425 rich after installing 1" spacer

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BigBlockMopar
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Re: 425 rich after installing 1" spacer

Post by BigBlockMopar » Tue Apr 04, 2017 4:49 pm

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At the location of the dark/black washer right under the 'valve', I'm thinking adding a very thin washer would put the valve deeper into its seating, and thus lean out the idle mixture.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.


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kikkegek
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Re: 425 rich after installing 1" spacer

Post by kikkegek » Tue Apr 04, 2017 5:00 pm

the regular gas valve en lean gas valve are shown on this link:

http://www.rasoenterprises.com/propane/ ... l-mixtures

standard valve
Image

lean valve
Image
daily: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.1 end gears - IMPCO425 mixer - IMPCO model E vaporizer
project: 1977 GMC C15 Suburban - 454 big block - TH400 - gasoline
sold: 1986 Chevrolet Suburban K20 Silverado

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kikkegek
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Re: 425 rich after installing 1" spacer

Post by kikkegek » Tue Apr 04, 2017 5:02 pm

looks like you have a lean valve in yours
daily: 1974 GMC 25HUNDRED Suburban - fresh rebuild 350 small block - TH350-NP203 - 4.1 end gears - IMPCO425 mixer - IMPCO model E vaporizer
project: 1977 GMC C15 Suburban - 454 big block - TH400 - gasoline
sold: 1986 Chevrolet Suburban K20 Silverado

BigBlockMopar
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Joined: Sun Sep 02, 2007 3:29 pm
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Re: 425 rich after installing 1" spacer

Post by BigBlockMopar » Tue Apr 04, 2017 5:05 pm

You posted the same pic as I did. That's not my gas valve. 8)

I'm not quite looking into changing valves or anything, simply because it has worked flawlessly before with the current valve.
Something changes in a relatively short time, twice on both 425 mixers I used on the engine.

I like to find out what has changed, but on the other side I'm also kinda 'done' with the situation and want to either try the OHG X450 mixer, or/and change to vapour injection very shortly.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

storm
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Re: 425 rich after installing 1" spacer

Post by storm » Tue Apr 04, 2017 8:46 pm

OK now I get what you mean, when you said "bottom" I was thinking the tip which is the lowest point of the assembly (i.e. the actual bottom).
I think adding a washer may be more trouble than it is worth. It may help to diagnose your issue but it may also cause more.
It seems to me you don't really want to "fix" the issue and really just want to move to a different system. Have you got an OHG to swap to?
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

BigBlockMopar
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Re: 425 rich after installing 1" spacer

Post by BigBlockMopar » Wed Apr 05, 2017 3:01 pm

Yes I also have an OHG X-450 laying around. Appears brand new. Complete with valveplate so swapping is easy if the vaporizer is changed along with it.
Also have another 450 which is just missing the main spring as far as I can tell. Bought both of them from forummember Sjak (Imperial73) last year.

The thing what annoys me most, is that these days when I finally have a nice programmable ignition system in the car which allows me to finetune the ignition, make the car even more fun to drive and possible improve economy as well, now the fuelsystem is feeding my engine a crap mixture.

If the 425's are actually the culprits, I won't be spending much time on them anymore. But I still hope to find the real reason they start to idle very rich over time on my engine, when they were good at the beginning.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

storm
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Re: 425 rich after installing 1" spacer

Post by storm » Wed Apr 05, 2017 4:11 pm

BigBlockMopar wrote:If the 425's are actually the culprits, I won't be spending much time on them anymore. But I still hope to find the real reason they start to idle very rich over time on my engine, when they were good at the beginning.
The only way that can be done is to actually do some testing but, and this is just what I am getting from your posts, you don't want to do that so it seems a bit futile to spend time working through it. To test it you will need a new gas valve and new idle diaphragm.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 425 rich after installing 1" spacer

Post by gottago » Fri Apr 07, 2017 3:00 pm

Remove the spacer. Reset, retest. Go from there.

BigBlockMopar
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Re: 425 rich after installing 1" spacer

Post by BigBlockMopar » Sat Apr 08, 2017 4:30 pm

No reason to buy and try new parts in the 425 as everything is still like brand new inside;

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Next I opened up the vaporizer and replaced the membrane with one from a new regulator. The old one was still leak free, but it already had started bubbling some time ago, and the bubbles were getting larger.
This didn't change anything in the AFR-values however.
Lever adjustment is just a 'smidgen' under the edge.
Tried swapping the spring from the other regular too, no change.
Took off the vapourhose for a peek inside, all looked well and clean.

As a quick 'fix' I decided the modify the springseat on the cap of the 425, so the spring sits a little higher and provides a little less pressure on the gas valve in the 425 bore.

Image

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This changed the AFR's favorably leaner from 11:1 to 13-14:1 AFR at idle.
Still, adjusting the idle mixture screw did absolutely nothing in the AFR. Totally unresponsive.

I knew that modifying the cap is not the solution to this problem, but it got the engine to idle and drive a bit fresher again.
I can always add a few washers below the spring to compensate again.

I started thinking maybe the lever spring inside the vaporizer wasn't the correct one after all (Since in the beginning, I had once added another light spring inside the current one to help get AFR where I wanted them to be).
Looked at a few other vaporizers I have, and only in one of them I could distinguise a blue color on the spring. All the others seem just plain chromed.

I know there are supposed to be blue or orange springs.
Anyone know what the correct spring rates are for these springs?

I've got a few new regulators, but with different numbers on the covers; one type says 2.5 lbs on the cover and the others say 0.36 lbs.
From what I've been able to tell, all of them have the same springs under the levers.

Here's a pic of an obvious blue spring I found in one of the regulators, all the others appear just chrome.

Image


Anyway,
Because the turning idle mixture screw does nothing at all, I'm now starting to suspect the vaporizer is maybe leaking a small amount of extra LPG internally, which becomes noticable at idle and renders the idle screw useless.
Will try to replace the vaporizer with a new one tomorrow and go from there.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
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Re: 425 rich after installing 1" spacer

Post by BigBlockMopar » Sun Apr 09, 2017 6:39 pm

Opened up the vaporizer today and dove a little deeper this time into the primary chamber.
Here I found a damaged valve and dried up, cakey sponge.

Replaced this with a valve and sponge from another fresh vaporizer and buttoned it back up.
Upon startup I didn't notice much or any difference.
So I tried swapping 425 top caps and also adding the 'extra' spring under the vaporizer lever.
With the extra spring installed in the current spring, the engine didn't start because the vaporizer didn't open up anymore.
Removed the extra spring so it's now all back to stock. Installed the non-altered cap back on the 425 and made the drive home.
Idle AFR's are still a little on the richside and while the idle mixture adjuster has become a bit responsive again, I still wasn't able to tune it leaner.
I left it there adn headed home.
During the trip home I stopped a few times to re-modify the idle mixture and max power setting.

AFR movements through the engine rpm and loadranges are not quite wanted I want to see, but better than before.


Image

Image
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

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