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  #106 (permalink)  
Old 11-19-2011, 07:11 PM
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It's not unusual to get oil blow-by when first starting an engine and before the rings are seated - which certainly doesn't help the idle. Get a set of NGK Iridium BPR6EIX (equivalent to standard BP6ES) plugs. $27 for a set of four on eBay. Two or three day free delivery. If your jetting is at least reasonably close, these will get you going.
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  #107 (permalink)  
Old 02-07-2012, 06:35 AM
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Well the project has awoken from its slumberů drowsy, but awake.

Sunday when I got done working on the race car I decided to spend a little time with the GTV. The clutch master cylinder was sized wrong so that needed to be replaced before driving and a couple of other details needed attention too; which have been resolved now. So I cranked her up and drove her out of her cave. Woohoo!

I did not go far and it was nothing close to smooth running at low rpms. Matter of fact I got to the far end of the block and she stalled out and did not want to restart After a minute or so she did start back up and I was able to take it around the block a couple of times.

The engine has a tendency to race while not under load. Also she continues to misfire while at idle. When under load those issues go away. I will probably find some time this week late in the evening to make some more runs up and down the rail road siding before going back to tuning the carbs. There is hardly any traffic by the shop at night and I will be able to put a few miles in without having to dodge cars if something does go bump.

Not as clean as I had imagine my first engine conversion, lol.
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  #108 (permalink)  
Old 02-12-2012, 02:42 PM
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Logged about 20 miles today!! She is much happier idling now, the back fires and missing has nearly completely cleared up. I am very happy about that.

I still have the engine racing issue though. I have tried to search the forums for what the cause of this might be but I have not turned up anything. If anyone has any thoughts on what might be causing the engine to race at idle please send me your ideas.

After the last run I pulled a spark plug from each cylinder and they looked good to my untrained eye. Take a look for your selves:


The fuel air mixture gauge while the engine is idling is still pegged at 18 (the highest ratio) but while driving it floats between 12 and 14. Assuming the gauge is accurate at idle then I am running supper lean...which I will need to address. Could this be causing the engine to race?

Regards,
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  #109 (permalink)  
Old 02-12-2012, 03:41 PM
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Could the racing be a linkage adjustment problem ? When it is happening can you push the butterflies closed a bit ? You may need an extra return spring , like on race cars .

As for the plugs they look good from hear. What kind of O2 sensor are you using ?
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  #110 (permalink)  
Old 02-13-2012, 05:25 AM
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Yep I have a return spring on the carbs. The butterflies are returning to closed when I lift the throttle. I have had the spring on them since final assembly.

My brother thinks it might be a spark timing issue. I am using the 3-d mapped ignition from Alfaholics so there is definitely the potential for a timing issue to appear only under certain conditions. I have an email out to Max now.

I am using an Innovate Motorsports Air/Fuel gauge I guess its a generic wide band O2 sensor. I have heard they are not the most accurate at idle. The who and where I heard it I cant recall.

Apperantly its fast by the way I did not do any timed speed runs yet but she will chirp the tires all they way into third gear!
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  #111 (permalink)  
Old 02-13-2012, 06:54 PM
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If you're that lean, could you have some sort of vacuum leak?

What is your spark advance at idle? You could have a bad map. Have you verified that the settings in the ECU fit your engine? I'm not sure what all configs are available, but if the ECU expects a sensor that isn't there that could cause issues as well.

Regards,
Lawrence
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  #112 (permalink)  
Old 02-14-2012, 05:07 AM
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Okay played some more last night. Here is a video of the engine idling, carb sync, and then finally the racing.

VIDEO0006.3gp - YouTube

After taking her for a nice little drive I returned to the shop to double check a few details. Max felt it was most probably a carb sync issue. So that was first on the list. And yes the carbs were not synced. An easy fix but that did not solve the problem.

Next I went from idle jets of 55F8 to 60F8. This did not solve the engine race issue but it the air/fuel ratio at idle did lower to about 16. Still too lean so I went with a set of 65F8s. This did not seem to help much; though I turned the idle screws back in a bit.

I checked for leaks. I could not detect any. I will wrap the flange between the carb and the intake manifold with duct tape tonight just so there is not doubt.

When idling the computer is reporting a spark advance of about 10 deg. When she is on her high idle (racing) the spark advance jumps up to 20-25 deg. I don't know if this is caused by the computer or its the computer compensating for something else.

The map is as provided by Alfaholics. With the exception of the cams and the differences between the head work I had done and what they do the motors are fairly close in build. There is probably a measurable difference in motor outputs but the map should be close enough.
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  #113 (permalink)  
Old 02-14-2012, 08:15 AM
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I agree with your brother that you may have a timing problem. Why don't you experiment with some different curves and see what you get?

While the color of your plugs look fine, if you are concerned about low rpm mixture settings, you might want to try a Colortune. It's decidedly low-tech but you can actually see the combustion process at idle and adjust accordingly. Also, are you sure you should be running extended reach plugs? Even with your flat-top pistons I'd personally feel a lot better with standard reach plugs. You can spend a lot more on spark plugs but garden variety Champion NC series plugs work very well, IMHO.

Finally, I haven't read all of your posts but how are you syncronizing your carburettors? For the past few years I've been using an air-flow tool called a "Syncrometer" that's accurate and easy to use.
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  #114 (permalink)  
Old 02-14-2012, 08:46 AM
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Thanks for the input 180out.

The map is as recommended by Max. Until I feel confident that all my mechanical issues are worked out I wont be messing with it. It just seems to me that the guy with the least experience did the mechanical work and the guy with a lot of experience did the software work; its probably something to do with the work done by the mechanic (me ) One step at a time.

Max has been spot on with all his pointers up to this point too. When he said just drive it he nailed it. Putting a few miles on her was enough to solve a lot of the issues that were causing me frustration. Currently he has asked me to check/change the location of my throttle lever return spring. He feels it is effecting the balance as it comes off idle.

I did not get around to the color tune last night but I will shortly.

The plugs are as Jim Steck recommends. A quick search of the BB turns up a number of people that have gotten this recommendation so I just went that route. They are cheap ($12 for the set) and will at least get me through the tuning phase. I read an interesting opinion somewhere along the line that stated there was so much spark available with the twin plugs that there is little point to spend big money on specialty plugs.

I am using that very tool. You can see it in action here as I show the balance at idle.
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  #115 (permalink)  
Old 02-14-2012, 08:44 PM
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I'll appologise up front, I've not read the full thread so perhaps I am pointing out what others already have.

I can't even see youtube at the moment, so I'll go on what has been writen on this last page.

You have a lean issue at idle, 18:1 apparently, and then 12 to14 elsewhere under load. To check plugs the engine must be cut during the condition you wish to see...ie full load engine plug reading....nail it then cut the engine and remove, otherwise you simply see the idle condition with a bit of a mix of everything else. That said, looks to me like your plugs show carbon build up at the base of the thread (running rich), with the tip displaying somewhat leanish conditions. As your meter suggests.
The fact that you have an A/F ratio meter really means that all you do when you check the plugs is confirm the meter probably works.

So, it's lean at idle, and that will tend to give high rpm. Have you checked the air idle screws? Do they have good seats? Are they even? (Count the turns as a starting point). They sound like they are wound out to far (maybe). Are the butterfly's all even, are they set to factory specs on angle...hell, are they a matched set and unbasterdised, or are they bitsa carbs that have not been pulled down and inspected? Of course, check for vaccuum leaks.
12 to 14 is pretty ordinary fueling for NA....well the 12 is not that great, waste of fuel really and will foul any plug given time...no point using long life iridium plugs in that scenario (not that you are but but I noted they were suggested....they were designed to increase service life on hard to get plugs in modern cars....you'll foul them well before then). 12.5:1 is as rish as you'd really want to go on turbo, and that's because the fuel at that ratio helps cool the charge and stay of some deontation under higher boost. On N.A, I would have expected high 13's as a good place to start. On that basis perhaps you can drop one jet size and repeat, see if you stay shy of 14.5 up top but lift the low down AF to something more paletable? Anyway, there are many out there that can tune a carbie better than me, so take it with a grain of salt. I ran 48's on a NORD 2ltr and found I was able to get AF between 13 and 14:1 (I think, I'll dig out the dyno run and confirm, it was always a compromise though, as these things are). I vaguely recall I was running 195 jets?...will also check.
Sorry if the above has already been said.
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  #116 (permalink)  
Old 02-14-2012, 08:59 PM
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I note of this you have tried, perhaps get vaccum gauges and check for even running as you suggest. I think I need to dig out my cabie setup figures, they are not ageeing with your approach and I need to remind myself of the numbers. I too used an f8. I just certain I was up around 195's....but maybe that was my rotary!! I promise to check it out. Anyway if you are changing jets and the issue remains, you'd better look more closely at bleed screws, balance and throttle plates.
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  #117 (permalink)  
Old 02-15-2012, 04:49 AM
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Took a look at my jetting and thought I would post, hope it helps. (NORD) big vlaves big cams and port with 48 webers.

hp at wheels =155 at 8600rpm
main jet=180, air corrector=160, idle jet=65F8
ended up about right on 175,155, 65F8
venturi-42mm
AF ratio - 13:1 from 4000-9000, 12.5:1 dipping to 11.5 at about 3500rpm (did not tune that out). Poor fueling a function of cam timing.

Could have tried a F16 or F2 emulsion tube, had I had more time with the car.

Hope it helps.
Mike
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  #118 (permalink)  
Old 02-15-2012, 06:47 AM
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Thanks Mike,

Regarding the plugs most likely, I just don't recall, the engine was idling for a little bit after pulling it back into the shop and pulling the plugs. The pictures should be from the idle condition; which is where my concern is. Thanks for the pointer though I will use that when I start tweaking the mid and upper range.

I too notices the carbon build up at the base. For what its worth these are the same plugs I was using when I first started the motor. At that time I was having a lot of back firing, blow by, and other unhealthy running conditions. Once I was able to drive the car and get the rings set these issues went away. That carbon might be left over from then. I probably should scrub them down and retest.

The carbs were new in box. 45 DCOE 152's. I am running the 65F8's right now and somewhere around 1-1/2 to 2 turns out on the idle mixture screws. Any further in causes the engine to stumble and further out causes the engine to race up past where the throttle stop screw is effective. Still the lean condition persists on the gauge. I pondered air leaks and have tested for this several times. Last night even; I sprayed the carb to intake manifold flange down with carb cleaner while the engine was running; no noticeable change. I did not do the duct tape; the idea of the glue from the tape heating up and making a mess deterred me.

Looks like my throttle linkage was a little snug on the throttle lever and the spring may not have been pulling evenly. Having a throttle return spring sent over from Alfaholics and will convert the throttle peddle assembly over to the Euro spec as the next step. Removing the throttle linkage helped the engine race issue. Not only did Max point me in that direction but so does the Weber troubleshooting guide <duck>

Thanks for posting your jetting numbers Mike. Its great to see where others have gone with their tuning. I am actually really surprised with the idle jets being as high as they are. A lot of folk report that 55 works for them. Two jets up from there and probably could go up further seems odd to me. Can there really be that much difference between motors' fuel needs at idle?

Not quite there yet but the progress that I have made this week has been great! Thanks to the whole community, without all your input and advice I would be lost.

Shortly I will have a write up on converting the mechanical tach to a electronic one with the original face. Need to adjust the readout, it is off a thousand or so rpm at the moment.

Regards,
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  #119 (permalink)  
Old 02-15-2012, 03:14 PM
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On idle jet sizing I guess we need to keep in mind the twin spark versus single spark. There would be all sorts of things that could impact sizing down low from a airflow perspective (with big cams). I'm no expert on that at all, I just tried base settings reccomended by PACE and then played on the dyno from there.

I have never run an O2 sensor on a big cam NA engine, just a turbo engine. If there is a lot of over lap, I just wonder if there is some unburnt oxygen escaping on overlap that is affecting the O2 sensor. It would see more oxygen and read more lean. I guess a way to check that would be to close the exhaust valve a couple of degree's earlier and see if that richened things up by itself? That to me would at least rule that out?. Just a thought, given your throttle linkage seems to be the cause of the higher revs, maybe the lean mixture is not carb related.
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  #120 (permalink)  
Old 02-15-2012, 06:56 PM
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I might have the idle right, see video. Let me know if the video works, should be on public view with the rest of the album. The O2 gauge shows her idling at about 13.

I drove her around some more tonight. With the spring back on and the adjustment to the throttle linkage the motor no longer races and idles well. With the racing gone I was able to tune the idle circuit and get to the result you see in the video. Every once and a while there is a small stumble when coming off idle.

While driving her around tonight I also noticed she runs rich now on the top end and a little in the mid range. This is good though I am making real progress. Soon I will be ready for the dyno to confirm and fine tune.

Buzzed, I to had/have my reservations about an O2 sensor. I mean its located down stream of what its trying to measure and its readings are coming from four different sources all individually tune-able. It just seems I am trying to cut a single blade of grass with a lawnmower. Shrug, I am glad I have it though I don't think I would have know that I was running as rich up top for a while.



I'll post some better pictures this weekend when I get a chance to drive it around in the day light.

Regards,
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