Hot Rods Let's talk Cadillac 331's, 365 and 390's

Wow. Nice corvette. I'll give that a shot. It was a ton of water. Water was pooling in the pipe and dripping from the muffler clamps. It seems that would indicate either the head gasket or a really visible catastrophic type of crack, right?

 

Hmmm. The exhaust ports should be pretty simple. The heat riser is weirdly shaped...

 

This one has piqued my interest.

 

I don’t know how to share a video but this is clear, right? There’s no reason bubbles should be coming up through that hole other than a crack, correct?

 

Dang…….

 

You need to find another head. Thats a bum deal , magnafluxing probably would not have showed that crack and I don't think its a common problem .It's a little odd that only the last cylinder looks like it was firing...

 

Makes me think I should check mine closer

 

I’m happy. You guys saved me a bunch of work. I would have reassembled it. I owe Moriarity a frosty beverage for sure.

I’m starting to remember the first guy who tried to rebuild my motor sent both the heads to a specialty shop to have cracks welded…. In hindsight I’m thinking that was not money well spent. Anyone have a spare head lying around? I’m assuming there’s no aftermarket heads that exist for these. Maybe eBay….

 

Check your local FB marketplace. I saw a set in Wichita, KS for $100.

 

. It’s interesting that you noticed that too. I only ran it for less than 15 minutes so I didn’t put a lot of thought into it. Hmmm….

 

I'm going to the machine shop tomorrow , he has a pretty good stash . If I find something I will PM you.

 

. Perfect. Drivers side. Thank you.

 

Thank you. Is that supposed to be the casting number? My casting number is 1473449

 

I spoke to Ross today so I could get some pistons for my build.
They called me back and asked a couple questions I need to find an answer for.

The first was that he wanted to know the width of the small end of the connecting rod. I can call my machinist tomorrow and have him measure mine, but I thought I might get an answer quicker here. So anyone know that dimension for a 331?

The second question was head gasket thickness. I can find gaskets available, but no info on thickness.
I called and left a message with best gasket, but thought I'd ask here too.

 

The problem you run into is getting the rod width. I found out that I can use a Pontiac 455 rod but the width on the more modern rods is about .100" wider than the Caddy.

I have a ball park on the original width, but I would hate to quote it to you and then you make the piston to fit that arbitrary number.

JE will build you an exact replica of your piston in a forged slug. Just send them your old piston.

 

I went through a gasket search putting mine together and it seems that best are actually the best available. But there is only one thickness that they offer. My machinist built a piston using an original piston and added to the top and sent that to jahns for them to make a custom piston for the build. I have the mock up one at home in a box somewhere but it was basically where that step up piece is to the edge screwed into the factory piston to get the compression ratio we wanted

 

I spoke with my machinist this morning and he just measured it for me right away. He came up with 1.38”
I went with Ross because we are a dealer and I get a price break. But also, since I’m doing 390 heads, I wanted to get some made so I could dial in the compression ratio.

As for the head gaskets, Best gasket called me back, and compressed thickness is .045”

 

Wow. That's pretty thick. I wonder what the quench will work out to be?

 

Mine ended up being 9:7-1 in the end with the best gasket

 

How come there is no love for the 429s? Is there anything that will work for them anywhere!

 

The 429’s are kinda the fat kid on the playground. If you pop for the 429, might as well go for the 472/500.

 

Done a couple 429s in customers cars and it was a hassle because they only made them a few years and parts are a little harder to get and yes I would have just gone with the larger 472 or 500 Cadillac

 

That figures, I got one in a 19,000 mi. 1966 Cadillac Calais and another from a 65 C.D.V. With the switch pitch trans.

 

I'm sure you could use them if you wanted, but they don't make many aftermarket parts for them. There is a group in New Mexico that deals with the newer Caddy stuff that might be able to help.
https://cad500parts.com/