That may not be a great comparison. A 4.7 liter engine making 330hp in running very near the top of its potential.....you will be. With extra vacuum in the manifold due to a restrictive carb will cause the air flow to drop, if it drops as much as the Ghibli, that will only give you 224hp On my race bike with 375cc cylinders, switching from a 40mm venturi to a 38mm cost 6 hp per cylinder. That was at a higher rpm, and it was a slightly higher output engine (but still had near stock idle and better than stock low end), I'm still guessing you don't want to even think about anything smaller than 36mm and that the bottom end and drivability will be as good or better than what tyou have now with 32 or 34.
Found this in the old cam thread when Kermit measured qv head flows using just the head. They are a bit higher down low but match Vic's very closely at higher flow. Stock QV head flow measured: Lift -- Kermit 0.10 -- 31.6 0.15 -- 51.5 0.20 -- 64.7 0.25 -- 80 0.30 -- 86 0.35 -- 89.2 0.40 -- 92.2 0.45 -- 94.2 Looks like all of the data is lining up. I'm hopeful.
The exhaust results are in and as expected the port is already more than plenty big, smaller would actually be better. It will just get a few touches here and there to smooth out the flow and drive the velocity up a bit. The stock QV/328 exhaust cam and valve are fine. Thats all good news for holding the cost down. Welding in the exhaust port would make it better, but is a ton of work for what gain there would be. On an NA engine there is maybe 2-5% at the most by welding, on my boosted engine it would probably let me run a little smaller blower like the math says I should have .but once you start welding the head needs to be re-heat-treated, all new seats and guides, probably deck it and line bore the cam journals its just not worth the effort. That kind of tells you just how messed up the stock head is by modern standards. There doesnt seem to be any reasonable way to get the intake flow higher than Vic got it, the intake valve size is up, the port size is up a bit, it wants 30% more lift in the intake cam and after all that the stock exhaust port is still too big. Crazy. Now all thats left is to figure out what to do about the intake cams. The 328 cam is a much better choice than QV, will work pretty well and can be had at a pretty reasonable price .but the head will just keep working better as lift goes up and the flow gets closer to the ideal numbers. Vic is working with webcam to see if he can come up with an intake cam he likes and see what they will do with pricing. A custom cam should add about 5% more hp over the 328 cam or maybe a little more, and that is across the board hp with increases from idle to redline .the kind of increase that is hard to say no to.
It looks like the pricing is going to be about $4500 which includes porting the head and matching the intake to it, new custom intake valves, re-cut the seats, regrind the exhaust valves, assemble and cc match head. If it needs guides, exhaust valves, springs or anything else its extra. Its not cheap, but get you on the path to a naturally aspirated engine that is closing in on 300rwhp (with EFI and compression), and it should pull hard right to redline instead of dying over 6800. In my case with boost on top of it, Im expecting a 120-150rwhp increase if I dont get crazy(er) with the boost.
Nice!!! If my engine needs more work that i hope you may be getting a PM in March as would like the help of your mechanic.
Mark I just saw your post on pricing, seems quite fair for all the work. What is your opinion on 348 intake cams, are they the same as 328? I think I would have to change the springs as they caused coil bind when I test fitted them in some stock QV heads. What are your thoughts on lighter followers, retainers, and using under bucket shims. CR
I have to go back and look, but as I recall, the 348 cams have more lift, and another 10-15 degrees of duration. The lift is good, the duration is bad unless you are planning on a 9000 rpm engine. I need to re-check my stuff (the next step), I installed crane cams MG migit valve springs. They dropped right in and I remember had plenty of travel.....I just don't remember how much but I think they will be good. I'll post something when I get that figured out. 328 springs should be plenty good to handle them too. The light weight valve train is a waste of money IMO unless you really want to bump the redline up quite a bit. I've been told the stock valves will not float until 10k.
I answered the 348 cam question too short the right or best cam is actually a very difficult question made harder because we are talking about 3 very different heads (QV/328, ported QV/328, 348). I dont have flow numbers for the 348, but I think I can make a good guess based on the stock power curve, so Ill go with my best guess. The stock QV/328 head and I believe the 348 head have decent peak flow for the port/valve size, but the low lift flow numbers are not real good. That means the head in inefficient and the air tends to travel a good distance off the port surface. In a perfect world, the valve would pop open instantly and low lift flow numbers wouldnt mean anything .but its not a perfect world. As a general rule, the less time the valves need to be open, the better the engine runs and the flatter the torque curve. The more efficient the head is and the more flow and velocity at low valve lifts, the less time the valve needs to be open which limits reversion, blow-down and all kinds of other bad things. On stock QV/328 heads, the stock 220 degrees (at .050 lift) cams get the engine to make peak torque around 5000-5500 and peak hp at 6800. With ported heads those same cams should make peat hp at 7700-8000 on a 3.0 liter and 7300-7600 on a 3.2. The reason is that the low lift flow numbers are so much better, the cam duration is used more effectively and it makes more power at every rpm and keeps making power right past redline. I think the stock 220 degrees is pretty good for a 3.2, but for a 3.0 with a stock redline is a little too much. I would like to see 210 or maybe 215 degrees at .050 lift to shift the hp peak down to 7500 or so where the head flow is a perfect match to the engine displacement. I know the less duration the happier my blower will be. A 348 head and cams feeds a 3.4 liter to 7200, so bolting it on a 3.0 should make peak power at 8100 or so. But it is not the same as the ported QV head with the 220 degree cam. The peak flow is lower by about 10% and Id guess and the low lift flows lower by 20-30%. To compensate, Ferrari added 20 degrees of duration to the 348 intake cam. He extra duration gets the cylinder mostly full, but the lower efficiency port means more energy loss, so its never as full as the ported head. Also, the added duration and the higher peak flow (without a higher velocity) does bad things to the bottom end performance and those bad things will be much more pronounced on the smaller 3.0 engine. Now it gets a little more complicated if thats possible. The same 348 cam in the ported QV head would move the hp peak up to around 9000, but the head really only flows enough air to feed the engine properly to 7500-7700. So what happens is the hp peak moves does movs to a higher rpm, but not 9000, more like 8200 or so and will probably be a few hp higher than before, but the hp/torque below 6000rpm will drop and you will probably lose 10% down off idle it is a classic over-cammed situation. Bumping the compression up helps and might get you back up to no loss down low. Its really not the best cam and the average hp will be lower than you would have with a cam that matched the head and engine. Now, re-flow the head to 130-140cfm to match the cam rpm and the engine will make 10-15% more peak hp with little if any loss at very low rpm and clear gains from 3000 up .provided you bumped the compression to match the big cams needs.. The bottom line is everything needs to match and the more efficient the design, the better the power curve with more power everywhere. A head that is 10 or 20% less efficient makes 10 or 20% less power, there is just no way around that, its a law of physics energy can be neither created nor destroyed, it can only be changed from 1 form to another. Turbulence or pressure drops in the flow path turn the flow energy into heat and mean less air gets into the cylinder.
Using Mark's computer program and Vic's head flow numbers, I superimposed them over a previous dyno run on my car. As you would hope and expect, the result is simply it no longer runs out of breath but the curve continues to climb to an extraordinary value. If correct, there would also be no loss of low end torque, although not much gain. If you look at the last half of the graph's power and torque, once you are much past 5000 rpm it's hang on for the ride with torque extending well and high to a power peak of almost 290 hp AT THE WHEELS. With stock cams. The smooth lines are the car now and the plotted points are the computer prediction. Remember, this is REAR WHEEL horsepower, with about 17% loss from flywheel hp. I'm hopeful. Image Unavailable, Please Login
Russ, I was afraid you were going to like the graph with the stock cams and they wouldn't be for sale any more Im really struggling mentally on this project. I dont have a budget to replace everything in the engine, but I want to get the best component matches I can afford that leaves me struggling with what to say is good enough and what I want to change. I think were both in the same boat with a few things. You could really use a set of pistons to bump up the compression to 10 or 10.5, and stronger pistons would let you spin the engine easily to 8000 or 8200 to take full advantage of the power that the engine is still making up there. I like the low compression but could use stronger pistons for the peace of mind and adding a few hundred revs to the redline isnt a bad thing but its $1000-$1500....I think I'm going to have to do it though. We could both use more lift in the intake cams with maybe a bit less duration (maybe). $2k to weld and grind the cams is a lot of money but its probably worth 5% more hp. I think I need to pull some duration out of the exhaust to get the blower working better, so thats like $600 to re-grind my exhaust cams .but it would be even better if I start with the taller lift 328 intake cams because the extra lift would let me pull out more duration but brings the total to $1200 for the exhaust. I need to think about this a bit more, but I'm leaning toward using 328 intakes and regrinding the stock exhaust. Id like to order the bigger blower to be sure, but I think with the exhaust cam fixed the small one will work. The small one is $2100 vs $3700 for the large . I think the small one is a bit better down low and would just barely work up top if the numbers are right, but I'm thinking it's too much money to risk, the big blower is a sure thing and will make 20+ more peak hp anyway. Its a slippery slope this hp game .the key is to make a plan in the beginning and stick to it, but Ive never been very good at that. I hate budgets.
Everything seems a bit of a compromise, but not really if it keeps you on the original target. My new bright idea of the day (BIOD) is to take the .368 lift intakes and have WEB grind the duration off to stock duration, saving a buttload of $$ vs. welding some new ones up. That would put the stock 3.2 cams back in your basket. Of course, we'll wait and see what Vic says. We are already well past my goal for the car, so I am having to temper the "fever" as well. I really want to hold at the low end torque I have or better, and increasing the lift on the stock profile would do that. I mean, come on, if this works I've got a 340 - 350 hp carburetted 3.2 liter Mondial with 240 - 250 ft-lbs of torque. It will have more capability than I will (at 10lbs/hp) and still be elegantly simple, DIY maintainable, reliable and not require upgrading everything else in the drivetrain. And with the carbs and new exhaust should sound good. Those old fashioned qualities to me are more appealing than most newer hyper-tech Ferraris, and I can still take the family on a trip. It will have and will be the best of everything. Simple is good. I'm hopeful.
I suggested that very thing to Vic for you yesterday. He's suppose to get a call from web with options today. Low end is all about compression ratio on high rpm engines. A little more Lobe separation angle (LSA) goes a long way to, but can hurt you up top. If it were my NA engine, I would spend the money on pistons to get the CR up before I ground cams. The cam buys you top end, the CR gets you bottom end which is where you drive most of the time. I'd also bump the LSA to at least the 109 euro spec. You can always add cams at the next major service if you still think you need them. You're going to have a winner with any of the options I think...it's all shades of grey we're talking about.
Thr stock Mondial 3.2 has really good torque out of the box actually, and the **original goal** was to just keep what I had. The thing about pistons is yes, they are the way to pick up compression, but the installation is $$$$ compared to cams $$ --basically a rebuild at that point and you might as well do Carillo rods, etc... That's why I am interested in decking the head just a bit while it's out, perhaps a half point or so, bringing me up to 9.7 or so (which is Euro spec). Talked to Vic and my homework assignment is to see just how close to the top of the cylinder the piston comes so we can get a more accurate combustion chanber volume, and thereby decide about decking. It's amazing to think this project just started out as a Weber/single distributor conversion for reliability and ease of maintenance.... I must say it is a lot of fun.
Update: Will be going in for the work in mid - March. Waiting on evaluation of cam issues. It's very interesting to follow this thread as well as the 348 guys who are putting 355 TB's and larger dual TBs and manifolds in the 348 section. http://www.ferrarichat.com/forum/showthread.php?t=135449 Will also be putting on the new tubi headers and new dual exhaust. Should be interesting. Will post dynos as soon as available, prob in April/May sometime.
For the 5 guys still following this... With the ported qv heads, how much hp (i.e. flow) is available from the original Ferrari 40DCNF carburretors? The most I have found documented is this 2 valve engine (3.2 liter cylinders, ported, 12:1, 272/266, 11/9.9mm, headers) at an engine dyno of 338 hp at 7800 rpm and 253 ft-lbs at 6500 rpm - all with a 34mm venturi. The graph is on the Carobu site and I have talked to them about this engine. So I am hopeful that with the ported 4 valve head and bigger valves, that this output or higher can be supported by the 34 or 36mm venturis on 40DCNF Webers at that rpm range. With this 2v/long duration cam profile, the power does not occur until after 5000 rpm with not much torque at all below 5100. Using the more efficient 4v head and shorter cam durations we're hoping to keep the low rpm flow high and maintain a good lower end while still maintaining strong flow up to 7700. Just looking at the graph, I do think they run out of carb at 7900rpm and could have made a bit more with a (very rare and difficult to obtain) 36mm venturi. There is a UK Fchatter with a 48IDF racing 3.0 liter gt/4 who states he gets 380 hp from a 2v, and I've asked what size venturis he is running. Should be interesting. Image Unavailable, Please Login
I may be one of only five but I'm watching and absorbing. I'm not a flow bench guru so I have nothing to ad at this point but it's all very interesting.
Russ, once your heads/manifolds/carb hit the flow bench it will be pretty easy to tell if the carbs are going to be a hold-up. Vic could even (and probably will) throw your manifold and carb straight on the practice head before he even starts porting your heads to see where you are and whether or not it looks like trouble. The heads are going to flow 112, and it seems like that should ok with those carbs I was thinking they were too small, but the engine I was building was a 9000 rpm with 148 of flow. You still might want the 36mm venturis, but Im starting to think youll be ok with the carbs .well know after bike week when they hit the flow bench.
I'm lurking as I'm learning a lot, good solid technical performance work like this is a new area for me.
Although not directly related to the qv head, I have been comparing two dyno charts of incresed displacement 2v off the wonderful Carobu site: A 3.2 liter 2v with carbs and Nicks 3.5 liter with throttle bodies. Interestingly, they BOTH dyno out at a max hp at 339 hp, but as expected the 3.2 is peaky with notta below 5000 (see below)while the 3.5 has gobs o' power down low, but is done by 7200 rpm. The 3.2 race engine as we saw below has 12:1 CR, ported heads; 272/266 cams with 11/9.9 lift & Weber 40 DCNFs yielding 339 hp@7800 and 253 ft-lbs at 6500 (deceptive, as above) The 3.5 engine has a 10.25 CR, ported heads, proprietary cams, and TWM throttle bodies w/ Electromotive ECU, yielding 339 hp @ 7200 rpm with a whopping 269 ft-lbs at 5700 It's pretty interesting to note the huge differences in the power bands of these engines with the same peak hp, and different displacements. In the 3.2 it takes a pretty wild cam to generate enough flow at higher rpm and sacrificing low end presumably due to honkin' overlap, while the larger engine starts flowing earlier as expected, but runs out of air before 7500. While we cannot directly compare cams, they both have the same head roughly that has been ported; I do not know if they retained the stock valves or not. Just something to stimulate thought through comparisons. Image Unavailable, Please Login Image Unavailable, Please Login
A couple other things to note. On the 3.2 graph, it really looks like the dyno run starts at 5000 rpm, the stuff below that looks like niose. The matching peak hp suggests the porting on both heads produced quite similar flow results, with the different rpm the peaks come at almost completely accounted fo by the displacement difference. Last, look at the smoothness of the EFI torque vs the up and down on the carb engine...that is the difference in the ability to control the mixture of the 2 systems.
While I don't think that just the bigger valves by themselves will increase the compression ratio (CR) as much (more of a mechanical ratio thing with swept versus combustion chamber volume), the issue of decking the heads and raising the CR is an interesting issue now playing out. While the preferred way of raising the CR is by changing to a piston that reduces the combustion chamber volume, another way is to mill some material off of the head surface causing the combustion chamber to sit a bit lower on the cylinder. This reduces the combustion chamber volume and raises the CR. While this works well many times, there are issues. Some of the main ones are valve clearence and minimum head thickness. Since the piston will be at the top of it's travel when the valves are open - sometimes these clearences are a bit tight already and shaving the head brings the valve closer to the piston. If you are also doing increased lift, well things keep getting closer and there may be a impact. Most manufacturers also specify a minimum head thickness for strength that you cannot go beyond, so this also limits how much material you can take off. Other issues include what type of combustion chamber design it is and how close the valve seats are to the edge of the combustion chamber already. Most premium street gas can support a CR of 10:1, and some cars today run up past 11. Our older cars generally have around +/- 9:1 whch used to be considered good even for a racing car years ago. Anecdotally, I've heard that the stated factory CR (Ferrari included) don't often match up to reality. We'll measure to see how much room the piston leaves in the bore, and add that to the head combustion chamber volume to get the real CR, and make a decision from there.
Following Grace Slick and the Airplanes advice, a quick word about what goes on before the induction runners. While early Ferrari V8s had a single airbox (plenum) feeding all eight cylinders, all 348 and later Ferrari V-8s have a separate induction plenum per side to take advantage of the 180 degree of "flat plane" crankshaft. This gives the characteristic of two four cylinder engines joined at the crankshaft with even exhaust and intake pulsing per side. So the reasoning for separate exhausts on a flat crank V-8 was applied to the even intake pulsing. The volume of the plenum allows some capacitance to ensure all cylinders are fed evenly. This optimization of flow that Ferrari used I applied to my intake to help feed the higher flowing ported heads after installation. In the 355 intake on the 348 thread, there are some cool photos of Mark's supercharged 308QV dual plenum and Dave's NA high flow dual plenums (both shown below). Flow is roughly proportional to the area of the throttle body, so I will include areas to better approximate flow and allow more direct comparisons. Each of Dave's plenums uses a 70 mm throttle body (3848 mm square area) feeding what looks like a 90mm (6361 square mm) plenum chamber for each bank. Remember also that the 308/328 K-jetronic uses a single 65mm (3318 square mm) for both banks. Dave and Marks also show the tapering of the intake track to promote flow velocity. In our 3.2 liter carburreted application, there are four 40 mm throttle bodies (Weber carburretors) per side (5026 square mm total) with 34 or 36mm venturis (3631 to 4071 mm square total) as the most narrow point. Two aluminum plenums were fabricated; with the challenge of a much lower bonnet clearance, an offset half oval plenum was built for each side, each ducted to a K&N cone filter at the side fresh air scoop feeding them. The area of each filter at the base was 7355 square mm which tapered slightly to feed the separate plenums through a 6588 sq. mm inlet. About as long as Mark and Dave's beautiful plenums although not as tall, the cross sectional area of each carb plenum taperd from 150mm wide x 63.5 mm tall (~7620 sqmm) to 135mm wide x 63.5mm tall (6588 sqmm). This taper front to back was taken from a Mercedes plenum idea to keep the velocity up to the rear cylinders while giving adequate capacitance to keep all of the throttles fed evenly. Below are photos of Mark's supercharged qv plenums, Dave's 348 high volume/flow plenums and finally the carburreted 3.2 application. Hope this is entertaining for some. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Wouldn't the amount of increase in CR from head modification be relative to the existing CR provided by the piston? In other words if milling the head using a 9:1 piston provides a .25 increase then a 10:1 piston may yeild .35 and a 11:1 a .50 increase. The seats are very close to the head surface but the chambers are very small. Because of this even small reductions in volume should have a large impact on CR.
