Navarro 8ba Heads

[69a]

Originally Posted by KiWinUS

Question. So if H&H built this engine what did Mike say about fouling plugs so often?

I never asked about the plug problem, as I only noticed it a couple of months ago. I had other issues at the time.

[tubman]

Originally Posted by Tim Ayers

They are beautifully cast and machined. Still made in the USA too.

If the Chinese ever get into it, we may see decent $395 finned aluminum heads again. If they can make $109 "shoebox" Ford three row radiators, I don't see why they couldn't make a decent set of cheap heads. Does anyone have any idea of why Offenhauser heads are usually priced hundreds of dollars higher than comparable Edelbrock's? Especially since the latest improvements.

So I guess we're all in agreement that all Edelbrock's use 3/4" reach plugs (and always have). Here's a link to the thread where we determined that Offenhauser heads (used to) need a 5/8" reach plug; which isn't made :https://www.fordbarn.com/forum/showt...ghlight=spacer. I hear that problem has been since corrected.

[KiWinUS]

Originally Posted by Tim Ayers

I will say, and I don't have any dyno info to back it up, the Cyclones I took over ran better. Just seat of the pants and to my ear, the throttle crack was sharper and crisper.

I may put them back on this winter.

I can get you the name of the sealer I used on the original 28 Miller OHV head. It has been driven for close to a year with no issues so far and it was throwaway.
Your wife may not be happy when you bake it in her over though. ��

[69a]

Originally Posted by Shoebox

I asked Mike about this subject, his response below.

On Jun 3, 2026, at 9:23 AM, Mike Herman <[email protected]> wrote:

 The electrode is not supposed to hanging out in the valve pocket or it will hit the valve

When the exhaust valve is fully open there is less than 1/16" gap between the valve and the cylinder head. This means the entire plug is up inside the thread. I have seen some heads where a recess is cast into the combustion chamber. The Edelbrock combustion chamber pictured in my previous post has a CNC machined recess to allow for the electrode to extend into the combustion chamber without hitting the valve. The Edelbrock combustion chamber looks great, the other one, not so much.

[KiWinUS]

Originally Posted by 69a

When the exhaust valve is fully open there is less than 1/16" gap between the valve and the cylinder head. This means the entire plug is up inside the thread. I have seen some heads where a recess is cast into the combustion chamber. The Edelbrock combustion chamber pictured in my previous post has a CNC machined recess to allow for the electrode to extend into the combustion chamber without hitting the valve. The Edelbrock combustion chamber looks great, the other one, not so much.

Only the latest Edelbrock are like that all earlier versions are more like the Navarro. I try to get the valve at .040 clearance to the cyl head. 55 plus years building these gems.
So what did Mike say about your plug fouling issues if he built the engine???

[Tim Ayers]

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Originally Posted by tubman

If the Chinese ever get into it, we may see decent $395 finned aluminum heads again. If they can make $109 "shoebox" Ford three row radiators, I don't see why they couldn't make a decent set of cheap heads. Does anyone have any idea of why Offenhauser heads are usually priced hundreds of dollars higher than comparable Edelbrock's? Especially since the latest improvements.

So I guess we're all in agreement that all Edelbrock's use 3/4" reach plugs (and always have). Here's a link to the thread where we determined that Offenhauser heads (used to) need a 5/8" reach plug; which isn't made :https://www.fordbarn.com/forum/showt...ghlight=spacer. I hear that problem has been since corrected.

Tubman,

Offy still does all of the finish work and final machining by hand in CA. I’d assume the higher cost is associated with the higher labor to finish their products.

[Tim Ayers]

Originally Posted by KiWinUS

I can get you the name of the sealer I used on the original 28 Miller OHV head. It has been driven for close to a year with no issues so far and it was throwaway.
Your wife may not be happy when you bake it in her over though. ��

I’ll text you. Thanks, Tony

[69a]

This is an Offy head, you can clearly see the relief cast into the combustion chamber, to allow the electrode to sit clear. This feature is obviously important to everyone except Navarro.

[KiWinUS]

Originally Posted by 69a

This is an Offy head, you can clearly see the relief cast into the combustion chamber, to allow the electrode to sit clear. This feature is obviously important to everyone except Navarro.

I ask you for the third time. What did Mike say about your plug fouling issues and spark plug shrouding you believe to be incorrect???
Do tell.

[tubman]

Originally Posted by Tim Ayers

Tubman,

Offy still does all of the finish work and final machining by hand in CA. I’d assume the higher cost is associated with the higher labor to finish their products.

Sounds to me like another mis-interpretation of basic economic theory that seems to be prevalent in this country these days. Maybe the Chinese should start making aftermarket finned aluminum heads.

[tubman]

Originally Posted by 69a

This is an Offy head, you can clearly see the relief cast into the combustion chamber, to allow the electrode to sit clear. This feature is obviously important to everyone except Navarro.

and Edmunds.

[69a]

Originally Posted by KiWinUS

I ask you for the third time. What did Mike say about your plug fouling issues and spark plug shrouding you believe to be incorrect???
Do tell.

I answered you in post #21.
PM me if you want more info.

[69a]

Originally Posted by tubman

and Edmunds.

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.

[Tim Ayers]

Originally Posted by tubman

Sounds to me like another mis-interpretation of basic economic theory that seems to be prevalent in this country these days. Maybe the Chinese should start making aftermarket finned aluminum heads.

I'm not sure if you are saying my comment is a mis-interpretation of basic economic theory or not, but Offy has tons of videos on social media showing them doing all the work by hand and being very proud of the fact. They use it as a marketing point. Someone needs to pay for that extra labor involved in production.

[KiWinUS]

Originally Posted by 69a

I answered you in post #21.
PM me if you want more info.

Thanks. I apologize I somehow missed it.
So the plug fouling had nothing to do with the heads as insinuated ?

[69a]

This is confusing. My first response was to SHOEBOX He was told by the vendor, that Navarro heads "are one of the best flowing heads". I cannot see much difference between any of the combustion chambers. I can see that there is only one head that has the entire spark plug up inside the thread. all of the others have a divit in the casting (Offy head pictured in my post #28) or machined (Edelbrock pictured in my post #4) The Evans heads do not have the divot, but the plug can extend into the combustion chamber without hitting the valve. I have been having the odd plug being fouled since day one. I have only just become aware of the fact that the plugs are shrouded by the casting. And I believe this is a possible cause. I did have a power valve leaking in my back carb (2X2 97's) that caused the two rear plugs to foul. But now it is completely random. Am I wrong thinking that the Spark should be produced in the air-flow, not 1/4" up inside a blind hole. I have never seen a OEM car or motorbike that doesn't have an exposed plug.
There was some confusion cased by me saying I had other issues, these were unrelated to the plugs fouling.

[69a]

An Evans head. From an earlier post by TUBMAN I think.

[KiWinUS]

Here we have original unmodified heads with correct and recommended H10 spark plug. Sharp script , Sharp block letter NOS Ford 81 head and an older Edelbrock 8ba. Also for those that remember from years past spacers were sold to prevent plugs fouling which pulled the plug up into the spark plug holes shrouding the plug and they worked.

[tubman]

That is my picture, and that is an Edmunds head, not an Evans. I have no experience with Evans heads, but as far as I know, Edmunds heads are the only ones with the spark plug moved far enough so it doesn't interfere with the exhaust valve. It allows the use if an extended tip plug, specifically a Champion L82YC. In Champion nomenclature, "L" means 14mm, 1/2" reach. while "82" is the heat range. "Y" means .060-.090" projected tip and "C" means a copper ground electrode. Please note that with this plug, the spark is well out in the combustion chamber, not up in a hole someplace.

This is not the place to expound upon combustion chamber theory, and anyone really interested should reference the works of Sir Harry Ricardo, who had this figured out 100 years ago. In an "L" head engine, combustion efficiency is mainly a result of efficient flame front travel. It will get a more robust manifestation when it has a mixture with good swirl (produced by proper quench) and a spark introduced in the midst of it. A set of properly massaged Edmunds heads does a far better job of this anything else out there (short of exotic custom built units.) I have also added a picture of an Edmunds head taken right down the spark plug hole, and there is nary a glimpse of a valve head in it. I have also added a picture of an L82YC plug in an Edmunds head along with the existing picture of a standard plug in the same head.

Barney Navarro did some wonderful stuff with flatheads (pop-up pistons and deep domed heads, for one) but it seems H&H picked the wrong heads to reproduce for street use. I will again reiterate that 100% of the ports and valves in a flathead Ford are in the block, so designing a head to be "the best flowing" seems to me to be a fools errand. Concentrating on compression and combustion efficiency would have been a much better idea. "OL' Ron" on this very forum was an advocate of the relocated plug, and often wondered why it hadn't been done.

[tubman]

Originally Posted by KiWinUS

Here we have original unmodified heads with correct and recommended H10 spark plug. Sharp script , Sharp block letter NOS Ford 81 head and an older Edelbrock 8ba. Also for those that remember from years past spacers were sold to prevent plugs fouling which pulled the plug up into the spark plug holes shrouding the plug and they worked.

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.