OK, ok...no ofense meant...like I said, when I was growing up, I thought that car was the coolest thing in the world. Now I've chaged tastes a little but, Ferrari's look good in ANY color, even flat green, like that german 456 in another thread. Call Abacus, they should treat you well and let me know when you're planning on coming to town, so I can stop by and say hello.
I just pulled the jets on my 78 and they are 125's. My owners manual rates the engine at 205 at the flywheel. I have no cats or emissions and pulled 176.5 rear wheel HP which is about 207 at the FW. The stock cams can be re-indexed to Euro event timing but will not net the same HP because the exhaust cam profiles are less aggressive than the early/Euro cams. I was told that if I was going to go to all of the trouble of changing cams that I should forget the early cams and just go with the P4 cams though they may be a bit "peakier". In todays age and technology one could have a set custom ground for close to the same price I would think, by Webcams. If not try Competition Cams or Lunati. Russ Turner (SNJ5) did a carb conversion to a 3.2 Mondial. He can tell you all about jetting! Very comprehensive thread. Power is nice to have but the key to quick times is MOMENTUM.
Where I'm gonna race my 308, MOMENTUM is called CHEATING! I'm not racing mine at the track, but maybe a little stoplight action now & then!
I'm really too new here to be posting advice... but anyway... I'm the new owner of a '78. Was completely stock with non-functioning smog pump. From my first drive it felt VERY lean. So I started readin gthe archives and found that the factory jetting was 125... significantly less than anything else. Apparently just stepping up the mains to 135 (same as '77) made a world of difference with no other changes. Step 2: I installed individual K&N filters. Frankly I don't care if actual performance drops due to hot air because the sound is AWESOME (reason enough by itself to own a Ferrari!). Noticeably leaned out the mixture even more to the point of a lean miss at some points. Step 3: On the adivce of others and in the archives, I'm pulling out my cats and replacing with straight pipe (for the track only! ;-) ) Decided NOT to use hollowed cats (which I also have...for sale) but to get pipes made. Step 4: Since every other post on Webers mentioned Mike at Pierce Manifolds, I called him. http://www.piercemanifolds.com/orderinst.htm He confirmed that with no other changes, stepping up the mains was a great idea. He further suggested that with the cams I have and the mods I've done, I would likely get my best peak power by changing up to 34mm venturis, 145 mains, and 50+ idles. He further said that while I could possibly get some improved driveability by playing with the air correction and emulsion tubes, those changes would not significantly change my power. He suggested an intermediate step might be to stay with the 32mm venturies and bump the mains up to 140 and to use a 50 idle. Suggesting buying LESS than I was prepared to? My idea of a great merchant! But as a newbie I'll end with a question... Currently running what I think is the original ignition system... and the tach reads 2x actual engine rpm when my foot is on the gas, actual with my foot off (and I assume the microswitch engaged). What "timing" or other igntion changes can I make to best take advantage of the freer breathing? Thanks! Bill
I run two Crane XR700 solid state ignition modules with optical triggers in each distributor and stock coils. Revs to 8,000 RPM without skipping a beat. Set 'em and forget 'em.
I've installed several Pertronix, Cranes, and MSD's.... but in a 308 is this something I can do myself or should the dizzies go to a specialist? Bill
You should be able to do this yourself. Aside from the mechanical aspects of actually installing the triggers and mounting the boxes, (mine are above the forward dizzy on the firewall), you need to set the triggers up at TDC by lining up the marks on the flywheel to 1-4 for the rear bank, rotate the distributor until the red light on the box comes on then roll the engine over to the 5-8 marks and do the same on the forward distributor watching for the red light on the other box. Then it's just a matter of setting the initial timing advance if/as required with a timing light. Some guys on this sight put BOTH triggers in one dizzy, 90 degrees apart if I am not mistaken. Both distributors still do the duty with this set up. Advance timing is still set up through both.
The most important thing to get right is the TOTAL advance for the distributor. Getting this right will do more for your power than all other factors. Once you get your points replaced with a Crane or Petronix system you want to set the timing to get your total advance to 32BTDC. If you don't understand the idea of total advance don't be embarrased but get a local mechanic to show you how to measure total advance on a normal car. The procedure is then pretty obvious on a Ferrari once you see how it works on other cars. I am really surprised that Mike Pierce recommended 140 main jets with 32mm venturis. After years of dyno tuning Webers at Rockwell Motorsports I think that would be way over the top, but I have guessed wrong before. Maybe he is right, but I would get that setup checked on a dyno.If you retain working catalytic converters and the air pump, these richer jets will give you red hot converters, so stick with the 125 mains.
geez, this thread got real technical. lemme see here, spasso you mentioned the exhaust cam profile is less aggressive than early/euro cams. well can i have that changed as well? john
hehehe, he can tell me all about jetting but all he'll get from me is a blank homer simpson stare in return. john
Yes, by ditching the EXHAUST cams and replacing with Euro spec cam from '76 or '77. If you scored a couple for cheap it could be an inexpensive way to gain 10 or 15 HP (relatively speaking of course) The US spec INTAKE cam is slightly different also so you may want to change all four cams. Pricey for the moderate HP gains. A perfect time to make the switch is during a 30k belt service. R & R the cams, adjust the valves, new cam seals and gaskets, low profile velocity stacks, go up a size on the main jets and check it out on a 4-gas analyzer and dyno to fine tune the set-up. An example; I have a friend with a 1975 308 GT4 that is quite fast. It really moves out compared to mine. Being a '75 it has the more aggressive "non-emissions" cams that mine has. Otherwise the engine is pretty much the same.
Beer...32 mm venturis=good throttle response...beer...F24 Emulsion tubes= good acceleration gas mixture...beer...135 - 140 main jets=more powerful air fuel mixture....beer...200 air corrector jets=good top end power mixture...beer.... See, that wasn't so hard... have fun! rt
If you can find the thread that SNJ5 did on the conversion just do what I did, read and learn. I've been reading and learning daily on this site for two years. It's amazing the accumilation of Ferrari information of all aspects that is found here. Just keep reading and asking questions, there are many more here much more qualified than I. master mechanics willing to share information.
spasso, my next 30K service is in 4 years! can't wait that long! i'll probably bite the bullet and get it done this year. i'll look up russ's thread on jetting...tomorrow. that sort of concentration effort only comes when i'm mostly awake. since i'm on the east coast, it's now past my bedtime. russ, mmmm beer and advice, they seem to go hand in hand. thanks for all the tech info. before reading this thread i had no idea there were intake/exhaust cams. i thought cams were cams. hell, i don't even know what they do! john
I asked Mike why the 140 instead of the 135 that I had read in the archives... he said it was because I was running the K&Ns and test pipes in place of the cats... Russ: what is your opinion of the advice to just leave the emulsion tubes and air correction jets alone? Bill
I ran a 78 that had test pipes, drop in K&N filter and swapped to 140 mains. (rest of the carbs were stock). Ran great on the dyno. With a fresh service it was pulling around 214 hp at the crank.
Just thought I would chime in with the jet talk. My car originally had 125 Main jets, which were changed to 140's. The idles were also changed from 55 to 60. The car ran do much better after that and Abacus really spent some time with the advance/distributors/timing, so I guess that's how I got the hp figures on my car.
Absolutely.....the point of distributor calibration, a bench test, is to confirm proper advance curves against the proper RPM. Being horizontal in our 308s doesn't help. If not functioning properly, TONS of bad things in addition to power loss can occur.......don't ask me how I know....LOL! BigTex "Fire Patrol" Bubba
Bill weber documentation states to change the air correction jet 3 steps in the opposite direction for every step in main. for example, going from 135 main and 200 AC, change to 140 main and 185 AC. this has worked wonders for my euro carb 308 on the dyno.....i have kept the emulsion tubes the same.
And don't forget (it was discussed in the old forum, but the information could be regenerated from the owner's manuals on owners.ferrari.com) that the advance curves are slightly different for the emissions cars, I think... Also, wrt main jets, I seem to have taken from the discussions on the old site that the hot setup for a freed up exhaust with good cams was 140 mains with 200 ACs. That's the consensus I came to from researching all the old threads.
