carb /intake manifold change up

[tree37]

hello folks. i was curious as to carb manifold set ups that you use down there. i have a 351w (1989). its got a holley 4160universal carb(i think its 600-650cfm) and stock intake manifold. im having problems with the secondaries not opening. its vaccuum oper. dont know if the spring is too heavy,or whatever, but becasue of its age adn its showing salt deposits in side the throats its time to rebuild it if nothing else. rather, i have been looking at edelbrock marine carbs and obviously you would want to mate it to a edelb intake. i like the high rise tunnel ones that are up from the engine heat a bit. i would get an actual edelbrock marine electric choke carb for that manifold. i was thinking 750-800cfm for the 351 windsor. your thoughts? is that too much? this last weekend there were issues with the fuel in valdez the first day we ran no problems and fish by the bucketfull. the next day i couldnt keep my motor lit. wouldnt idle. changed fuel filters(luckily napa was open) and drained the primary and secondary bowls and started over. readjusted the curb idle and all seemed to be well. the second day the choke on the holley wouldnt work right so i cleaned and wired brushed the connections and i guess that was is. i also ran a can of seafoam through the carb. man i like that stuff. maybe its a gimmick but i like how it seems to work for me. we finished the trip with our max limit of fish. i just tuned the boat before we left and even had to replace the main seal. i just want to maybe upgrade and avoid wrenching on the boat when we should be fishing. the 4160 holley seems to be a universal and reliable carb....but i was wondering what you guys run on your jet boats down there in the edelbrock set ups? :cheers: tree37(scott)

[BassinFever]

Nothing wrong with the Holley marine carbs but they do need to be rebuilt every few years. There is a small cork "0" ring that dries out and can make your secondarys inoperable.

I like the Edelbrock carbs better though I think they offer a tad bit better fuel economy. You can buy a stip Kit and they are almost infinatly adjustable. More so than the Holley. A 600-650 will be all you need on your 351. The only thing you would notice if you go bigger would be in your pocket book. Aluminum intakes are very corrosive even in fresh water. If it`s coated it will be better but the coatings havn`t been out long enough to know how much longer the intake will last. It would have to be coated internally also. A high rise intake would wake up your engine some, but make sure you chose a low to midrange intake. No air gap or Torquer type manifolds.

[tree37]

hey thanks bassin. where is the cork o ring? is it on the float adjustment screw on the secondary bowl or is it in teh secondary spring and diaphragm housing? good point on the internal coating of manifold. its permashine. it think. i was told u can run auto trans fluid in your gas tank to help with the sea air anti corrosion. ive got an 80gal tank. when u look inside the carb you can see some white salty looking clusters. i cleaned them out before we left and i cleaned out the primary ans secondary bowls and floats. but if thats happening i wonder what you can run in your fuel (ie marvel mystery, sea foam, atf) that will help it not corrode so fast. i average 4 trips a summer to salt water. so im learning something each time i go. i didnt realize just the air was bad until i looked at my pistol. it was starting to rust just from sitting there. crazy.

[Orca]

If I were to redo the carb/manifold, I would put on an edl. Performer EPS with Permastar coating and the marine Performer carb in 600 cfm. Smaller will be better for fuel atomization. If they had a 500 cfm, I would put that on. I would have to find the table, but 500 cfm is good to about 4500 rpm on a 350. Bigger carbs just mean you can run higher RPM and thus higher HP (high HP racing applications). I always run 3000 - 3500 rmp and no more, so big bore carb is not needed.

High rise manifolds are generally for race applications making more power at higher RPMs. For low end torque and power down low, you will not want the high rise. To control carb (over)heating, you can use a phenolic spacer between the carb and manifold. A 4-hole spacer will give slight improvement in low end power.

You really shouldn't have salting problems with 4 trips / year. Many boats sit moored in the salt for years, and pasts start to fall off or die in 10 years or so. That should be a lifetime for you.

Also, I would only use the aluminum manifold if you have a closed cooling system with anti-freeze.

[tree37]

well thanks orca. this was a used boat i bought. so i have replaced a main seal, a starter, plugs, oils and filters etc, but i dont want to have problems when im on the ocean if i can help it. i heard 4 coast guard calls this last weekend for dead in the water. so that said i just am wanting to do the proper maintennance and maybe upgrade. i like the smaller cfm idea. i do custom carpentry work and i did make a new cowling cover but at rpms i make a lot of heat. the guage never moves past 175-180 but man its hot under the cover. i patterned it after the original that had the marine carpet coming off etc. i think i need to cut some vents fore and maybe put in like a soffit vent material to help circ fresh air to the motor. dissipate some heat. also with the smaller carb and non racing manifold im gonna be ok with compatibility with my jet. its a berk single with an "a" impeller. so i didnt need the more rpms anyway right? i think the range was around 3500 cruising. seems to work ok anyway.

[BassinFever]

where is the cork o ring?



The ring is under the Vacume diaphram where it mates to the main carb body.

I manage a large car collection and we use Marvel Mystery oil as per recomendation on the bottle in all the cars, we also use seafoam as a fuel conditioner. Collector cars set a lot and the mystery oil keeps the gaskets from dying out. Works for us.