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08-23-2020, 08:29 PM | #41 | |
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Re: AutoLite 216's in Offy heads
Quote:
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. |
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08-23-2020, 08:39 PM | #42 |
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Re: AutoLite 216's in Offy heads
So your saying a .625 inch reach plug would hit the exhaust valve?? Then why wouldn't a .125 shorter plug at .500 work?
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08-23-2020, 08:42 PM | #43 |
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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.
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08-23-2020, 08:50 PM | #44 |
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Re: AutoLite 216's in Offy heads
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08-23-2020, 08:51 PM | #45 |
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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. |
08-23-2020, 09:03 PM | #46 |
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Re: AutoLite 216's in Offy heads
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08-23-2020, 09:10 PM | #47 | |
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Re: AutoLite 216's in Offy heads
Quote:
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08-24-2020, 02:02 PM | #48 | |
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Re: AutoLite 216's in Offy heads
Quote:
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. |
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08-24-2020, 02:20 PM | #49 | |
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Re: AutoLite 216's in Offy heads
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This is something I'd need to see in front of me in order to make heads or tails of it. |
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08-24-2020, 03:59 PM | #50 |
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Re: AutoLite 216's in Offy heads
Too many cats . . . and too many cat skinners it seems . . .
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08-24-2020, 04:30 PM | #51 |
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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!
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08-24-2020, 05:57 PM | #52 |
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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.
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08-24-2020, 06:14 PM | #53 |
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Re: AutoLite 216's in Offy heads
Just one question. Are these new or used heads?
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08-24-2020, 06:25 PM | #54 |
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Re: AutoLite 216's in Offy heads
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08-24-2020, 06:45 PM | #55 |
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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. |
08-24-2020, 06:53 PM | #56 |
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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.
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08-24-2020, 07:11 PM | #57 | |
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Re: AutoLite 216's in Offy heads
Quote:
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).
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08-24-2020, 07:23 PM | #58 | |
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Re: AutoLite 216's in Offy heads
Quote:
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 |
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08-25-2020, 04:11 PM | #59 |
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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.
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08-25-2020, 05:24 PM | #60 |
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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. |
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