I have a new set of roller rockers for a big block Chevy. I know that they can be used on my 250 six by installing screw in studs. Is it worth the effort. The six now has an aluminum valve cover,a Mercruiser, so clearance shouldn't be a problem.

The six ratio is 7.5 to 1 & the big block is 7.0 to 1. When I had the cam ground for my 153 four cylinder we took that into consideration so I could use the BB roller rockers that I had. Even with the Mercruiser cover you may need a spacer and to round the corner on the end rockers, not sure. I think anything that reduces stress on the valve train is good. I don't know how they would effect pushrod length or if pushrod guide plates are needed.

In sticking with what Beater stated. It's been a long time but I bet they still sell them. They were sold at Jegs. They were steel roller tipped rockers. I think you could get them in 1.72. Much smaller than most roller rockers. I remember there being stamped roller tipped rockers but I read somewhere they weren't as durable.

Do a search for BBC steel roller tipped rockers.

I know that doesn't answer the main question but it does give you another option for hardware.

Yes, they can be used if the head is machined for 7/16 screw in studs. Most aftermarket BBC rockers use that size, so verify that's what the rockers are. Several disadvantages though, the Mercruiser valve cover still does not provide adequate clearance for roller rockers and as has been mentioned, the rocker ratio is less on the BBC rockers, so you end up with less valve lift and duration by using them. So in some ways a reduced benefit by using them.

Comp Cams makes a stainless heavy duty roller rocker for the Chevy 153/181 and the Chevy six cylinders! 1.75:1 and capable of withstanding anything that the bulky aluminum rockers can tolerate. They will fit under the Mercruiser rocker cover without modification!! Ultra Pro Magnum XD Rocker, part# 1827-12 for the six cylinder.

More than one of my drag and round track friends are swearing by these and they are more mechanically efficient than aluminum too!!

OK, Going way back here. I have a set of roller rockers I got from Lee Lasley (leelites) several years ago. They are for some Ford V8 but are said to be the same ones sold on line as Chevy six. This has been discussed here somewhere.

I used those stamped roller tip rockers on the 350 in my Blazer and they have done fine. They have to be easier on the rocker & valve stem at least. I didn't know there was a 1.75 version.

The 1827s aren't stamped rockers.These are forged stainless and have replaceable roller bearing trunions.

Jonah mentioned the stamped ones. Pretty neat deals.