| Author |
Message |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1677
Registered: 12-2000
| | Posted on Tuesday, March 12, 2002 - 7:37 pm: | |
Thanks David.
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david handa (Davehanda)
Junior Member
Username: Davehanda
Post Number: 90
Registered: 5-2001
| | Posted on Tuesday, March 12, 2002 - 7:29 pm: | |
Peter,
Here are the specs from my 1978 308 GTS/GTB owners manual:
main jet 125
Air correction 200
Idle jet 55
air idle hole 1.40 |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 587
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 7:07 pm: | |
Thanks for the input Greg and Peter. I think I will stick with the stock idle jets. Maybe one day I will try different ones. I have heard about people changing jets to compensate for wear on an engine etc. Greg you are right a carb car will not start as quickly as a FI car. I just wanted to see how other carb cars started cold. I appreciate the info. |
Greg Rodgers (Joechristmas)
Junior Member
Username: Joechristmas
Post Number: 148
Registered: 3-2001
| | Posted on Tuesday, March 12, 2002 - 7:00 pm: | |
Peter, I remember when you had the jet issue. I think 55s are probably the best. My car ran well with them. Rich, Your cold starting sounds good. It won't fire and stay lit like a fuel injected car but it will usually start but yes, you will have to use the throttle for a little while. I would only use the choke after the car was started but very rarely. They are cheap enough so getting a set and trying them out wouldn't be a bad idea but I have heard of issues running bigger jets. I love how you can go real low rpms and the car won't bog or stall out. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1675
Registered: 12-2000
| | Posted on Tuesday, March 12, 2002 - 6:38 pm: | |
I sometimes give it one pump of the pedal and it'll fire right away. If you pump it many times, you may be flooding it slightly (not enough to kill it, but, alot to try to burn it all).
Yes, you shouldn't have to use the choke at all. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 585
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 6:31 pm: | |
I know what you mean. I can go down to about 1500-1800 and the car doesn't even hesitate. Well, how is your cold starting. Mine is pump the accel. a few times and it will light but I will have to blip the throttle for a little while and then it will be ok. I don't use the choke. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1673
Registered: 12-2000
| | Posted on Tuesday, March 12, 2002 - 6:19 pm: | |
P.S. Starting cold is no problem with me either with stock idle jets. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1672
Registered: 12-2000
| | Posted on Tuesday, March 12, 2002 - 6:15 pm: | |
Richelson, if you jump to larger idles, it may be a little too "fat" (It may bog down slightly). Looking at my Haynes/Weber manual our carbs are set-up similarly (yours is a '78?). The differences are:
-Idle jets: GT4=0.55 / GTS=0.50
-Air idle hole: GT4=1.70 / GTS=1.50
-Main jets: GT4=1.35 / GTS=1.30
Jets would be easy to change, but what they call "Air idle holes" I'm not sure. It could be the small brass bushes on top of the carb bodies, or the actual orifice in the throttle bore. Both would require drilling to enlarge and that's a one-shot deal (not suggested).
Jets however are easy to change and inexpensive. You can try it if you like. My experience has been the stock idles perform the best, I can drive it down to ~1800 RPM in 5th and pull away cleanly. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 576
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 11:27 am: | |
Ken your are getting into something different. Every model is different. A QV hits higher rpms at a different speed than a carb car. A Bosch injected Esprit is quite different from an S1 with dellortos. Again lets get back to the topic on hand. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 575
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 11:25 am: | |
We are getting off of the subject. I would like to bring it back to the original subject but I will answer some of your questions. There is nothing wrong with its performance. The question was does different idle jets increase cold starting. Ken you are talking about carbon build up. Well you are getting into plug heat ranges etc. Hot plugs are much different that colder plugs. the most logical thing I would think is too ask me what type of plugs I am running etc. If you would like to create a different topic about where you drive your car rpm wise please do but this is getting way off the subject. It has quite a bit of power in the lower rpm range. I don't think it is accurate to say it doesn't hit its stride until after 4000 either. |
Ken (Allyn)
Junior Member
Username: Allyn
Post Number: 227
Registered: 10-2001
| | Posted on Tuesday, March 12, 2002 - 11:19 am: | |
I can't speak for Ferraris, but I suspect like my Lotus the power band in the higher gears is more than 1/2 the distance to redline. |
Jeff 77 GTB (Jbk)
Junior Member
Username: Jbk
Post Number: 61
Registered: 4-2001
| | Posted on Tuesday, March 12, 2002 - 11:14 am: | |
I love to take it to redline. Doesn't even feel like it hits its stride until it's above 4K. What a rush to come out of a sweeper at 4500 in 3rd and wind it out through the gears! To each his own. |
Ken (Allyn)
Junior Member
Username: Allyn
Post Number: 226
Registered: 10-2001
| | Posted on Tuesday, March 12, 2002 - 11:09 am: | |
I'm no carb expert; my mechanic told me to not be shy about high revs if I don't want to see him very often. It stands to reason that's true. Ever hear of an 'Italian tune up'? Same theory: it heats up and cleans the engine, keeps your jets clean, etc. Granted a Twin Cam is not a Ferrari engine but they're not all that different in what's good for them and what's bad. There was a thread on HP from a dyno test and some old 308's measured quite low. There was the opinion this was a carb related problem yet the owners seem to just complain the Ferrari is under powered since they don't know how it's SUPPOSED to be. I suggest you rev out your Ferrari a lot for a month on every trip and post back here and tell us if your car is any different. You may be surprised. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 573
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 10:54 am: | |
I just don't agree with what you are saying. My car doesn't have poor performance and I have had Lotus before. Good cars but my Lotus never needed to be revved to redline and I had webers and dellortos. I just don't follow your logic. Why would it need a rebuild? A Lotus is a totally different car then a Ferrari also. I don't think it my car would feel that a favor has been done.
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Ken (Allyn)
Junior Member
Username: Allyn
Post Number: 224
Registered: 10-2001
| | Posted on Tuesday, March 12, 2002 - 10:46 am: | |
Weber carbs in particular need to be driven hard to stay in shape. Staying at 4000 RPM on a high revvng engine will cost you in frequent rebuilds, or in performance if you ignore them. Do your carbs a favor and redline that thing at least once every trip (after a suitable warm up of course. I don't have a Ferrari, I have a Lotus, and my carbs never give me any problem in part because I hit my redline (6800) every time. I wish I had an 8000 redline like you guys just for the sound! |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 566
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 6:29 am: | |
I will look into them. Thanks for the info. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 563
Registered: 12-2001
| | Posted on Tuesday, March 12, 2002 - 5:58 am: | |
I think your question, Tim, doesn't warrant a response. Do you own a Ferrari? Then don't ask me this kind of question and if you obtain one use it that way you would like. If you have info on the idle jets please present it if not please don't get off the subject. |
stacy o'blenes (Stacy)
New member
Username: Stacy
Post Number: 37
Registered: 8-2001
| | Posted on Monday, March 11, 2002 - 9:49 pm: | |
I have bought stuff from piercemanifolds. Excellent service, they seem to know their stuff. The prices were good. |
Tim N (Timn88)
Member
Username: Timn88
Post Number: 515
Registered: 6-2001
| | Posted on Monday, March 11, 2002 - 9:00 pm: | |
How can you enjoy the car below 4000rpm? |
Bill Sebestyen (Bill308)
Junior Member
Username: Bill308
Post Number: 118
Registered: 5-2001
| | Posted on Monday, March 11, 2002 - 8:27 pm: | |
The normal F-car suppliers should have idle jets. I would insist on new jets unless you have a microscope to verify the bores clean and haven't been drilled. Bill |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1665
Registered: 12-2000
| | Posted on Monday, March 11, 2002 - 7:01 pm: | |
Rarely above 4000 RPM?
I got my idle jets from Bayless Fiat in Georgia. Reasonably priced and arrived quickly.
Pierce Manifolds in CA. is also a big supplier, although, I haven't dealt with them.
http://www.baylessfiat.com
http://www.piercemanifolds.com |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 551
Registered: 12-2001
| | Posted on Monday, March 11, 2002 - 5:54 am: | |
Where is the best place to order Weber parts? i have heard that there is a place that has everything for them but I don't know the name of the company. My car drives fine but I normally stay below 4000 rpm and was wondering what is the best way to go since I am rarely above 4000 rpm. |
Bill Sebestyen (Bill308)
Junior Member
Username: Bill308
Post Number: 115
Registered: 5-2001
| | Posted on Friday, March 08, 2002 - 6:01 pm: | |
I believe 60 idle jets are the next size richer. All else being equal, they will provide a richer emulsified mixture for most driving conditions, at least until the main jets come in. Whether they will improve your cold starting and allow easier low rpm driving depends on your engine, gasoline content, and driving style. Idle jets are easy to change and will probably cost you about $5 each. Give it a try and see.
If the engine tends to load up or foul plugs when hot, it's probably better to go back to the 55's. Idle air correctors on DCNF carbs, I believe, are fixed while main jet air correctors are changeable. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 531
Registered: 12-2001
| | Posted on Friday, March 08, 2002 - 2:53 pm: | |
I was wondering what happens if I increase my idle jets? Will this make for easier cold starting and easier low rpm driving? I have the stock 55s in I believe. |