Zeinth Carb Parts/gasket sets

[m139h2otruck]

Anyone know where to get carb kits for the replacement Zenith carbs issued during the '80s for the gasser 5 tons? Have one on the water truck, works great, and have a spare, but would like to have at least one spare parts/gasket kit on the shelf just in case. Had to steal the gov. diaphragm out of the spare , as the first one was split (new). Even the second one was not too good. Have tried to talk to Zenith, who even sent me the engineering drawing for the gov. diaphragm, but they won't make a kit & don't have any on the shelf.

Also have two of the original alum. Holleys, one rebuilt with all new parts and one new rebuild kit, but in typical Holley fashion, just too rich at idle with the settings correct on the rpm and idle air jets. The Zenith idles great, at 400-500 rpm for hours at a time without loading up or fouling plugs.

 

[wreckerman893]

Not to hijack the thread but the 5-ton wrecker for sale near me has the gasser in it and I was wondering what the CFM on the Zenith carb is?
I was thinking of ways to improve fuel milage and I thought that builidng a custom intake and header for it might be possible.
Are the intake and exhaust manifolds made together on these engines?
Maybe sub a four barrel Holley for the big Zenith. I know a lot of commercial gas burners came with Holleys.
I know a muffler dude that has a plasma cutter and tubing bender. He says he can make a header for it. I have seen his work and he has made some decent custom exhaust systems.
Still woking on the manifold concept.
What say the faithful

 

[devilman96]

If you have numbers on the carb you should be able to order it at any INTELLIGENT auto parts store... If not I am sure Memphis can ether supply or point you into a direction on them...

Improved fuel mileage on a 5 ton?....... Buy a CUCV??? lol

 

[BEASTMASTER]

memphis equip should have the kits , well did mine last year

 

[m139h2otruck]

I would guess that the Holley/Zenith carbs for these engines would be about 400 cfm based on the 602 cid and 2800-3000 rpm of the engine. The smallest 4V Holley carb that is easy to get is 390 cfm, used on 6 cylinders and small V8's. We used a 500 cfm AFB Carter/Ed on a 232 cid slant six that is capable of 6000 rpm easily and it works just great (the AFB style carb has an air door, so the engine only opens the door the amount actually needed).

The R6602 uses a 12 port head(s) with a port layout of E-I-I-E-I-E-E-I-E-I-I-E all on the right side of the engine. The aluminum intake is heated by the exhaust manifold at the common connection, and this is mandatory if you want any amount of good drivability. You would need to make two port plates with a layout of E-I-I-E-I-E and start welding from there.

I think that the existing manifold setup is adequate for the rpm range of this engine, it just needs less restriction on the exhaust (already 4") and the air filter on the intake (oil bath). One of the greatest drawbacks of this engine is the very low compression @ 6.7-6.9:1 ratio. It has huge chambers with the valves recessed way into the head and the pistons located way down into the cylinder @ TDC. This was mandated by the Army so they could burn almost anything for gas in the high 70's to low 80's octane rating range. The static timing is also very low at 5 degrees with a very limited advance built into the distributor. I think that if you got this engine up to temperature, it would run on #1 fuel (jet fuel) with no problems!!

I would make a carb adapter (existing carb is 6 bolt) and mount a Holley 2V @ about 350-500 cfm, with a low restriction air cleaner, raise the compression ratio to 7-7.2:1 by cutting the heads IF there is enough meat in the decks to cut that much, use an open or nearly open exhaust (very loud!!) and try to advance the timing a small amount. You MIGHT then make 230 hp instead of 196 hp (who knows!!).

The other option which was floated on this forum a while ago is to turbo the engine. With it's diesel like build, low compression ratio and low rpm rating, I think this would work better than any other option. A low pressure (6-8 psi) turbo blowing through the existing carb & intake with a free flow exhaust should work well and get you in the range of 235-250 hp (maybe). I did buy a 5 ton multi turbo with this thought in mind.

Comments?

 

[m139h2otruck]

Not sure about the kits for the Zenith, but did get a Holley (GI issue) kit from them to rebuild the first Holley carb. Will have to check on the availabliity of the Zenith kits again.

Beastmaster, did you have a gasser wrecker in southern Mass?

Thanks

 

[JasonS]

I think that it would be interesting and not that tough to have dual exhaust and two intakes fed by holley 2300 two bbls. It seems that it is very hard to get a complete burn on these engines. I wonder how much a hot ignition and spark plugs with an extended tip and wider gap would help.

 

[m139h2otruck]

Chrysler slant 6 engines have an aftermarket alum. intake by Offy that uses two standard 1V stock type carbs in a layout like you are suggesting. Some guys machine these out and use two Weber 2V's with good luck. The problem with the R6602 is the port layout is not evenly spaced like a slant 6 or a Ford 300, it's like a 258 Jeep motor, with some of the intake ports siamesed together and some not. Also, this motor being twice as big as even the "big" 300 Ford has 2 heads like the multis, so the replacement manifolds need to be built to take this into consideration.

The ignition system on these motors does not have to deal with high rpm like a smaller motor (max 3,000 rpm vs 6,000+). The stock setup seems to work well so far on our truck. As the dist. is sealed and uses 24 volts it would be hard to upgrade to an MSD type box. I guess that you could maybe find a 12 volt standard dizzy and use a voltage step-down just for the ignition, but the gains would be very small for the costs involved and the mess you would have to contend with.

The exhaust is a full 4" all the way to the rather small muffler right under/behind the cab next to the transfer case. We were running just a 3 1/2" tip-down right out of the muffler, but as the original was 45 years old and starting to get holes in it, we installed an oval Walker truck unit by welding on the 4" flange to the front and using just a 4" 90 out the back pointed straight down. Noise is not that bad, and I have to believe that the back pressure is less than the original.

I still think that a low pressure blow through turbo setup with the carb in the stock location and the turbo mounted directly to the exhaust manifold outlet would be the setup to use on a "hi-po" R6602. You would keep the rpm below 3,000 and makeup for the low compression that is stock in these motors with the turbo. Would make for a very interesting project, ie, a turbo-ed bobbed 5 ton with 1600x20 tires, front winch and small rear bed. Have or can put my hands on all the parts, just need the time.