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Hi...i'm taking the 2 bbl manifold and carb off my 327 and am getting ready to prep the 327 4 bbl manifold. I'm going to take it apart, have it blasted, new hot spot gasket, painted or powder coated, and then reassembled and have the faces milled flat.

I did the same to my 2 bbl manifold (save the milling) and noticed lately that once the car is good and hot (not a 15 minute drive, like a 40 minute one) it rolls over fine but won't fire. I have 3-4 psi fuel pressure at the carb when this happens, and have the insulating spacer and new gaskets, etc installed and have the little exhaust flapper valve connected with a spring to always keep the exhaust routing directly out without hitting the manifold.

The thing is, i noticed that even in that position a fair amount of exhaust works on the hot spot, and i'm wondering if the fuel just isn't vaporizing as soon as it hits that when being squirted in with the jets when trying to start it. If there's a chance to work with the hot spot, its now before i have machine work done.

I was thinking of making a plate that pretty much matches the hot spot gasket, solid about 1/16 in thick, and putting a gasket on each side of it sandwiching it between the manifolds to block off the hot spot more solidly. I figure i'll have to have the thickness of the plate and extra gasket milled off one of the hot spot surfaces so that the intake and exhaust ports on the face aren't on a different horizontal plane after adding something so thick in.


Does anyone have any experience with this or other similar ideas? Do you think it would make any difference or do you think the intake side of the hot spot is just going to hit that temperature no matter what and it won't matter? Or maybe the 4bbl isn't as prone to this issue for some reason or i should look at mixing diesel in as some have done?


I don't believe i have a pump/line/tank issue, with good pressure at the carb and a full bowl of gas with 3-4psi behind it, vapor lock in the line can't be a culprit in my mind.

Of course, it could be ignition i guess which i'm working on, but then i don't think it'd be as easy to start cold as it is (it fires RIGHT up.)

I know from experience that coils can fail when hot but work (apparently) fine when cold.

I have a question. If the fuel is not boiling off before it goes into the carb throat, why would you think that vaporizing early on it's way to the cylinder would be a problem?

Thanks,

Tom

Coil is brand new napa, and have had several coils on the car with no change in ignition work i've been doing, or hot start issue changes, good or bad.


I don't think the carb is too hot itself, i think when you hit the gas to start and the accelerator pumps shoot the 2 streams of gas into the manifold, they hit that hot spot and boil off and the mixture therefore is way off (for starting) when it hits the cylinders. I mean i could check with a spray bottle of gas i guess. Get it so it won't start and then take the air cleaner off and have someone try to start while i spray some gas in.

vaporizing gas with a spray bottle by heat and electrical is a good way to die though.

Let's think about this a bit. There were hundreds of thousands of straight 8 Packards made with essentially the same engine, distributor, carb, manifold etc. All of them did not have this problem. To go through the time and trouble to modify your engine while there are thousands on the road still in original configuration does not make sense.

However there is wisdom in spraying gas in the carb and having someone start it. Yes the risk of death is there but I heard that in heaven everyone who owned a Packard in this life gets the choice of a brand new early Twin Six or a later Twelve. Custom bodied open cars, of course.

Back to reality. When all else fails, read the manual. Works when assembling gas grilles, kids furniture and diagnosing Packards.

51-4 Factory Service Manual sez:

#8 Hard starting when engine is hot: This condition is usually caused by an over-supply of fuel. Very rarely an igniiton coil....

Leaky needle and seat
Choke valve sticking or incorrect setting of choke
Carb main discharge nozzles not seating or loose
Faulty coil

Unless someone is a highly experienced engine designeer I don;t think they can comment on your modification questions.
I will say one thing, Packard sure knew what it was doing and we are but mere mortals.

My advice, look both ways before you cross and follow the factory service manual.

Fred,

It could be just carb related, i had this one professionally rebuilt, but even as much as i'm an expert in my field, i make mistakes so there could still be a carb issue even though this guy is an expert in his, and with lots of packard experience.

I do wonder though, why there are so many of us with this specific issue that people are mixing diesel, etc. in and looking for solutions to issues that don't seem to be worn out parts or classic line vapor lock.

I was thinking that if this is the exact problem, it would be because fuel is more different now than then and maybe this is one of the slight symptoms of the changes over the years. I just didn't know if fuel now had a lower boiling point or something. I viewed this more as an adjustment for the future of the car, like people putting larger jets in for ethanol fuel.



I could do the gas test, and also check hot spark when car is hot, and then also try starting it while manually running the choke. Shutting the choke should give it less fuel and it should fire, right?

If it is the carb with the choke valve sticking or carb main discharge nozzles (because i don't know what those are), it's moot because the 4 bbl is going on. It might be the cause of the rough idle i'm chasing too.

I'm going to rule out faulty coil, and leaky needle and seat because those have been double checked, and coil setting because it starts great cold and when warmed up the throttle blade is wide open straight up and down. That's what you aim for right?

Some terminology clarification is needed. I believe what you are calling the "throttle blade" is the round plate at the top of the carburetor throat, about 2" in daimeter. If so, that is the "choke valve" per Pkd Svc Manual terminolgy, in common parlance it is called the "choke" Yes, when the car is warmed up it should be up and down and wide open.

I'm also wondering what causes the starting problem that so many seem to have. I have straight 8's and V8's which are well maintained adn have no such problems. We sell old parts, but we do not have 1950's gas in stock so we use the same gas everyone else does.

I'm an engineer and like to understand a problem. There are those who have hard starting cars and install a 6/12volt battery and their starting problems are over. I like to diagnose and fix the problem, accelerator pump, bad battery cables etc etc??

More later, dinner time.

Cortcomp: YOu said above "Shutting the choke should give it less fuel and it should fire, right?"


You also said you lack some auto knowledge, all of us do. The statement above from your post indicates that you do not know how a carburetor works, as such your major undertaking with the exhaust butterfly valve to fix the problem is ill advised. East Grand Boulevard had rooms full of engineers who knew more than all of us on packardinfo. Shutting it off will give cold running problems including carburetor icing which can be very dangerous as the car will stop running unespectedly.

Shutting the choke "chokes" off the air and increases the fuel/air mixture giving the engine more fuel in effect.

Long and short of it, I'm going to bow out here. Suggest you take your car to a mechanic who is an expert diagnostician AND bring along a copy of the 51-4 Factory Service Manual.

good luck

PS My everyday car is a low mileage '78 Buick Electra, built before ethanol/new gas was invented. It does not boil, vapor lock and it ALWAYS STARTS, hot, cold or otherwise. If the gas were the culprit my car would exhibit the same symptoms as your car.

I'm sorry, i typed the last response in a very large hurry heading out the door.

"You said you lack some auto knowledge, all of us do. The statement above from your post indicates that you do not know how a carburetor works"

I'm sorry, i meant it would give it less air and it should fire, right?, as in if it's a LEAN condition as opposed to the rich condition you were referring to. I was saying how i could test the opposite of your test to verify results if your theory works. It should start and run testing with your idea, and NOT start shutting the choke if your theory is correct, and if it's too lean (my thoughts) are correct, it would be the opposite.

I know the throttle blades are on the bottom of the carb venturi and the choke blade is on the top. I just didn't know they called it a choke valve in Packard terminology.

I DO know a ton about carburetter theory and certain models for the myriad of vehicles i own and work on, what i lack is experience with this model on this motor type...a super low compression flat head that run a little warmer and lazier than motors i'm used to. That misstatement was my mistake; basically calling me ignorant about it was yours.

Suggesting that this motor and your one-step-before-modern day OHV V8 likely quadrajet fed GM motor would have the same issues on different gas IS apples to oranges. Your motor is basically the same as my Pontiac 428, albeit with more emissions gear. Likely a buick 350 or olds 401 but whatever. I wouldn't expect the same trouble from a given source on those motors as i would on ours, or ours vs a 19-teens Packard. The difference in technology on the OHV higher compression v8 means they'll run ok no matter what some backyard mechanic does to them. Our motors are a bit more finicky. The 428 starts and runs without a hitch and perfectly...no matter what off the shelf carb or old thing from a swap meet i throw on. You just don't get that with old 6v low compression motors, jet sizes, etc have to be decently close to correct if you want trouble free performance. Like you said, i could just make it 12v alternator battery etc. OR i could find the cause or contributing causes to the hot start/rough idle issue.





"Shjutting it off will give cold running problems including carburetor icing which can be very dangerous as the car will stop running unespectedly."

That just won't happen, and you know it. No one is taking their packard out to get the family Christmas tree anymore. I'm willing to sacrifice time needed to warm up in chilly weather and longer warm up times before really laying on any pedal for long term ease of use. EVEN if i took it out in the snow, the under hood temps alone would be enough to keep the carb and pump warm and toasty. The convection alone would be fine, and even if i blocked the heat riser with a plate (like so many people do on so many different engine models of many years with varying degrees of success), the exhaust is still connected, metal to metal, with the intake and will heat it more than enough. Who on here is complaining about having a Packard that's running too cold under the hood, in any weather?!



I totally see your point that a fuel mixture issue could be the problem here vs me approaching it likely incorrectly from a heat standpoint, but you can't do enough to keep almost any motor (or tranny) running cooler to help it last longer. I'm not trying to run a 100 degree Packard, i want it to run smooth and the right heat range helps do that. However, we're not using the car as the factory intended in all weather types and temp, and i would attempt slight changes and modifications IF they provided more reliability for MY normal usage.

Anyways, thank you for the help, you gave me something interesting to test with to verify if my carb was, in fact, refurbed properly if there may be an internal issue the pro didn't catch. Thanks for that, i do like to double check anything i have the ability to verify instead of taking someones word for it that it's fixed.

I think you should wait and try the new manifold and carb and not modify the heat riser at this point. With the new parts, you are going to have a totally different set up. Like you said, the new carb and manifold may solve a lot of your problems. It will be a little more work if it doesn't work having to take the manifold off again, but I think you would rather have it work unmodified than modified right?

If it still is not fixed, try the diesel fuel additive. If that works, you will rule out most other possibilities and narrow it down to the fuel. Maybe a little tweaking of the settings at that point will give you the performance you should have and you would no longer need the diesel. Just my

"but I think you would rather have it work unmodified than modified right?"

Correct, just sounding the idea that this might be a culprit for some reason today, and wondering if anyone had blocked it off or filled it like people do on a lot of V8s. Also curious if people had tried it what results they found.

After the manifold and carb switch, yes, if it still happens i'll try diesel. It's a band aid, but plentiful around here. It wouldn't be THAT bad of a long term fix for me, but i prefer to hop in and go with no worries, like the man that owned one when it was new.

I'll be following up in the "chasing rough idle...compression?" thread so i'm not working in to places, as it seems that some of freds points lead me to conclude that this problem and the rough idle issue may be the same culprit, and that it's not the engine being to hot that's causing it not to fire, it's that some other system like ignition or fuel is not handing things like they should after the engine is fully warmed.

So, done with this thread, i'll keep it in the other.