This is the set up I use. For a 1995 impala SS. Mine are just junkyard units but you can buy em pretty cheap new. https://www.ebay.com/p/Radiator-Cond...6153714&chn=ps

 

Dwell's the degrees the distributor cam rotates to drive the primary ignition circuit. That's it plain and simple. Dwell drives that circuit would you not agree that is what Dwell does?

 

I think it's an airflow issue, as well. However, I might argue this one point more emphatically. There is NO overheating issue while driving 'at speed'. There is a overheating issue at idle. You agree with that?

 

Yes but if it was off he wouldn't want to drive down the road. It would be misfiring and doing stuff where one would not drive down the road long enough to see their engine overheat. Again im not debating the fact of theory im saying its not probable in his case due to the facts he provided . The dwell does not control spark timing it controls spark output. He would have driveability issues like I mentioned.

 

Thank you for this information. This makes sense. So, to a degree though, I would still argue, the engine does care about the orientation of the distributor and you more or less said that didn't you? To achieve this "orientation", you can use #1 or #6 position depending on the crank position of those 2 cylinders. Does it matter if either one of those two cylinders are @ TDC? Why can't you use any other cylinder then? Sorry, I'm probably being a little thick as a brick here, but I think you said I can't use any other position other than #1 or #6, is that correct?

 

"180 out" is a term used when the distributor is dropped in the right spot, but number 1 is on tdc of the exhaust stroke instead of the compression stroke. The engine won't start and backfire. If the engine runs good and is in time I wouldn't dwell on the ignition and look elsewhere for the cause of the overheating.

 

Chief simply put the cam controls valve timing. The distributor controls spark. You have to make those 2 work. Where and how you get them to sync up does not matter so long as the spark sequence is correct for the valve timing . many of the procedures are just formalities to help techs. Like lining up the #1 lug on the dist. to the #1 cylinder. It does not matter it makes it easier. You can set up a distributor to the 3 cylinder if you can find out when and where the rest of the sequence of events fall into place. ( not saying you can alter the firing order)

 

That is correct. It wouldn't budge 180 out, but it would move quite well anywhere between TDC and ~ 45* and, as some often do, you can noodle with the timing and the carburetor in an "attempt" to compensate and that engine to many daily drivers would never even be notice, I would argue. Yet, if all the fuel does not ignite at TDC, fuel will continue to burn well into the exhaust and cause an overheating condition - the one I am arguing for. At speed, this would be minimal/negligible as the heat would be rapidly dissipated. At idle, you would run into an overheated state for the lack of heat dissipation. That's essentially my argument.

 

Copper, I'm spot-on with that reasoning - no issues. Yet, timing is more than when the spark arrives, it is also the 'duration' of the burn and the voltage of the spark arriving within the cylinder.

 

"The dwell is adjusted by setting the points gap to a specified distance at maximum opening. A narrower gap gives more dwell and a wider gap gives less. Taking it to extremes, excessive dwell means that the points close too soon after opening, cutting off the magnetic field collapse before the charged coil delivers all its energy. Too little dwell gives the magnetic flux (coil charge) insufficient time to build up to maximum."

Yes we agree with that, fans do little to nothing at hwy speeds, a fan comes into play to supplement the lack of airflow at low speeds. The reason we were going through the ignition circuit first is because the op described his issue as something that came on out of the ordinary in previous threads. Apparently that is not the case based on his ignition settings as pointed out above.

 

I agree with that but that's not the issue he is having. he would have had driveability issues if he had a weak spark due to improper dwell. Even if the dwell was off you still have a spark occurring when you need it so combustion still happens its just not an efficient combustion and will lack power and driving issues. Now if the timing was rearded then you would get what you mentioned where the fuel reignited on its way out and it overheats but that happens fast when it does.

 

I will argue the fans not working at crusing speeds. I tried that on my olds. Fans off 200. fans on while crusing 180. Just my experience.

 

I may not have said it the same as yourself, but I agree with you completely. What I would like to suggest or to get confirmed however (and, since you're referring back to points [so-to-speak]) is this. In a conventional breaker points/distributor the breaker points open and close specifically with the rotation of the lobes contained on the distributor shaft. The "lobes" contained on the distributor shaft are in direct correlation to the amount of degrees the cam rotates, the pistons move up/down, and the valves open/close. The 'firing' of the (again, we'll simply refer to breaker points even though this is handled by the HEI module) high voltage to supply energy is based firstly upon the degrees which the cam rotates. In either a conventional breaker points setup or an HEI setup, the delta is simply the nominal degrees of dwell time remains the same in conventional breaker points as engine RPM increases while an HEI setup the degrees of dwell time increases with an increase in RPM.

 

 

OK. So, I'll concede the distributor is probably established in the correct position/orientation. I'm going to lunge forward with my only wild-card. I have been reading this thread with some diligence. I still think it's timing and not air flow and I still think it is retarded.

Therefore, since I injected my angst/haste into this conversation, we have not heard back from the OP regarding Eric's suggestion to employ manifold vacuum instead of ported from the carburetor. Employing manifold vacuum should provide constant vacuum and increase the timing providing a cooler running engine at idle.

 

Because when the fans were off the blades were actually impeding airflow, with them on not so much.



The shaft in the distributor is driven by the cam which operates the valves, which is driven by the crank shaft that moves the pistons, all three are mechanically timed to each other. There are 8 lobes on the distributor shaft equal distance to each other. Again, dwell is the amount of time the points remain closed, and timing is the at what point in the piston stroke your spark ignites the fuel charge to get efficient power and a complete clean burn.

 

When you put it that way eric then yes I agree.

 

Ok, I had major overheating issues when I ran my 403. That Griffin rad should be good with dual 1.25" cores, people have leak issues with them, not cooling issues. What water pump and pulleys are you running? The bigger A/C crank pulleys turn the water pump faster. I ran an under drive pulley, it made things worse. A closed impeller pump may help but didn't help me. Also what thermostat? I used a Mr Gasket thermostat that felt like it was working at idle. Then as I drove it began to close. It got so I drove insanely fast or it would hit 250 degrees. Also what amps does your Derale fan pull? I see they are no longer US made but some still draw nearly 50 amps. You should be able to hear your fans come on, I can with headers and fairly loud 2.5" exhaust. The factory Dodge Stratus fans I run pull more than 40 amps, a single 40 amp relay will not last with them, no matter what brand.

 

How about putting back what there in the first place and seeing if it is ok again?. A distributor swap results in overheating?, So go back to start, still overheating?, then another fault has also occurred. Back to running normally?, then the new setup is either faulty or incorrectly installed.

Roger.

 

Question: are the fans pullers or pushers and would that make a difference in this case?

 

[QUOTE=coppercutlass;1147983]I dont think you have a timing issue. Look more into your radiator and fans. How big are your fans and how big is your radiator. I learned this a few years ago on CFM and area coverage /QUOTE]

The cooling system is how it was when I bought the car about 5 years ago. It has a large Griffin alloy radiator and has a large Derales single puller fan (engine bay side) as well as the fan controller.As nothng has been changed, apart from the local mechanic changing the thermostat and I can see/hear the fan running when it should it is not a matter of too small a fan for instance as the system has worked fine for a long time.

 

Dwell is purely a function of the HEI module and as such is not adjustable in any way. This is true of all HEI modules as far as I know.

 

[QUOTE=Sarum;1150119]I suggest you try Eric's suggestion in Post #14.... hooking up the vacuum advance to manifold vacuum.

 

Hi Roger, The reason I replaced the original HEI distributor was because it jammed up on itself and stopped functioning so I can't go right back to where I started from.

However I think it is worthwhile having a pause and listing what I do and don't know.

Parts Replaced
Thermostat
Water pump
Coolant - lots and lots of it.
Fan controller and relay swapped out - no change so am going to swap back again shortly

Other stuff
Water pump drive belt checked for tension
Water hose put into the thermostat area to check that water was able to come out the bottom of the engine
Water hose put into top of radiator and checked to see what sort of flow came out the bottom.
Fan controller and relay checked for operation at correct temps as well as manually switching fan on.

1) The temp gauge sender is in the block and as I can see temperature drops at highway speeds on the gauge I have to assume that the new water pump is doing its job and water is circulating i.e passing through the radiator and back to the engine with lower temp coolant.
2) There is no fault with the fan controller or relay
3) When I hear the relay activate the fan can be heard running normally.
4) No difference when fan was switched on manually during slow speed driving, the engine temp would continue to rise.

NEXT STEP As far as the next step is concerned I am going to swap out the Pertronix multiple spark producing HEI module with a known good 4 pin standard module and see what happens.

 

Yes, I agree with what you are saying but before I order a head gasket leak test kit I am going to swap out the Pertronix module with a standard one as the Pertronix component is the only thing that has some "computer magic" going on.I hope this is the cause as I am running out of options fast.
One of the other things that got changed about the same time was the PCV system - changed out to SS braided hose and a catch tank installed.
The last thing I did was to rehash all of the vacuum lines again with SS braided hose, install a multi port block with a vacuum gauge and another gauge under the dash. The vacuum line feed for the distributor comes straight off a port on the intake manifold and is stand alone.

 

What thermostat was used? I would try pulling it, I eliminated low speed overheating by removing it. The Mr Gasket thermostat was a POS, it got even worse at speed. I went to a Robert Shaw high flow thermostat and it improved things a lot. Do you know how cfm that fan puts out? Does it cover the whole rad?

 

Leave the vacuum pick up alone (if it was there in the firest place) until you have run through the rest of your checks. But once you have found and rectified the overheating issue I strongly agree with Eric. Put the vacuum pick up on to a ported source.

Roger.