As you know, I'm pretty new at this. Getting my rockers and pushrods installed, and need to set valve clearance properly. I read Glen Chaffin's post from a few years ago on setting proper valve clearance, and would like to know if that same procedure works with the RAJO OHV system, and if so, where is the 0.010 - 0.015 clearance measured at? Between the valve stem and the tappet when the valve is seated? Thanks for any help. Dave
I would use .012 when the cam is on the bottom side lobe.
Thanks, Joe. Where do I measure the 0.012? Between the valve stem and the rocker tappet? That's the only place to make an adjustment.. Dave
Thanks, Roger. One other question (slight thread drift, but not much); is there any interface or connection between the lifters and the pushrods other than the ends of each against each other? I have the stock lifters, I believe. But I also have pushrods with holes near the lifter ends, and a new set of short pins that I think should be used there, but I don't know what they should be holding? Please see the photo below. Am I missing parts here? Thanks.
I think .012 is not not enough for a OHV set up (fine for a flathead). You risk burning your exhaust valves when it warms up the first time. .018-.020 would be my starting point cold. You will get a bit of "clatter". Ideally reset it HOT and running!
Pushrods with holes; never seen those on a OHV before. Shouldn't hurt anything
Maybe the pushrods are improvised and used to be valves?
Were sometimes extra springs used on the pushrods? I'm thinking if the pushrod is tight as a valve stem in the former valve guide, maybe it needs some help with a light spring to keep contact with the tappet at higher rpm:s?
That's a cool idea Roger. The springs would be in the same location as normal valves springs right? I would guess you'd want them to be a little lighter though. The combined load of pushrod springs and the OHV spring might cause some rapid wear on the cam.
A setup like that is called a "rev kit", racers sometimes use them, see pic below of a kit installed on a big block Chevy with roller lifters.
Thanks, all. If I were to use some light springs there, I would need some kind of retainer, and the pins would hold the retainer in place, I'm thinking. Anyone have a pic of a RAJO head with this kind of set-up? Thant would answer alot of my questions. Thanks again.
i have the same set up as you, and i was puzzeled that the push rod just sits on the lifter loose with no centering, or holding device. i can see the wear on the old push rods from bouncing around in the holes in the block. seems kinda wimpy, but thats how they were. i have been told that some folks dive into the top of the lifter with a ball end mill, then make a ball on the push rod, or some use adjustable lifters and thread a ball end into the thread, and, i have heard the new ones being made by mark chaffin have a cap similar to whats on the top. i havnt got there yet, maybe some others will tell more
My RAJO has been on since the early 1960's and the push rods are still a very nice fit in the old valve guides, I don't think bouncing around ones would be good to maintain an even clearance through the tappet system.
I'm having trouble following this discussion. I'm thinking that some are talking about valve stems and some are talking about push rods. I'm not familiar with RAJO overhead valve set ups, but most overhead valve trains I've ever seen have a push rod supported at the bottom by some sort of "indent" in the tappet or lifter, and by the rocker arm at the top end of the push rod. The bottom end of the push rod moves straight up and down with the movement of the tappet or lifter, but because of the fact that the top end of the push rod moves in relation to the arc described by the rocker arm, the angle of the push rod changes with each up and down movement. Therefore, there's no way that the push rod could be supported by a guide; it must only be supported at the top and bottom end (only).
Harold - If you view the left o the first photo, you can see the top of the pushrod engage the rocker arm with a ball and socket fitting. In the next photo down, you can see the other end of the pushrod as it meets the lifter. The guides aren't a tight fit, but they're not rattling around much either.
What I did find is that as Mark posted, the pushrods, where they meet the lifters, should have light springs with retainers, and are pinned to keep the retainers in place (hence the holes in the end of the rod). I found the springs and retainers in a jar of "spare" parts my dad had relocated and had forgotten about.
Thanks to Seth and Roger also for the memory jog that made me go look for those springs!
Harold, I agree with you when talking modern/higher revs etc, the lift of a T cam isn't much and the push rods are long, I just popped the rocker cover off and checked with a dial indicator, the movement of the pushrod at the rocker arm ball cap is only a few thou in it's up/down travel.
my thoughts allways were with harold, the rocker is traveling in a radius, not straight up-and-down, however kerry has proved that is not as much of a problem as one would think. i looked, and my original push rods also have the holes at the bottom, and i also have the same looking springs that i all ways assumed were the valve springs. some where in this forum the discussion of correct valve spring presure was listed, and my springs were very very weak to what was posted, so i just thought new ones were in need. mark chaffin gave me a part # he uses for some case tractor valve springs he uses, sorry its not home, at my valve guys rite now, pm me if anyone needs it. my rajo is a model 31, the cross flow 8 valve before the b came out.b valve covers do not fit, anyone got one to look at?
My Fronty pushrods don't have the hole, and no aux springs, of course. The pushrods just float around during valve closed cycle. There is a little wear on the pushrod sides where they go through the rocker stands, but no biggie.
Clayton- contact me off forum- I have the correct valve cover for your head- yes they are different than a B cover. dmcgearsatyahoodotcom
I keep desperately hoping I will find a Rajo head at a garage sale, antique shop, something. I want one really bad but don't have $4,200 to get a new one from Mark.
Mine's a Model 30, which was apparently the first one they made. Manufacture date seems to be early 1920, as they came out with the Model 31 (like Clayton has and Noel Bullock used) later in 1920. Mine has four exhaust ports and one intake port (in the center) on the right side of the head, with the plugs on the left.