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Author Topic: jetting alcohol carb  (Read 1281 times)
corncob
2stroke
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Location: Southern Indiana

« on: August 28, 2006, 08:18:12 pm »

I want to change to 750 alcohol carb. Haven't had any experience with alcohol and need some advise on starting point for jet size.  40 over 351, ported performer rpm heads. car runs 6.90  1/8 mile with 750 gas carb. I got carb from friend that had it on 406.  Any help would be appreciated. thanks Roger
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knucklefux
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Location: columbus, ga

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« Reply #1 on: August 28, 2006, 10:37:21 pm »

have you changed the whole setup over to alky?  i know you need massive amounts of it, like twice as much.  i would say, therefore, that you need twice the jet to run the same engine on alcohol.  you also need a garden hose to supply the fuel to/from the pump.  really, you need an alcohol specific fuel system.  and you need to drain it when it's not in use...it will make everything in the system rust.

if you already knew all of that ^^^ i apologize.

also, i'm not an alky expert either, so if you blow up your engine with twice the jet, don't blame me...
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igo1090
4 Banger
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Location: catonsville, md

« Reply #2 on: September 02, 2006, 09:54:13 am »

corncob.  sounds like u are planning to do the conversion yourself.  not a good idea unless u really kno what you're doing.  its not just bigger jets.  other passages must be modified.  generally the jetting ends up in the 165-190 area, depending on how the builder does the mods.  the simplest way to this is to buy from a pro like rupert, sinke, apd, aed, etc.  usually runs about $450 plus your carb.  some guys pick up a decent ebay carb to have converted.  talk to some experts.  when a pro does the carb and if you were accurate about your combo, the most u might have to do is tweak the idle mixture screws.  no rejetting.

an overkill fuel system is not mandated.  if u must buy new, then go a little big if u have the bucks.  i supply a 600hp stroker using a 140 mallory alcohol pump, -8 supply & return lines, -6 to the carb.  i've swapped in a bigger pump with no change in et.  am i at the edge of this system?  probably.  a 250 pump with -10 to the reg and -8 to the carb would probably do over 750 hp.

the alky stays in it all season.  i run the carb dry, and cap the breather on the cell at the end of the day.  drain it for the winter, put fresh floats, needle o-rings, accel diaphrams in the carb.  alky dries out rubber things.  after about 7-8 yrs, the internal rubber in the braided hose started to crack and leak.  teflon lined would eliminate that.  alky corrodes/wears alum fittings.  true.  some of my fittings are about 15 yrs old and show erosion.  steel or stainless would cure this.  friend of mine cracked 2 alum fuel tanks on his dragster about 2 yrs apart.  found the alky would corrode the internal edge of the welds and the tire shake did the rest.  hasnt happened since.

if u have other questions, pm me.  i've been running alky since 1991.  im not an expert, but i havent burned my car up either.  yet.
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dave shea
s/st 1818, s/p 1018, h/r 1564
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