Cyl Head 3947041

[jdv69z]

Looking at a head #3947041 with casting date of C21 9; Has 5/8" tapered seat plugs. Is this a 69 produced head for 1970 model year? I thought 69's have the 13/16" plugs with the washers. Or could it have been changed?
 
Jimmy V.

[1968RSZ28]

http://www.camaros.org/forum/index.php?topic=1168.0

Paul

[z28z11]

Jimmy,

Colvin references this in his 65-69 Chevrolet by the Numbers, and in the 70- up book also (I'll paraphrase) - "65-69 cars came with "N" series heads, or flat gasket spark plug seats. All 1970 and later model year cars were produced with a "peanut" or tapered spark plug seat. It is possible, due to late model releases in 1970, that 2 cylinder heads could have close or matching casting dates and be tapped for different type spark plugs."

Regards,
Steve

[KevinW]

The 041 head was used primarily on SS350 Camaros.  The 69 Models were made until Nov of 69.  So this head was made March 21 of 69, well within the model year. Maybe it was modified?

[jdv69z]

What I thought. This head has inserts for unleaded fuel so maybe it was modified for tapered seat plugs. But I don't know why someone would do that. Either that or it wasn't used until 1970 production. But that seems hard to believe as well. There is another head that came with this one. I'll have to check the date on that one.

Jimmy V.

[jdv69z]

Other head is same date

Jimmy V.

[KevinW]

I have a set of D69 041 heads in the basement, I have to take a quick look at the plug holes

[KevinW]

Oh yea, I am running a set of E69 heads on my SS350 and they have the regular flat plugs.

[KevinW]

Yes, the D69 have the same flat plug holes.

[tmodel66]

What I thought. This head has inserts for unleaded fuel so maybe it was modified for tapered seat plugs. But I don't know why someone would do that. Either that or it wasn't used until 1970 production. But that seems hard to believe as well. There is another head that came with this one. I'll have to check the date on that one.

Jimmy V.

Jimmy it's been a while. Refresh my memory on the unleaded fuel inserts. I can't get the picture in my mind.

[JohnZ]

What I thought. This head has inserts for unleaded fuel so maybe it was modified for tapered seat plugs. But I don't know why someone would do that. Either that or it wasn't used until 1970 production. But that seems hard to believe as well. There is another head that came with this one. I'll have to check the date on that one.

Jimmy V.

Jimmy it's been a while. Refresh my memory on the unleaded fuel inserts. I can't get the picture in my mind.

If it has hardened seat inserts, they were done in a machine shop somewhere - Chevrolet never used them. Unleaded gas wasn't mandated until 1975, and Chevrolet responded with electrically induction-hardened seat areas in the cast iron.