[gmoran]

I've got a LT1 out of a 1994 Buick Roadmaster (with the iron heads). I am rebuilding the engine and I was lapping the valves when I noticed the exhaust valves in my heads were different on each side. The passenger side has dished exhaust valves and seats quite nicely with the head once I got a good lap on it. The driver side has flat exhaust valves and the mating seat is very small, even after lapping. I don't like the way the valves seat on the driver side and I was wondering if maybe someone has gotten to this engine before me? Should all the valves be dished? If so, what should I replace the flat valves with?

 

[cocobolo95]

Sounds like someone has either switched valves on one of the heads. Or a used cylinder head from another model or year was installed.

Keep in mind that chevy used the lt1 & the l99 which looks like a lt1, but is 265 cubic inches 4.3 liters. I imagine the valves on a l99 engine might be different from lt1.

Also aftermarket replacement parts are many times slightly different than OEM parts.

 

[gmoran]

They are both 10125320 B-Body iron heads, confirmed with the casting number on each. Just that one head had the flat valves and the other had dished valves. The one with the flat valves also had aftermarket stem seals so I guess someone got in there at some point. The valves are supposed to be dished, right? I really don't like the way the flat valves seat as it's a very thin seat compared to what I was able to get with the dished valves but I think it'd be cheaper for me to get a used set of aluminum heads than to buy 4 new exhaust valves tbh.

 

[gmoran]

Just got out my micrometer and gauge pins to check the valve stems and bores. One side is 0.341" which is stock and the other side is 0.349"..... Which sucks because I found the stock 0.341" valves at oreillys for $12 ea but they won't fit the bored head...

 

[cocobolo95]

GM made over sized valves for these heads. Unfortunately, due to age of car, finding a set would be tough.

Try checking Napa for oversized valves.

 

[gmoran]

GM made over sized valves for these heads. Unfortunately, due to age of car, finding a set would be tough.

Try checking Napa for oversized valves.

I think I will just run them as is. The motor was running when I tore it down, no reason it shouldn't once it's back together. I'll just start looking for a set of alu heads.

 

[gmoran]

At a closer look, the oversized valves are also cut for double groove locks. How can I go about identifying the valves in the modified head?