I hear port volume a lot from the US car guys but it really doesnt actually mean anything to performance. I guess the thought is measuring port volume is an easy way to tell if the ports are all the same but in true there are an infinite number or port variations that will yield identical volumes so the number is nearly useless for comparing ports as far as I can tell .but the US car guys always want to tell me about their port volume. What actually works is knowing the flow velocity at the valve seat. The higher the velocity for any given flow, the better the cylinder will fill, the better the fuel will atomize, the more turbulence in the combustion chamber and the more hp you make. Velocity helps everything. At 10in H2O pressure on the flow bench 195-200 fpm is possible at the seat when everything is right and when you are in that range the torque curve will be wide and flat and volumetric efficiency will be up in the 120% range meaning gobs of both torque and hp. So, the velocity is in my opinion the most important number, it tells you if you are building a good engine or not. The second number is the actual flow. You cant make hp without air and the peak flow number tells you how much hp is possible. A lot of guys get focused on this number and forget the velocity number which is what leads to horror stories of over-ported or peaky engines. Making flow with a small efficient port is good, making flow by just hogging out the port and stuffing in big valves is bad. All the general stuff said, lets talk specifics. Ferrari in the 70s and 80s did what a lot of people did at that time and made high velocity ports. The port/runner is kind of hour glass shaped area wise with the smallest and highest velocity part right about in the middle then the port area increases all the way to the valves. It works, but understanding has changed and we now know it is not an optimum design because diffusing (going from small to big) is always inefficient and causes you to really just hit a hp wall that you simply cant get past. The 2 valve head has a valve and seat ID big enough for 400+ hp of air but is only flowing 240hp or air and the QV and TR heads are similar. There are 2 ways to fix the ports. The first is to weld in the port up by the valve and fit smaller valves. This will let you make maybe 10% more hp while fattening up the torque curve. The second option is to open up the other end of the port and the whole manifold enough to match the valve seat area or better yet taper larger at about 4 degrees from the seat all the way out. This will let you make 30+% more hp with a fatter torque curve and is basically what I was doing with the TR heads and had the flow up just about 30% with the stock valves ..before I realized I need to buy cams anyway and decided to make the engine spin another couple thousand rpm which meant I needed even more air and required opening up the port until I found water jacket and still wishing they were bigger. A 308 engine with stock cams (early carb or QV .2vi cams s*ck) the heads done right and EFI should make 320+ hp without any problem and the one engine I know was done right and dynod does and does it with more low end power and better driveability than a stock engine. The numbers always work out, there may very well be a way to do it that is better yet, but you can get 30+% more power today going to the numbers the way we understand them today vs what was the hot ticket in the 70s.
A lot of things matter. The current thought is the swirl is all about fuel mixing, but I guess there are as many options as people.
Incisive analysis indeed! Big kudos to you Mark for a very clearly written explanation. I am going to copy this to the 348 forum and see if anybody has tried this approach. If a 308 can get 320, my 3.4 should be able to get 360, and that along with more low end would be enough for me. Just looking at the cutaway drawings in the service manual, I can see that the runners are 0 degrees from the port entrance to the plenum - not bad, but not good either. Thanks!!
There is no question a 348 should be able to make more power than it does. The 348 head is the same as the QV/328 with the port opened up a little bit, but it's still not right. The rummor is that ITBs help, but no one seems to have actual dyno numbers that prove it. Good luck and post numbers
You might try talking to the folks at APR, www.goapr.com, in Alabama. They have a machine that does "stereolithography (SLA) prototyping" I believe this makes cost-effective short-run castings possible, although whether or not they take outside work is unknown. I was speaking to my friend who has worked on Ferraris since the 400i was new in the showroom, and he wondered if you were going to try to do anything about the 400's chain stretch issue. He said that the factory recommendation was to change the chain every 25,000 miles, because it is so long, stretches, and the tensioner has a limited take-up range.
I got started drilled and milling the oil holes and slots in the cam billets....tiny little things. This is going to take awhile. Image Unavailable, Please Login
I've got the flywheel design about done I guess. It weighs about 9.55 lbs by itself and 18 assembled with the ring gear and clutch. Im honestly not sure how light to go, the engine will have tons of low end torque so I shouldnt need much to make the car drive nice around town. I left it ½ thick where the clutch mounts thinking it would be good it the flywheel is rigid .it might be over kill but I'm thinking better safe than sorry and it's already less than 1/2 the weight of the stock assemble I think. Image Unavailable, Please Login Image Unavailable, Please Login
The guys at work are trying to convince me that the flywheel really wants to be aluminum. That would drop the flywheel itself to 3.3 lb and full assembly to 11.8 lb. More to think about.
Dont forget to take cam advice from them too LMAO. I wouldnt go too light because of the trade off you may encounter. 1/2 the weight of the original doesnt suck too bad
It's not the cam guys, it's the machinists who'll end up making it since it 's a bit for my little lathe....and I suspect their main interest is that aluminum cuts way faster then the RC30 4140 steel I was talking about first. I definitely don't want a car that stalls trying to pull away from stop signs. 4 cylinder engines with light flywheels are just awful. On the QV engine I went to the light weight clutch but left the flywheel nearly stock weight and I really didn't notice the difference. That was say 2/3-3/4 stock weight and 8 cylinders. With 12 cylinders the power pulses are 33% closer together and there is more about 50% more weight in the crank so I know the flywheel can get lighter with no problem.....I'm just not sure how much lighter. At the moment Im leaning toward the aluminum because at $92 the material is $200 less than the chunk of 4140 and ½ the price of plain mild steel but I dont wan driving it to suck because I made it too light. I could make it from aluminum and just leave more metal on it I guess as a 3rd option. I hate decisions like this ..
No need. I've got a tilton triple disc carbon-caron clutch....which actually has 7 discs in it in spite of the 3 disc name. The discs alternate with 4 that spin with the engine and 3 that spin with the trans. The disc touching the flywheel is fixed and spins with the flywheel so all the flywheel needs to do is provide a flat rigid surface for everything to push against. It's a pretty slick set-up.
Sounds cool, I get the picture. Too bad you cant do the F1 race car setup with the crank inches from the ground with that style clutch.
The valve seat cutting showed up today so whenever I finish the oil holes on the cams and free up the mill I can see what it does for flow. It seems there is never a shortage of stuff to do.....
I've read that you can get strange and interesting things happening when the clutch is heavier than the flywheel and takes over it's job. Can't find any references atm, but it would bear researching. Mind you, all I play with is inline 4's!
Unless you expect to do some serious racing I would recommend a more or less stock weight steel flywheel.
Traditionally the light flywheel is for quicker REV characteristics. If you aren't racing the car I would think that the negligible penalty of a steel flywheel would be unnoticed on the street. Longevity of the flywheel is another factor. The last thing I want in a 750 HP engine is a wimpy flywheel.
I've looked into AL flywheels, from what I've found to light and they chatter, then again the multi disk arrangement will chatter as it is. the bolt holes will ofcourse need to be 'serted and proper torque used, or it'll come apart. Often an aluminum flywheel will create low speed bucking problems. Also, the ring gear can come loose if it's not staked in. If the aluminum flywheel gets hot, it will expand much more than the steel ring gear. When it cools off, the ring gear will lose its press fit and come loose. some sites with info on design and problems/fixes http://www.indigospeed.com/ICR_Pro_Racing_Products.html http://www.10000rpm.com/ http://www.fidanza.com/Aluminum-Flywheels.aspx
here's another site you might want to bookmark http://www.eng-tips.com/threadminder.cfm?pid=108&page=1 great nerdy info and support
another good one for reading, take it in steps ALOT of info... http://mb-soft.com/public2/engine.html
How am I ever going to get the car into the 8s in the 1/4 with a stock weight flywheel? Just kiding.....mostly. I am honestly very confused about flywheel weight. The ferrari V12 flywheel is very much like the V8 flywheel when clearly a V12 doesn't need the same about of flywheel. Looking further dino's use pretty much the same flywheel too. Looking at the flywheel itself it appears to be just about as light as they could make it and still work with the clutch and starter properly. On the 360 they moved the starter which let them shrink the OD about 1 1/2 inches which cuts the inertia or flywheel effect by about 33% making it as small and light as possible while still working with the clutch and very similar to the inertia of the set-up I had on the QV which was indistinguishable from stock IMO. On my harley race bike years ago I removed about 2/3 of the stock weight and about ¾ the stock inertia from the flywheel/crank assembly and I honestly couldnt tell the difference riding or launching it, or idleing it, but it sure was snappy when you hit the throttle. A group of 5 Buell engineers hear it run on the dyno and came over and quized me about the engine for almost an hour .and the following year the Buells had a new light weight flywheel that was about ½ the original weight because I didnt tell them exactly how light I had gone. On the testimonial side I think I hear as many or more people cursing light flywheels at praising them but I never know any of the engine details the experience was with. Often when a light flywheel is going on big carb and big cams are also going into the engine which can mess up the engine driveability badly all by themselves so I dont know. When I bought the clutch the tilton guys didnt see any problem at all with setting it up for the street on the lightest flywheel they could make. They were quite confident Id be happy. So here I am trying to make a decision based on very little data and a whole lot of hear-say.
The carbon clutch will chatter, but isn't too bad really. As I mentioned to Newman, the clutch plates don't run against the flywheel so there is no wear concern and very little heat ends up in the flywheel. Also I'll be using a 360 rig gear which is a blot on design so there is no concern about expansion rates between the flywheel and ring gear.
Just make sure it's a streetable clutch. The triple disk clutchs we use with the sintered metal disks are pretty digital. I'm not sure what they use for the street.
It is. I ran it on my last supercharged engine in the car. When I bought it about 6 years ago it was the only one of the race type clutches that any manufacturer recomended for street use. It's definitely not as smooth as a stock type clutch but it's pretty easy to modulate and of the 6-10 people I let drive the car no one ever had a problem of even commented on it unless asked so I won't say on a scale of race to street it's about 80% of the way to street when set up properly.
