| Author |
Message |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 2831
Registered: 2-2001
| | Posted on Friday, June 07, 2002 - 10:38 pm: | |
Bill, I agree with you especially the first sentence of your comment, that it may or maynot help. That is my point. I would check the mixture adjs. first, a simple adj., with the synchrometer to see if there was any improvement. If not I would continue as you have suggested. If the adjustments do clear up the problem then I would drive the car for its performance and probably do a check of the timing. To me it just seems like a simple approach to a problem that this may be all it is. As I said before if no improvement is shown then continue. The popping and the blurping sounds and the richness just sounds like the mixture adjs. are not correct and I would try the easiest thing first. You can always readjust the mixture screws later if it doesn't correct the problem. I respect what you are saying only I would do it somewhat differently to start. Thanks again for your help a little while ago RE: my throttle linkage. Still respecting your opinion, Magoo |
Bill Sebestyen (Bill308)
Junior Member
Username: Bill308
Post Number: 250
Registered: 5-2001
| | Posted on Friday, June 07, 2002 - 7:42 pm: | |
Magoo,
I agree that mixture adjustment may alleviate Terry's problem, but it may not. The problem is that all the other items influence the mixture settings. If the carbs are a little rich because the floats are set too high, you can compensate with a leaner mixture adjustment. This however means the low and mid range will be fine but the mains may not be correct. If there is a wire or plug problem, performing a mixture adjustment may help or may make it worse. If the timing is not correct, the engine will probably want a richer or leaner mixture to compensate. My philosophy is to make sure all items that can affect mixture adjustment are correct, then set the mixtures. I�m sure others will do things differently, but I prefer a very systematic approach, especially on a relatively unknown car. When I rebuilt my carbs, I found a variety of jets and air correctors and the floats weren�t even close. The mechanical advance in my distributors, were shot and two of the ball studs on the carb linkage were loose. All of these items influenced the mixture and balance adjustments. Sometimes it�s better to bite the bullet and check everything so you know that it�s right. If problems still remain, at least you�re eliminated a lot of unknowns and will have some idea where to look for other porblems.
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James Angle (Angleman)
New member
Username: Angleman
Post Number: 4
Registered: 6-2002
| | Posted on Friday, June 07, 2002 - 6:34 pm: | |
Before you start messing with any of that, make sure all of your exhaust connections are tight. Especially the manifolds coming right off of the engine. I don't have a ferrari (yet) but any sort of small exhaust leak, can cause exactly what you are describing. Especially if you say it didn't start acting up until after you drove if for a while. Bolts could have vibrated loose. It would save you a lot frustration, and money. Also, check for holes in the manifolds as well.
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Terry Springer (Tspringer)
Junior Member
Username: Tspringer
Post Number: 79
Registered: 4-2002
| | Posted on Friday, June 07, 2002 - 4:23 pm: | |
Is adjusting the idle mixture going to effect the mixture at higher RPM ? Or is this really just part of getting the carbs in sync?
I need to buy an syncronizer meter, the one I have is the ancient tube type. I want the newer barrel type. Do you need two of these? It would appear to be helpful to have one on the choke being adjusted and the other on the choke next to it?
I am planning on checking/cleaning the plugs first. The plug boots are junk and I have replacements. Then I will check the timing to make sure its not way off. Then I will sync the carbs.
The cam covers also look like crap and the entire engine bay is not detailed as I would like... so I am going to be ripping stuff apart and cleaning / painting / polishing a bunch of stuff.
Im going to start another thread on removing the emission control stuff. I want it all in a box, none on the car...
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magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 2828
Registered: 2-2001
| | Posted on Thursday, June 06, 2002 - 10:07 pm: | |
Guys, All you say is true and I don't deny that there are other things that could be the cause also but the idle speed mixture adj. screws are "likely" what has been fooled with since their access is easy and has gotten the carbs out of balance. What is the problem with checking those first with a Synchrometer rather then setting the floats etc..That's a lot of work if the mixture is the only thing off. If the carbs are off now they will affect the settings anyway. If they come inline all the additional work is not required. If it does not correct it go from there. You can always adjust the mixture screws if the problem is something else. Seems like the most fundamental way to approach the problem. Anyway that's what I would do. I guess different folks different strokes. Just My opinion guys, Best Regards, |
Steve (Steve)
Junior Member
Username: Steve
Post Number: 158
Registered: 2-2001
| | Posted on Thursday, June 06, 2002 - 8:59 pm: | |
Terry I also have a 77 GTB and love them carb's. Magoo is starting in the most likely spot but before I would play with the webers I'd look at the last time the car was tuned up. I found that the points are the most prone ares that affects the early 308's. I went with a pointless update but before I did this I always verified point gap and then timing.So if you haven't had had a tune up start there. Plugs , wires , points and condensors , check plug wire extensions , sync. the carbs.Also take the retard points out of the circuit. I still get a slight carb. lag on touching the accelerator but I can work with it. Also I don't know what you mean when you let off of the gas. Does it backfire or just exhaust noise. Could be in the smog stuff if you still have it attached or a leak in the exhaust.I found the webers to be bullet proof once set.Most of the deteriation comes from points/plugs.I get a little black smoke and it runs a little rich but when you nail it it revs easy up to 7500.Take your time you'll work it out. |
Bill Sebestyen (Bill308)
Junior Member
Username: Bill308
Post Number: 247
Registered: 5-2001
| | Posted on Thursday, June 06, 2002 - 8:48 pm: | |
Terry,
You want to be sure everything else is right before you start working on the carbs, because they will affect your settings.
Check your plugs and wires and all electrical connections, especially to the coil.
I'm not sure what the static ignition setting on euro cars is, but if you don't have to worry about emissions testing, 6-8 degrees BTDC should get you into a useful area. I think its generally agreed that US specification cars generally are set up with relatively retarded ignition timing. I don't think I'd go more that 40 degrees BTDC total advance though. Ensure that the advance on both distributors is smooth and equal.
If the ignition system is where you want it, and the rest of the engine checks out ok, then do the carbs.
Start by setting the float levels. This is also a good time to inventory and clean the jets and emulsion tubes. After reassembly, synchronize the air flows, both on the throttle stops and just off the throttle stops. Magoo is rightt in suggesting you need a synchrometer to do this correctly. When all airflows are equal, get the engine good and hot and you can then set the idle mixtures. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 2827
Registered: 2-2001
| | Posted on Thursday, June 06, 2002 - 7:37 pm: | |
Terry, Before I did anything I would balance the carbs. The popping burpling and richness more than likely is the carbs.. I would start with adjusting the idle speed mixture adjusting screws on each carb.. You should use a synchrometer to do this because it is much easier and gets you on the right setting quicker than doing it only by ear. There are other things that can cause your problem but I would start there first. If this doesn't completely solve your problem and you want to go through this in detail rather then on line you can e-mail me. This could be a drawn out process. Regards, |
Terry Springer (Tspringer)
Junior Member
Username: Tspringer
Post Number: 78
Registered: 4-2002
| | Posted on Thursday, June 06, 2002 - 4:01 pm: | |
Well, my '77 308GTB arrived and I have been driving it non-stop! This car really is a blast to drive. Since last sunday I have put close to 400 miles on it.
I am ordering motor mounts as it needs all 4 replaced (pre-purchase inspection turned this up). It shifts ok, but I'm sure it will be much better when the mounts are new.
The car has also started developing a slight running problem. It appears to be running a bit too rich? Under deceleration in pretty much any gear there is a good bit of popping and burbling from the exhaust, like unburnt fuel still burning off in the exhaust. Also, at low revs if you give it a bootful of throttle, it will stumble a bit before taking off. Runs hard and good at higher rpm. When going up or down my steep driveway, it is unhappy and wants to choke down. It doesnt appear to throw any smoke under acceleration but will puff a small amount of black smoke on startup sometimes. No white or blue smoke at all.
I have tried the "Italian tuneup" method but the low rpm hesitation and such persists. I also am not positive the car is pulling as hard as it could even at higher rpm, this is my first 308 and I have no reference point.
I have not had time to even look around or clean up the engine compartment. My first thought is to check if the plugs are foul and then check the timing. I dont know if the car has the timing retarded for emission inspection for the prior owner... but here in GA I have no inspection and want to do away with the emissions stuff.
I was thinking of setting the timing to euro specs? Switching to a high performance coils? Different jets in the carbs? A microswitch problem at the throttle pedal? Hmmmmmmmmmmmmm
Any ideas of where to start on this kind of problem? |
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