I was going to change my plugs tonight and I was wondering if I could cut the crush washers off on a series 4 motor?
I know it can be done on a series 5.

 

I know the leading will be fine, but leave them on the trailing. The very edge of my leading plugs barely touches the rotor housing(the trailing only has a small hole, so the plug has something to hit before the rotor). Im going to replace my plugs, and leave the cruch washer on the trailing plugs, and I would recommend that for anyone else too.

 

thanks, I was hoping it would be you that answered. I thought you would know

 

Why would someone want to do this?

Brian

 

higher compression, as little as it is. I don't know what pluses there are besides the higher compression.

 

you also get the spark closer to the combustion chamber. this has the bigger effect than the higher commpression

 

can you do this on a series 6 engine? 13b-rew

 

DONT do this on a turbo motor!! You do not want to increase your compression.

 

i cut mines on all four plugs this weekend...still runs...somehow...

 

I cut the washers off the "top" plugs, but not the bottom.

 

You should have done it the other way around. On my top plugs, the edge of the plug looks like it was touching the rotor housing.

 

Been that way for over 100 miles so far, no ill effects, but I'll pull the plug and see if it has marks on it later.

 

You might as well go ahead and cut the washers off the leading(bottom) plugs too.

 

I pulled the plugs and they look...........................GREAT!

No scarring, or any marks of contact whatsoever.

 

Mazdaspeed7 runs his car preaty high up in the rpm range, according to prior posts. So maybe that is why his trailing plugs got nicked. Due to the increased rpms the clearence would be shortened and maybe enough to contact the plug. Reving to a lower peak of maybe 7500 rpms might prevent it from happening.

 

I can see I am going to have to take a pic of the rotor housing. There is NO WAY the trailing plugs could hit anything inside the chamber. Give me a few minutes and Ill have a few pics up. Ill get a pic of the clearance of the leading too.

 

The pic is kinda blurry, Ill try to get a better one up later. There is a plug in the leading hole WITH the crush washer cut off, so you can see theres still plenty of clearance.

 

I just measured a 1990 n/a rotor housing I had in the garage and a NGK plug(leading) WITH the cruch washer cut off. Heres what I got:

trailing hole, center - .893"
trailing hole, edge - .863"
Leading hole - .924"
Spark plug - .840

So it will fit with NO clearance problems whatsoever.

 

got the washers cut off of my 86 works fine and dandy, no problems.

 

How did your trailing plugs get nicked then?

 

how far in do you actually screw the plugs? Do you need one of those funny "skinny" plug sockets to get it in further?

-Tesla

 

Beats me. Might just be a freak occurance. If it does it on the next set of plugs I will worry.

Telsa, I havent needed one of those special sockets yet.

 

Instead of removing washers how'bout just use the BUR9EQP, the threaded part is slightly longer than the 7EQ by 1/8".

 

I feel really stupid now that I know why. I had put an extra set of leading plugs in the trailing hole because the trailings needed replacing,and I had a pair of perfectly good leading plugs laying around. The leading plugs are .1" longer than the trailing(im pretty sure, its been a while since I measured it). I put it some proper trailing plugs, and all was good. Leading plugs will work, but you must leave the crush washer on it.

Good idea, ka8legend. That might be worth a try.

And this thread is back from the dead, seems to have been happening to a lot of old n/a threads lately