WHAT'S LIMITING MY POWER?!?!

You mentioned a cracked wire or plug (edit: you actually said boot but which boot)? Did you check that out and what about the extenders. Did you put new ones in or just put the old ones back on. You checked the DFU units were sparking but it could easily be a bad wire or extender not getting good spark all the way to the plug.

I second checking the plugs especially if they are new. They will tell you a lot based on how they are burning. How good is the guy who re-synched the carbs? Just because the throttle goes to the stop doesn't mean they are opening all the way either.

Also since you have the airbox off spray some carb cleaner in those babies. They could be gummed up from old gas and just sitting around.

 

Couple more things. I bought a magnetic spark plug socket. It makes the job a whole lot easier. Also not sure as I hadn't seen it mentioned, but if this is a GTS the best way to reach the front bank is to take the top off and stand between the seats. MUCH easier than trying to reach in over the sides.

 

Gotta take the decklid off too, though ---- which is kinda tedious to put back on and get all the gaps lined up correctly.

 

I would never consider removing the "hood" to replace spark plugs. Can't imagine adding an order of magnitude more work that is not necessary.

I haven't had any trouble removing the front bank plugs with a normal spark plug socket and the appropriate extensions/ratchet. Yeah - it takes longer than the rear but I'd guess it's not more than 2x/3x the time.

 

How far does it rev up when not in gear?, is it sluggish or slow to rev when not in gear?

I know this will start an argument for some but I don't like platinum, iridium or other fancy plugs in these engines. Champion copper plug or bosch silver is best. champion 415 #RN9YC, I'm not saying this is why it's not revving, it's just an odd detail point for me.

Is the fuel system providing fuel to each carb? are they balanced and synch'd? I don't recall but did a ferrari shop or one familiar with ferrari engines handle the belt service and actually confirm proper cam timing?

Is it hard to start? does it fire up quickly? what is the idle speed?

btw, #8 looks a bit lean and #1 looks ok. Reading plugs is hard via pics and technically should be done on plugs that have been run at load then engine cut before idling, typically I'll do a run down the road or 'strip' and cut the engine before coming to idle and pull the plugs hot. It's not for the inexperienced or timid. Idle no load spark and flame front is very different from loaded at speed. But one can still get a close approximation from reading cold plugs.

Oh and for pulling plugs, if I don't have my handy aircraft plugsocket with magnet handy then a short length of rubber hose that holds onto the plug works great for R&R once loosened with a socket.

 

This may be a silly question but is there a rev limiter in this ignition system? I believe there is so what is it set at?

 

why up-jetted?
It'd be interesting to note the CO% at idle. ideal should be under 2%, carbon monoxide is unburned fuel. The test ports that have usually been removed were for checking CO and was a quick way to see if the cylinders were balanced and if any were rich/lean. really useful with carbs.

 

Yes indeed. Why the jet increase and was it done reasonably ?!

At this point, all your (wildcat) problems could be representative of an engine that is simply running way too fuel-rich and is bogging down as a result. Spark plugs may reveal this upon close examination, but if your mechanic buddy has a tail pipe gas analyzer available, testing this would not be a waste of your time.

 

On the other hand, with all the caveats Scott has mentioned in mind, plug #8 looks like it has burning very lean (or spark timing going way too early) to me ?

......so, I think you may have a variety of air/fuel mix problems going on.

Perhaps, it's time to start at square 1 and go through the basics --- because something elemental is not right here.

 

What about the ignition advance? How does it work on these systems, is there any vacuum advance or or just a pre-set curve in the unit?

 

Agree on not pulling the engine lid to do those front plugs. Try switching the position of the extension and the u-joint. You should be able to reach from the sides of the car for those plugs, but if that's difficult, you can stand on the back seats and work through the gap.

 

Glad to see you are making progress. As I said earlier, narrow down each system: fuel, air, ignition, one thing at a time. Although it is tough to wait, you really have to be systematic about solving the problems and it will take time. I spent almost 4 years off and on getting things sorted out and now have to fine tune my carbs and timing on a dyno now that the engine is fully broken in. But solving problems is easier now because I know the status of most systems and individual parts.

I think you really need to finalize checking the ignition, especually the ground wires, but I think if its firing on all 8 cylinders at 5K, it should be able to fire them at 7.5K.

Air filter-new or old?

Fuel-this is where I think you are getting a restriction. When you think about the carbs, and the fact that you have 4 of them with dual throats, that creates many, many possible problem areas, Then figure all the jets, hoses, accelerator pump diaphrams, gaskets, floats and valves, throttle shafts and throttle plates, springs, linkages and choke assemblies, any of which could be a problem. Bottom line-pull the carbs, rebuild them and your car will run better!

Even if you get it running OK, eventually you will need to work on the carbs. Do it once and you will all set for a long time. You really don't want to take off and re-install all four carbs more that once, along with the airbox, which is also a treat. Too may mounting screws and too many in-accessable fastener as well as the 16 spacers for the airbox that can be lost forever.

This car is new to you and its full history is only partially known, so its up to you to stabilize it by attending to each system, so you will know what is done. It will also give you an opportunity to really get to know the car.

Your car seems like mine in that the body was straight and rust free, that is a huge plus. Paint and bodywork is really expensive. Fixing the mechanical systems is more reasonable, but there are more systems to check, a lot more parts and everything often affects everything else. There is a fine line between a 308 that runs pretty good and one that runs close or as good to factory specs, especially after all these years and with today's gasoline. the XDI is a great start, but I think carb rebuilds are eventually necessary.

Also, no need to pull the rear lid for spark plug removal. Sometimes, I stand on a small stool by the side of the car to gain some extra reach or use the space between the roof and rear lid to get down in there. The factory tool actually works pretty good for the plugs. Pay attention to what socket, swivel and extension you use. Even write it down so 6 months from now you can do it again. Pulling the plugs is the easy part compared to what lies ahead to get you car sorted.

 

As for carburetor jetting and setup, one size does not fit all. Carbs work by a pressure differential, the difference between the low pressure in the cylinder and the atmospheric pressure of where the engine is. Add in humidity and seasonal fuel blends and it's quickly apparent that each and every situation will need to be fine tuned to it's unique operating condition.

Strange as it may sound, it would have been prudent to leave the carbs untouched and see how it ran before making changes. At this point you've crossed the threshold to where removing the carbs and rebuilding them to stock and also going thru the fuel supply system is the best way forward.

The ignition system is check'd good from the sound of it.
fuel and carbs are unknown.
camshaft timing is unknown.

when it's lugging does it sound like there is knocking or pinging? any smoke at the exhaust? most are not aware that there is rich misfire as well as lean misfire.

 

"It is NOT slow or sluggish to rev, in or out of gear, but just doesn't have any more power after a certain point."

So would you say it accelerates "normally" in any gear but then signs off at 5500 RPM?

Low float level/lack of sufficient fuel pump volume to supply the carbs at full load could cause the abrupt "shut down" as the carbs run out of fuel. Obviously, the pump is supposed to be able to supply sufficient fuel to exceed the flow out of the carbs at maximum load but an old pump may not be doing the job or an obstruction at the pump's intake or output side could cause it as well.

 

Mike, (and Justin!) I don't think it's a fuel SUPPLY problem since it happens without load.

If it can't deliver enough fuel to support the high revs, it should have a problem at a much lower speed under load and especially in higher gears when you've spent time building up to the dry point, as opposed to getting there in a short time in neutral.

I may have missed some of the relevant details, but I believe there are still some questions around the ignition, right? Does your timing light have an RPM mode? I'd put my light into RPM mode and buzz the engine up to the point it quits revving and see if the timing light RPM drops, indicating the rev limiting of the ignition was activating.

Or take the car back to the place that installed it, say, "The PPI on this car didn't mention a gross lack of power at high RPM, now it has one, please plug in your computer and let's check that the ignition is behaving properly". I'm expecting that the installation wasn't cheap and that this will be quick & easy to monitor so they'd do such a thing gratis to assist a customer. Since they seem to do carb tuning also, they should be expecting you'll be back as the mystery deepens...

 

OK, I misunderstood your most recent post - you are right re the fuel and, as I originally thought, I believe it is an ignition issue of some sort, NOT a fuel issue of any kind. If the engine can't rev even under no load, it can't be a fueling problem because it takes very little fuel and rather a small throttle opening to rev to redline in neutral. If it can't do that, it seems there is some sort of limitation being imposed by the ignition. The same thought applies to a plugged exhaust - not much load on that either in neutral, regardless of RPM.

I think your idea to return it to whoever installed the ignition and have it thoroughly checked out is a good idea. Maybe there is some sort of warranty in effect as well?

 

Answered my own question by looking at the manual.

The advance curve is set by external controls on the unit, at a number of RPM points. Are they set correctly and any timing offset of the sensor vs TDC has been factored in?

 

The answer was a bit vague though, I made the assumption that the engine has no issue revving to redline out of gear but once on the road under load the power drops after 5k rpm. If it'll run to redline out of gear then the ignition is ok. Timing curve is very basic on the XDi units. So by that assumption I'd look at cam timing and fuel delivery. I don't follow the process of changing the jetting on the carbs before checking to see how it ran, to me it's shop 101 to first check baseline operation and go from there, otherwise you end up chasing ghosts to sort problems.