Navarro 8ba Heads

[KiWinUS]

Originally Posted by tubman

I thought the intent of installing aftermarket heads on these engines was to increase performance? Addressing plug fouling this way has no place here. Your first two pictures are of the biggest mistake one can make with aftermarket heads, and that it to try to use the "recommended H10 spark plug" (your words) in them. Just about all of them are made to use longer reach plugs because aluminum is not as strong as cast ion and requires the extra threads. Edmunds takes 1/2 reach plugs, Edelbrocks take 3/4" reach plugs, and so on. Why would the manufacturers make heads with 3/4" of thread just to put in a plug with 3/16"? The goal here is combustion efficiency and maximum flame front travel. You'll get neither of those with the plug waaaay up in the head.

Not disagreeing with you in anyway. Just sharing information not my opinions. I know what I want but that’s another subject and irrelevant here.

[tubman]

No problem. It was just that I thought your post was a little unclear and that some would take it that Champion H10's (or equivalent) were recommended for use in aftermarket heads. In fact, they are recommended for use in stock cast iron heads only and their use in the vast majority of aftermarket heads is wrong and can result in poor running, plug fouling, and even mechanical damage.

[tubman]

Originally Posted by 69a

Perhaps I am wrong, but the Edmonds heads look like you could use a longer plug without interfering with the valves. The plug location appears to be between the valves.

You are correct. To me, that is the improvement with Edmunds heads that set them above the rest. Actually, the plug is below the valves.

[69a]

Thank you TUBMAN that explains it perfectly. I did mean Edmunds in my previous post, not Evans.
I think Shoebox was being gaslit by the vendor in post #8.

[Shoebox]

Originally Posted by 69a

Thank you TUBMAN that explains it perfectly. I did mean Edmunds in my previous post, not Evans.
I think Shoebox was being gaslit by the vendor in post #8.

"Gaslighting is a form of psychological manipulation where one person causes another to doubt their own memory, perception, or sense of reality."

Hmmm, had to look that one up.

[tubman]

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After all of this, I'm starting to wonder about H&H Flatheads.

[Bored&Stroked]

As noted by some of the posts, the bottom of the spark plug should be just about flush with the chamber - it should not be recessed/shrouded. This picture (posted above) is how they should look (regardless of head manufacturer). It is important that your plug reach/depth achieves this - but does NOT have any plug threads out in the chamber (as that can cause a hot-spot and detonation).

Surface Gap Plugs: Be very careful in using these - it takes a lot of energy to "jump the gap". I tried them for shits and giggles on my 32 Cab engine with a new Vertex mag on it. They ended up frying the magneto coil . . . so I went back to good ole' NGK plugs.

Original Aftermarket Heads: Companies like Edelbrock and Navarro (back in the day) all used the same plugs as stock Forks --> Champion H10 length (which I believe is 7/16).

Later on, newer versions of their heads (and other manufacturers) switched over to 3/4" length plugs. I always prefer 3/4" length plugs (if the heads I'm using are available with them) - given the HUGE variety of plug choices that are available in this length.

Here is the picture (posted earlier) of how the plugs should look - regardless of manufacturer and chamber design:

IMG_1027.jpg

[tubman]

Thanks for chiming in Dale; your experience is always appreciated.

I knew the surface gap plugs were hard on the equipment, but a Vertex coil? Dang, they only cost me a couple of distributor caps.

[petehoovie]

Originally Posted by Bored&Stroked

As noted by some of the posts, the bottom of the spark plug should be just about flush with the chamber - it should not be recessed/shrouded. This picture (posted above) is how they should look (regardless of head manufacturer). It is important that your plug reach/depth achieves this - but does NOT have any plug threads out in the chamber (as that can cause a hot-spot and detonation).

Surface Gap Plugs: Be very careful in using these - it takes a lot of energy to "jump the gap". I tried them for shits and giggles on my 32 Cab engine with a new Vertex mag on it. They ended up frying the magneto coil . . . so I went back to good ole' NGK plugs.

Original Aftermarket Heads: Companies like Edelbrock and Navarro (back in the day) all used the same plugs as stock Forks --> Champion H10 length (which I believe is 7/16).

Later on, newer versions of their heads (and other manufacturers) switched over to 3/4" length plugs. I always prefer 3/4" length plugs (if the heads I'm using are available with them) - given the HUGE variety of plug choices that are available in this length.

Here is the picture (posted earlier) of how the plugs should look - regardless of manufacturer and chamber design:

Attachment 586430

[Ziggster]

For further reference, here are some pics of my stk cast iron Ford head showing the recess for the sparkplug. I have a pic somewhere with the NGK plug installed, but can’t find it right now. The clearance between the electrode and exh valve was 0.128” with a 0.055” thk Felpro gasket installed.

[Ziggster]

Found a pic.

[petehoovie]

Originally Posted by Ziggster

For further reference, here are some pics of my stk cast iron Ford head showing the recess for the sparkplug. I have a pic somewhere with the NGK plug installed, but can’t find it right now. The clearance between the electrode and exh valve was 0.128” with a 0.055” thk Felpro gasket installed.

[petehoovie]

Originally Posted by Ziggster

Found a pic.

[KiWinUS]

Originally Posted by Bored&Stroked

As noted by some of the posts, the bottom of the spark plug should be just about flush with the chamber - it should not be recessed/shrouded. This picture (posted above) is how they should look (regardless of head manufacturer). It is important that your plug reach/depth achieves this - but does NOT have any plug threads out in the chamber (as that can cause a hot-spot and detonation).

Surface Gap Plugs: Be very careful in using these - it takes a lot of energy to "jump the gap". I tried them for shits and giggles on my 32 Cab engine with a new Vertex mag on it. They ended up frying the magneto coil . . . so I went back to good ole' NGK plugs.

Original Aftermarket Heads: Companies like Edelbrock and Navarro (back in the day) all used the same plugs as stock Forks --> Champion H10 length (which I believe is 7/16).

Later on, newer versions of their heads (and other manufacturers) switched over to 3/4" length plugs. I always prefer 3/4" length plugs (if the heads I'm using are available with them) - given the HUGE variety of plug choices that are available in this length.

Here is the picture (posted earlier) of how the plugs should look - regardless of manufacturer and chamber design:

Attachment 586430

Thanks Dale for confirming what I had suggested earlier great info.