MPG experiment, 1976 Dart Lite

[Backtobasics]

My head is spinning now. I wish one of you pros lived closer, cause despite a solid competitency in automotive, a great deal of what you speak of with the timing I just don't understand.
I do not have a 76 factory service manual.
The "vacuum amplifier" and governor, is beyond my knowledge, I guess I should post up good pictures at org, and let you pros pick it over.
I will call some of the speed shops to see if anyone has a distributor machine.

Mine has alum hood, intake and bumper supports. Trunk is all steel, and does not appear to be replace at any point, the color and fade matches the rest of the car.

[Backtobasics]

I presume the timing chain swap is a "line up the dots" kind of deal?

[Will]

Nice thread. This is really cool to see this kind of build on a car from 1976. That car is older than most people on this site. I love it!!!! No school like old school.

[ALS]

Originally Posted by Will

Nice thread. This is really cool to see this kind of build on a car from 1976. That car is older than most people on this site. I love it!!!! No school like old school.

Tell me about. If I was under six foot I would be trying to stuff a 2.0L TDI
into a 1974 SAAB Sonett III.

Can you say at least 80 mpg highway. The car weighs in at 1800 lbs and has a .32 Cd.

[ceej]

Dot to Dot is going to get you in the ball park. Just make sure to line them up before taking things apart, then don't disturb the engine. Sometimes dot to dot is #1, other times #6. It doesn't matter which as long as it goes together the same as it came apart.
The Feather and Lite used the MP 244 cam. It was the "Marine Cam" prior to 1971, then became the OEM stock mechanical cam up until the hydraulic engines became standard. The stock cam that came in these cars is excellent.
Other good choices for a a cam would be the Erson RV10M, the RV15M, and a special RV15M RDP designed by Doug Dutra. Erson will do custom grinds to order, as will comp cams and many others. Some folks have found issues with Comp Cams blanks where the timed oiling passage doesn't match up to the cam bearing passages. There are methods for fixing this. It's a darn good idea to check in any event! If the passage isn't properly alligned, there will be top end oiling issues.
I haven't heard of any issues with the OEM or Erson offerings.
I run the Erson RV15M RDP straight up. It is actually advanced about 3° from the cam card, which matches up to the regular RV15M rather than the RDP lobe center. The cam in question carries 110° lobe centers.
Degreeing in requires a degree wheel. You will need a piston stop, or preferrably, head removal, which is the best way to do it. Once top dead center has been identified, and the degree wheel set, a dial indicator is placed on the intake lifter to determine when the cam event is occuring at .050" lobe Lift. This is easiest to do with a "Special" Tall Lifter that can be built with a flat upper face to indicate to.
Finding top dead center will also allow you to mark the balancer accurately if the outer ring has slipped. This is common, and a lot of folks end up setting timing based on a mark that is in the wrong place.

It is more difficult to do with the head on, but not impossible. It is important that valve train Geometry is correct. Varying thickness head gaskets and any head or deck cuts can change the angle of the pushrod, and thereby the amount of measured lift at the pushrod end of the rocker. Affixing the indicating device is also harder with the head on, depending on the type of indicator base you have available.

The reason degreeing the cam is important is there are variations in manufacturing of the timing sets, and to an extent, the accuracy of the cam grind. When buying a timing set, stick with good stuff, not bargain. Melling is "Good Stuff." A double row timing set can be used to improve accuracy, but there are oiling issues that need to be addressed. You can also go to a true roller chain setup, but they are very expensive, and not really needed for the engine speeds most slant sixes see. Make note of how everything comes off with the timing set. There is an oil deflector that is important to avoid flooding the front seal.
While some folks seem to think nothing of driving the lower timing set gear onto the crank, I strictly install with an installation tool. I don't like beating the snot out of my thrust bearings.

To test the timing chain to see if it's part of the problem, pull the cap and rotate the engine by hand till the rotor starts to turn. Stop, note where the crank is in reference to the timing mark, then rotate the engine the other direction. The rotor should start moving immediately. If you have to rotate the crank very far before the rotor starts to move, the chain is shot.

One of the most important tune up evolutions with the slant six is valve lash. If you find excessive noise, or more often, an exhaust miss, the lash likely needs to be addressed. As the lash tightens up, you will have a miss, and vacuum will not be good. Lash can be set static to start with, but to obtain best results, should be done with the engine running and up to full temperature.
Once you have a handle on setting to factory spec, there are further fine tuning methods that can be used to obtain best results. We can go into that later if you wish.

CJ

[Backtobasics]

1976 Dodge Dart Dart Lite Gas Mileage (Dart Lite) - EcoModder.com

I filled up Saturday afternoon.
I was no happy with results.
19.17 MPG (no correction factor for tire diameter difference of 3%)

My brother and I looked over underhood. PCV hose was unhooked, vacuum ports on carb had cracks, and the enitre carb was loose, the nuts had worked loose.
We cleaned up these hiccups, and adjusted idle down, and adjusted air fuel mixture screw for best idle. The car ran GREAT on the way home.

Sunday I checked oil and struck nothing. I park it over rocks, and I guess the leak is still significant. I swapped the valve cover gasket a while back, and it got better, but there must be something else. It was very low.

Ultimately, the MPG was very close to last time, and there were several factors counting against the MPG. With the vacuum leaks solved, idle and air fuel adjusted, plus full of oil, it should be a much happy camper.

[Superturnier]

I think changing the carburettor model from 1 barrel to 2 barrels would give some improvement in mpg.
Primary venturi could be small size as it it used mainly for cruising
Secondary venturi could be much bigger giving you power for the occasional accelerations.
My accelerator pump is not working, and it's not needed, because I have quite small primary venturi on my carburetor.
Smaller venturi atomizes fuel better on lower rpm.

[Backtobasics]

Originally Posted by Superturnier

I think changing the carburettor model from 1 barrel to 2 barrels would give some improvement in mpg.
Primary venturi could be small size as it it used mainly for cruising
Secondary venturi could be much bigger giving you power for the occasional accelerations.
My accelerator pump is not working, and it's not needed, because I have quite small primary venturi on my carburetor.
Smaller venturi atomizes fuel better on lower rpm.

I like the idea, but I am not aware of a commonly available carburetor in 2 barrel configuration that is spread bore, or said another way, small primary and large secondary. 4 barrel carbs can be had this way, and I have one waiting for later stages, that is configured this way. Do you know of a staggered 2 bbl carb?

[MechEngVT]

On the carburetor, I would agree a 2bbl stands to offer improvement. Wouldn't necessary say you want spread bore on a 2bbl though. As long as the primary isn't larger than your 1bbl and you can set up the secondary so that you're next to never opening it you can jet your primary a little leaner and use the richer secondary to fight ping at WOT. Fix your vacuum leaks and cracked hoses, then look at your idling. A "loose" lash setup is noisy but tends to increase idle speed independently of carburetor stop and idle jetting due to improved torque from reduced valve overlap.

Why drop a sought-after muscle car axle in? The 7.25 has a (undeserved IHMO) bad reputation, but that came from much heavier cars. I know a guy with a tube-frame, glass-bodied, blown 350 SBC T-bucket that's running a 7.25 he got for $25 because he needed "something" to get the car on the ground. He's still running it last I checked; the car weighs so little it breaks traction before it could possible break the axle. Your car isn't as light as his, but it isn't as wild as his either (he refuses to dyno but estimated 800 hp based on his jetting).

Anyway, even a truck 8.25 could work; I have one in a Ramcharger that's running 3.21 gears and I had heard a numerically lower gearset was available for that axle. Pre-84 should have the small bolt pattern your car has also.

Getting the timing set updated may help, but you might want to consider a new camshaft. I've seen older engines (305 chevy) wear down cam lobes to be visibly different than a "stock grind" replacement.

If you acknowledge blow-by and are losing oil without identifying a leak, look into a compression test and even a leak-down test. Figure out how badly worn your engine is; you might want to do a hone/re-ring or even an overbore to clean things up. Pull a plug and see if it's fouling also.

[Backtobasics]

I am going to jet the carb up tonight. Slant 6 pros seem to find that a 2-3 step up in jet flows enough to keep the carb out of the power valve, and gives better MPG. We adjusted air fuel to highest RPM and then adjusted idle screw down, it idles smooth as glass, and I can hardly hear it run.

The reason for the 8 3/4 is "tune ability" With the drop out center section, I can switch between the 3.23 and 3.55 center sections to see which give best overall results. The 7.25 is working, but whining, probably from old age. The 8 3/4 has the strength for the power adder down the road....

The cam is a concern, sounds like it might be past it prime. I don't really want to put a new cam in older motor, so I might put the cam into the new engine.

It had a fair amount of blow by without the PCV valve hooked up. With it hooked properly, there is no blowby coming out of the vent. It seems as if the PCV is actually doing it's job, creating positive crankcase ventilation, which should also help ring seal.
The oil loss is a leak for sure, I put a pan underneath, and it is leaking. I thought the leak was solved with the valve cover. I am suspecting the fuel pump, perhaps the gasket has failed.

In addition, this is an "enthusiast build" that wants to be efficient. I have a spare /6 that is getting a rebuild, ported head, windage tricks in oil pan to reduce drag, etc. This car will get the engine, a 4 speed OD trans, and 8 3/4 in a weekend swap. Once it is dialed in a bit, it is getting a Grand National turbo (231 CI vs 225 CI).

I will pull plugs tonight, and check out cap and rotor, that is a good idea.
THANKS FOR ALL THE INPUT!