Help with 39 plymouth idle/mixture problems

OK ladies and gentlemen I need some Help

I have been working hard for the past two months completely redoing a 39 plymouth pickup.
pretty much on no budget and no time. so I dont want there any crap about the cheap whitwall radials!!
Its a surprise for a friend who was fellow team leader back in the day. He gets home from afganistan satarday and though the truck is not even close to done I would like him to be able to drive it for a few weeks before finishing bodywork and paint and etc etc...I did spray it with some black lacquer but I am really only half way done on the body...but haveing it in the driveway looking shiny when he pulles in was important to the wife.

I didnt post a build thread since I don't know if he peeks around here or not!

I think the problem has alot to do with the fact that I installed headers onto the mopar flat six, which in turn deleted the heat exchanger on the intake manifold.

I can tune the carb to idle well, and run well at WOT but not both.
I have the carb adjusted so that it idles well when cold at full choke and idle ok 3/4 open when warmed up.
When I drive it if I have it choked or partlially choked when warm it will idles fine but brakes up at full throttle, if I open the choke it will run good at full throttle but dies when I stop at a light etc... unless I pull the choke knob first.

Fuel delivery doesnt seem to be an issue, I have an electric pump and eliminated the paper filter I was running before the pump and have a high flow one after the pump now.... no change and the filter stayes full of gas.

I have run it without an air filter and with a tiny restrictive paper filter, no real change.

I have tested for intake leaks and can't find any.

any ideas??

give me a few minutes and I will upload some photos of the truck before and after...


joshes truck 054 by jforouhar, on Flickr


joshes truck 057 by jforouhar, on Flickr


joshes truck 048 by jforouhar, on Flickr


joshes truck 072 by jforouhar, on Flickr


joshes truck 071 by jforouhar, on Flickr


joshes truck 081 by jforouhar, on Flickr


joshes truck 080 by jforouhar, on Flickr


joshes truck 077 by jforouhar, on Flickr


joshes truck 076 by jforouhar, on Flickr


joshes truck 074 by jforouhar, on Flickr

 

"I think the problem has alot to do with the fact that I installed headers onto the mopar flat six, which in turn deleted the heat exchanger on the intake manifold."

Believe me I'm not totally sure of where the problem lies, but the above quote may have something to do with it.

Years ago, I had to replace the heat exchanger on my '53 Buick...after that I also sealed a minor leak on the manifold. It ran fine then.

Are you sure there are no minor cracks/leaks in the manifold ?

Hope you do get it running...fine looking MoPar !

Jonnie King www.legends.thewwbc.net

 

Thanks!the paint still needs alot of work but he can drive it for now... its running but I want him to be able to floor it and sit comfortably at a stoplight with any fiddling or issues!!...it might just take like 20 minutes to warm up now with the headers? I am gonna go over the intake again for the millionth time but I think the intake needs some heat....but I know guys run these headers, maybe only with aluminum intakes?..maybe just in arizona?

 

well i worked on it some more torqued the intake down, and took it for LONG drive, I think this truck just takes a half hour to warm up!!
anybody got any suggestion to improve drivabilty?

 

If it is cold and/or damp there in your area, then it really does need a heated manifold or...something that "might" help, is a preheat hose leading to the air intake. (air cleaner)

 

its cold AND wet!

what do you mean by preheat hose?
would an aluminum manifold help?

 

Langdon's Stovebolt offers a bolt on water heated plate to heat the intake...
http://stoveboltengineco.com/catalog/store/#ecwid:category=361513&mode=product&product=1409130

 

Without that exh heat under the intake,..it'll be cold hearted, until fully warmed up.

4TTRUK

 

"pre heat" hose,...would be like the thermstatic type air cleaners of the 70's had...There was a flex hose, from the exh manifold, that went to the air cleaner inlet snout. The idea was faster warm up, for emissions purposes, but it may help, in your situation.

4TTRUK

 

this sounds REALLY dumb- but it sounds like you have trash in the carb.

 

no trash in the carb, its that cold intake causing trouble, I am really sure about it, it runs nice after about a half hour. I think that maybe I could make an electric intake heater, made of an electric coil that would sit right where the old heat exchange was...that turns off at a certain temp...like around 200 or so...

 

could you wrap the exhaust to the intake with tinfoil to hold heat in
looks like you need some heat to the bottom of the carb to help driveability
if it has sat awhile you may have to clean out gunk out of carb this is gonna take some tinkering to make work

you may have to consider running a exhaust tube under the carb or some other method of quick heat up

 

i may be stepping on peoples toes- but if its built well and its not extremely cold temps, it shouldnt need a choke.


so to me, it means something is either gooey- sticky- clogged- or perhaps not right/adjusted correctly.

 

Says the guy from texas !!!
no toes hurt...
the carb is rebuilt, there might be some adjustment issues but every vehicle I own including 6 vintage harleys a model A, a dodge dart, a nova need to be choked for a few minutes here even in the summer even with heat exchangers intact, tiny aluminum manifolds tucked between aircooled cylinders etc....temps at night here are 20's and 30's for most of the year except summer when its in the 40's at night...
guess im a genius for putting headers on this flatty

 

this would be great but the truck doesn't start circulating coolant for 15 minutes.

 

:shrugs:

who rebuilt it, how it got rebuilt, and environmental conditions really play into the situation.

for the 2 years i ran a holly truck avenger on my junk, it never needed a choke and ran like fuel injection.
I would say have a professional go over the carb and see if something is missing in the link.

good luck with it, i can try to help you with 2 guys i know who do carbs for a living if you need the help

 

thanks! I think the fact that your in texas and I'min the foothills of the cascades in a frosty rainforest might change the fuel needs. a friend of mine built me a 68 FL shovel in Arizona and when he got it up here he couldn't even get it started after about five squirts and with the enricher on...I had to fatten all the jets to keep it from detonating.

I might take you up on the rebuild!! the carbs age and condition is contributing I am sure even after I rebuilt it but like I said it runs great once the temp gets up to 160 or so.....but who knows this is a surprise...when he gets it tomarrow he might just think to himself " I can't wait to put an LS1 in it and toss that boat anchor"..and strip that lacquer!

 

what type of temps are we talking about? the coldest it gets here is about 30 degrees, but humidity is anywhere from 40-100% all the time.


and, i will do anything i can to help another HAMB'er

 

its consistently below freezing or near at night much of the year...in the winter it gets into the 40s most days. summer is two months of the year here so we don't need to even talk about that....its 100% humidity...ie raining everyday.
choking a vehicle is standard around here to get it started and keep it running here until your on the road and moving for a few minutes....but not 20!

 

dutch, is that truck avenger a single barrel carb?..what do they run cash wise?

 

It needs to be plumbed from the aft cyl head fitting through the plate to the heater and then to the water pump to circulate coolant all the time like a bypass if I remember correctly.

What temp thermostat are you running? In my B2B I used a 180F in Minnesota to run it in winter...

It's a good looking truck and I'm sure the owner is going to be stoked when he gets back!!!

Didn't some of the Ford Inline sixes from the 70's use a coolant heated carb base spacer? Maybe something like that could be done easier?

 

Ahh! thanks that would do it! I wasn't thinking...a carb based spacer would be ideal I would think. I will have to check it out.
Good news is they got bad weather in germany so he is stuck, his wife isn't happy but I am..he doesn't get back until monday now so I have a few days to work. I already started wet sanding some of my peal out.
I hope he is happy, he doesn't even know this thing exists. maybe it will introduce him to traditional hot rods.
jay

 

I hate those little crome air cleaners why put and air cleaner on your car thats sized for a lawn mower. They just don't flow enough air at high RPM it's like running with the choke on. It won't look as cool but I'd try to find a cleaner that can pick up heat from the exhaust like the 70s OEM stuff.

 

thanks for the suggestion and help sunbeam!! every little bit helps

this truck runs no different without a filter installed at WOT...maybe if it had a two barrel, or a 4 barrel but with a tiny singe barrel carb with tubes, and jets, and butterflies, chokes, sitting in the barrel the air cleaner makes seems to make little difference, and oh by the way this small cubic inch flatty maxes out at 3grand...but yeah it would be nice to pick up some gases from the valve covers...except its a flathead

the truck runs great once its up to temp, but that takes about 30 minutes so whatever solutio I come up with needs to "stop" working after I get to operating temps

 

Well I an also in Texas and I have a 48 P-15 with the 218 I/6. I have split exhaust with no heat to the box, blocked on both sides. I run Carter YH carburetors without any type of choke and even in the teens it runs just fine. Now the second carburetor should lean the mixture if you do not increase main jet size which I did not do and it is plenty rich all the way through its range. Check for a leak at the carburetor base and at the throttle body to float bowl gasket. It sounds like you have an air leak causing the idle mixture to be too lean.

 

Do you have a thermostat in it ?

 

no, its a 4bbl 670. 'bout 400 bucks

 

yeah, but I am going to put a "hotter" one in it like a 180..I just reused the one that was in it since it seemed ok.

 

sounds like too much carb for this little flatty, might need to find a two barrel though.

 

I checked it again with ether around all the gaskets and the throttle shaft..might try a new carb..or convince him he needs a dual aluminum intake and carbs to match!!!...no idle change with the ether by the way.
It also is running GREAT when its warm so if there is a leak pesky leak its sealing off at op temp?maybe?