spark plugs and compression

Reply Subscribe

Thread Tools

Search this Thread

Aug 16, 2004 | 08:25 AM

76 F150 Ranger XLT

Thread Starter

Senior User

Joined: Feb 2004

Posts: 185

Likes: 0

From: Crownsville, MD

spark plugs and compression

This is kinda goofy, but I remember reading somewhere (it may have been a Chevy buildup in a magazine; sorry) that if you remove the spark plug gasket (washer?), the plug takes up more space in the combustion chamber and increases compression. The article claimed it reduced the chamber volume by about 1 cc (seems high to me). Could you do this with an FE? What are the consequences? It seems like the spark plug gasket is there for a reason and you may actually lose compression if it leaks.

Aug 16, 2004 | 10:16 AM

Freightrain

Lead Driver

Joined: Jan 2003

Posts: 9,893

Likes: 12

From: Ohio

Sounds like a Chebby story......

.....and it picked up 20 hp......

The washer is the gasket/seal. I would see a bigger issue with keeping a seal then picking up ANY compression. We're talking less than a drop of water here...maybe. Not worth even measuring.

Maybe Warren Johnson did a test to see if it made a difference. I don't see any of us noticing a difference.

Last edited by Freightrain; Aug 16, 2004 at 10:21 AM.

Aug 16, 2004 | 10:46 AM

Post Fiend

Joined: Feb 2000

Posts: 5,130

Likes: 8

From: Brea CA

We don't run gaskets on the plugs for a FE. Instead the seat is tapered, much better heat transfer from the plug to head.

Aug 16, 2004 | 12:17 PM

76 F150 Ranger XLT

Thread Starter

Senior User

Joined: Feb 2004

Posts: 185

Likes: 0

From: Crownsville, MD

OK, that makes sense. Better heat transfer, cooler plug temperatures, less chance for preignition (or is it detonation? I always confuse the two).

BB,
Is there a trick to machining the taper or can any decent machinist figure it out? Is this sort of common knowledge among machinists?

Even if I never use them, I love learning all these little tricks that people use when building an engine. Thanks for the info.

Aug 16, 2004 | 12:28 PM

tastyklair

Elder User

Joined: Jan 2004

Posts: 867

Likes: 0

From: Eastern Pa

Even though it is a minute amount of distance we are talking about, if the threaded area of the plug begins to stick into the chamber that is going to be a source for detonation to start. Thats why plugs are made in different "reaches". If you put the right heat range but wrong reach in a hole, that end of the plugs' threads are going to get glowing hot real quick. Stick with the gasket.

Aug 16, 2004 | 12:39 PM

Post Fiend

Joined: Feb 2000

Posts: 5,130

Likes: 8

From: Brea CA

Quote:

Originally Posted by 76 F150 Ranger XLT

BB,
Is there a trick to machining the taper or can any decent machinist figure it out? Is this sort of common knowledge among machinists?

I've never had to screw around with the seats in the heads. That's the way they come from the factory and never had a problem with them sealing.

When changing plugs, I like to wipe down the seat to make sure there's no crud. If your engine is pumping oil, you'd be surprised how much can get past the threads.