casting Number 3964290

[Mark B.]

Guys, I have a 69 427 L36 motor, which the block is 3963512 with a date of J28-9. The intake is original and the heads are original from what I was told by the owner. The book says casting # 3931063 is the correct #. When i pulled the valves covers it has 3964290 with dates J22-9 and J27-9 which would make sense on the dates for the final assembly of the motor.

I was told that late in 69 the factory started rolling into 70 parts which would make sense of the casting numbers on my motor Is that True?

Mark

[Joe L.]

Re: casting Number 3964290

Guys, I have a 69 427 L36 motor, which the block is 3963512 with a date of J28-9. The intake is original and the heads are original from what I was told by the owner. The book says casting # 3931063 is the correct #. When i pulled the valves covers it has 3964290 with dates J22-9 and J27-9 which would make sense on the dates for the final assembly of the motor.

I was told that late in 69 the factory started rolling into 70 parts which would make sense of the casting numbers on my motor Is that True?

Mark

Mark------


There's no doubt the 3964290 heads were used in late 1969 for oval port big blocks. So, while these heads were used in 1970, they are also (late) 1969 heads.

[Patrick B.]

Re: casting Number 3964290

October (J casting) 1969 was the 1970 model year for Chevrolets except Corvettes and Camaros.

[Rick N.]

Re: casting Number 3964290

I have a pair of 063 castings that are dated late December 1969.
These heads were NOT discontinued before the end of the 1969 model year.

[Patrick B.]

Re: casting Number 3964290

Usually, it is very hard to distinguish a 9 from an 8 on the casting dates. l would bet that the 063 heads in question are December 68. What is the VIN range of the car they are associated with? Any pics?

[Rick N.]

Re: casting Number 3964290

Usually, it is very hard to distinguish a 9 from an 8 on the casting dates. l would bet that the 063 heads in question are December 68. What is the VIN range of the car they are associated with? Any pics?

It's not hard at All to distinguish that it's a 9

**EDIT**

FWIW... I've owned these cylinder heads since 1982

[Rick N.]

Re: casting Number 3964290

Here is casting date and Number

[Patrick B.]

Re: casting Number 3964290

Here is casting date and Number

You are right. I think it is very unusual for GM to continue the obsolete casting after the replacement casting has gone into production.

[Joe L.]

Re: casting Number 3964290

You are right. I think it is very unusual for GM to continue the obsolete casting after the replacement casting has gone into production.

Patrick------

If the patterns were in decent condition, it's possible that the 3931063 heads were manufactured for pre-1970 oval port applications for SERVICE after the introduction of the 3964290 heads. The only real difference between the 2 head castings was the spark plug seat configuration. While the 3964290 could be machined for either gasketed or tapered seat plugs, I could see GM continuing to cast the 3931063 for SERVICE of gasketed seat applications.

As an example of this, the GM #3859326 waterpump casting was last used in PRODUCTION for any application in 1968 (for Z-28 Camaro). The GM #3839175 waterpump casting was last used in PRODUCTION for any application in 1965. However, both castings were manufactured well into the 80's and, possibly, the 90's for SERVICE.

[Edward B.]

Re: casting Number 3964290

For the 1969 Camaro, (while we don't have a TON of data points, we DO have enough to give a generalization), the 3931063 was last used in production during the mid to late July, 1969 time frame. The 3964290 heads start to show up in very early August, 1969. That's about as close as I can come to narrowing it down. I would imagine the Corvette would be the same, but it would be interesting to verify this.

My L36 was assembled on October 14th, 1969 and the heads (3964290) are dated October 8th and October 11th, 1969. My car's build date was October 21st, 1969.

I'd like to hear from the L36 guys in the early July through late August, 1969 time frame to see if the Corvette transition was the same as the Camaro.

Ed