Spark plugs 383

[66Satellite47]

Grabbed this from another site. Heads and their comparison.

516, 1966 and earlier, Flat Port Floor, Closed Chamber, 2.08" Intake / 1.60" Exhaust
915, 1967 only, High Huber Hump Intake Port Floor, Closed Chamber, 2.08" Intake Valve / 1.60" Exhaust (low perf), 1.74" Exhaust on HP Engines
906, '68 to 1970, High Huber Hump Intake Port Floor, Open Chamber, 2.08" Intake Valve / 1.74"Exhaust (All)
902/346/452, 1971 & up, Low Port Floor W/swirl hump on siamesed inner Port wall(acts like a short turn), 2.08" Intake, 1.74" Exhaust(All)

Bee you are mixing up the issue. It's not the intake port design, it's the lump on the outside of the spark plug. Those are motor home heads that use the different spark plug.

 

[Gus chiggins]

Bee you are mixing up the issue. It's not the intake port design, it's the lump on the outside of the spark plug. Those are motor home heads that use the different spark plug.

It looks like Champion RV9YC will work

 

[BeepBeepRR]

Bee you are mixing up the issue. It's not the intake port design, it's the lump on the outside of the spark plug. Those are motor home heads that use the different spark plug.

No I am not mixing up the issue. lol I was showing him that the intake and exhaust are the same size as the 906 heads. He was thinking he was bamboozeled with weird heads. Also that the heads are just a later date head. I also told him that the larger spark plugs will not fit in the heads. I had the same heads and the same plugs and they would not fit. I was reassuring him that the heads are fine.

 

[BeepBeepRR]

I posted the pictures of the 452's compared to the 906's above. I know the issues because I had the issues. The bump out is the issue as I stated.

 

[Gus chiggins]

I just wanted to say thank you to the FBBO members that responded to my problem. I just wish the company where I bought the motor should have at least specified the heads they were using. At first i was thinking stripped threads in the head( motor, not my head???)

 

[Gus chiggins]

They are probably 452 heads that have the bump out and wont allow the larger spark plugs. Same issue I had with the RV heads. I should have had the guy mill the heads in that area. The bump is aright next to the spark plug hole sand only allows the smaller shanked plugs.

452s with the bump.

View attachment 1281064

906 without.

Just a quick question on the 452 heads with the bump out, was that made that way for cooling the plug area?

 

[BeepBeepRR]

Apparently they have 2 versions of the 452 heads. There is a regular head and takes the bigger plugs. Then the industrial/RV head has the smaller plugs. Check this video. I do not know the answer to your question about cooling.

 

[66Satellite47]

The RV or Industrial head is a different casting, cooling passages are different. Not sure why they have the same casting number. They are different.

 

[Gus chiggins]

Apparently they have 2 versions of the 452 heads. There is a regular head and takes the bigger plugs. Then the industrial/RV head has the smaller plugs. Check this video. I do not know the answer to your question about cooling.

Thanks, it was hard to tell at first which heads i have. Being bolted on the engine with "stuff" in the way until i had to look, and confirm by touch to feel the hump by the plug hole.

 

[Geoff 2]

NGK 5 heat range are the correct plugs. I would only use Champions in my lawn mower...if I didn't like my lawn mower.

 

[Dave6T4]

I have used "452" heads on two of my builds, and they both took Champion RJ12YC's.

 

[Gus chiggins]

I have used "452" heads on two of my builds, and they both took Champion RJ12YC's.

Yes, because they were not RV/INDUSTRIAL heads, these heads had the bump at the spark plug hole, and take a tapered plug.