Outer Limits 4x4 Board

Re the gas carby setup.....

I have spoken to a couple of gas gods about the gas carby and both said the same thing..... little or no great advantage, in other words its only a slight improvment over a fuel carby/mixer setup....




BUT......





They did come up with a very interesting idea they had both done with MAJOR improvements for sole gas motors..... its simple and dead set easy too and it shouldnt cost you anywhere near the price of a gas carby either !!!!!






sounds good yes ?????








interested ??????








well I'm gunna try it first before I tell ya

Kingy !!!!!

Thanx for the info,
Lemme know what you find out

it's steam technology isn't it?

bj, add some tech!

Thought I'd get a crack at it this w/end but time is dissapering fast, so here's the mod details for you to try if you get the time....

1/ cant do this mod with the "snorkel" setup ..... must use the "bell" adaptor that goes between the mixer and the carby.... as seen in the first pic.

2/ you'll need a throttle body off of a carby that fits the manifold ( with or without an addaptor) so we end up with tha butterflys bolted to the manifold .... doesnt matter if its Holley or Rochester throttle body but the Rochester will give slightly better ecconomy under normal use over the Holley...... left hand right shoulder the top half of the carby

3/ the hard/easy bit....
All we do is put the "bell" directly onto the throttle body and attach it so there's no airleaks. I had for experimentel reasons intended to just use Urathane for a trial run and then machine up a permanate solution if it worked.


Sounds simple enough hey !!!
The gas carby setup is almost exactly the same in principle but the "throat" is where the restriction lies and its this restriction that causes the horsepower loss. The restriction in the petrol carby is worse because of the small venturies..... so basically the gas carby is a "petrol carby" but without the small venturies, the restriction is still there but is smaller thus the improved HP over the petrol carby.

By removing ALL throats & venturies the HP increase is dramatic as is the ecconomy, the mixer is not inhibbited in any way, lets face it ... we dont need anything between the mixer and the butterflys except an adaptor to join the two pieces together.

The mixer in this setup could be an Impco series 1&2 and will handle a 350 / 400 chev without any dramas. this is because its largely the restriction of the throats and venturies that decreases the series 1&2 performance.
The Impco series 45 & 70 is the recemended mixer for 350 / 400 chevs but its the chosen unit because of 2 reasons.... 1 to overcome the restriction and secondly for high reving motors ( IE: 5000 rpm )

As for the inlet manifold it's self ( and I dont know what type youre running) , the singleplane manifold apparently works slightly better with this setup but either single or duel plane manifolds work well.

I'm running the stock castiron manifold at the moment and rochester carby...... I hope that I can use the rochestor butterflys directly onto the manifold and then place a spreadbore to squarebore adaptor on that then witha bit of machining lathe out a groove for the "bell" addaptor to sit in, then drill & tap a couple of small bolt holes to hold it together.... then finnally bolt the mixer on as normal !........... maybe next w/end

Kingy

I have a Edelbrock Torquer manifold and Quadrajet at the moment. So basically what you are saying is mount the gas mixer (the type like in your pic and are standard on GQ gas setups etc) directly to the carby base plate with only the butterflys via an adaptor?

I'm very interested to see how you go, If it works OK I'll probably hit you up to do one for me

yep thats right !!!!
the petrol carby is basically an addaptor between the mixer and butterflys..... so why have it there !

V8Patrol wrote:yep thats right !!!!
the petrol carby is basically an addaptor between the mixer and butterflys..... so why have it there !

So I ain't completely stupid Keep me up to date.

PS What converter are you using? I want to see if I can use my old one.

the dude that tuned and certified my LPG said he has tried exactly what you are talking about doing on the nissan "Nikki" carbs and it makes no difference at all over just throwing the mixer on top of the complete carb.. hope it works out better on your rochester/holley gear?

Wendle wrote:the dude that tuned and certified my LPG said he has tried exactly what you are talking about doing on the nissan "Nikki" carbs and it makes no difference at all over just throwing the mixer on top of the complete carb.. hope it works out better on your rochester/holley gear?

Been told that it really only works on larger capacity motors, .... no real effect on a 4 litre motor for example but 5 litre and up see's a marked improvement.
I just need some time to try it at the moment

6.5 Litres here

only 6.3L here but i have a real gas setup nah looks like a good cheap alternative. good luck mate.

its not a cheap alternative, its basically exactlty the same thing. All you need is the butterflys, there is no atomisation or "mixing" happening in a gas carby/baseplate. This is how straight gas was setup before, all you did was make an adaptor plate to suit the mixer adaptor.

what works the best on high capacity motors is a impco 425, this mixer is best suited to sit right atop a holley or rochester baseplate. Also, remember if you want even better gas performace and econmy you havto regraph your dizzy to suit, and put in electronic ignition and a big coil.

Jes

jessie928 wrote:its not a cheap alternative, its basically exactlty the same thing. All you need is the butterflys, there is no atomisation or "mixing" happening in a gas carby/baseplate. This is how straight gas was setup before, all you did was make an adaptor plate to suit the mixer adaptor.

what works the best on high capacity motors is a impco 425, this mixer is best suited to sit right atop a holley or rochester baseplate. Also, remember if you want even better gas performace and econmy you havto regraph your dizzy to suit, and put in electronic ignition and a big coil.

Jes

Long time no see..... how are ya mate !

Impco Model 'L' converter fitted
45-70 Impco Mixer fitted
electronic dizzy fitted
electronic dizzy regraphed

all on a 350 chev..... all I need is the time to make the adaptor that goes between the mixer and the butterflys......

Kingy

p/s ... I'll edit the post name so it's "SEARCH" friendly !!!

quick question.. do you lose your choke? fuel cut on overrun?

V8Patrol wrote:

jessie928 wrote:its not a cheap alternative, its basically exactlty the same thing. All you need is the butterflys, there is no atomisation or "mixing" happening in a gas carby/baseplate. This is how straight gas was setup before, all you did was make an adaptor plate to suit the mixer adaptor.

what works the best on high capacity motors is a impco 425, this mixer is best suited to sit right atop a holley or rochester baseplate. Also, remember if you want even better gas performace and econmy you havto regraph your dizzy to suit, and put in electronic ignition and a big coil.

Jes

Long time no see..... how are ya mate !

Impco Model 'L' converter fitted
425 Impco Mixer fitted
electronic dizzy fitted
electronic dizzy regraphed

all on a 350 chev..... all I need is the time to make the adaptor that goes between the mixer and the butterflys......

Kingy

p/s ... I'll edit the post name so it's "SEARCH" friendly !!!

Yeah i know been busy, had to get rid of some unnessesary clutter in my life, namely the missus.. LOL

not bad thanks mate, you Sound like you have been busy

Jes

[quote="Wendle"]quick question.. do you lose your choke? fuel cut on overrun?[/quote

on all dual fuel cars you loose the choke, because the fuel is coming from the top, not from inside, if you pull the choke, you cut off the air and the fuel. no straight gas set up has a choke either, as the choke is mounted to the top of the petrol carb, and you have pulled that off, to fit the gas carb.

V8Patrol wrote:

jessie928 wrote:its not a cheap alternative, its basically exactlty the same thing. All you need is the butterflys, there is no atomisation or "mixing" happening in a gas carby/baseplate. This is how straight gas was setup before, all you did was make an adaptor plate to suit the mixer adaptor.

what works the best on high capacity motors is a impco 425, this mixer is best suited to sit right atop a holley or rochester baseplate. Also, remember if you want even better gas performace and econmy you havto regraph your dizzy to suit, and put in electronic ignition and a big coil.

Jes

Long time no see..... how are ya mate !

Impco Model 'L' converter fitted
425 Impco Mixer fitted
electronic dizzy fitted
electronic dizzy regraphed

all on a 350 chev..... all I need is the time to make the adaptor that goes between the mixer and the butterflys......

Kingy

p/s ... I'll edit the post name so it's "SEARCH" friendly !!!

What does an impco 425 Mixer actually look like?

CRUSHU wrote:

Wendle wrote:quick question.. do you lose your choke? fuel cut on overrun?

on all dual fuel cars you loose the choke, because the fuel is coming from the top, not from inside, if you pull the choke, you cut off the air and the fuel. no straight gas set up has a choke either, as the choke is mounted to the top of the petrol carb, and you have pulled that off, to fit the gas carb.

I have a straight gas setup, and still have the factory auto choke/high idle and all hooked up. still have the top of the carb as well.

I think there was a bit of confusion back there.....

The Impco 425 is the straight gas carby.....

The impco 45-70 is the mixer that is recemended for big motors.

There is also some confusion about the converter/mixer types....

There is 2 types... COMPLEX .... & .... SIMPLEX

One system uses a simplex converter wich only converts the liquid to vapour and has NO function as to the flow rate for the motor...its the complex mixer actually does the flow control

In the other system the complex converter does both the converting from liquid to vapour and the flow rate while the simplex mixer ( usually just a gas ring as pictured) only directs the gas into the engine.

Here is the setup I run on my other toy. It's a 425 mixer on an impco base plate. The converter is mounted directly to the back of the mixer. This is a fairly strong 351 Cleavland and it has no problems keeping up with demand. You can also see it looks quite neat mounted this way.

The "choke" setup for the Impco system is done by fitting an additional gas lockout valve to the converter and then a hose from that to the carby. Once its wired in and a button installed the user simply presses the button for a cold start and a "shot" of gas is injected into the carby/motor, some people call this a "prime".
The priming is the same as a choke setup in that is gives the cold motor a burst of additional fuel in order to start. I wired my ute up to the starter motor so that every time the key was turned the motor was primed, this worked great in winter but failed completly in summer ...... reason being the prime was there for cold starts only and in summer the prime flodded the motor on starts when the motor was hot.

I'll try n get a pic of the setup when the new owner of my ute visits next !

Kingy

Last pics.

BTW you can see in the middle of the converter on the top surface there is a button. this is where the choke solenoid attaches to.

isnt that the manual primer? its a button which pushes on the diaphram that lets more gas into the mixer.

on my setup it has a fitting that screws into the side of the convertor and the lock off screws onto that.

MaccA

P.S. jesse928. this IS, a cheaper solution to MY setup.

383FJ45 wrote:isnt that the manual primer? its a button which pushes on the diaphram that lets more gas into the mixer.

on my setup it has a fitting that screws into the side of the convertor and the lock off screws onto that.

MaccA

P.S. jesse928. this IS, a cheaper solution to MY setup.

most Impco converters have the manual push in button, but the setup you have is the common conversion for a prime cold start.

yeah but its still able to prime without the lock off. all you do is push the button. the lockoff is just a quicker way of priming.

thats a sweeet straight gas setup!

BTW, the impco 425 works well with dual fuel setups running high performance large capacity engines also, as does the 300A 20 series for small engines and the 300a 45-70 series for larger ( mild) engines..
running a hipo 454 you need 2 425's running much leaner that the factory setting... with a larger capacity engine its not that you cant get enough gas into the engine, its the single mixer cant flow enough air.

Jes