hello all.
my 72 plymouth valiant 4door / L6 198cu has a holley 1920 on it right now and its giving me alot of problems.

I would like to purchace a second holley 1920 that is / rebuilt and or known to be a ok working carb... ive read on here that purchacing a factory reubilt unit is generaly a terrible idea.. so if anyone here has a good working spare to sell to me I would gladly buy it to have / and try out on my engine....

I have a complete 1920 rebuild kit for my carb - but am hesitant to take it all apart and try to fix it only to bolt it back on and have it work worse than before. the thing is barely drivable now as is...

recent problems -
engine idle speed once warmed up hovers around 700 rpm in park/n and when in gear it surges down to about 450rpm up to 650 rpm but sounds liek it wants to choke out all the time.. and has stalled on me a fiew times already like this. ive not had more than 500 miles on the car since ive owned it - and it has gotten progressively worse over the time ive had it to now. this is not a instant thing that just poped up.
when at a stop sign / or stop light I have to throw the car in neutral to keep it running enough rpm to safely not stall out.

the engine runs happily down the road. actually above 1K rpm is has alot of pep and realley is nice to drive but engine idle sucks.

I have the set screw for engine idle ajusted all the way in.
to get it to go in any further I would have to take out that spring thats on there now because its ajusted all the way as far as the spring will allow.

I live in south FL usa for shipping the carb to me
lmk if anyone out there can help me out

and if you need any pix of my setup id be glad to post em
this is my ride

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1972 Plymouth Valiant / slant 6 auto

o yes - the engine has the automatic choke feature that has the little jobber spring mounted to the exaust manafold that connects to the choke of the carb... about a month ago I had ajusted that rod to allow the choke to open up sooner by a little bit because my cold idle was super high at like 1500 rpm and it would slam hard when I put it in gear.

fuel filter is brand new - and fuel lines are good.
the carb used to have issues sealing the float bowl to the base - and would leak a little gas here and there - and I also believe I might have some float sticking issues - but thats probly my fault because my car has hydraulics suspension and I abuse it by hopping the car driving and what not. I know its probly terrible for the engine to use the hydraulics when driving - due to the re direction of oil during extreme suspension movments.


I have a sun tac - I know its not the best but it is probly semi acurate
along with the 3 cluster of guages to know what my stats are.
engine runs happily at 190 / 195 deg. all the time oil psi is 40 when rpm is above 750 - but at the hesitant idle in gear 500 rpm or so I only get about 25psi oil and 500 rpm = 12volts but 850 rpm = 14volts.

I know thats random info - but it might be useful

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1972 Plymouth Valiant / slant 6 auto

There could be a number of things going on here....however I can make a few recommendations based on the excellent advice that I've received here....advice, I might add, that once followed, produced a very smooth idle in my Valiant:

- Go ahead and rebuild that carb. I just rebuilt my 1920 and it's a very simple carb. Just get it good and clean. Go buy a can of the spray carb cleaner and use the whole can up cleaning and recleaning every nook and cranny. I used the Walker kit that is highly recommended on this forum and it was worth it.

- Adjust your valves. My slant wasn't silky smooth at idle until I did this.

- Check for misc. vacuum leaks that might exist in old hoses and other places, like the PCV valve grommet, etc. (and while you're at it, replace that PCV valve for good measure.

- Since you've been bouncing that thing around, you should check for loose nuts/bolts/etc where there is the potential for a vacuum leak....like the base of the carburetor, and the intake manifold-to-head connections. Just be sure to tighten these nuts up carefully, when the engine is cold.

These are some good starting points.....if you've done all of these, there's more to do and check, but this should get you started.

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1954 Ford, Tudor Mainline
1976 Plymouth Valiant, 4 door


www.automotive-ninja.com

brian72valiant,

The first thing I would do is move that fuel filter over to the fender........the gas will just boil where it's at with the hood shut. This will affect how the carb responds allot....!
It is very unsafe in that location and could cause a engine fire.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I will move that fuel filter pronto. !
thanks for the advice on it.


still searching for a good 1920 to have as a back up incase mine gets worse. I fear the throttle shafts are worn and vaccume leaks are actually a part of my carb. all vaccume lines are replaced with good rubber - so there are no leaks from the hoses.

will check the pvc gromet - and I have a replacment pvc valve to install actually sitting in the box here at my desk.

and will get on the check for loose hardware around the engine bay.
all manafold stud nuts and carb mounting pieces will be torqued.

im pretty shure that my valves are actually good and quiet still. so they will not be ajusted just yet....

will report back tomorrow about what I can figure out / along with a new set of spark plugs - and maby I can post a picture of how the current spark plugs look after a fiew months of on / off driving since i have a truck also.

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1972 Plymouth Valiant / slant 6 auto

The two valves that were the furthest out of adjustment on my /6 weren't making a bit of noise.

So, don't make any assumptions purely based on if they're rattling or not. Since the car is new to you, it's worth knowing for sure what the adjustment status is with the valves.

It's a cheap, easy thing to check and correct and could potentially yield big dividends.

I personally hadn't ever adjusted valves on a running engine before, but I'm sold now on it being a superior way to get them accurately adjusted.

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1954 Ford, Tudor Mainline
1976 Plymouth Valiant, 4 door


www.automotive-ninja.com

I will second that!
Doc had suggested loosening mine up more than stock which is .010 and .020 to .012 and .022 and the mileage went up along the vacuum readings and with low end torque.
So a little more noise equates to more seat time and it is much less apt to burn a valve.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I just threw in some new plugs - mainly to get all the old ones out ( by old I only mean a fiew months ) - but to get a reading off of them - and see what they look like sad to say its not amazing or good.

plugs # 5,4,1 all have a verry white chalky build up on the tips and around the electrode

and plugs # 6,3,2 look like they are having a cleaner burn
but plug # 6 also looks alot darker than the rest

maby I will have to give the valves some ajustment
and possibly do a cranking compression test on all 6 holes
just to see if any of them are way out of spec.


will try and post some pix of the spark plugs - maby you guys can read them better than I know about telling how the burn is on them.
edit - here r the pix - plugs are champion RN14YC - am I suposed to remove the crush washers on them ?




im not feeling super happy about all the diffrent readings each cylinder is telling me... what would you guys think would cause this ? / rings / un ajusted valves / burned valves ? ? leaky intake manafold ???

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1972 Plymouth Valiant / slant 6 auto

Do a valve lash adjustment. Dont forget they flip in the middle.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Yes, your suppose to remove the washers per SL6Dan's recommendation.
You may have some vacuum leaks on a the lean cylinders.
How many turns out is the mixture screw at currently?

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Allways adjust your valves first,has been known to fix what you think are carb problems.Guzzi Mark

I got down and dirty today - and ajusted the valves with the engine running at temp.

checked my work a fiew times...
I think I did pretty good.

my exaust valves were more or less set a little tighter than the .020 that they were suposed to be at - so I ended up having to loosen most of those up and only a couple of the intake valves were a bit tighter to start off with than the .010 that I set them all to.

its funny tho - when I started out I had the carb ajusted to idle at about 750 rpm... and when I checked the tac when I was done ajusting it was up at 950 rpm.. so maby getting them all set was a super good idea - I would like to personaly thank slant 6 dan for posting how to set the valves hot with engine idling... I found his how to post somewhere after searching it out a while - maby a mod here can post that thread up in the frequently asked question section as there is TONS of good information in it and I am shure I will have to re search it out again next time I want to re set the valves again.

so any how - when I was in the process of setting the valves with the valve cover off - engine running I was noticing some nice steady little streams of white smoke coming up thru the engine block and venting out up top where the oil drains back down thru.... is this semi normal ?
or is this a good indication of pretty worn out piston rings ? = blow by ?

I guess a cranking compression test is next.
but now the engine seems to idle along a bit smoother than before - a road test is up for tonights agenda to see how she reacts.


another question for you all here - about engine idle in neutral / park and when in gear.... seems to me like when I put the car in gear, but keep it stationary with a foot on the brake the engine rpm drops a good amount... im shure its fine but maby mine is a little exessive. I always keep an eye on the tranny fluid level - as I had a verry slight drip or 2 ocasionaly on the garage floor but I rarely ever need to top off the tranny... so my question to you guys is this :
how much rpm drop do you get when you put it in gear and hold the brake down to keep stoped ?

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1972 Plymouth Valiant / slant 6 auto

Mine when set to 750 rpm, will drop down to little over 600-625 with lights, radio, wipers, heater and electric fan on. It will idle that way for hours, generally 2 hours our more in bad freeway traffic on my trips home from work. The stock lash setting or a little looser keeps the idle steady like a clock ticking. It also improves a inch or so on the vacuum gauge and low end torque and overall mileage.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

yeah I was going for .010 and .020 but If I had any doubt about it I set it maby a tiny hair looser since im an amature at ajusting the valves maby they are actually set to .011 and .021 but im fairly shure they are all with in spec now at least...

took the car for a good drive tonight.
it stalled once while I was slowing down for a stop light - coasting and I watched the tacomater just steadily fall down till it died - but I was able to fire it right back up in neutral and keep going with traffic.

sucks tho - this stalling issue has me baffled.

my idle is set in park to hover at about a thousand rpm
and in gear its steady at 750 rpm.
driving down the road my engine never goes above 2300 rpm

I wonder if I could have tranny problems like a failing torque converter that is acting sluggish and causing the engine rpm to fall ?

next test I guess will have to be a cranking compression test
and then test again with a fiew squirts of engine oil down the spark plug holes to see how diffrent the readings are.

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1972 Plymouth Valiant / slant 6 auto

If you have an excessive rpm drop when you place it in gear, it may be a mechanical advance spring needs to be checked. There shouldn't be much mechanical advance till you get to 1000 rpm. if you are seeing a noticeable change in base timing idling in gear and out, inspect your advance springs. When it's not spinning, the springs shouldn't be loose on the perches.

CJ

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Part of Tyrde-Browne Racing