AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,917
- Reaction score
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When you start advancing the idle-timing, don't be surprised if she likes over 40 degrees.
What will happen, as you begin adding timing, is that the idle rpm will go up. So then you will want to back off the speed screw, but doing so will reduce the fuel coming from the Transfer slots, making her idle lean. So then you will crank OUT the Idle mixture screws to get the missing fuel.
So now it idles.
But if you keep going this way, eventually, you will run into two things;
1) you will get a tip-in sag, which is a momentary hesitation, caused by the transfers being too lean. and
2) the extra Idle timing will show up as too much idle power, and if the stall speed is close to stock, then it will bang the trans ever harder on the N/P to in-gear shift.
So when you see these things happening realize what is going on, and back up the timing.
Now, I gotta tell ya, by trying to solve an overheating issue with idle-timing and mixture screws, you are, IMO, trying to bandaid a bad situation. I can tell you that I have had three different cams in my Eddie-headed 11/1, 367, and they all ran just fine right down to 5* of Idle-advance. The biggest cam was the 292/292/108 Mopar. This cam was tried, Installed from 4* retarded to 8* advanced, and she was still good down to 5*ignition advance. The next cam was a 270/276/110 (My Favorite), in straight up, and the current cam is a 276/286/110 in at 4* advanced.
I run a Commando 4-speed with 3.55s and the only way to drive it, at under 4mph, is to idle it down to 550/500, and the only way to do this and have her still pulling herself is to reduce the timing to 5* or less.
She will idle all-day on that, without any sign of overheating.
Therefore,
IMO,
it is foolishness to attempt to solve this overheat problem using ignition timing, and/or Idle AFR,
Especially in light of the statement, that the engine was fine with the iron heads, that just came off it.
IDK what your engine's problem is gonna turn out to be,
but if I was a betting man, as it stands, with no other changes from the iron heads,
Timing and idle-AFR are NOT gonna solve it. Band-aid it maybe, but not very good ones.
Did you IR gun check your rad yet , looking for a 30*F temp drop from top to bottom? This is the only way to check the efficiency of your system at Idle.
Also, if you're gonna start fooling with the timing, you better start with knowing exactly where TDC *1 cylinder is.
When I have a Hard-to-solve problem like this; I do this;
I dump whatever is in the cooling system out, and install straight water.
I remove the thermostat, and install a restrictor washer in it's place.
I install a big direct-drive fan, with 7 fixed, all-steel blades.
I reach over to the distributor, and without regard to any specific timing number, I start cranking timing in, a few degrees atta time, until additional timing, produces no additional rpm, then I retard the timing just a tad.
If the rpm climbs over 1000, then I back up the speed screw down to 800, and readjust the mixture screws as may be necessary.
I leave the hood open.
I step back and wait.
At regular intervals, I check the water temp by IR Gun, top to bottom, looking for ~30*F difference.
You cannot get a more ideal situation than this.
If the engine still overheats;
she has either a water circulation issue, or a mechanical issue.
AS for circulation:
I cool the rad by spraying a heavy mist onto the fins, back to an acceptable temp. At this time the direct-drive fan should be pumping that water-laden air out the back of it, and all over your engine. Obviously, if the air is going the other way, something is dead-wrong.
So once the temp is back down, and well below the boiling point of straight water, the next thing I want to know is; is the water circulating?
I shut off the engine. I remove the top hose off the rad and shove a pipe in it, to redirect the water to "down". I cap the spigot and open the cap. I install my shop water hose into the water neck, turn it on, then start her up. Water should almost immediately begin to gush out of the top-hose. The lower hose should NOT be sucked flat. The shop hose should be just barely keeping up at wide open. The coolant temperature should be falling. Depending on the size of the restrictor I installed, the temp could fall to below 160. This is how it should work.
If it does not work like this, Now I gotta figure out, the why of it.
And the First thing Ima gonna check is how fast the water runs thru the rad. And the Second thing I'm gonna look at, is the Bottom hose, making sure that there is no shoprag in it!, and none in the WP inlet either....
Next is to make sure the WP is turning in the correct rotation
If all of this, by some miracle turns out to be fine, then there are just about two things left, those brand new heads are not circulating properly; or that engine is generating a chitload of friction, which in your case we can likely rule out, because it ran fine with iron heads.
AS for a mechanical issue;
I just gotta ask; is hot air coming out of BOTH tailpipes..... and
If you are running Log manifolds, is there a chance that something got into the exhaust system during the head-swap, and plugged the mufflers?
The reason I ask is because, with log-manifolds, and a restricted exhaust system, the exhaust from one cylinder can easily be re-routed into a nearby cylinder, that is on it's overlap cycle, and may even travel up into the intake manifold. This can happen 4 times per revolution, 3200 times per minute at 800rpm......... Now imagine your engine sucking that hot air down, that only a few inches away and less than two seconds ago, was at 350>450 *F.
What will happen, as you begin adding timing, is that the idle rpm will go up. So then you will want to back off the speed screw, but doing so will reduce the fuel coming from the Transfer slots, making her idle lean. So then you will crank OUT the Idle mixture screws to get the missing fuel.
So now it idles.
But if you keep going this way, eventually, you will run into two things;
1) you will get a tip-in sag, which is a momentary hesitation, caused by the transfers being too lean. and
2) the extra Idle timing will show up as too much idle power, and if the stall speed is close to stock, then it will bang the trans ever harder on the N/P to in-gear shift.
So when you see these things happening realize what is going on, and back up the timing.
Now, I gotta tell ya, by trying to solve an overheating issue with idle-timing and mixture screws, you are, IMO, trying to bandaid a bad situation. I can tell you that I have had three different cams in my Eddie-headed 11/1, 367, and they all ran just fine right down to 5* of Idle-advance. The biggest cam was the 292/292/108 Mopar. This cam was tried, Installed from 4* retarded to 8* advanced, and she was still good down to 5*ignition advance. The next cam was a 270/276/110 (My Favorite), in straight up, and the current cam is a 276/286/110 in at 4* advanced.
I run a Commando 4-speed with 3.55s and the only way to drive it, at under 4mph, is to idle it down to 550/500, and the only way to do this and have her still pulling herself is to reduce the timing to 5* or less.
She will idle all-day on that, without any sign of overheating.
Therefore,
IMO,
it is foolishness to attempt to solve this overheat problem using ignition timing, and/or Idle AFR,
Especially in light of the statement, that the engine was fine with the iron heads, that just came off it.
IDK what your engine's problem is gonna turn out to be,
but if I was a betting man, as it stands, with no other changes from the iron heads,
Timing and idle-AFR are NOT gonna solve it. Band-aid it maybe, but not very good ones.
Did you IR gun check your rad yet , looking for a 30*F temp drop from top to bottom? This is the only way to check the efficiency of your system at Idle.
Also, if you're gonna start fooling with the timing, you better start with knowing exactly where TDC *1 cylinder is.
When I have a Hard-to-solve problem like this; I do this;
I dump whatever is in the cooling system out, and install straight water.
I remove the thermostat, and install a restrictor washer in it's place.
I install a big direct-drive fan, with 7 fixed, all-steel blades.
I reach over to the distributor, and without regard to any specific timing number, I start cranking timing in, a few degrees atta time, until additional timing, produces no additional rpm, then I retard the timing just a tad.
If the rpm climbs over 1000, then I back up the speed screw down to 800, and readjust the mixture screws as may be necessary.
I leave the hood open.
I step back and wait.
At regular intervals, I check the water temp by IR Gun, top to bottom, looking for ~30*F difference.
You cannot get a more ideal situation than this.
If the engine still overheats;
she has either a water circulation issue, or a mechanical issue.
AS for circulation:
I cool the rad by spraying a heavy mist onto the fins, back to an acceptable temp. At this time the direct-drive fan should be pumping that water-laden air out the back of it, and all over your engine. Obviously, if the air is going the other way, something is dead-wrong.
So once the temp is back down, and well below the boiling point of straight water, the next thing I want to know is; is the water circulating?
I shut off the engine. I remove the top hose off the rad and shove a pipe in it, to redirect the water to "down". I cap the spigot and open the cap. I install my shop water hose into the water neck, turn it on, then start her up. Water should almost immediately begin to gush out of the top-hose. The lower hose should NOT be sucked flat. The shop hose should be just barely keeping up at wide open. The coolant temperature should be falling. Depending on the size of the restrictor I installed, the temp could fall to below 160. This is how it should work.
If it does not work like this, Now I gotta figure out, the why of it.
And the First thing Ima gonna check is how fast the water runs thru the rad. And the Second thing I'm gonna look at, is the Bottom hose, making sure that there is no shoprag in it!, and none in the WP inlet either....
Next is to make sure the WP is turning in the correct rotation
If all of this, by some miracle turns out to be fine, then there are just about two things left, those brand new heads are not circulating properly; or that engine is generating a chitload of friction, which in your case we can likely rule out, because it ran fine with iron heads.
AS for a mechanical issue;
I just gotta ask; is hot air coming out of BOTH tailpipes..... and
If you are running Log manifolds, is there a chance that something got into the exhaust system during the head-swap, and plugged the mufflers?
The reason I ask is because, with log-manifolds, and a restricted exhaust system, the exhaust from one cylinder can easily be re-routed into a nearby cylinder, that is on it's overlap cycle, and may even travel up into the intake manifold. This can happen 4 times per revolution, 3200 times per minute at 800rpm......... Now imagine your engine sucking that hot air down, that only a few inches away and less than two seconds ago, was at 350>450 *F.
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