Hi all, I'm after a set of oversize valves, exhaust and inlet. I've seen 1.70 and 1.44 advertised on ebay before but can't find anyone now. Can anyone point me in the right direction?

SI Valves

http://www.sivalves.com/

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There was a guy, I believe the trade name was enginebuilder that did high quality 1.70 and 1.44 valves for the slant, in the standard slant six stem diameter and length.
he has retired, those valves are no longer available.
As an alternative, I have heard of folks using 318 valves, that allows one to stay with the 3/8 valve stem, but they are a bit longer.
Others have used Chevy valves or Ford valves, with the head OD trimmed back. That gets you a thinner valve stem.

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Chrysler big block exhaust valves are also 3/8 stem and closer to the needed length. (about .100 longer)
For exhaust, the early 361 / 383 1.6 exhaust valve should have the head trimmed to clear the side of the SL6's cylinder.
The 440's 1.74 exhaust valve works good as a SL6 intake valve.
These valves use a taller 1.8 valve spring that can often be helpful when running a higher lift SL6 cam.
DD

Doc, I had heard of that, however since I have never seen actually held a Chrysler big block valve in my hand,,,
I did not want to say that.

Because ,,,don't exhaust valves normally have a tulip shape profile under the valve head and for an intake, a nail shape under valve head profile is preferred?

just asking,,,

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

You are correct that the "nail head" intake valve is better for flow in a SL6.
Truth is that the flow difference between the tulip and the nail head is small compared to just getting a bigger valve in there.
There are some nail head BB exhaust valves so shop around.
DD

I'm using Ford 2.3 "Pinto" valves with Pontiac guides and 318 springs. Can't give you much more information about it because my machinist did all the work, but it was way cheaper than SI valves.

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I bought some SBI 1.60" BB units and cut them down to 1.50", they had an odd raised ring on the chamber face of the head. I completely removed that feature to bring the margin back to normal, but they weren't anywhere near concentric, including the "divot" portion. I had purchased extras to experiment with, so I had enough to select 6 usable ones, but just the same...........
No doubt, with the advent of common small-stem usage, it is a good choice to go with if You are willing to make the needed changes & accommodations.

Here are the part #'s from the SI valves catalog:

I am listing the oversize ones: 1.70" / 1.44"



Greg

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I might add a small word of caution/tip to anyone using exhaust valves for intakes, especially if You're using aftermarket stainless units. It's not always best to buy the "best", because quality valves have profiles and chamfers/angle cuts that are a big help to flow OUT of the chamber and into the port,......
otherwise known as REVERSION on an intake valve,......definitely NOT a desirable feature there.
If I compare (3) 1.81" stainless units for a BBM for example, the Manley had the "best" margin features, the Milodon was "good", and the MP unit was the "worst".....but would be the best raw piece to start with especially if You were planning on Your own custom profile............................

For what's it worth I have changed out the valve guides,used the Ford 300 6 cylinder intake and exhaust valves.