Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 08-23-2020, 08:29 PM   #41
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by GOSFAST View Post
Offenhauser has always been a problem with getting the spark plugs where they should be sitting?

Over here we use the Autolite 3924, .750" reach, with a .125" spacer on the top side!
If I did this the exhaust valve would hit the plug.

Where I grew up there was a speed shop in Glendale, CA on Victory Boulevard. When they handed over a new set of 375 Offy heads I wonder what plugs they offered the customer.
qmdv is offline   Reply With Quote
Old 08-23-2020, 08:39 PM   #42
JSeery
Senior Member
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 15,448
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by qmdv View Post
If I did this the exhaust valve would hit the plug.

Where I grew up there was a speed shop in Glendale, CA on Victory Boulevard. When they handed over a new set of 375 Offy heads I wonder what plugs they offered the customer.
So your saying a .625 inch reach plug would hit the exhaust valve?? Then why wouldn't a .125 shorter plug at .500 work?
JSeery is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 08-23-2020, 08:42 PM   #43
estout81
Senior Member
 
estout81's Avatar
 
Join Date: Jun 2010
Location: Utica, Ohio
Posts: 500
Default Re: AutoLite 216's in Offy heads

I don't think a flathead will ever see 1500 PSI cylinder pressure. A 14mm plug has about a 1/4 sq. in. surface so, .25 x 1500 = 375. Don't think that will blow out a spark plug.
estout81 is offline   Reply With Quote
Old 08-23-2020, 08:50 PM   #44
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by JSeery View Post
So your saying a .625 inch reach plug would hit the exhaust valve?? Then why wouldn't a .125 shorter plug at .500 work?
Will be looking for Autolite 4092's tomorrow. That will give right close to .050 clearance.
qmdv is offline   Reply With Quote
Old 08-23-2020, 08:51 PM   #45
estout81
Senior Member
 
estout81's Avatar
 
Join Date: Jun 2010
Location: Utica, Ohio
Posts: 500
Default Re: AutoLite 216's in Offy heads

JSeery,
See post 19. The picture shows Autolite 4092 plugs [ 1/2 in. reach]. The chamfer takes out a little less than a 1/8 in.
estout81 is offline   Reply With Quote
Old 08-23-2020, 09:03 PM   #46
JSeery
Senior Member
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 15,448
Default Re: AutoLite 216's in Offy heads

Sponsored Links (Register now to hide all advertisements)
Quote:
Originally Posted by estout81 View Post
JSeery,
See post 19. The picture shows Autolite 4092 plugs [ 1/2 in. reach]. The chamfer takes out a little less than a 1/8 in.
That's where I'm getting lost I guess. 1/8 in = .125 So if you add the .125 to the plug reach you get .500 + .125 = .625 which is what the long reach plugs with the spacers are and no chamfer is required. What am I missing here and how would this cause the plug to hit the exhaust valve? Is the valve at maximum lift that close to the roof of the cylinder? If it is, then the plug is going to have to be shrouded up in the threads or the plug is not going to be able to have an extend electrode below the thread surface of the plug.
JSeery is offline   Reply With Quote
Old 08-23-2020, 09:10 PM   #47
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by JSeery View Post
That's where I'm getting lost I guess. 1/8 in = .125 So if you add the .125 to the plug reach you get .500 + .125 = .625 which is what the long reach plugs with the spacers are and no chamfer is required. What am I missing here and how would this cause the plug to hit the exhaust valve? Is the valve at maximum lift that close to the roof of the cylinder? If it is, then the plug is going to have to be shrouded up in the threads or the plug is not going to be able to have an extend electrode below the thread surface of the plug.
How is chamfering out 1/8 in the chamber adding to the reach. Since the heads are installed and am not inclined to pull them I will just put in the 4092's and see how it runs.
qmdv is offline   Reply With Quote
Old 08-24-2020, 02:02 PM   #48
JSeery
Senior Member
 
JSeery's Avatar
 
Join Date: Nov 2012
Location: Wichita KS
Posts: 15,448
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by qmdv View Post
How is chamfering out 1/8 in the chamber adding to the reach. Since the heads are installed and am not inclined to pull them I will just put in the 4092's and see how it runs.
Who said anything about the chamfer increasing the reach?? I was attempting to understand how adding a spacer ring would increase the reach, as in cause interference between the plug electrode and the exhaust valve.

I normally like these type of discussions, but I have to admit I can't understand this one at all. Guess I just need to accept defeat (in my ability to follow the discussion) and move on.
JSeery is offline   Reply With Quote
Old 08-24-2020, 02:20 PM   #49
Tim Ayers
Senior Member
 
Join Date: May 2010
Location: NJ
Posts: 4,022
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by JSeery View Post
Who said anything about the chamfer increasing the reach?? I was attempting to understand how adding a spacer ring would increase the reach, as in cause interference between the plug electrode and the exhaust valve.

I normally like these type of discussions, but I have to admit I can't understand this one at all. Guess I just need to accept defeat (in my ability to follow the discussion) and move on.
I'm with you. I gave up a few days ago. I'm not placing blaming on anyone, I am just having a terrible time following the progression.

This is something I'd need to see in front of me in order to make heads or tails of it.
Tim Ayers is online now   Reply With Quote
Old 08-24-2020, 03:59 PM   #50
Bored&Stroked
Senior Member
 
Bored&Stroked's Avatar
 
Join Date: Jan 2011
Location: Central Ohio
Posts: 2,892
Default Re: AutoLite 216's in Offy heads

Too many cats . . . and too many cat skinners it seems . . .
Bored&Stroked is offline   Reply With Quote
Old 08-24-2020, 04:30 PM   #51
GOSFAST
Senior Member
 
GOSFAST's Avatar
 
Join Date: May 2010
Location: Long Island, NY
Posts: 1,052
Default Re: AutoLite 216's in Offy heads

We've been using the .125" spacer for over 35 years now, never a single issue??

I've personally had numerous discussions with both Tay (Offenhauser) and Vince (his "main" man), that have gone nowhere, like beating a dead horse. What we've learned over here is stay with the Edelbrock's, they got their act together. Always have for the most part! My only issue with them really was over the "enlarging" of the head bolt holes back when. This is non-issue here, as we "pin" all heads and blocks together anyway!

Thanks, Gary in N.Y.

P.S. "JSeery", I'm also sort of confused myself here, but I do know your thinking is OK!
GOSFAST is offline   Reply With Quote
Old 08-24-2020, 05:57 PM   #52
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

Then let me try again. I have offy 375 heads. With exhaust valve fully open there is .615 between the top of the exhaust valve and the spark plug mating face on top of the heads. If I used 3/4 reach plugs with a .125 spacer, the plug would interfere with the valve and that would be bad news. I was hoping that somebody had some help they good give. This task would be a lot easier if I had heads with deeper combustion chambers.
qmdv is offline   Reply With Quote
Old 08-24-2020, 06:14 PM   #53
tubman
Senior Member
 
tubman's Avatar
 
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 6,993
Default Re: AutoLite 216's in Offy heads

Just one question. Are these new or used heads?
tubman is offline   Reply With Quote
Old 08-24-2020, 06:25 PM   #54
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by tubman View Post
Just one question. Are these new or used heads?
Probably at least 60 years old. Very good condition. I do believe that Offy only makes 400's and 425's today
qmdv is offline   Reply With Quote
Old 08-24-2020, 06:45 PM   #55
Bored&Stroked
Senior Member
 
Bored&Stroked's Avatar
 
Join Date: Jan 2011
Location: Central Ohio
Posts: 2,892
Default Re: AutoLite 216's in Offy heads

Given that the valves are angled and the actual location of the spark plug hole and that a standard head gasket is about .052 thick, are you measuring the clearance at the location where the spark plug is oriented to the valve (with a head gasket in place) - or the top side of the valve (toward the intake) - which has a different height?

Consider that your particular block, cam, head, valve seat depth, valve type combination is specific to your particular motor - nobody can tell you exactly what to do. The answer is "it depends" . . . on a lot of different factors. In the end, the dimensions are what drives your options - plain and simple.

All you need to do is clay the top of the valve at full lift - with a head gasket in place and a couple studs/bolts and see what the exact amount of clearance you have above the valve in the exact location. Then, you know what you have to work with - and can determine how deep the plug can go.

Once you know that, then you can determine which plugs you can use (given the length, heat range and electrode type) and how many potential spacers (or not) you need to utilize. You'll have options as to how you want to address your specific dimensions. If you need a shorter reach plug (and then have threads showing in the chamber side), you can chamfer and also maybe add a power-slot in the head as Gary has shown.

There are lots of ways to address any potential issue - just decide which plugs you want to run and therefore what you need to do.

Good luck!
B&S

Last edited by Bored&Stroked; 08-24-2020 at 06:58 PM.
Bored&Stroked is offline   Reply With Quote
Old 08-24-2020, 06:53 PM   #56
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

The heads are installed with the gasket in place. I am measuring through the spark plug hole from where the spark plug mates to the head to the valve face when it is fully open.
qmdv is offline   Reply With Quote
Old 08-24-2020, 07:11 PM   #57
GOSFAST
Senior Member
 
GOSFAST's Avatar
 
Join Date: May 2010
Location: Long Island, NY
Posts: 1,052
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by qmdv View Post
Then let me try again. I have offy 375 heads. With exhaust valve fully open there is .615 between the top of the exhaust valve and the spark plug mating face on top of the heads. If I used 3/4 reach plugs with a .125 spacer, the plug would interfere with the valve and that would be bad news. I was hoping that somebody had some help they good give. This task would be a lot easier if I had heads with deeper combustion chambers.
Just to keep things clear here, you don't necessarily need the .125" spacers, you can make them any length to get the job done!

The .125" spacers happen to fit the Offy heads we generally work on here!

Thanks, Gary in N.Y.

P.S. Here's an example, if you start with the .750" plug and make the spacers .250" you now have a .500" reach plug. You also need to consider the plug washer thickness, .025" (nominally).
GOSFAST is offline   Reply With Quote
Old 08-24-2020, 07:23 PM   #58
qmdv
Senior Member
 
qmdv's Avatar
 
Join Date: Dec 2012
Location: Nor Cal
Posts: 850
Default Re: AutoLite 216's in Offy heads

Quote:
Originally Posted by GOSFAST View Post

P.S. Here's an example, if you start with the .750" plug and make the spacers .250" you now have a .500" reach plug. You also need to consider the plug washer thickness, .025" (nominally).
So what is the advantage of a 3/4 reach with a .250 spacer over a 1/2 reach plug.
Oh these are very old heads. probably older than the average age on this forum. Who knows what has been done to them as they are not talking to me. Wishing now that I had bought new Edlebrocks
qmdv is offline   Reply With Quote
Old 08-25-2020, 04:11 PM   #59
Bored&Stroked
Senior Member
 
Bored&Stroked's Avatar
 
Join Date: Jan 2011
Location: Central Ohio
Posts: 2,892
Default Re: AutoLite 216's in Offy heads

The advantage of 3/4" reach plugs is that you have the widest selection of brands, insulator types, heat ranges, plug application types, etc.. If you've found a 1/2" reach plug that you like, no real reason to go to all the effort to worry about 3/4" reach plugs - but you asked the question.
Bored&Stroked is offline   Reply With Quote
Old 08-25-2020, 05:24 PM   #60
Mart
Senior Member
 
Mart's Avatar
 
Join Date: May 2010
Location: Solihull, England.
Posts: 6,892
Default Re: AutoLite 216's in Offy heads

I have offenhauser heads on the French motor in my roadster. I run 216s. A few years ago I did what I thought at the time was the clever thing to do and chamfered the holes from the underside. It runs great and never caused me concern. If I were doing it today I might reconsider and try and use a longer plug.
Fingers crossed I'll get away with it.
Mart.
Mart is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 08:27 PM.