Proper Plugs for a KA24E

Before the last race I put a fresh head on the car. Nothing unusual, just cleaned up, port matched and new seals. It was not plained. New plugs, wires, cap, etc at the same time.

At the track the car was really down on power and was getting hot. It seemed like it was detonating although I could not hear it. At the track we played with the ignition timing, check the cam timing as best we could with not much luck. It was way down on power and I couldn't run it hard for long without it getting too honda. Another racer that was helping said I probably had the wrong plugs in it. I can't remeber if he said it should be hotter or colder and I would know what that means anyway http://Forum.ImprovedTouring.com/it/smile.gif I left convinced I still had a timing problem of some sort and never came back.

Reading NGK's site today, it said that running too hot a plug can cause detonation and over heating. I checked my old plugs and new plugs, both NGK but different numbers. Sorry, I don't have the numbers here.

Does this sound like it could be my problem?
Can anyone recomend the proper plug for the car? The motor is pretty much bone stock, I run an open exhaust with a stock manifold at the track.

Thanks
Corey

Corey,
For racing, I have always been told, and live by "cooler is better". NGK makes a "7" plug for the 240sx but you will propably have to hunt around for them. "7" is cooler than "6", ect. It has to do with the amount of area and depth of the recess around the ceramic part that sticks into the cylinder.
It sounds like a timing issue to me. I don't think that plugs would make that huge of a difference. I think you need to recheck your cam timing. Also, make sure you "burped" the coolant at the thermostat housing, and that you problem isn't related to air in the system. That too will cause the car to run hot, and these engines don't like the heat. Hope that helps

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

[This message has been edited by Tristan Smith (edited July 06, 2004).]

Corey,
I used the NGK Iridium BKR6IEX plugs with pretty good luck. They always looked good when I checked them.

I agree with Tristan though. I don't think being off by a heat range or even two would cause what you've described. If the timing is advanced too far, that will cause it to detonate, overheat, and lose top end power. If the water temp gets too high, it will lose even more power. I used less timing than the factory called for. Dyno testing showed 6 degrees initial advance was what mine liked. Yours could be slightly different because of the stock manifold. (I think the factory spec is 14 degrees advanced IIRC)

Good Luck
Jim

It definity felt like a timing issue at the track. And yes, it ran worse as it got hotter and started to detonate more. It will be a few weeks before I can get the car out again but I will follow up when I do.

I didn't change the ignition timing when I changed the head but I have changed it since then trying to fix the problem. Not sure what I was running for the last year or so, around 15-16 I think. It was as far advanced as I could get it and seemed to work well before the changes. I have since pulled the distributer out and repositioned it by a tooth so that I have some adjustment both ways again. That is not a fun job. I'm surprised 6 degrees works best. I thought more advance was good, assuming you don't go to far as start detonating.

Can I verify the cam timing by just removing the valve cover or should I pull the front cover off. I did not remove the cover when I changed the head, I had already done the chain and tensioner the year before. I think there is a mark on the cam gear that is supposed to be pointing straight up, but is that straight up relative to the floor or the motor? The motor sits in the car at a slight agle.

Thanks for the help

Corey,
To check the cam timing, you only need to remove the valve cover. Set the crank pulley at TDC. Be sure to use the correct mark, they are a little confusing. The dowel pin in the cam gear should be lined up with the arrow cast into the first cam journal.
The shop manual has pretty detailed diagram of reinstalling the oil pump so that the distributor lines up properly. (line up a mark on the pump body with a mark on the shaft) If you follow it, you will have plenty of adjustment.
When I set the timing on an engine, I set it by total timing. This is what the engine sees in races. Initial timing is only a reference point. IIRC, with 6 degrees initial, the total timing at 4000 rpm was 36 degrees. With 15 degrees initial, it goes to 45 at 4000. I know it seems contrary to common wisdom, but the dyno seemed to like these numbers also http://Forum.ImprovedTouring.com/it/smile.gif

Hope this helps..
Jim
[email protected]

[This message has been edited by ITA240 (edited July 07, 2004).]

Corey -

Just wondering - did the car run ok when it was cold? How hot was it that day? These cars have a well-earned reputation for being hot-heads. I know I spent half of my first track day (mid-July, mid-90's) running around with the heater blasting. Since I installed a Koyo radiator I've had no problems with heat, and that is with NGK ZFR5E plugs and 94 octane gas (w/stock internals). I have to agree with Jim & Tristan it sounds like something more than just wrong plugs, either ignition or maybe even cam timing.

One other thought, did you check the head for straightness before you put it back on? It wouldn't take much of a leak in the head gasket area to cause the problems you're describing.

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Earl R
Aspiring 240SX pilot

Corey,

Set the timing per the FSM, with no more than recommended. These motors do not like the timing advanced more than the manual says. They tend to get all funky like yours did if you do.

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

Quote:

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Originally posted by erlrich:
Corey -

Just wondering - did the car run ok when it was cold? How hot was it that day? These cars have a well-earned reputation for being hot-heads. I know I spent half of my first track day (mid-July, mid-90's) running around with the heater blasting. Since I installed a Koyo radiator I've had no problems with heat, and that is with NGK ZFR5E plugs and 94 octane gas (w/stock internals). I have to agree with Jim & Tristan it sounds like something more than just wrong plugs, either ignition or maybe even cam timing.

One other thought, did you check the head for straightness before you put it back on? It wouldn't take much of a leak in the head gasket area to cause the problems you're describing.

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When it was cold it just seemed down on power, obviously it got worse as it got hotter. The temp that day was fine, lower than usual. I do usually run the car with the heater blasting though since I run the stock rad. I told them to plain the head at the machine shop but the didn't because it was good and straight. Compression is very good across the board.

I appreciate all the help. It will be a few weeks before I can try it again but I will report back. Before then I plan to change the plugs, check the cam timing and reset the ignition timing to stock.

BTW, as far as cooling I am pretty much stock less the clutch fan. I have run the car like that for a while. I usually leave the heater on and make sure I do a cool down lap before hitting the pits. I have an electric fan on a switch but I only use it in the pits etc since I figure there is enough air moving through it at race speeds.

I think you should get a bigger radiator. Whether you use one of the off the shelf "racing" radiators out there (check ebay), or get a custom one built (I recommend a double pass). As much as these motors don't like heat and to be turned at the rpms we tend to turn them at in race trim, you need all the radiator you can get. Also, not sure about your set up, but you need an oil cooler and oil temp gauge. I have my temp gauge sender BEFORE the oil cooler and see temps of 220-230 coming out of the motor on a hot day.

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

We use Champion C61Y plugs in all our 3 and 4 valve IT prep engines. They are equal to a 7 or 8 range NGK plug.