alcohol carburator to gas


bigjeep
02-08-2002, 05:14 PM
hi there,


i woul like to know if you can switch an alky carb to a gas carb , i think the only thing i would need to do is down jet it since the jets are the only thing that is to big ,


before you say no it will not work , my engine is a small chevy 355 it has dart race heads fulley ported {they flow 305 cfm } i have 14.1 compression and a roller cam the size of the rockys {.725 lift and 320 duration }


somebody let me know im in a hurry for the carb

texan
02-08-2002, 11:24 PM
What gasoline do you plan on running? Also, alcohol fueled motor require about twice the nromal fuel delivery of gas, that's more than just carb jetting. But before you even get into that, it's highly unlikely that 14:1 compression will work with the gasoline you are planning to run.

bigjeep
02-09-2002, 12:16 PM
hi there,

i use 114 octane pro stock race fuel if this helps any

please note im just looking for a second opion on this carb if it will or will not work

PART
02-09-2002, 01:23 PM
i cant speak from experince but im fairly sure that even race gas @ 114 would still not resist detonation enough to survive 14.1 compression. besides if uve already got the fuel system set up to run alki y switch back, unless u wanna run on the street ? which wouldnt be legal either becuase ur not allowed to run race gas on the street either... i guess im saying that ur question doesnt make a whole lot of sense..
if u need numbers to prove it i can look them up but im too lazy right now.....LATER

texan
02-09-2002, 01:37 PM
114 will easily run at 14:1 compression, the relative octane rating of methanol isn't even that high (around 106 if memory serves me).

I looked into it a bit more, and found that almost all cars running alcohol use conversion kits on what used to be gasoline carbs. You are right that the same cfm carb should likely be used, however the fuel bowls, metering block and of course jets are unique to the alcohol setup. The fuel delivery is so much higher that things must be redesigned to work with it, it's not just jetting. Now I see no reason why you can't convert the carb (what carb is it?) back to gasoline duty, but I highly doubt running with alcohol metering blocks and other specifically designed hard parts will work, the engine is likely to run extremely rich. Basically, what I'm saying is you need to rebuild the carb or purchase a new one specifically for gasoline duty.

bigjeep
02-09-2002, 02:40 PM
hi there,

my carb is a holley hp series i tought that becuase it has the alky metering blockes that they would be almost the same as a dominator gas carb beacuse they have bigger metering blocks for higher revving engines , i tought that if i use gas jets it should work

GTStang
02-11-2002, 01:03 AM
My only thing is if you read bout his engine, it is set-up like a pure drag car motor and made for alcohol. Using 114 I'm sure might cut it but with high compression engines they use alcohol not as much for its octane but do to it's chemical properties under high compression it's less likely to dentonate. I could be wrong but this is what I have been told. So you can correct me also but like some1 said before. Why would u wanna switch to gas? If your thinking bout street duty with this motor your gonna have bigger problems than just converting it to use gas IMO

TheMan5952
02-11-2002, 11:21 AM
That's what an octane rating is, it's ability to resist detonation at high compression, you basically repeated your self GTstang. just leting ya know.

bigjeep
02-11-2002, 02:57 PM
hi there,


your right this is going to be a drag motor and it must see street duty , so thats why im going with gas , i also dont wont to change my oil all the time with alcohol .

GTStang
02-13-2002, 09:54 PM
Originally posted by TheMan5952
That's what an octane rating is, it's ability to resist detonation at high compression, you basically repeated your self GTstang. just leting ya know.

Octane is not the only thing that will dictate dentonation when you are talking of a fuel other than gas. That was my point. Just letting you know

texan
02-14-2002, 12:00 PM
Originally posted by GTStang
Octane is not the only thing that will dictate dentonation when you are talking of a fuel other than gas. That was my point. Just letting you know

What specific fuel property does alcohol have, other than a high relative octane rating, that helps it to resist detonation?

SaabJohan
02-15-2002, 09:25 PM
When converting from alcohol (methanol) to gasoline the engines power will decrease. This is because of methanols very low SAFR, which is only 6.5 compared to gasolines 14.7. Gasoline contains more energy than methanol, 44 MJ/kg against 20 MJ/kg (this is why methanol engines have higher fuel flow). But if we compare 20/6.5 = 3.08, 44/14.7 = 2.99, we'll find that the higher energy contain can't compensate for the lower SAFR.
Methanol have a density of 792 kg/m^3, RON 105 and MON 92.
High octane racefuels often have lower energy contents than standard fuels.

When converting, be sure that fuellines can withstand the new fuel. This is mostly a problem when converting to methanol but it's best to be sure.

TheMan5952
02-21-2002, 11:07 AM
ok, I was usin octane because that's what is probaly most comparable between gas and alchohol other than the cooling capabilities of alcohol.

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