Caddy hop up 331 to 390+

I've got a 53 331 that I want to build up. I read Cadillacin Marcus' thread on early cads, but I'm unclear about the use of 365 (56-58) heads. I've heard that they are the same as the 390's, but are the rocker shafts also the same, or are they like the 331? Anyone know for sure?

 

www.chipscaddys.com hed be able to let you most likely.

 

I can give you my observations between one set of '56 365 heads I have, and one set of '60 390 heads I was given. The valves are farther apart in the 390, allowing for bigger valves to be fitted. The ports appear to be the same size, BUT, the center exhaust ports are different. On the 390's ( still siamezed ) there is a cast-in devider in the head, directing the exhaust out the port, rather then towards the ajoining port. This devider does not go all the way to the exhaust flange, but is is quite obvious. Also, since the valves are placed farther apart, I believe if you use the 390 heads, you should use the pushrods (longer?) from a 390. Thats the limit to my knowledge on the subject, looking forward to other resoponses. Mark.

 

The 390 heads were the best of the breed. And, they will bolt on to your 331 engine.

I've got some resources that say the pushrods on the 390 are longer than the 365/331's. One resource says the deck height of the 390 was increased from the 365 engine to accomodate the stroke increase starting with the 1959 model year which took the 365 and grew it to 390. I'm in the process of verifying the deck heights of the 331/365/390 family of engines.

If you are going to throw money at a set of heads, go for the 390 heads. Use Studebaker rockers for the valve train, they bolt on and they are adjustable.

 

How can the 390s have a taller deck, when '49-'62 intakes interchange?

 

Heathen, I'm editing my post, thanks for spotting that discrepancy. I have been doing my research on these engines and one of the reference books that I have may be wrong. Time to reverify some measurements!!

 

Talk to Chris at http://www.cad500parts.com - he's a HAMBer and can help you out with advice and parts!

~Jason

 

I wasnt aware cad company had anything to do with the early cad stuff. I've used them numerous times for 472 and 500 parts, and they seemed so specialized in that field, I assume thats all they did. That's what happens when you assume...