I'm of the understanding that the 428 & 428CJ rocker arm shaft aluminum stands are dimensionally compatible, with respect to width and shaft bore centerline to stand base dimensions, with each other and the 427LR shaft cast iron stands. Is that a safe understanding?
Is there a benefit to replacing the standard 428 & 428CJ aluminum shaft stands with the 427LR steel shaft stands?
I'm also of the understanding that the 427MR rocker arm shaft cast iron stands are slightly wider, approx. 0.015", than the 427LR shaft stands. That would be 0.0075" rocker arm pad to valve stem offset per side. If 427MR shaft stands are used as replacements for 428 or 428CJ shaft stands, what damage is likely to happen?
The 428 and 428CJ heads have large bevels where oil feeds through the head to the rocker arm shafts, such that neither the 427LR nor the 427MR shaft stands would restrict oil to the rocker arms on 428 heads.
I hope all this makes sense. Please correct me where I'm mistaken.
Steve
427 MR stands are about .050" shorter and they are also wider. That may or may not cause the valve train geometry to be out of whack.
The 428 CJ / SCJ used the same setup as a 390 of the same year so the rockers are not adjustable. As you noted the 427 LR stuff is dimensionally the same but the rockers and pushrods are different and have to be swapped as a group. The adjustable rockers from the 427 LR are an advantage if you have a non - stock camshaft. The steel 427LR stands are stronger - but only needed if you have aftermarket stronger valve springs.
If you are using a stock or mild cam with mild valve spring pressure there is no advantage to changing those parts. The 427 adjustable rocker arms are not a great design, the adjusters get loose after one adjustment. Harland Sharp offers a better set of rocker arms / shafts / stands if you need to go adjustable. They are not free, but the quality is exquisite.
Thanks Royce. I did not know that the 427MR shaft stands were shorter as well as wider. I thought I could use them instead of the aluminum stands that were used on the 428PI and 428CJ engines. I was mistaken.
I'm working on rebuilding a date code correct block to replace the original block that was cracked. When building this new engine I'll very likely keep it in stock configuration and use the stock aluminum supports, unless I can find a set of reasonably priced, good 427LR cast iron supports.
The engine currently in the car is a 428CJ I yanked out of a '69 Cobra Torino. Its CJ heads have Precision Oil Pump's components; rocker shafts, shaft supports (including shaft end supports), roller tip adjustable rockers, push rods, and solid rocker arm spacers and shims. It's a little stronger than stock, and I like the increased durability in the valve train.
Thanks again for sharing your knowledge.
Steve
And what Royce means is that the overall height is not necessarily different, it's the shaft hole through the stand. MR holes are ~.050" lower in the stand than LR. My MR stands are ~.014" overall taller than the LR. HR stands are overall shorter than either MR/LR, obviously.
Doug's system is the equal of the Harland Sharp system, maybe even a bit stronger. Totally unnecessary if you have a stock or near stock valve spring and camshaft though. A bit more expensive due to the unusual pushrods.
Quote from: 8T03S1425 on December 12, 2022, 11:03:18 PM
Thanks Royce. I did not know that the 427MR shaft stands were shorter as well as wider. I thought I could use them instead of the aluminum stands that were used on the 428PI and 428CJ engines. I was mistaken.
I'm working on rebuilding a date code correct block to replace the original block that was cracked. When building this new engine I'll very likely keep it in stock configuration and use the stock aluminum supports, unless I can find a set of reasonably priced, good 427LR cast iron supports.
The engine currently in the car is a 428CJ I yanked out of a '69 Cobra Torino. Its CJ heads have Precision Oil Pump's components; rocker shafts, shaft supports (including shaft end supports), roller tip adjustable rockers, push rods, and solid rocker arm spacers and shims. It's a little stronger than stock, and I like the increased durability in the valve train.
Thanks again for sharing your knowledge.
Steve