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Engine setting issue
https://slantsix.org/forum/viewtopic.php?t=54282		 Page 1 of 2
Author:  ILMopars [ Fri Jan 10, 2014 6:50 am ]
Post subject:  Engine setting issue
Here's the deal: I have my 225 and I set to exact factory specs ( TDC, 650 in N w/ high beams on, engine at operating temp, lash set correctly). Now, engine pops and misses and only pulls 15"hg. Needle quivers, blip the throttle and it goes to 0, then 20-21 and back to 13 and slowly goes to 15 again. If I increase the idle speed to improve the vacuum it goes to 1100. However at 1100 it is too high for smooth trans engagement. So, what can I do to get the idle at 650-700 and have vacuum of 18-19?

Add'l info: uses 91-93 octane, 100psi on all cylinders, new plugs and wires and cap, 45amp charging system w/ 1240CA battery, no PB, no PS, no AC.
Author:  DusterIdiot [ Fri Jan 10, 2014 8:01 am ]
Post subject:  What about?
How's the valve lash?

Here are some vacc. gauge readings, I would suggest getting a petersen guide (per Dan) that should have a page with this and more illustrations on reading the vacc. gauge.

http://www.freeasestudyguides.com/graph ... adings.gif

http://www.gregsengine.com/using-a-vacuum-gauge.html

-D.Idiot
Author:  ILMopars [ Fri Jan 10, 2014 4:33 pm ]
Post subject: 
I know how to read a vacuum guage. The lash is set to FSM specs.
Author:  Doc [ Fri Jan 10, 2014 4:40 pm ]
Post subject: 
Try going looser on the lash... especially the exhaust lash.
Doing that tends to improve vacuum and can smooth-out the idle.
DD
Author:  Aggressive Ted [ Fri Jan 10, 2014 6:05 pm ]
Post subject: 
I would never run zero degrees on a 70 engine.
A 74 maybe since the distributor is way different. But even on a 74 I would run 5 or 6 degrees minimum. It will be a dog at zero degrees....ask me how I know? I got one......been there done that......until Doc woke me up to what was going on....

If you go up to 10 or 12 degrees initial you will see 18 to 19" vacuum and feel some spunk! Do what Doc says.....longer lash on the exhaust brings up the readings and the torque and the mileage. .012 and .022 at least....
Author:  ILMopars [ Fri Jan 10, 2014 6:08 pm ]
Post subject: 
Ok will do. But has to wait until the 19 when I get back.
Author:  ILMopars [ Fri Jan 10, 2014 6:48 pm ]
Post subject: 
Just curious, what is the issue running TDC if it is the spec? What problems does this cause? In other words what has changed since 1970 to make the 225 run different timing?
Author:  Aggressive Ted [ Fri Jan 10, 2014 9:14 pm ]
Post subject: 
Quote:
Just curious, what is the issue running TDC if it is the spec? What problems does this cause? In other words what has changed since 1970 to make the 225 run different timing?
There have been several different distributor curves and vacuum advance changes to get more power and mileage since 1970.

The 1970 advance is very limited. At 2000 rpm you only get 12 to 14 degrees mechanical and the vacuum advance is only adding 5 to 7 degrees at 16". So if initial is at zero your getting about 21 degrees at 2000 rpm when your at 16". That would be fine for a truck pulling a heavy load.

As a comparison at 2000 rpm I am at 50 degrees. Worst mileage on short 4 mile hops is 22 mpg. It only gets better the longer the drive on up to 25+ mpg mainly being limited to the heavy weight of my car and the square boxy body of a 74 Swinger.

The idle will pop and fart and not be very smooth at zero degrees plus you get run at shut off when it is hot out. In other words the engine acts like a tired dog. Not that much fun to drive.....no wonder old folks never went much over 35 mph in the old Valiants. My Swinger used to ping so bad when I first got it and ran stock timing....it was sad. :cry:

After coming this site and getting an ear full of good tips from Doc, DI, CJ, Reed and others, my old engine really woke up! :D
Author:  DusterIdiot [ Fri Jan 10, 2014 9:40 pm ]
Post subject:  Yep...
Quote:
Just curious, what is the issue running TDC if it is the spec? What problems does this cause? In other words what has changed since 1970 to make the 225 run different timing?
A lot has changed, we no longer have leaded gas, and unless you are running non-ethanol super (a waste of money on a stock engine), the current gasoline is "watered down"...

The spec is to meet emission standards at the time, it is not tailored for power, and is not tailored for max. mileage potential....

Ted has stated, using some timing improvements the slant will wake up...

The reason to run more initial, allows for the lazy low compression engine to light the fire early on the mix in the chamber...giving it time to complete it's burn across the cylinder face and chamber and actually get a more complete burn (also hopefully building a little more pressure sooner), modern engines use other tricks unavailable to us in a stock plug and play format to help make the burn more complete (more turbulence in the air/fuel mix from swirl ports, more squish from quench heads, better atomization and uniform distribution from EFI)...In 1976 mopar was trying to find better ways to get their power back after smog laws strangled engines on the market...one way to combat it, was to use a shorter advance and more initial timing...The slant was never intended to be a performance engine, but it reacts like any of mopar's other blocks to the same kind of power tuning (especially ignition and timing).

We are now at a point where our knowledge has gone far beyond what the mopar engineers expected and attained with this engine...so literally we are writing our own specs as we figure out that some simple improvements out shadow a set of outdated points and heavy springs from 40 years back...

The spec will get you by for now, but there is much more potential that is not being utilized with the stock curve.

-D.Idiot
Author:  69a100 [ Sat Jan 11, 2014 8:09 am ]
Post subject: 
Just because the book calls for something doesn't mean that that's where the engine runs best or where you should put it. You need to dial in a motor to what it wants and where it runs the best and is the happiest. It is what it is.
Author:  ILMopars [ Sat Jan 11, 2014 2:29 pm ]
Post subject: 
I run E-10 93 octane most of the time, sometimes 100% gasoline 91 octane, and 100 octane rarely. Fuel used to be 10 cents between each grade, now it's 20 cents. From what I understand, regular in 1970 was 90 octane, premium was 104, and Super Premium was 110 octane. However, I understand it was not under the same R+M/2 method. So what fuel is best for a 225 with stock timing (TDC), and what is best for your recommendation of 10-12° BTC?

I'm asking because I get about 300-320 miles per tank, which seems low. I want at least 400 miles per tank.
Author:  wjajr [ Sun Jan 12, 2014 8:06 am ]
Post subject: 
I want at least 400 miles per tank.


Low tech solution:
I'd be looking for a larger tank. LOL
Author:  DusterIdiot [ Sun Jan 12, 2014 10:15 am ]
Post subject:  Lol...
Quote:
Low tech solution:
I'd be looking for a larger tank. LOL
Sadly, mopar only used one style of tank for the A-body (with emission tubing variations)...Depending on the filler neck the tank could have the capacity of (18 gallons- 1967 A-body...16 gallons Early 70's A-body...14 gallons for 1976 Feather Duster/Dart Lite)...
Quote:
I want at least 400 miles per tank.
Sadly because of EPA the pumps tend to be finicky about our old gas tanks and tend to "click off" sooner than expected and not fill the tank 100%...Now technically if his Dart had the 18 gallon filler neck, and actually filled the tank...400/18=22.2 mpg....this is easily achievable by a stock slant doing 100% highway driving, assuming that the engine is in good shape... I would say the not so low tech approach would be to rebuild the engine and head to make a mileage/torque build, then recurve the distributor for mileage, and that may put the car in the 24-25 mpg range...

Realistically I think he's up against 400/16=25 and will need to pencil out a better setup...
Quote:
From what I understand, regular in 1970 was 90 octane, premium was 104, and Super Premium was 110 octane.
This varied depending on the part of the country you were in, Here in Oregon "Ethyl' was 108..then when unleaded was offered in the early 70's
Ehtyl pumps only got 104 for a while...about the late 70's we only got 87/89/92 out of the pumps (anyone on the East coast remember Sunoco "260"?. The octane number is only an index of the fuel's ability to combat knock in a certain type of test engine (typically it's a 1 cylinder at a specific compression, running a lot of timing)...It is not an indicator of the amount of energy that could be utilized from the blend during a perfect burn....(alcohol has a higher knock index, but only has about 80-90% of the energy that gasoline does...so with E10 on an old car with less compression than the modern cars, expect to lose about 5-10% of the mpg the car may have gotten back in the day).

I would only run 87/89 E-10 in an older car and recurve the distributor, if the engine was new and I went hogwild on the distributor recurve but the cost justified the gains in mileage then I would run super (92), anything higher than 92 is a waste in an 8:1 SCR engine.

2 cents,

-D.Idiot
Author:  '67 Dart 270 [ Sun Jan 12, 2014 5:53 pm ]
Post subject:  octane...
I run only 91 or better, I've tried some "low test" gas a few times, and I get some dieseling at shut off. The slant runs absolutely perfectly on the premium, it doesn't like lower octane gas. Might be the compression, the head and deck have been milled more than a few times. I'll run a compression check eventually, but she definitely doesn't like low octane...
Author:  ILMopars [ Mon Jan 13, 2014 7:32 am ]
Post subject: 
The gas pumps I use never click off too early, they click off after gas burps out all over my paint. Mine is the 18 gallon tank.
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