Thread: 496 fouling plugs

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OK, am going crazy!!!! got a built 496 stroked engine runs great for about 6 miles or about 10 minutes of running. The plugs are completely carbon fouled. I went from a Holley 850 double pumper to a 750double pumper then to Edelbrock Easy Street EFI same thing. Change the plugs runs great then they foul Timing is at 16 bt I have been told to go to 12deg and some say 20deg am going nuts I just want to drive my car I have talked to Edelbrock and blue print engines still same thing. am at about 9200ft about sea level. running HEI with a MSD mod.

I don't think you're going crazy.. have you tested the fuel pump pressure? You may be pushing gas past the needle/seat.

OH, and welcome aboard CHR. We're a bunch of picture hounds so share some when you get'em..

Welcome to CHR!!

I looked through the instructions for the Edelbrock E Street system and it requires 50-60psi on the fuel feed, so that means you had to have installed their fuel supply system if it was running. The other thing I noticed is that the E-Street ECU does not control the engine spark (no spark map, no EFI distributor) but instead simply says "Set timing to OEM requirements". It's only a fuel controller, and seems to me that the only thing that could cause it to be running that rich is the wide band O2 sensor getting blinded by an exhaust leak, allowing ambient O2 to be sucked into the stream which would tell the ECU to dump in fuel. The E instructions are crystal clear about the importance of the exhaust system being leak free around the sensor.

If you're confident with the O2 sensor I'd concentrate on the ignition system, and verify that it's all good. I would think that you want your base timing to be around 12 degrees, and around 34 to 36 all in for the street. Two things come to mind - 1) are you changing out the plugs after they're fouled, or just cleaning them up and putting them back in?; and 2) have you verified that you don't have one of the counterfeit MSD units that flooded the market a while back - Counterfeit MSD 6AL Ignitions | Consumer Alert

yes I have there fuel system and it pushing 6o psi steady exhaust is good. the timing I have changed from 16 to 20 at idle if I go much low it does not like to idle to good. I was changing the plug but after 4 sets I just started using a machine and checking them but hand. Edelbrock said timing should be at 20 a racing friend said it should be at 12

Your at 9200 feet------------you need a much bigger carb to let in enough of that THIN air without getting into the secondaries, and some very finely tuned jets-The fuel system supply---go back to an engine driven oem type pump----use a genuine Multi sparp MSD---no cutting corners------run more timing advance--with that thin air, there isn't much static compression so spark knock isn't probably happening-----------


At higher altitudes you should of just supercharged a small block---------you will have a hard time getting enough air into that 494------


And also-what are you running for fuel??????????????

its the Edelbrock E Street EFI high pump octane

is your pump gas there 93? or 91?


If you want to run fuel injected you will need to go to a set of injectors that are much smaller and/or run a recalibration on mass airflow---------


the MAP settings/readings ? will be very likely wayyyyyyyyyyy out of sorts at your altotute

Originally Posted by jerry clayton

is your pump gas there 93? or 91?


If you want to run fuel injected you will need to go to a set of injectors that are much smaller and/or run a recalibration on mass airflow---------


the MAP settings/readings ? will be very likely wayyyyyyyyyyy out of sorts at your altotute

I think the thin air approach may well be part of the answer, but MAP is Manifold Absolute Pressure, which accounts for altitude vs Gauge Pressure. That's one of the benefits of EFI over a carb - they change as you climb the mountain to account for the low barometric pressure.

So just what is the absolute pressure at 9200 ?????????IIRC? you lose about one inch pressure per thousand feet--because of the low MAP it will be feeding lots of fuel---------------
http://www.sablesys.com/baro-altitude.html

Originally Posted by jerry clayton

So just what is the absolute pressure at 9200 ?????????IIRC? you lose about one inch pressure per thousand feet--because of the low MAP it will be feeding lots of fuel---------------
Sable Systems

Jerry, not to argue with you, but the fuel map looks at rpm, MAP, and then assigns fuel flow which on the E Street is then going to be trimmed in a feedback loop using the wide band O2 readings. If the O2 reading is good, then you take the barometric pressure for the day, which at 9200 feet is going to be about 21.2 to 21.3, and subtract the engine vacuum at any given rpm to yield MAP. Indeed the MAP numbers are going to be significantly lower than they will be in KC or St Louis, where our barometric pressure is generally around 30 inches of mercury. You're in the ballpark on the change, it's 0.89inHG per 1000 feet of elevation change. The Fuel map takes all of this into account, but it will be operating on a reduced range of pressure until the car goes down the mountain. This is why one would NOT want to block out the portion of the curve above say 23inHG - the engine would have no map for operation if the car left home. (PS - I didn't see your Sable Systems attachment before I replied, not that it really matters.)

Bob, I'd keep the E-Street over going back to a carb, especially at your altitude.

If this is a self learning system, you will never get it to work starting off at 9200 feet if you foul the plugs in 6 miles-----------


You could take the car to a lower altitude and start there , let it learn, and then drive it progressively back to the higher levels--maybe-----------


The highest pressure that the map will read will be the baro at 9200ft----------and it that reading it will flood the engine with the duty cycle injectors he probably has-----MAP does not compare anything to any thing--it is the ABSOLUTE pressure in the intake manifold where the sensor is located----------it will (on an NA engine) it will always be equal or less than baro at that altitude, never more (unless supercharged)------------


And on many builds/tuning deals that I have been involved wit, it has been almost a consistant occurrence that many basic auto things have had one or several discreps that violate the tuning process==== exhaust/vacume leaks, temp sensors mounted (or completely missing) Teflon tape, poor grounds----------this fouling plugs in 6 miles 10 minutes-------SHOUTS out the likely hood of more than one, possibly several ----------

Originally Posted by jerry clayton

....You could take the car to a lower altitude and start there , let it learn, and then drive it progressively back to the higher levels--maybe-----------

Now that's a great idea if it's something that works for Bob. It may be fouling the plugs before it can "learn" the baseline. Bob, call Jeff Robbins at Edelbrock, and see what he says about this approach. He was a key member of the E-Street development team for more than a year, and knows their EFI systems backwards and forwards. I'll PM you his direct number.

If you can't get Jeff, ask for Antron Griffin or best bet is Chris Johnson


Mention that Corey/Jerry Clayton sent you--------

Just talked to Edelbrock today tech deparment don't know the person's name. but they said with the reading of 20.94 arf and a reading of 17.92 arf sp the car is already running lean. and also to run the car at 17 degrees. started the car and ran it after cleaning the plugs again I had little to no throttle response and once I got the car up to 2100 rpm you could smell the gas fumes really bad. took it back down to idle ran it for a couple minutes at idle pulled a couple plugs starting to foul again. I would appreciate it if someone could give me a good phone number to reach someone who knows what they are talking about at Edelbrock I would even be willing to take the car down to 4500 feet and try there. last time I took it down to that level with a 750 Holly Double Pumper same problem started to foul the plugs and you could smell nothing but gas. I am hooked up to manifold vacuum have had people say port it and manifold my cam is Cam Specs:


Cam Type: Roller
.566 Intake .566 Exhaust
242 Intake / 248 Exhaust duration
@ .050 - 112 degree lobe separation

I had a problem like that once, but the motor was not brand new but I moved to a higher elevation from sea level.
I found that the Autolite spark plugs last longer with out fouling out or ruining the plug, they just stood up better and lasted longer.
Probably like they said not enough air and running to rich on the fuel.
Kurt