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Fuel/Heat Distribution Problem
https://slantsix.org/forum/viewtopic.php?t=36398		 Page 1 of 2
Author:  SV162 [ Tue Jul 21, 2009 9:48 pm ]
Post subject:  Fuel/Heat Distribution Problem
Does anyone elses engine suffer from fuel/heat distribution issues?

Here's my problem.

I have an ongoing issue with my number 6 and number 1 plug running rich, or at least having the appearance of running rich(#6 black and sooty and #1 dark brown) with the other 4 plugs perfect(white to light tan).
If I go for a long drive and get up to a good running temp number 1 will look like the middle 4 plugs and number 6 will be dark brown/black with a tan ring around the top of the porcelain. If I go for a really long drive I can get number 6 to a brown/tan colour.

Now this does not effect how the engine runs, it used to cause a missfire but the addition of a Crane Hi-6 ignition fixed that, it's just really annoying because I can't fix it.

It seems to me that the number six plug can't get to it's "self cleaning temp". I've been told that the 2 end cylinders run cooler than the middle 4, particularly number 6....???? I have noticed on one occasion when I removed my plugs to check them I could hold the number 6 plug in my hand but there's no chance I could hold any of the others, they were still too hot.

I've also been told that Slant 6s do suffer from uneven fuel distribution, but I've seen other engines plugs and although some do have differing color, they're not as extreme as mine.

This issue has happened with different carb/intake/engine configurations. The only constant being the engine block.

I think it's a fuel/heat related issue but I just don't know for sure. Would a hotter plug in the 2 end cylinders fix this?? Or would that lead to other problems?

Any advice is appreciated.
Cheers, Jon.
Author:  wjajr [ Wed Jul 22, 2009 4:01 am ]
Post subject: 
I run a hotter plug in number 1 & 6 than the other four. All six plugs look to be the same color. I don't drive this car much, just a few thousand miles a year.
Author:  66aCUDA [ Wed Jul 22, 2009 5:07 am ]
Post subject: 
WOW I had not even thought of that. Cool idea! thanks for sharing.
Frank
Author:  Charrlie_S [ Wed Jul 22, 2009 5:47 am ]
Post subject: 
If you are running a stock exhaust manifold, make sure the manifold heat riser is operating properly.
Author:  Aggressive Ted [ Wed Jul 22, 2009 3:27 pm ]
Post subject: 
Jon,

My 225 used to run like that even after I increased the compression from 7.5 to 9.5 to one. The #1 and 6 plug's running that dark really got me mad but got me to thinking about better heat distribution.

1. So I got rid of the stock fan and installed an electric fan,
2. used a 210 degree switch,
3. installed a heat deflector to keep the number one runner warm and the carb from boiling over,
4. installed a aluminum intake.
5. a 195 degree Super Stat,
6. pulled the heat riser out which helped even out the plug color the most,
7. installed water injection
8. installed a MSD Blaster 2 coil
9. and the single .85 ohm resistor which provides a full 10 volts to the coil at 600 rpm idle, instead of the dual ballast that only put out 4.5 volts to the coil.

Take a look at the red link below my name then click on the picture to put it into full slide show mode.

Notice my plugs have been in there for a long time and are all running a very light tan/beige color. So the combination works. I kept at it making the changes in the list until the engine began to run correctly. It makes awesome power and the idle is extremely consistent with out the HEI mod or Capacitive Discharge upgrade.

The mileage also went way up for both city and freeway. :D :!:
Author:  SV162 [ Wed Jul 22, 2009 6:33 pm ]
Post subject: 
Thanks for the replys. It's nice to know I'm not alone with this.

I'll try a hotter plug in the end cylinders and see how that goes.

Just to address a couple of the points you guys made here's a "cut and paste" of my current engine build.
238cid Slant 6, 3.5" pistons
Rollmaster dual row timing chain
Head shaved 0.100" and ported and pollished with Ford 302W inlet and exhaust valves with heavy duty springs, retainers etc.
Cam specs .295"(cam lift)@ 280deg Exh .295"(cam lift)@ 270deg. I think .295" cam lift equates to about .445" valve lift(not 100% on that)
Block decked(a little bit)
390 4BBL Holley on a Cain aluminium intake
Genie headers
USA style high volume oil pump
Crane Hi-6 ignition triggered by Pertronix Ignitor
CVR high torque starter

Compression ratio hasn't been calculated yet, the new head has only been on for a week. The higher compression has definitely cleaned up the plugs in the front 5 cylinders, and to some extent number 6 is cleaner than it was with the old lower comp head.

Thanks again guys.

P.S. Ted, I can't see any of your photos in the link ????
EDIT: I can see the pics now :) I like your Dart Ted, very nice.
Author:  SV162 [ Mon Jul 27, 2009 11:17 pm ]
Post subject: 
Just following up on this.
I'm now running a hotter plug in number 1 and 6 cylinders. Plug in number 1 now has the same color as the middle 4, and the plug in number 6 is not the same as the rest but a lot cleaner than it was. I'm thinking things will get better once we get into some warmer weather over here.
Author:  FrankRaso [ Tue Jul 28, 2009 10:03 am ]
Post subject: 
Since you are running headers, there is no hot spot under the carburetor which allows liquid gasoline to flow along the intake manifold's floor. Since #6 cylinder is the lowest, it makes sense that much of the liquid fuel flows to this cylinder which then causes it to run rich. As confirmed by Ted, removing the manifold heat control valve makes the most difference because the intake manifold now receives full exhaust heat. Any fuel that falls out of the air stream below the carburetor becomes vaporized when it hits the intake manifold's floor.

Changing to a hotter plug does not cure the problem. It just compensates for the over-rich condition.

Intake Manifold Heat
Author:  Aggressive Ted [ Tue Jul 28, 2009 10:25 am ]
Post subject: 
Frank,

Nice article!

To add to this, by removing the heat control valve you not only get great manifold heat immediately after fire up, but by running a aluminum manifold it heats up even faster. Not having the stock fan spinning is another plus. By not having air blowing over the intake it heats up even faster.......another good point to running a electric fan.

First thing in the morning my engine is significantly more drivable and peppier, not sluggish like it was before until it warmed up.
Author:  wjajr [ Tue Jul 28, 2009 11:21 am ]
Post subject: 
SV162,

Two more cents...

A few photos of my carburetor ice prone Clifford Intake that caused all kinds of drivability & poor fuel economy problems before I made a Rasco knock-off hydronic hot spot. The car was un drivable under 35 degrees last fall suffering from carburetor icing, and was getting about nine miles per gallon.

I just pulled a few spark plugs as this thread has captured my interest to see how my old crate is combusting with the hot spot rigged up. I have driven about 1500 miles on these new plugs. Plug #1 & 6 are hotter than the other four: #1- slight reddish tan with a bit more build up; #2- light tan; #5 light tan; #6- slightly darker light tan. In all cases the white porcelain can be detected under the tan deposits. My Holley 390 primaries are mounted forward of the manifold center line.

Image
Here a home made hot from two strata of 1/2" aluminum stock, and two brass fittings I got at a hardware store.

Image
Heater hose connected to brass fittings.

Image
Installed on engine, spliced into the heater loop, sorry dosn't show much.
Author:  Aggressive Ted [ Tue Jul 28, 2009 11:36 am ]
Post subject: 
wjajr,

Nice work!
How is the mileage now?
Author:  SV162 [ Tue Jul 28, 2009 6:46 pm ]
Post subject: 
Thanks for the link Frank, that is a good article. And thanks for pics and run down of your setup wjajr.

I can see that I'm dealing with two problems, but both are dependent on the same thing, engine temp. If the engine is running warmer then the intake is warmer helping to vapourise the fuel, and the spark plugs will run warmer helping them to self clean. Does that make sense??

Like I said in my earlier post, I'll wait till the weather warms up and things will improve. Through most of the year where I am there is no need for manifold heating or chokes because overnight temps don't get below 12*C (55*F). Having said that, I will look into manifold heating because I'm always looking at ways of improving the drivablity of my car.
Author:  FrankRaso [ Tue Jul 28, 2009 8:31 pm ]
Post subject: 
Intake manifold heat is useful all year because the vaporisation of gasoline produces a refrigeration effect. You should experience better drivability with an intake manifold hot spot even in hot summer temperatures.
Author:  wjajr [ Wed Jul 29, 2009 4:49 am ]
Post subject: 
Aggressive Ted:
Quote:
How is the mileage now?
I haven't been fastidious with the fuel mileage note keeping; after all, it is only gas. I did check a few times where I rolled on a few hundred miles in a single day traveling to shows, and it was 19 to 20 mpg. Not as good as some of the others on the board, I suspect my cam has a something to do with the lower mpg. A small price to pay when most people mistaken that loping idle, while cruising into a car show, for that of a 340...LAL When I open the hood, priceless.

Oh, one other note; I run a 180 or 185 degree thermostat. Sorry, can't find a note listing that bit of info, must have been on an unauthorized floater.
Author:  Aggressive Ted [ Wed Jul 29, 2009 12:52 pm ]
Post subject: 
wjajr,

Very good! Sounds like your hot spot adapter works!

Hopefully some day you will figure out what cam you have in there....... :D
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