Anything new to report?
All is right in the jungle. I'm going to get it over to the dyno soon. I have the mixture set just about right, but not after tons of trial and error. The final arrangement is: 60 idles 130 mains 200 ac F24 tubes 45 pump jets I tried lots and lots of combinations. Too many. Anyway. I promise a vid is coming soon! On the dyno I plan on experimenting with two specific lobe centers. 108 intake 108 exhaust and 104 intake 108 exhaust. Ferrari engines generally like very tight lobe center but I'm very curious what this particular cam grind will yield with a slightly retarded intake. I have adjustable timing gears on now so changing it will be a snap.
I am new here and just read your posts about your engine build. Congrats on a great build. One thing that might be of interest to you though. Large base circle cams will give you great lift area (more time your valve is open) with the same lift and a more gentle valve acceleration. Did you also consider a higher lift? .500 to .550 with a large base circle diameter would have helped you on the low flowing heads. the only draw back that comes to mind would be additional cost of the cams if they are not a common item for the engine.
Hey welcome. The base circles on these cams are pretty much a set size due to the tappets and placement of the cams in general. I could have customized a grind with a bit more lift by making custom guides which allowed a bit more room essentially making the stem seal to sit lower on the guide, but there's no way in getting up to .500 even by doing that. Also, the tappet does not have adequate area to make that work either as I believe the cam lobe face would hit the tappet outside of the tappet and probably hit the aluminum housing the tappet as well. I'm pretty close to the absolute limit with what I'm running right now. Ferrari 2v heads are just 'like' this and there's not much we can do about it. Even Ferrari's 'race' grind of this era (called 'P6') didn't even have the same lift I am running now, but rather it was around .375 but obviously with gobs of duration which was: 267 @ .050.
Here we go. Taken while timing the 5-8 bank. Image Unavailable, Please Login Image Unavailable, Please Login
little vid. badazz. running a bit rich but no worries. sounds good. I'll have an in-car vid soon. http://www.youtube.com/watch?v=oEm6BGwTyuc&feature=youtu.be
So, the final jetting I have as of now is: F24 tubes, 130 mains, 200ac, 60 idles, 36mm chokes (!!!) I may experiment more with one size smaller pump jets as the mixture goes quite rich at tip in, so I'll try 35s again and see how they go. I tried them once before and the engine didn't really like it, but that was with F36 tubes. This engine will simply not run right with F36 tubes over 5k rpm. They go entirely too lean regardless what I do. F24s are definitely the ticket.
great vid were rubber or silicon molds made of your port after it was worked on? Do you have any images of the cross section of the 308/328 port (2v)?
No molds. What I essentially did was install a larger ID and OD valve seat which left a 1mm shoulder around where the prior small valve seat sat flush to the bowl. I then removed that material and blended the bowl to the throat so it suited the new seat ID. Seat was cut with a multiangle cutter obviously. The big flow difference for this intake port was actually the nailhead style valve. The seat helped but the larger flat backcut valve made a substantial difference at low lifts and a nice difference at higher lifts as well. I'm sure a head cross section drawing is around here somewhere..... these heads have a terrible port design though. The port needs to begin about an inch north of where it does. There isn't any decent short side radius either.
stick a go-pro on your bumper right above the exhaust and let us hear that beauty bark. or just tape your cam on the bumper.
Yeah I am trying to find one but can't. I am going to do some work on some heads but I prefer to do my research before cutting. I followed the post on the other ferrari board but need a crossectional view. If any one can help me find one I'd really appreciate it. I know you're proud of that new engine I would be. It definitely sounds great.
Here we go. There are some cross sectional drawings in here: http://ferrari.stevejenkins.com/books/308GT4_workshop.pdf
perfect a terrible port (at least for performance) is an understatement but I see a spot of improvement. Thank you very much for the infor.
lol. yes! It's bad. Nothing that A LOT of welding and hand finishing can't fix. Maybe even some drilling for the new port. It is what it is ya know. I used 44mm valves and did what I could really. The 4v heads are just tons better and don't require much to really get them flowing. I could have used a set of 348 heads but: would have to buy the heads (duh), the cams would cost double, more valves (more $$), and then I would pretty much have to inject it (ITB setup) cause carbs just wouldn't do it. So the cost per BHP would have gone out of the atmosphere, although I have no doubt I could get around 400bhp doing it that way.
yeah i know what you mean. horsepower = money^2. I have the ability to weld and port so it will be a fun project. just need to find the parts without breaking the bank first haha.
well actually im going to design a new head. the first thing I need to do is get a head and do some layouts. From there I will have to make some rapid prototype pieces to test the port and make final changes. Once those are complete I can make the final design revisions.
