauge I picked up at Advanced Auto, but it was only reading 1.5 - 2 lbs of fuel pressure. I ran this fuel pump before the rebuild with no issues, but that was 4.5 years ago. Book says I need between 2.2 - 2.8 lbs of fuel pressure to adequately feed two carbs. When the float bowls are full of fuel, it will jump off the line nicely, but quickly relaxes the power and gives you the big throttle noise and no GO. My money is on this fuel pump correction solving a lot of the issues, but not all the issues. I'm sure this engine will need lots of tweaking to get the most out of it.

I remember cam timing being a big power gain years ago. I used the Apple motors adjustable cam gear with the inserts back then, but there wasn't any scientific reasoning to the adjustments other than seat of your pants performance. Now with the fully adjustable cam gear from Midwest X1/9, I have to be a little more scientific about the adjustments. Just setting up the cam for an even split was an adventure. :)

Thanks for the advice,
 
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Tom... Vaccuum advance...

I don't know what your purpose for the car is... but if yur wanting smooth street operation with low-test fuels... I find a properly working vacuum advance on these small engines is a real TREAT!

I also don't know with duals if there will be enough vacuum at the usual ports in order for it to operate.

But I digress for a bit... I'm unsure if you realize that a vaccuum advance actually causes a bit of an instantaneous "retard" as you open the throttle(s) so the engine has a moment to catch up in order to stop PINGING and BACKFIRES and POWERLOSS. Usually, this is NOT an issue when racing as power is not supplied gradually, and a lot of shifting involved.

But on the street... a vacuum advance (prior to ECU's) is a real nice tool to have and something you MAY wanna spend some time getting to work on your car.

Frankly, if I were running duals, header and a cam... I would run strickly with a properly curved centrifical... set up for the specifics of this particular engine... which in a non-electronic contolled engine, means a bit of trial and error. Once you know what you are looking for, a distributor testor and a short stack of weights to trim and modify would be the easiest choice to experiment with before installing the dizzy back into the engine.

Good luck and keep us posted with what you are doing. Tell the LOAN OFFICER this sort of thing will not break the bank and send her off to do some more Christmas shopping!

HA!
 
32MM Venturies.

Tom if you have a vacuum port on any of the runners and a length of tubing connect it to a vacuum gauge.

32's on 4 barrels are quite large for this engine and there is the possiblity that the vacuum is dropping off and starving the engine for fuel at higher rpm's under load. If you have good bottom end from a start, this is telling me that you are running on the idle circuit of the carb which is providing a good air fuel ratio. As the butterfly opens the draw of air and fuel is now from the main jet circuit. If the velocity drops to quickly, ( low vacuum ) then the ratio will go lean and not recover until the butterfly is closed again. A simple way of proving the theory is to obstruct the top of the barrels with duct tape and or cardboard as a tempoary measure. Then go for test drive. If you find that the car preforms better, then you are left with either changing the venturies to a smaller 28MM size or installing larger main jets and air correction jets that will provide the fuel at lower air velocities in the barrel.

The DCNF if set up correctly will allow you to remove the emulsion tubes when the car is idling as it is running on the idle circuit of the carb. The fuel in this case enters on the edge of the butterfly through 5 or 6 small holes drilled into the side of the barrel. In under carbed. cars if the idle circuit is jetted to small removing the emulsion tubes will kill the engine as the idle is being provided by both the idle and main jet circuits.

Consider the above after your fuel pump change/regulator pressure increase as a pump that will not allow enough fuel to flow will lower the fuel level in the bowl and and require more vacuum to drag the fuel into carb barrel.

Keep us informed to your progress.

TonyK

Grimsby Ontario Canada.
 
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To be fair...

my wife has let me spend over $600 on my X 1/9 this month. She has been more than generous. :D
 
Whoops... its getting a bit sensitive here...

But as long as she's only spending 3X as much as you are... then that's fair!

HA! At least that's the way it is in my house... I could never keep up!

I'm only messing with ya... But on a serious note... this car really doesn't demand the kinda money most others would. A typical 4 barrel carb, manifold and linkage for a SBC Chevy would run 600 easy.

My wife ONCE made a comment about what I had spent on the FIAT and I replied that in the 25 years I've owned that car... from the initial 4000 bucks I paid for it in '83... I've only spent 2500 on it over all those years. And in the last 3 years... I've spent the same amount of money on the maintenance of HER car. She's never said another word...

I know Steve Hoelscher and Alex Kovatch both invested many dollars to make their racers competitive... but it was a relative pittance compared to their competition! Pennies on the dollar... That's just one more reason why WE GRIN all the time... HA!
 
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