Yeah, that's what I thought, but that is where I get the highest idle. I was always under the assumption that I should adjust the idle screws for the highest idle, is that correct? This is why I tried the 60 idle jets. With those I could adjust the screws down to about 3 turns, but I was loading up the plugs. Not only that, but my mpg went to something like under 10 and I did get the warning light that one of the cats was overheating. Sure signs that I was too rich, right?
A process I utilized with my webers on the 308 goes something like this. Pull all idle jets and blow air thru the jets and passageways. Put idle jets back in. Make sure the car is up to temp. Back off on the throttle linkage stop screws so you are running on just the idle circuit thru the progression holes. Adjust each mixture screw until max idle is achieved, then back off on that screw about a ¼ turn, then proceed to next idle screw. Then go back and double check all settings. You should be able to get enough idle just off the idle circuit and with the idle stop screws backed off all the way. Hope this helps..
Henry, Beg, borrow or steal an LM1 gas analyzer. Take all the guesswork out. Works!! I tweaked the mixture in both of mine in a couple hours. I borrowed one from a friend locally. Birdman
I think this is really good, but I would only back off an 1/8 of a turn. I live life on the edge.... Some folks would tell you if it is more than 2 or 3 turns, it's time for a different jet. That is a bit of a discussion over a pint or two of hard cider in my opinion... The LM-1 or -2 really does give you a great look at what is really going on and some peace of mind. And remember, you only do this after you are sure your ignition advance settings are dead-on. Don't worry about being a little lean much at off power idle as well - once the airbox and filter go on, the mixture is going to get richer as the restriction to flow is added which will functionally draw a wee bit more gas and make it a wee bit richer. And, the way these are transitioned jetted, once any throttle is applied it gets really rich really quick. With the stock muffled airbox the restriction is significant in it's effect on mixture. you'll see earlier in this thread as that restriction was removed, the carbs needed some rejetting to handle the increased flow.
Russ, I just took a closer look at my airbox today. The two snorkels lead not only to an open area in the front but equally to bowed out sides of the air box as well, literally letting all but the back forth of the air filter breath freely. I still think it would be interesting to redesign the box allowing air to be pulled from both sides as well as funneling air to the oil cooler from the one side. Thought you wanted to know. Ciao, George
Hey Russ, On your set up, you opened up the "throat" of the airbox right? If I tried doing the same without enlarging the throat, do you know what K&N part would work?
Yes, I am familiar with the Merak airbox. While there is a lot to be gained by opening up both sides of the air filter in a 308 (as Cavallo has done with his hoses), I think Maserati did a good job allowing unobstructed airflow to the larger area of the filter, as opposed to the 308. This is precisely why I do not use a filter in the 308 airbox, but mount a K&N cone filter at the nose, then shape the airpath for velocity. Cavallo has opened up two more flow paths to the back and remote parts of the filter, which doesn't look so factory engineered, but I would imagine works very well. I would stick with the Maserati stock box on the Merak for the most part...unless you wanted to place two cone filters at the end of the feed hoses.
I do not use the stock filter inside the airbox, but rather a K&N cone filter on the end of an extended snout simply on the front of the box. This allows max air availability and velocity at the velocity stacks, and a fully exposed element with summed suction pulses for best air flow and filtration. There is not a standard K&N that fits on the end on the stock box, but if you get the biggest cone filter they make, any shop can put an oval opening on the snout that the filter can clamp to. A tube filter in the air duct seemingly would work well also. Will post a photo tonight when I get home.
Heres the idea, then the filter sits in the side vent airflow; the "throat" was opened up when the obstructive noise absorbant fiberglass packing was removed from the snout. Image Unavailable, Please Login
I just purchased a '79 GTS this weekend, my first Ferrari, and came across this thread searching for some cheap easy performance upgrades. Very interesting read. Just spent the better half of the afternoon reading it in it's entirety. Worth bringing back. Couple questions and/or ideas. It seems that most are in agreement that a setup with both individual air cleaners for each carb working in conjunction with a "gutted" air box would be the ultimate setup. It seems that this was attempted with the stock air box but the air cleaners used would not clear the top of the box. Now I am not sure if this is something that has come out since the original attempt or not, but there are several 1 3/4" tall air cleaners available at Pierce Manifolds now for DCNFs, the cleaners in the original attempt appear to be 2 1/2" tall. Perhaps these may fit inside the stock air box? http://www.piercemanifolds.com/airfilters.htm If there are still fitment issues with the 1 3/4" tall filters Pierce also has a filter/screen setup that filters to .009". From reading the thread it appears everyone was reluctant to try these screens due to the limited filtering capabilities. With these screens I would assume that the only elemenct that could get into the carbs would be moisutre. With the air box in place though I believe that should then become a moot point. Any thoughts/suggestions/or am I missing something? I am going to be about a three hour drive away from my car while it gets sorted out, took on a bit of a project, so I don't have anything in front of me to check out first hand.
I just read through this excellent thread and bringing back to the attention of the carb community. Of course I immediately went down and looked at my air box and I also have mesh and fiberglass in my '77. Something else to fix, but this entire thread is one of the best I've come across in years.
I bought an early 308 airbox with the steel mesh and fiberglass removed. I had to use an oil cooler intake tube for the airbox intake due to longer snout on my original 78 airbox. I had already increased the jets in the carbs to get my GTS to smog in California. The gas in California is too lean for the original carb settings. Once installed, I drove it and it sounds great. You can hear the carbs singing. I love the feedback it provides while accelerating through the gears. Reminds me of my past Dinos, Lamborghini Espada, and 365GTC/4. The music of the carbs. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Switched Main Jets from 125 stock to 135 and Air Correctors 200 stock to 190 based on the guidance on this thread. Idle jets from 55 stock to 65 to pass smog testing due to lean California premium gasoline. Engine responds better at low end and above 4K. Above 4k, the engine accelerates quicker and is more responsive. Excellent Weber music with windows down. Love it!!!!
If you can find a shop with a dyno, and bring along a few different jets, you can really fine tune it.
This is a relatively old thread, but I thought I’d ask for thoughts on these from Pierce; I’m tired of removing and installing that @$#! airbox! My first concern is spark suppression. I live in Orlando so dust and debris is not a concern at least for me. Any comments are most welcome. Thanks very much. 1978 GTS. Dane Image Unavailable, Please Login
Unfortunately, those will ingest hot, underbonnet air (rather than cool, outside air). Also, there's a lot of dust/debris everywhere -- a fine screen is OK for a racecar (not worrying about engine longevity), but not so great for a road car IMO. There are similar units that have more of a real air filter that would be a better choice if you want to go that way (and accept the hotter air issue) -- an example (and I'm sure others have more pics): Image Unavailable, Please Login
Steve, As always, I respect and appreciate your opinion. Thank you. Admitting my ignorance, I didn’t know those screens were designed towards race cars. I’m all about engine longevity! Pierce also has these options: Image Unavailable, Please Login Image Unavailable, Please Login
