PCV issues?/hesitation

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navcadpilot

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I have a 1965 Dodge Dart slant 6 with Rochester 2 barrel carb.
I'm trying to sort out the PCV system.
I suspect that this engine has been reconfigured and is not OEM
There is a PCV valve in the valve cover, which also has a vented oil fill cap.
There is a hose from the PCV valve to the base of the carb, however, disconnecting the hose with the engine running has no effect.
Upon removing the carb, I see the hole in the base of the carb for PCV but no matching hole in the intake manifold.
My reason for researching this is that the car hesitates when starting from a stop and stalls when you nail it in the road. It idles fine but the idle adjust screw has no effect, even screwed all the way in.
I thought that I was fixing this by replacing the carb with a new one. Float level is correct
I also have a 1963 440 and this carb works great on it without hesitation.
Distributor is new with new vacuum advance and the mechanical advance works as it should. Ignition timing is as per specs.
I suspect that the issue is related to the PCV system but I am at a loss.
Any help guys?
 
It is pretty simple. Whatever port (should be 3/8 hose) that the PCV and hose are attached to should be full manifold vacuum. You should be able to pull the PCV out of the valve cover and feel vacuum with your finger. If you remove the PCV from that end of the hose, the engine will not want to idle, and you should hear and feel a huge vacuum leak. Some carbs have a 3/8 port and some do not. I've never heard of a carb with a 3/8 hose fitting that is NOT full vacuum, unless someone plugged it or got the wrong base gasket, etc.
 
1965 Dart with a slant six is not OEM with a two barrel carb. So it is very possible there is a mismatch between the carb and the manifold. Also I'm not positive, but I don't think any slant six got a Rochester 2bbl carb. It is possible you could modify the base gasket so the carb will see vacuum. But I don't think that is your problem. Sounds like a bad accelerator pump shot.
If I'm not mistaken the 2 bbl carb on a big block has a larger bolt pattern then the 2 bbl carb for a small block or a slant six. So something doesn't seem right. can you post some pics of the carb and the manifold?
 
The 1963 440 also has the slant 6. When I take the carb off the Dart and put it on the 440, the 440 runs perfectly. If not the PCV system, I can't see why it wouldn't work equally well on both engines. Did you note on my first thread that the intake manifold does not have a hole that matches the PCV hole in the underside of the carb? That is why there is no vacuum at the PCV valve or carb hose port. If the 1965 Dart did not come OEM with a PCV system then this is likely the correct intake manifold, however, if it did come OEM with a PCV system, then this must be the wrong intake manifold. I have not been able to determine if the 1965 Dart came OEM withg a PCV system. I feel certain that if I drill a matching home in the manifold that I will have vacuum at the PCV, but I'm hesitating to do that unless I have some confidence that it will address the hesitation issue.
I know from the limited records that I have that the Dart had a Carter 2 barrel carb before the Rochester was installed. But once agian, if the Rochester works well on the 440 why doesn't it work equally well on the Dart? Seems to me that the major difference between the two is the PCV system.
I appreciate all your comments- please keep them coming.
 
Followup note. I had dismissed the accelerator pump as the issue as it pumps perfectly when installed on the 440. Did you also note my comment that the idle mixture screw has no effect, even when screwed all the way in.
I considered trying to determine what the OEM carb was, but once again, if the Rochester works on the slant 6 440, why not the Dart?
There is a snake in the grass here and my instincts tell me that it's related to the PCV system, or a vacuum leak. I have closed the vacuum port to the heater controls and nothing has changed. Other than the missing hole in the manifold, the carb gaskets seem to have the right configuation for matching the carb base and maniifold.
I'm sure that one of you has an answer for me!
 
Look at the carb mounting gasket on both engines. See if they are the same. Without knowing what you have, I'm poking around in the dark. Since neither engine has the original intake/carb I don't know what you have. That's why I asked if you could post any pictures. Myself, I have trouble posting pictures.
Are both manifolds cast iron, or one piece cast aluminum, or welded 2 piece aluminum?
 
Thanks Charrlie,
Right now I am working on last years troubleshooting. I had to put the Dart in storage for the winter since I had no warm place to work on it. I will check both gaskets as you suggest as soon as I get the Dart back where I can work on it. It's looking like spring here in New Hampshire but the cold hangs on. I will have it out soon and will respond. I am just trying to get a head start on the project.
Everyone's comments have been appreciated.
I hope that they wil keep coming.
 
If we can see some pictures of the two barrel that would help tremendously.
 
You are swapping the carb from one engine to another that is twice as big [ 225...440 ]. Roch 2bbls were used on 455 GM engines, which one have you got? Off a 455, or smaller engine.

The PCV on the 225 could be carboned up, which might explain why it doesn't seem to make any difference.
 
Bewy said:
You are swapping the carb from one engine to another that is twice as big [ 225...440 ]. Roch 2bbls were used on 455 GM engines, which one have you got? Off a 455, or smaller engine.

The PCV on the 225 could be carboned up, which might explain why it doesn't seem to make any difference.
Click to expand...
Both engines are 225 slant six's. I made that same mistake. The 440 is the car model of the 1963, not the engine size. See posts #4 and #5
 
As I noted earlier in my thread both engines are slant 6s. There is no vacuum at the carb PCV hose pipe, thus the PCV valve is not the culprit.
For now i am going to drop my concern about the PCV system causing the hesitation and start searching for an intake vacuum leak. I should remember-- one step at a time.
I'll post a report later
Thanks Everyone.
 
navcadpilot said:
If the 1965 Dart did not come OEM with a PCV system then this is likely the correct intake manifold
Click to expand...

PCV was standard equipment everywhere starting in '63 ('62 in NY; '61 in CA).

There is no "correct" 2bbl intake manifold for a '65 Slant-6; the first factory 2bbl setup on the Slant-6—not available in the US or Canada—started in '67. Not til '77 in upper North America. None of the 2bbl intakes has a pass-through port on the carb mount pad for PCV; that's only on the Slant-6 1bbl carbs. The 2bbl PCV porting is via the throttle body and/or the carb base gasket + insulator.

navcadpilot said:
feel certain that if I drill a matching home in the manifold that I will have vacuum at the PCV, but I'm hesitating to do that unless I have some confidence that it will address the hesitation issue.
Click to expand...

You should make the PCV system work regardless of whether it will address your hesitation issue.
 
When I first got my current/6 fired up after a rebuild, and super 6 conversion, I added a plastic insulator/spacer between the carb and intake, I had a problem with no pcv, as well. Saw smoke thru the oil hole and thought "oh ****" I screwed up the overhaul/ but all I had to do was to cut the divider between the 2 barrels out and it unblocked the vacuum access hole for the pcv and all is now good.
 
Thanks for this volaredon-- it is helpful.
I spoke in error when i said that it had a 2 barrel carb-- I was working from last years memories (I'm 85 so all memories are suspect!)
It has a single barrel Rochester because single barrel Carters are not available as cores.
I found a small vacuum leak that I will explore tomorrow.
Based on your comments, I need to explore the carb gasket.
I brfught it home from storage today so now I can get started on troubleshooting.
Although still occassionaly below freezing here at night, days are getting warmer!
 
If the carb is calibrated for a PCV, and you install it in such a way that the PCV is not able to function, then
in order for the engine to idle, the speed screw will need to be cranked quite a bit higher, for the engine to get the missing PCV air.
Of course cranking in the speed-screw, will run the throttle blade up the transfer slot, making the engine idle rich and
reducing the vacuum signal to the mixture screws...... which, if the throttle valve is quite far outta sync, will then "do nothing".
Therefore; fixing the PCV is the first step in returning your engine to normal.
AS to the hesitation, IDK. But Ima thinking, with the throttle open so far, the accelerator pump diaphragm is already quite far down on it's stroke, and maybe it just hasn't got enough capacity left.
Furthermore, again with the throttle blade so far up the transfer slot, I suppose, part of the slot is now passing air at idle, which would reduce the signal, and when you step on it, the T-slot may take a bit of time to come back on line.

Course who knows were the timing is at or how tight the valves are lashed............
 
if the idle mix screws are not making a difference, are you running on the main system at idle?
could it be idling away merrily on a feed from the main circuit hence the idle circuit adjustment has no imapct.

the driver is often not enough initial timing for todays ethanol petrol so the throttle needs to be open to achieve a decent idle speed and enough idle torque to turn over the converter/trans in neutral and not stall as you move into drive

not so sure that creates a stumble but it certianly is one of many ways that the idle mix screws become ineffective.

i have no PCV on mine due to weber carbs and i must admit my rear main seal doesn't do its job as well as it used to, conincidence or cause?
 
Last edited:
I want to thank all of you for your replies.
The problem turned out to be ignition timing.
I had replaced the damper, timing chain, and cam gear.
The new damper has several notches for timing-- I'm guessing that it fits several vehicles.
Anyway, I was using the wrong detent for timing. The one I picked was determined by checking that the #1 valves were both closed with the valve cover off. As it turns out, not a very accurate way to do it.
I figured this out by using a piston stop tool to determine TDC accurately.
Simple solution for a vexing problem!
 
navcadpilot said:
I spoke in error when i said that it had a 2 barrel carb--It has a single barrel Rochester
Click to expand...

What kind, exactly, intended for what kind of motor? This is a carburetor-shaped can of worms. Good Slant-6 carburetors are harder to get than they used to be, but they're not impossible yet; you may wind up finding it easiest and best to go back to a more application-appropriate carb of one kind or another.

Does this car have the rotating-rod throttle control common to all pre-'67 Slant-6 A-bodies except '65-'66 with factory A/C? Or a cable-type setup?
 
Dave999 said:
if the idle mix screws are not making a difference, are you running on the main system at idle?
could it be idling away merrily on a feed from the main circuit hence the idle circuit adjustment has no imapct.

the driver is often not enough initial timing for todays ethanol petrol so the throttle needs to be open to achieve a decent idle speed and enough idle torque to turn over the converter/trans in neutral and not stall as you move into drive

not so sure that creates a stumble but it certianly is one of many ways that the idle mix screws become ineffective.

i have no PCV on mine due to weber carbs and i must admit my rear main seal doesn't do its job as well as it used to, conincidence or cause?
Click to expand...
Millions of vehicles came without PCV valves. It could also be argued that they also leaked more than more modern engines. lol So cause? I don't know, maybe that's a little strong. Contributor maybe.
 
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