Because of non repairable cracks that go from 2 of the exhaust valve seat out I am getting parts together to do the 28 Chevrolet OHV conversion.
A little history on this block, it has never been surfaced but the casting over the ports is too thin to take valve seats. It has been checked for flatness and is good to go in that respect. (I think someone else posted about have the same problem in the last few months)The number matches the title so don't want to mess with changing that. I have a 1928 Chevrolet head on hand and the adapter plate is on it's way. The plate is an early style with full round holes for piston pop up so will not be a real increase in compression. I have read most postings on on this type of conversions and have had some experience with the Model A Jern Thunderbolt conversion.
My question is; I get how to do the rocker end of the push rod. How do you do the lifter end, does the push rod just sit on the lifter and held in center by the hole the valve use to go through? I would imagine it would be the same for Rajo or any of the others.
I don't claim to be a expert on the subject but I just finished doing that same conversion on my 1924 block this last summer. I put the push rods right down the valve guides and they lined up perfectly with the lifters. I did however half to make a very slight bend on the two end rocker arms for proper alignment. The motor runs beautifully.
Jim, do you have one piece push rods all the way? Slightly smaller diameter than the valve guides so they can follow the rocker sideways? Extra return springs? Did you get the push rods from Neal Jern? By the way, is there any news if someone is continuing the business after Jern's death?
By the way, Merry Christmas everybody
Most of the push rods I have seen are rounded on both ends, so as Roger asked, what did you use for push rods? Does yours have cups with flat ends that sit on the lifters?
(Message edited by redmodelt on December 25, 2014)
What I did was picked up some round stock at the steel yard, 5/16 diameter and cut it to length and put a very slight bevel around the ends. and yes they are one piece rods. I didn't have any Chevrolet push rods so I also had to machine the end caps that connect to the rocker arm adjusting screws. Hope this helps. Jim
I have had a 28 Chevy head out in the shop for years, and I guess I should go ahead and put it on an engine. Not sure where to buy one of the adapter plates though, if anyone has any info on that I would appreciate a message. I have a CNC Milling machine and could make one if I had a drawing, but not sure if they are out there anywhere. Any help would be appreciated. Thanks
I use modified adjustable lifters and 1/4" pushrods. The adjustable lifter has a 1/4-28 screw which I replace with an equivalent socket-head screw. By drilling out the socket you can make a nice cup to receive the spherical-end pushrods. Of course this all requires pulling the cam and old lifters...at least the valves are out.
I also have a 28 Chevy head and would like to set up an engine with the conversion at some time. If someone is handling the Jern business, I would be interested.
The home page says to check back in January of 1915.
Good idea on the socket head screws.
The plate I am getting comes with a blue print before I even think about making copies I need it in hand to check copy right on it.
Mark: They could very well have a copywrite, if they don't I would sure like to buy a copy. Thanks
Mark Chaffin sells his lifter things which are a cup shaped deal to accept ball end push rods and it screws into the threads on adjustable lifters. some also use ford Y block lifters which are cupped, but larger in diameter.
God Jul to Roger and Merry Christmas to the rest of you!
By old Scandinavian tradition Christmas lasts for 20 days, so on January 13th the Christmas tree came down.
Interesting that your machinest considers the block to thin for seat replacement, our Canadian blocks are traditionally thinner than USA ones and seats have and are fitted protruding by a bee's d''k into the port just on the manifold side of the block, never given any problems that I know of.
The Jern kit comes with a short push rod with a flat bottom against the lifter and a cup end at the other side and a longer one, 6 3/4" with a ball end and cup for the valve lifter ball.
The shorter one had to be cut down in diameter just a little to suit the valve stem. Or You have to hone them instead. Easier to sand the rod some.
Because the T valve stem don't line up with the chevy valve lifter he made the push rod in two pieces.
I might get by with putting a seat but the crack runs along the roof of the port, drilling and pinning, I would risk breaking a chunk out. Besides, this is something I have wanted to do every sense I first heard about this type conversion.
My tree goes up a day or two before Christmas and comes down about mid January.
Merry Christmas and Happy New Year.
Thomas; read your post again and it sunk in what you are saying.