Hello to all,                                                                                                                         
                                                                                                                                         
Having grown tired of the complexity and fiddling and fuel leakage of the standard Z-S carburetors, I purchased a set of brand new Mikuni HSR42 carburetors about a year ago. Source was: Vintage Performance Specialties in the US. http://www.v-performance.com/products/air_fuel.html  The kit sat idle until the end of this past summer. Since I had to replace my cylinder head and one piston due to a somewhat related problem, I decided to go for the carburetor swap as well.                                                                     
                                                                                                                                                I wanted to keep the original black plastic airbox, get rid of the aluminum airbox with a plan to create a high mount air intake prefilter in the gap between the front of the 1314A box and the back of the cab. The universal generic carb-to-air cleaner rings from VPS are finely machined and are available both with predrilled mounting holes or undrilled. I actually chose to go with Mikuni product designed to mount a single HSR42 to a Harley motorcycle found what I needed on Amazon. They seal the carb mouth with a large O-ring. Since the truck will be operation in dusty conditions at times I wanted the tightest seal possible. Because these are a slide fit, by simply loosening a small turnbuckle between the airbox face and the manifild heat shield, the intact plastic airbox can be removed in under a minute. Replacing the airbox is a little more fiddly so it takes about 60 seconds.
                                                                                                                                         
Idle is very easy to adjust, throttle response is healthy and happy through the full range and the standard jetting choices from VPS seem to be spot on. More definitive testing will be ongoing over the next month or two. If you have any questions, feel free to ask. I am easiest to reach at: tgbforwardthinging(at)gmail(dot)com.                                       
                                                                                                                                         
Take care.                                                                                                                           
Jim Molloy                                                                                                                  Waldersee Farm                                                                     
http://www.northwestmogfest.com

Hello Jim,
thanks for the information. I'm curious about your experiences.
Regards
Uli

Hmmm....you are probably one of the least likely folks to have missed this discussion back then, even on the old mailinglist, but you are aware that the alu filter box modification by the Swedish military was done not just for easier filter access, but even more to prevent (oily) filters catching (back)fire?

Hello WJM,                                                                                                                           
                                                                                                                                           
  My first truck was a 1976 TGB11 that was transfered to a community fire brigade six months after It first encountered military service. It was never equipped with the aluminim airbox but only used the plastic box. To my know, neither the Volvo 164 (B30A equipped) or the Volvo 140 (B20 equipped) ever had a more remote upstream airbox yet were equipped with the same two piece plastic airbox system used on the TGB truck. With that first truck, I did notice a puddle of oil collecting in the lower trough of the carb side half but I never noted any oil staining of the air filter element. It did prompt me to diligently check that area every 2-3 months and wipe out the small amount of oil present at those intervals.

I guess i must have missed the discussions about the two reasons for the addition of the aluminum box on some TGB trucks. I figured that it was primarily was for greater ease in changing the filter element. Trying to remove and replace the four spring hook clips in the very cramped space was never much fun. My new set-up makes for a much simpler and far less frustrating process.                               
                                                                                                                                         
With the Mikuni carburetor conversion, I have modified the interior of the airbox to include a pair of narrow mesh screens between the throats of the carburetors and the air filter element. These have two functions: 1) flame front retardation and 2) prevention of carburetor foreign body ingestion. I have two additional engine bay modifications planned for the 1314A. One is to further simplify the intake manifold vacuum system and to modify the crankcase ventilation system to include an actual oil trap bottlei and an inline wire brush filter (eg gun barrel brass bore brush in the connecting hose) between the engine and lower port on the air cleaner box.                                                  I do appreciate your imput. 

Take care,

Jim Molloy

IIRC the original setup (filter in black plastic airbox directly above the carburettors) was slightly unsafe. In the black airbox oil from the crankcase ventilation and / or gasoline from the carburettor ventilation can lead to a quite soaked filter. The wick effect of the filter and the heat from below could lead to inflammation. Again IIRC unfortunately even minutes after the car had been turned off. So the inflammable element was moved to a new location, and maybe that's why the new case is made of metal.

tegebe,
Since Volvo never used found the need to use anything but the original two piece plastic box with filter inside, I must assume the increase risk of fire must be unique ot the TGB...specifically, where it is driven.  Due to the combination of minimal oil pooling in the filter box (as seen with the B30A equipped sedans) AND steep upward, downard and right side vehicle angles, it makes sense that oil could then start to a saturate the nearby air filter paper element.

In my case, the placement of a small inline oil trap/dump can between the valve cover crankcase ventilation port and the air cleaner box ventilation port should take the risk of motor oil saturation to close to zero and take up  a great deal less space than the additional aluminum air filter box and mounting brackets and hardware.                                                                                            Take care.                                                                                                                               
Jim

Btw, the argument/reasoning of any of our Volvo's having a 'firetruck-pedigree' is not a strong one, possibly even contrary:

None of the C306 firetrucks I ever saw had the secondary alu-boxes, even despite some/many of them at least initially being serviced by the same Militaer-Werkstat (they also did the alu-zink conversion for civil owners)
Actually, mine was retrofitted (on my request) from a batch that came from the halfway stalled military project (either that was already a slow multi-year process, or they got caught too suddenly, when most of the C3-Series was removed from activce duty).
Oddly, the guy/shop handling the production of those boxes turned out to be a former neighbour of Tatanka on his old location, so my retrofit was found by only one phone-call....:))

As for firebrigades: remember that many in Sweden are volunteers.
One of my C306's was equipped with an open header/air-intake, for which the original engine cover lacked the necessary space, by about an inch.
So they cut the cover, put the filter in, and left the original vinyl cover intact.
No, these do not dampen sound much, on their own....:))
Also, possibly the main reason for having changed the airfilter in the first place, they had a can of QuickStart laying in the center console.
Just for being near-impossible to start normally, at least warm, probably also cold in sub-zero temperatures.
Would also stall easily, for having zero torque at lower RPM.
IOW, each shift at low speed meant danger.
Only full-throttle shifting kept you on the safe side of this combustion-Twilight-Zone.

'Drive it like you stole it.'

Official instructions given to me by the Chief Firebrigade....:))
(volunteers, also doing event-support (open-air concerts))
(so they probably already had hearing-impairments, not bothered much by additional sounds straight from the engine bay....:))