Hi guys, well this is a repost i posted a while back in T-bricks, but since there is so much traffic as usual it got bumped off the map.

My cylinder 4 is running a little hot, I pulled the plug a while back and the electrode arm had a thin white deposit on it. I thought it may be a defective CFI injector, so i moved that injector to cyl 2 and ran it for a bit. But the same thing occured, every plug looked fine other than cyl 4. I then tried bumping up my req fuel and running it a lot richer. Same thing occured, except now the plug is black everywhere except for the electrode arm which again has the thin white coating. No damage has occured on the insulator/electrode or anything like that so i dont think ive done any damage to the engine, but i would feel a lot better if it didnt do this.


I am running plugs with a level 6 heat rating gapped to 32 thou. Im interested to know if any of you have had similar problems and if i should be worrying.

Thanks

BTW: its the b21ft

"plugs with a level 6 heat rating" doesn't say much. NGK BPR6ES, is that what you mean? That's stock, just to clear up any possible confusion.

What intake manifold are you using? I assume it's the EFI one. What elbow are you using to get into the throttle body? The B230FTs used a sort of double elbow: first bending down and then bending left. The theory is that this elbow is designed to straighten the airflow a bit more so as not to bias the flow towards the back two cylinders. I never ran with this elbow and I never noticed any problems, but with this elbow I can see more air going towards #4 specifically (bottom rear runner, just where the air would be pointed as it's coming out the bottom of the rubber elbow and through the throttle body).

HOWEVER, I have NEVER believed that this would make much of a difference, despite other folk claiming to the contrary. What I think is much more likely is that the rear cylinder runs hottest, which seems kind of obvious when you think about the way the cooling system is desiged.

Try this: Open your heater all the way and drive like that for a few days, after you've cleaned your plugs. If that makes a difference, it's because the added coolant flow from the back of the head and through the heater core has cooled down the rear cylinder.

I've never liked the way the 240 heater control valve is set up. It blocks flow through the heater core when it's shut off, but also blocks all flow through that hose when it's shut off. That's what's blowing frost plugs, I'm thinking. Redesign that system so that coolant BYPASSES the heater core when the heater is shut off, and you'll get better cooling plus reduce pressure in the block.

I've blown out 2 frost plugs and 5 heater cores because of the way that system is set up.

correct



yea im running with the heater core bypassed right now so there is flow back there, seems a little odd as i would think that it would be better than with the heater core attached.

I am using the EFI b230 intake with just a vibrant brand elbow to the throttle body, i admit it does not quite fit right so it could be bias towards the rear cylinders. I have a spare elbow i just picked up so maybe ill run it with that and see if there is any change. However since the cyl 4 plug is black everywhere else but the electrode arm i would assume that its not leaning out on that cyl??

One guy responded on tbricks claiming his old porsche did that and it was normal but i haven't heard of anyone claiming it to be normal for a b21ft.


is 32 thou pretty normal for a plug gap or is that to tight??

actually scratch that im running a bp7es, i believe this is a colder than stock plug, i switched to this to see if it solved the problem.

here is a pic of the plug, sorry about the quality

In Volvo #1 I used to have a B21F bored out to the first overbore size for a B23. The B21 head was shaved a bit too on that car. It had K-jet and a K-cam. Between the thin cylinder walls and the higher compression (causing some pinging now and then) and the fact that cyls 3 & 4 are furthest from the water pump, those cylinders ran the hottest, especially no. 4. In fact, oon trips through the mountains I used to routinely melt stock heat range plugs in cylinder 4 and sometimes even cylinder 3. My solution was to run a plug that was 2 series cooler in cylinder 4 and 1 series cooler in cyl 3. I ran the stock range BPR6ES plugs in cyls 1 & 2. That seemed to work ok and pretty much eliminated the plug melting/cracking problems in cyls 3 & 4.

IMHO if you're not actually melting or causing the insulator around the center electrode on your no. 4 plug to crack then your problem is not anything to worry about. Cyl 4 will always be the hottest as it is furthest from the water pump. If you start losing no. 4 plugs then you might want to think about running a slightly cooler plug in that cylinder.

If you're still concerned about it then concentrate on improving the cooling system in your car to make the whole engine run cooler. Try flushing and washing the bugs & dirt out from between the fins on your rad and possibly switch to an e-fan iif your car doesn't have one. Red Line has a product/coolant additive that will make your car run cooler. I believe it's some sort of surfactant and I hear it works pretty well. I think it's used in racing quite a lot.

Hope this helps,

Roger

I am heebing up a 140 choke cable to a heater bypass valve. Not for everyone. Ghetto, and you have to remember to push the "choke" in if you want heat, but it should keep my 240 happy as i beat it within an inch of its life.