[mk e]

I believe optimal intake runner length for my flow was determined to be a bit over 19 inches. Don't ask me how the computer came up with that because I have zero idea

The length is about rpm mostly.

frequency = harmonic number x (speed of sound in the pipe)/(2)(length of the vibrating air column)

For an engine the frequency to use is f=rpm/2/60

The signal is strongest wiht the 1st harmonic and gets small as you go 2nd, 3rd, ect. Normally the 1st harmonic yields a pipe that is way to long to package under the hood (headers are normally the 1st harmonic) and on a 308 something around 19" would be the 2nd harmonic....which is also pretty long. Intakes are normally the 3rd harmonic which would be about 12.5" if 19" is the 2nd.

 

[duck.co.za]

mk e what do you think about the shape of the 355 TB ? Could it easily be made to work ? You are not going to be able to get a constant taper from valve to butterfly ?
Possibly Hyabusa TB's are a better option ?

 

[mk e]

mk e what do you think about the shape of the 355 TB ? Could it easily be made to work ? You are not going to be able to get a constant taper from valve to butterfly ?
Possibly Hyabusa TB's are a better option ?

I think the only decent option is to saw off the head side of the manifold an inch or so below the throttle plate where the runner is still pretty round and then weld on what you need to mate to the head.

Hyabusa or similar TBs are a fine answer too but you still need to fab an intake for them so they are probably about the same amount of work to use, just cheaper to buy.

 

[ferraripilot]

I would think having the 355 throttle linkages would be the largest advantage.

 

[duck.co.za]

I think the only decent option is to saw off the head side of the manifold an inch or so below the throttle plate where the runner is still pretty round and then weld on what you need to mate to the head.

Hyabusa or similar TBs are a fine answer too but you still need to fab an intake for them so they are probably about the same amount of work to use, just cheaper to buy.

Thought about that , just the injector bore is quite close to the other end ?

John throttle linkage is definatley a plus

 

[mk e]

Thought about that , just the injector bore is quite close to the other end ?

John throttle linkage is definatley a plus

I'm not sure that matters very much.....I guess in a perfect world it would fall in a node (or is it antinode?) where the air air isn't oscillating which for a 3rd harmonic tune is the 1/4, 1/2, 3/4 positions...I guess

 

[duck.co.za]

Here's a great shot of the 355 linkage . Note the injectors are on the outside ? I would think they need to be swopped around so they are on the inside firing down the port ?

 

[tazandjan]

I looked at your cam specs and note they have their timing references at .35 mm rather than the .50 mm commonly used by Ferrari. Think that will give you any trouble degreeing the cams or is the ramp steep enough to provide some movement?

 

[mk e]

Here's a great shot of the 355 linkage . Note the injectors are on the outside ? I would think they need to be swopped around so they are on the inside firing down the port ?

For a 2v it's probably better to have the injectors inside to get a better shot at the valve but on a 4v outside is probably about as good and might be better.

 

[ferraripilot]

I looked at your cam specs and note they have their timing references at .35 mm rather than the .50 mm commonly used by Ferrari. Think that will give you any trouble degreeing the cams or is the ramp steep enough to provide some movement?

The ramp is indeed quite steep, but they have specified it be checked at .35mm lift and 1.25mm lift with zero shim clearance if I am reading it correctly. The timing sheet states, "w/o clearance at .35mm and 1.25mm".

Correct me if I am wrong, but Ferrari has it checked with .020 shim clearance don't they? Or is it zero clearance and check for .020 lift?

 

[mk e]

Correct me if I am wrong, but Ferrari has it checked with .020 shim clearance don't they? Or is it zero clearance and check for .020 lift?

It's zero clearance and 0.50mm (.020") lift I'm pretty sure.

 

[duck.co.za]

It's zero clearance and 0.50mm (.020") lift I'm pretty sure.

That's how I did mine .

 

[tazandjan]

Mark- You are correct, it is 0.50", so you have to change shims on four valves to check clearances. At normal clearances, the ramp is just too flat to get accurate readings.

 

[ferraripilot]

Just as an FYI to the above, I am not going to run 108/108 lobe centers as the timing sheet suggests, but rather if I have the intake valve clearance (which I believe I do) I am going to run 104/108. Stock lobe centers on these are very tight and the P6 cams I played with would barely run until I had them extremely tight and they ended up being something like 98/100. The intake valve likes to close a little earlier on these motors.

I'm wonder though if the additional stroke will change my paradigm as the piston will remain at TDC for a hair longer thereby further increasing combustion efficiency.

 

[ferraripilot]

Eagerly waiting my crankshaft now.

Rods factory spec is: 1.8854-1.8859

all my rods measure out after being machined @

#1 1.8858
#2 1.8858
#3 1.8859
#4 1.8860
#5 1.8857
#6 1.8861
#7 1.8859
#8 1.8859


A couple are tiny bit over spec but I don't think .0002 is going to hurt anything unless the crank is at the low end of its tolerances. I am shooting for .0025 rod clearance.

 

[bretm]

...all my rods measure out after being machined @ ...

Very cool.

I might have missed it, but are you using the stock rods still? Did you have to have them machined (big end and little end)? How do they do it?

 

[ferraripilot]

Still using stock rods. I had the big end re-sized and the bushing in the small end replaced even though the small end probably didn't need it.


Strangely, every last one of my rods were .0005 out of round but also the diameter even at the widest area was at the very tightest end of the specification and below. The tightest was 1.8853 (min spec is 1.8854).

Anyway, to re-size the big end you must remove the rod bolts and then grind a little off the end cap mating surface to the rod and the rods mating surface to the end cap. This causes the ID of the big end to obviously be smaller but the point is to provide room to round out the hole to required spec. To cut out further details of machine set up etc, the rod machine in essence is set to desired ID and the rod is then honed to perfectly round spec. My new rod bearings are .0002 thicker than my previous bearings so I had these done to the high end of the spec which is listed as 1.8859. Also, any time new rod bolts are used (I threw some ARP in there), the rods must be resized as the new bolts will grab and seat things just a hair differently. The new ARP bolts are incredibly tight compared to OEM and there was some difference in how they mounted.

For OEM purposes and non-performance stuff, .001 rod to crank journal clearance is recommended per inch of shaft. So if the Ferrari motor were a vanilla run-about engine, the clearance would be about .0019. For high performance stuff, another .0005 is recommended on top of that to .0024. However, the Ferrari and Porsche specs alike both say up to .0035 is ok for a new engine. That's WAY too much IMO but they are the experts right. Ferrari and Porsche both have excellent oiling systems so I guess not to worry right.


The small end bushings I replaced had a clearance of .0008-.0009 which is definitely within spec. Anyway I replaced them anyway and have .0007. Not a big difference but is definitely further testament to how robust these little engines can be not to mention how good the oiling systems are

 

[bretm]

Interesting stuff. Thanks for the explanation - it's an awesome project that you've got going. Of course I came up with more questions though.

Are the OEM rod ends the same on the 308 con rods as they are on the 360 rods? ie, when you're resizing them are you just cleaning them up or is there a difference right off the factory line between the two.

Are the main bearing journals the same size on a 308 as they are on the 360?

 

[reggazz312t]

Just wondering

Hi, have you ever driven a 250 or 275? They rev fantastic,have you driven a 330,they rumble rev,they dont zip. A 365 has a better rip than a 330. My point is stroking Ferrari engines is the wrong way to go. Bigger bores gives more zip in the revs and stroking makes them rumble. I want 3.3 litres and lite crank & titianium rods with a big bore for high end HP.I would like to ask the pros what is the largest bore possible on 308s?

 

[duck.co.za]

Interesting stuff. Thanks for the explanation - it's an awesome project that you've got going. Of course I came up with more questions though.

Are the OEM rod ends the same on the 308 con rods as they are on the 360 rods? ie, when you're resizing them are you just cleaning them up or is there a difference right off the factory line between the two.

Are the main bearing journals the same size on a 308 as they are on the 360?

Sizing is pretty much identical except for the gudgeon pin which Ferrari increased in diameter to 20mm . When I fitted 355 rods ( which are similar to 360 rods except for the rod bolt detail ) to my 308 . I had the pistons made with 20mm gudgeon pins . Others have just bushed the small end down ! I saved 1,4kg changing from steel to Ti ?