Problems getting an OHG x450 running right

[Evil66]

Hi Guys,

I have a small block Mopar engine in a 1966 Valiant, engine would have roughly 320 - 330hp on petrol but I want to keep it on straight LPG if possible.

Current setup has a single impco 425 and Elko E500 (nolff produced) vapouriser which is supposed to be rated around 320hp, idles great, drives nice, excellent mid range throttle response but seems to run out of gas under quick acceleration (read wheelspin) and higher in the rev range between gears.

I tried an OHG x450 on it the other day as I had read they were rated a bit higher than the Impco 425. It was very hard to start, had to prime it twice when cold to get it running and it will only rev to a certain point (driving it or free revving) as if it has a governor on it and will not rev any further.

I have checked the OHG out, slides dont appear to be stuck, adjusted the idle and t pieced the power valve to the PCV line and it seems to operate fine.

Have been reading that you need a certain spring in the vapouriser to be compatible with the OHG mixer as they operate on a different vacuum, could this cause the issues I am having with the OHG mixer?

Thanks for any advice.

[C3H8]

Frustrating. I had a response all typed and (*******)computer locked up Start over I guess.

Nolff regulator are compatible with both IMPCO and Nolff mixers with a minor modification.
IMPCO mixers work with a secondary pressure rating of -1.5" water column.
Nolff mixers work with a secondary pressure rating of -.5" water column.

The rating of the regulator is easily changed by replacing the secondary spring under the secondary diaphragm. The springs are colour dyed for their rating.
Blue spring is -1.5"
Orange spring is -.5"
An orange spring on IMPCO will usually result in richer mixtues.
A blue spring with a Nolff mixer will usually results in lean mixtures. (hard starting and leaner cruise and WOT mixtures)

Both mixers are normally capable of supplying small block engines with no problems. How big is your engine? Does it have a really high RPM you can reach? The 425 has a CFM rating of 476 CFM. The X450 could be 500 or so but I'm not 100% positive on it's rating.

The common mistakes I see on these systems is using the manual power valve in these mixers to control the cruise or mid range mixtures. The mixers have three specific operating areas using a gas valve on the 425 or metering rods on the X450. Gas valves are frequently referred to as bullets as they resemble the head of bullets when viewed.
- The widest portion of the bullet or metering rod is the idle section. This can be adjusted with a manual adjuster that bypasses fuel on a 425 and air on an X450.
- The mid range is the area between the widest portion and the smallest portion of the gas valve or metering rods. This is not adjustable on a 425. On an X450 the mixtures can be changed marginally by raising or lowering the metering valves a few thousands of an inch.
- The last or smallest portion of gas valve (bullet) is the WOT area. This is usually biased rich. The WOT mixtures can be controlled by the main load screw at the inlet of the mixer. It should only be used for WOT mixtures. Usually above 3800 RPM and gas pedal 85% or more applied.

Using the power valve to control cruise mixtures will limit the power of the engine by causing lean mixtures and limit the RPM of the engine (like a governor).

Lastly you mentioned a vacuum power valve T'eed into the PCV. I expect you are referring to the vacuum assist port on the X450. The instructions may say to use vacuum off the PCV but typically the PCV vacuum is a poor selection for a vacuum source for anything except the PCV. A better choice is a vacuum port off the intake manifold. PCV's have a controlled leak at the other end and this can affect the vacuum reading depending on the condition of the PCV valve.

[Evil66]

Thanks for the detailed reply, it isn't easy to find a lot out there for the ohg x450.

Not sure where to start looking for different coloured springs for the regulator, been told the right spring to suit the ohg mixer will be hard to find, anyone know where I can source one?

Engine is a roughly 324 cubes but has a mild cam and edelbrock heads and about 10.5:1 compression so has a reasonable rev range but I did try and keep the horsepower down so I could keep it on LPG.

[C3H8]

Where are you located? One of our members will quite likely be able to provide a distributor you can contact reasonably close. If not there are distributors that will ship or mail you the springs. We can help with contact info. This is one of the reasons I wish members would at least put the country they live in as part of there profile. It saves having to ask.

[Evil66]

Profile updated, sorry just joined and hadn't finalised it.

Have tried a few places out here but the OHG stuff hasn't been made for a while and majority use impco or gasresearch out here.

Even if someone can point me to a supplier in the US that would stock them I can get some posted out. Appreciate the assistance.

[C3H8]

I'm pretty sure I can find you one in Canada if no one jumps in from your area. My business partner used to have them and there may be one on the shelf. Other then that I know of a couple of companies in the USA that would likely have them. Friday night here so I can't find out until next Monday (Tuesday your time I believe).

[storm]

I don't know of anyone who does OHG parts in Australia anymore. You could try LG MotorGas in Victoria. I contacted them a few years ago about OHG parts and they emailed me back with the reply to call them by phone indicating they had some material. Other than them I think Australia is a OHG wasteland and parts are impossible to find.

[Evil66]

Thanks for the replies guys.

C3h8, if you find anywhere the sells them any advice would be greatly appreciated.

Took the car out for a run last night, when taking off hard and you get a lot of wheel spin the car actually cuts out like it runs out of gas. Will restart after a few cranks of the starter.

Really hoping I can get the ohg mixer working on it, be a real shame to have go back to petrol on this car.

A friend of mine has an ohgx1 regulator in his shed, would these have been setup to run with an ohg mixer or is it likely it would be setup to suit an impco mixer?

[C3H8]

I'll see what I can find starting tomorrow. I already checked with my business partner and he did not have one. I will call a couple of places and see if I can get you a contact. A similar regulator to the X1 is currently marketed by Woodward as the H420. The secondary springs might be the same. I'll find out.

[storm]

Sorry I thought you were only discussing the mixer before.
If you want a convertor/regulator just purchase a LG B2. They are LG's copy of the X1 and the repair kits for these fit the X1 and the H240.

[flatblack]

If this helps....That spring you need i bought from 2 places to use the model e's with my 2 x450 carbs on my dual carb setup. I bought one from nash fuel http://www.nashfuel.com/ and the other from Propane Systems: Buddy: 877-403-7827 http://www.alternatefuel.com bgamel@alternatefuel.com


I have a woodward n-420 and an x-1, both need to be rebuilt. They didnt work as well as the new model e's do. I would pull apart the x450 and make sure the insides are super clean and that it slides nice and easy, The meetering rods come off easy and should also slide free. Also make sure the lil enrichment valve doesn't stick. Even if it looks clean it may not be, it doesnt take much. I messed with the metering rods alot and a little bit is alot, a few thousandths and its super rich or lean. Be patient and mess with it some.. A rebuild kit also can be purchased from alternative fuel .com that i posted above. Its a bunch of orings and a gasket, i did both of mine for under 15.00.