Low Profile V-Stack Install Mods Update-308

Russ, I would certainly believe that. I might try a set of .57's in it if I can find some. The thing is clearly rich at idle. But then again it runs so well, maybe I won't mess with it. What do you think, Mr. Carb Guru?

Birdman

 

I think a set of 57's would be good - even Mike Pierce uses 'off sizes in his applications to get exactly what he wants. I'm using 53s in the 3.2. Easy enough to do. Be sure the idle screws are set ok and I think you'll be killing fewer small animals behind you and fouling fewer plugs.

best
rt
Not a Guru cause I don't understand why a guy who takes pictures of fish is called 'Birdman'...

 

Russ,
I thought .57's were an off the shelf jet size for these. I think I saw them on a webpage someplace. I'll have to research that.

As to the Birdman thing, it's a nickname I've had for years, long before I was involved in fish pics! All my friends call me that, and I actually sign e-mails that way occasionally by accident when I mean to put my real name!

If you want a real mystery, try to figure out why Mr. Doody has that nickname!

Birdman

 

FYI:
One the jetting I used, the 308 was not stock.
The heads were ported, cams set for more top end power, and higher compression pistons, afermarket ignition. oversize pulleys, etc.
As I recall, I ended up with the following:
Mains 140, up from 135's
ACJ 195 same as before
Emulsion tubes 136 "" " "
Idle jets 60 " " "
I would note that the throttle plates were drilled with a .040 drill to assist setting the air bypass for a smoother transition without getting into the intermediate jets feed holes, which are just off idle, as the throttle is opened. This drilling mod I found in a Weber book and it helps in setting up the idle (throttle plate position) without getting into the intermediate circut, which is a common headache in dialing the 40DCNF's in.
HTH
Kermit

 

The surest sign it is getting more air is that it may be running a little leaner than before.

Congratulations - it worked!!

The difference between the old box and open air horns was 0.5 - 1.0 A/F leaner on my old dyno runs. You're already a bit light with 125 mains, so if you put 135s or 140s in with this airbox mod, I'm bettin' 10 hp or better you can feel, esp. with a K&N. Should take about 30 - 45 minutes to change the main jets. It may also take a bit longer to catch when cold, as it is a bit leaner with not only the improved airflow, but with the improved flow the air will be a bit cooler as well (also way good). Be sure to wait until it comes up to temperature - your bypass jets may be just fine - you're just getting more air. And remember all of this will be a bit magnified at speed with increased airflow

Again - congrats.
Should be fun.

 

I have read this thread and I am looking for clarifacation on this issue:

Is there a dyno record of what these low profile stacks do for a 308 without any other modifications including any airbox mods?

Simply put a baseline and after install of the stacks that show an increase in power directly and EXCLUSIVELY related to the stacks.

What I have read is that there is no exclusive dyno report on these stacks and if I am wrong I would like to know.

 

Okay, the devil is here! It looks like quite a bit of manufacturing time went into sound deadening/intake size & shaping of the stock box. I'm all for making motors breathe easier, getting more power, etc. But I have to wonder why Ferrari would put all that crap in there in the first place. It adds weight, costs $ in terms of manuf. time. So why?

I'll be looking for a box to mod assuredly if the data and road use results prove that the mods free things up. I pose the why question due to a factory glitch/design oversight I was exposed to in my mechanic days. Those who know me recall I spent 7 years as a factory trained wrench for BMW motorcycles (1984-1991). Big deal...perhaps, but I went from carbs to AFC EFI, than later to motronic FI. in that short span of time and came across many A/F related run problems from new units right out of the crate.

Okay, the most bizarre thing that occured was when the last of the carbed bikes went from a circular/donut air cleaner element to a flat element. The bizarre thing was this:

All the bikes, 1000cc, 800cc and the 650 cc all used the same air-box intake snorkels. Twin snorkels having equal sized snouts under the fuel tank. The 1000cc bikes were fine, the smaller displacements had a horrific flat spot in the mid range. We at the dealer level tried different main jets, needle heights etc...all to no avail.

The fix? Drill four 5mm holes in ONE of the snouts, at apex of the snout's intake radius. No s**t, this was a factory service bulletin. IT Worked! Later 800cc & 650cc units were shipped with intake snouts that were no longer matched in intake area like the 1 liter bikes. One snout was now significantly smaller than the other.

I never studied fluid dynamics in college so I can't describe what created the flat spot initially in the smaller motors. The fix created turbulence to prevent the flat spot in the mid range.

So again, why did Ferrari put all that crap in the airbox...and could someone better educate me on what could cause a flow restriction that I've described?
PeterB.

 

I'd love to find out the reasoning behind the madness of the airbox's "stuffing!" It would be great to find those engineers and get an answer to the "why." I would be very curious to get a spark-plug reading after a really spirited run, to see if any of the 8 chokes get air starved in the manner I described with those old German twin cyls. A sports car engine should breathe, sound exciting, be light weight, yada, yada. Still I wonder what the intent really was...

The vacuum flapper, well, mine is there too...and functional. Shut off engine, fumes are trapped and plumbed into the charcoal canister.

Sound deadening, how much louder is it without? I can't imagine Ferrari had a problem with intake noise for DOT cert.???

I do hope it's nice on the 12th as I plan to attend dyno day. Our cars are '78's, yours modified, mine stock, everything is there cats too. It will be a rough but fun comparison. PeterB.

 

It is quite louder without the silencing - a very full deep induction sound.
My thought is not the DOT, but rather Switzerland, is a reason: they are famous for strict noise regulation.

 

Thanks much for the info!!! I'll try it both ways with the idle jets as I'm playing with it and report back the difference...

Bill

 

Was our US airbox also used in some Euro countries? The Swiss are noise sensitive, but it's an external noise issue for gov. cert...I don't think it would be a cabin noise issue, that is for gov. cert.?

If it's loud only under hard acceleration, yahoo! Makes the sports car experience even better!

 

Paul,
Thank you for your interest in our product The dyno sheet you requested is going to be posted later, as it is a bit large for me to upload. Another poster has offered to post it.
This is as you asked, just the stock air filter housing, with stock air horns, followed by the same air box, untouched, with the LPHF horns
HTH,
Kermit

 

Well, I went and pulled my air box down off the wall last night and took a look at it. I have a US 1977 308 GTB. I took off the lid, and darn if there wasnt all that crap in mine too. There would be no real possible way for any part of the airfilter, excepting that part in the "window" of the snorkle area, to flow any air at all. Mine was the same as any pictures that have been posted, and had the same big pile of fiberglass and mesh laying in a wad on the floor.
Ya know, between pretty polished intake ports that dont match manifolds, pistons that stop .055" short of top dead center, and now this air cleaner garbage, I really wonder what they were trying to do with these cars. And with all the enthusiasts around the world playing with these cars, why did it take almost 30 years for someone to notice the aircleaned being filled with that crap? I dont need a degree in fluid dynamics to see what I seen, that aircleaner was purposely messed up, and at this point I dont even care why. Obviously if the car is popping and needs richer jets, it was starving for air. It will be interesting to see some dyno results comparing a plugged box vs an opened up one with stock air horns. Makes me wonder if the stock air horns mean anything anymore either. Maybe Kermit is on to something there as well. Talk about a detuned racing engine.
Would anyone have a baseline starting point for jet and emmulsion tubes for 10.4:1 compression, P6 cams, with the airbox mod and port matching? Its sounding like 145-150 mains wouldnt be oversize, no?

 

Paul
I run P6 with 44 DCNF/34mm venturis/52 idles/145 mains/F24 emulsions and 185 (I think) emulsions. I have also been running 200 needles which I'll pull down to 175s.
Philip