threading expansion plug holes

[David K]

Guys,

 

I just finished a nice little n42/n47 motor 2 weeks ago. I fired it up 3 days ago and havent been able to get the motor to run right. Today i figured out the AFM spring tension wheel needed to be turned another turn. Everything was running well, so i revved it up and down in the driveway and an expansion plug popped out of the block. I shut the motor down within 2 seconds.

 

I swear up and down that all the plugs were in the block as best as they could when i installed them. I rubbed grey silicone on the mating surface of the block, and also on the plugs themselves. They were super tight when i put them in. This crap just scares me, i wanna drive cross country.

 

After i cleaned up the mess, i came in and read a little bit on a Ford forum. I found that some of the guys racing their cars are threading the expansion plug holes and sticking some threaded plugs in the block. Theres a couple of guys doing the same with the oil gallies on their Datsun motors, so why not the expansion plugs. I dont plan on taking the car anywhere itll get cold enough to pop a plug. As you can see, the threaded expansion plug mod is popular enough that Ford Racing offers a complete kit for race applications http://store.summitracing.com/partdetail.asp?part=FMS-M-6026-B302&view=1&N=150+150 My zx will see many high speed track events. I will not drive it on the street as much as a drive it on the track.

 

I expect BRAAP and others who build serious motors to give me some input on these threaded plugs

[Pop N Wood]

I think Garrett had the definitive thread on popping expansion plugs.

 

IIRC silicon on the plugs was a bad idea.

 

There were lots of very good ideas.

 

Try looking up that thread

[z-ya]

I use a very thin film of silicone sealant on the plugs. You need to get all of the grease and oil off first with brake cleaner or acetone. I know one of the Bob Sharp engine builders, and they epoxy them in on all out 15:1 CR race motors.

 

If it popped out, it sounds like you have other issues. I have never had one pop out of my turbo motor, and I've done many track events with it. Is your head gasket sealing well? If you have a head gasket leak into the water jacket, it might cause one to pop out when your under boost.