By looking at a head- how can you tell if it needs the old style flat w/ washer style plug- or the tapered seat type plug.

Went to change the plugs in my girlfriends 69 307 camaro- Guy who sold me the car had already bought plugs for it- Went to Schmucks auto parts and verified the part was correct for the car- went home- pulled out the old plugs- which were the flat washer style- The new ones are tapered seat style. :confused: :confused:

I looked at the heads- The spark plug opening looks basically the same as on my 70 elky which has tapered seat plugs in it. :confused:

Does it matter? Is it just a new style of plug? that will work in any opening? Maybe my elky has the wrong ones in it?

I'll try and take a pic of the spark plug opening on the camaro tonight and post it.

Thanks!

Heads that take the washered plugs have a flat landing to accept the washer. Heads that take the tapered seat plugs have a tapered seat. It's hard to tell by looking at them on the engine but you can tell the difference by touch.

Rich- Will the tapered ones have any kind of flat area, or will it basically go from being cast straight into being tapered? The camaro ones definittly have a machined flat area around the hole...

This really has got me wondering if i've got the wrong kind of plugs on my elky...

I'm trying to figure out what I have too. I haven't tried feeling the hole, yet. Can a gasketed plug be used in the tapered hole? Wondering if the previous owner of the motor got it right or not. I have gasketed in there now.

Tim.

Ok... I bought some gasketed AC plugs for the camaro- because i'm 99.99% sure the gasket ones are correct (since that is what was on there before and it ran awesome)

While replacing them- i left one out- and took one out of my elky (it has tapered plugs) THE HOLES ARE IDENTICAL.. except for the inner edge has worn down a bit due to tapered plugs having been used in it for so long... Otherwise they look exactly the same.

I test installed the gasketed plug in my elky and it fit just fine... So My question is- What would you expect to happen if you were to run the wrong type (tapered instead of shouldered) in an engine?
The shouldered plugs are about 1/8" shorter (less sticking into the head vs the tapered plugs) What kind of difference will that make?

I'm gonna grab another pack of the AC shouldered plugs tomorrow and put them in the elky and see what it does...

My dad has some flat seat heads and we were in a hurry and just stuck some tapered seat plugs in and it runs just fine, we arent even gonna bother changing them out anymore.

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=29;t=003163;p=4

http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=29;t=002343#000013

Just watch out when using a gasketed plug in a tapered seat head as the gasket can end up getting stuck in the plug hole as they get wedged in the tapered portion. Couple of guys here and that I have talked with found gaskets stuck in the plug hole after reading the above threads.

The best way to tell (70 and later heads use tapered seat) is to go to kragen or somewhere that is displaying a crate engine and look. Using one of those little dentist mirrors (the ones they use to look at the backside of your teeth) will help you see the plug seat better with the engine installed

I have detailed pictures that were sent to me from a fellow member of both type heads side by side that might help. It is hard to tell when the mill is in the car but the pics helped me out and those two threads cover it all.

email me if you would like to see them - alegri@sbcglobal.net

ok here's the picture's hope they're not too large..

Starts with the gasketed seats;
http://chevelles.com/showroom/lance-w/290gasketedhead4-70pic1.JPG http://chevelles.com/showroom/lance-w/290gasketedhead4-70pic2.JPG

Now the taper seats:
http://chevelles.com/showroom/lance-w/290taperseat3-70pic1.JPG http://chevelles.com/showroom/lance-w/290taperseat3-70pic2.JPG

Note: The production dates on these two sets of heads are backwards from what you would expect. The gasketed heads having a date stamp after the taper seats. The taper seats would you think have a younger/newer date stamp :rolleyes:

Lance

Thanks Lance. I initially forgot who sent those to me and ultimately cleared up my confusion. graemlins/beers.gif graemlins/thumbsup.gif

Over and out.

Ok- After looking at those pics- on heads with tapered holes- The inner edge would be fairly defined, IE: Obviously tapered (appears to be in those pics) right?

The heads on my elky have had tapered seat plugs in them since before i bought it- I just replaced exactly what was in it before.

When i pulled the plug out of the head on my car last night- It looked identical to the camaro's one- Which had a sharp(not tapered) edge around the hole- The only difference is on my car, that edge was worn down a little bit, but not nearly as much as that picture shows...

I'm fairly confident that my car was supposed to have the other kind of plugs in it. I will get a set today after work and give it a try!

Thanks for posting the pics and the links guys! It helps a ton!

Barista had a set of heads on his BBC that required tapered plugs but the guy before him had installed gasket plugs. He discovered the error at some point and felt it ran just a little better with the correct plugs. I would think tapered plugs in a gasket-style hole wouldn't cause as much problems as the other way around.

They should have made the plug styles different hole sizes so you couldn't mix them up!