| Author |
Message |
Larry (Larry)
| | Posted on Sunday, April 22, 2001 - 1:20 pm: | |
man, this is puzzling! wish i could add something more but, i think everyone has added all that can be suggested. sorry. btw, mine's 09990 jan. 75. welcome Rob! good luck, Larry |
'75 308 GT4 (Peter)
| | Posted on Saturday, April 21, 2001 - 10:03 pm: | |
Sorry Rob, didn't answer your question before in respect to plugs. The thread body (exposed part to the combustion chamber) should have soot and the insulator should be tan to brown colour (chocolat-milk colour is the average). |
'75 308 GT4 (Peter)
| | Posted on Saturday, April 21, 2001 - 9:32 pm: | |
Yes, I got my cap from the dealer.
Herbert, he has a '75 like mine... no cats. But something to consider as well, if he has the original ANSA crap, it probably rotted out and the crud could be blocking partially (long shot). |
Herbert E. Gault (Irfgt)
| | Posted on Saturday, April 21, 2001 - 4:00 pm: | |
If your car has a catalytic converter on each bank I would bet on it being partially clogged for the red hot bank. Mine did the same thing and removing the cat. fixed it. |
Rob Breton (Parilla)
| | Posted on Saturday, April 21, 2001 - 8:31 am: | |
The plugs on the rear looked a little white / glazed which would indicate a lean mixture?? The front looked real good. Did you buy your coolant cap from a dealer?? |
'75 308 GT4 (Peter)
| | Posted on Saturday, April 21, 2001 - 12:33 am: | |
My old cap was a two-ear type and rated at 0.9bar (about 13 psi). I got a new cap that is the later four-ear type (all that they had) and rated at 1.1bar (about 16 psi). All this means is that the boiling point will be raised slighlty (?, trying to go back to High School chem.)
By the way, what did the plugs look like? Plug-cut the best way to check (real world conditions). |
Rob Breton (Parilla)
| | Posted on Friday, April 20, 2001 - 9:04 pm: | |
Well I'm really puzzled now. My Ferrari mechanic checked it out and found that bank to be running lean but not excessively so! But all of the input and logic tells me it is running rich?
What's strange is the car is running really good"
other then the glowing header. I don't want to drive the car that way and cause a valve to go.
The only other thing going on is the coolant occasionally boiling out of the tank but I think it is due to a weak cap! By the way does anybody know what pressure rating the cap should be. |
'75 308 GT4 (Peter)
| | Posted on Friday, April 20, 2001 - 7:01 pm: | |
Wow, the GT4 owners are coming out of the wood-works now...excellent!
Timothy, those little tubes are for the following systems:
The 4-into-1: Feeds the Sinistra bank only from the carbon canister. This is a way for excess fuel vapours in the gas-tanks to be consumed by the engine.
Both 2-into-1: Are located on the Destra bank and draw vacuum to operate the Diverter valves for the air-pump emission system. From 1978 onwards, only one 2-into-1 tubes draw vacuum (for only one air-pump now). The other one is connected to the carbon canister as well.
I've done that before to "improve" exhaust emissions, except not to the extent of unbolting the manifold flanges (just the collector-to-downpipe flange). I did this to my daily driver, not the Ferrari. Success was negligible. |
Timothy J. Dressel (Tjd)
| | Posted on Friday, April 20, 2001 - 1:14 pm: | |
Rob,
I, too, have a �75 308gt4 (Peter, I�ve enjoyed your contributions), still apart at this time.
There�s a metal tube running from under each carb (into the carb-to-head casting) to a common tube for the bank, forming a kind of "mini-manifold," as I call it. If I recall correctly, the forward bank has a four-to-one tube, and the rear bank has two two-to-one tubes. I don�t remember to what they�re connected (my 308 is in more pieces than yours, Peter). I suggest you make sure there�s not a leak into the "mini-manifold(s)," i.e., tube(s). Start by disconnecting the hose(s) from the tube(s), and plug it (them); and check for leaks from the tubes. See if you still get the glowing. There may be a leak in the device(s) to which the tube(s) is/are connected or in the connecting hose(s).
There�s another possibility. The previous owner of my car had told me that he saw his exh. manifold glowing after his mechanic had left the exh. manifold bolts loose (as an attempt to pass an emissions test with an otherwise rich condition). So you might check form exh. manifold leaks.
--tjd |
'75 308 GT4 (Peter)
| | Posted on Friday, April 20, 2001 - 12:29 am: | |
Well same coast, but a little farther North... B.C. Canada.
As a little side project of mine (like I don't need enough already), I've been compiling a list of ALL chassis numbers of the GT4 series, hopefully which I'll post on the web in the future. I've written down a S/N: 09982, but my only notes were the colour; Red Boxer/Tan. Did you just get this car? I think I've seen it for sale in the FML recently (I have a list of a couple of hundred cars, so I'm a little disorganised now...). |
Rob Breton (Parilla)
| | Posted on Thursday, April 19, 2001 - 9:23 pm: | |
The car is running great other then the red hot header and making good power. I'm in the process of locating a drawing for the Weber carb before I start turning screws. I'm hoping to get to the carbs this weekend and see what's going on. It's strange When I tested the rear bank it registered as running lean. But most of the folks I've talked to have mentioned an over rich condition.
The choke system is not hooked up, and the timing is set equally on both banks. Thanks for all the input guys It's killing me not to be able to drive ! By the way Peter My Chassis # 09982 Jan, 1975. I saw the shot of your car Looks good! What neck of the woods are you located ?? I'm in So. Cal. |
Ulf Modig (Ulf308qv)
| | Posted on Thursday, April 19, 2001 - 8:46 pm: | |
Rob, it sounds like an ignition problem to me, but if your timing is according to specs you might want to check the rear bank camshaft timing. Also make sure that your exhaust is not blocked. Is your car low on power?
Good Luck |
'75 308 GT4 (Peter)
| | Posted on Thursday, April 19, 2001 - 7:31 pm: | |
5 degrees advanced dist. setting? I've had mine at 7° BTDC which should be if you don't have dual points. 3° ATDC for R2 points as per Owner's/ Workshop manual.
I've never had this problem. My heatshields are fine. Apparently, the underbelly pans had a scoop that directed air-flow to the diff. to keep it cool (as the exhaust, even with the sheild got things "warm"). Could this also be a problem? FYI: I don't have any belly pans on my car...as well as a pile of other things...
Rob, what's the serial number of your car? Mine's 10576, an April 1975 car. Click on my name above to see a picture of it. What does yours look like? |
Jeff Fiedler (Muck)
| | Posted on Thursday, April 19, 2001 - 7:23 pm: | |
Rob-I had a similar problem with one carb on the rear bank of my 308 it turned out to be the accelarator pump demand valve it was not closing. causing a rich condtion at idle. two of the four headers glowed. I replaced valves in all four carbs. The cost is about $8.00 per valve I think the part no. is 79706.100 WEB. You dont have to pull the carbs just the tops. this may or maynot be your problem but it sounds like your running rich, maybe check needles&seats, float level,chokes.double check carb sync,make sure the rear throttle shafts are closing all the way at idle and not drawing fuel from the prorressive circuit. good luck! |
Rob Breton (Parilla)
| | Posted on Thursday, April 19, 2001 - 4:37 pm: | |
I will check the choke setup this weekend since the focus was on the carbs I appreciate the input. |
Craig Dewey (Craigfl)
| | Posted on Thursday, April 19, 2001 - 4:33 pm: | |
David has the best explanation I've heard so far. Red hot sounds like fuel burning in the exhaust to me..... |
David Jones (Dave)
| | Posted on Thursday, April 19, 2001 - 4:21 pm: | |
Just a long shot, but have you checked out the chokes to make shure they are all linked...
The guy I bought my 308 from left the choke on and did the same thing, burned up the heatshield on the rear bank....
Dave |
Rob Breton (Parilla)
| | Posted on Thursday, April 19, 2001 - 1:24 pm: | |
Both distributor banks are currently set at 5 deg advanced, Another thing I plan on trying out is to go to a colder plug, I think what is in there now is a BP60ES and probably try a BP70ES plug. |
Steve (Steve)
| | Posted on Thursday, April 19, 2001 - 11:44 am: | |
Rob you may want to check the timing on the rear distributor or the distributor itself. It may be running to far advanced and causing the problem. Also the advance weights may be stuck. Steve |
Rob Lay (Rob328gts)
| | Posted on Thursday, April 19, 2001 - 10:08 am: | |
Flashbacks to '80s Ferrari F1 Turbo engines. |
Steve Magnusson (91tr)
| | Posted on Thursday, April 19, 2001 - 9:52 am: | |
Well, it's a bit remarkable that all 4 have the same problem since they don't share a common fuel source (although I guess two carbs could have the same problem). |
Rob Breton (Parilla)
| | Posted on Thursday, April 19, 2001 - 8:30 am: | |
Other then the glowing rear exhaust header the car actually runs great. I checked the timing, synched the carbs everything else is right on the money. Someone had mentioned to me about checking the plugs and I did the rear bank is running leaner then the front?? I cant figure it out!! |
Jeff Fiedler (Muck)
| | Posted on Thursday, April 19, 2001 - 12:36 am: | |
Rob- i've had this problem on my 78 carbed gts.How does your car idle? is there any backfire when you turn the key off? how about high emissions are your eyes watering in the garage? |
Rob Breton (Parilla)
| | Posted on Wednesday, April 18, 2001 - 6:15 pm: | |
Thanks Billy,The rear bank is running a little leaner then the front. I will be looking at the carb jetting to see what is going on as well as any leaks. |
billy zissis (89tr)
| | Posted on Wednesday, April 18, 2001 - 5:50 pm: | |
Rob when I had my 308gts it did the same. I found out my problem was a vacuum leak that made the engine run lean. So even if you do not have a vacuum leak check if you are running lean. |
Rob Breton (Parilla)
| | Posted on Wednesday, April 18, 2001 - 5:45 pm: | |
Yes all 4 tubes glow equally. So much so that the Aluminum heat shield is melting in spots. |
Steve Magnusson (91tr)
| | Posted on Wednesday, April 18, 2001 - 5:35 pm: | |
Rob -- do you mean all 4 rear bank exhaust tubes "glow" equally? |
Rob Breton (Parilla)
| | Posted on Wednesday, April 18, 2001 - 5:23 pm: | |
I am new to you chat although I've been actively
checking out and absorbing all the great info on this page. I have a 75 308 GT/4 that has a problem with the rear header bank glowing red hot
after only a couple of minutes of run time. At first I thought it was the air pump excessively burning gasses but after I looked under the car and found the front header bank in a normal condition I have become concerned. My next step is to go and check if all the carbs have been jetted properly/same?? Has anyone experienced this problem or have any insight that could help. |