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Shortening my Chrome-Moly push rods

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I found an area machine shop that can cut down the length of my Chrome-Moly tubular push rods. I need to cut .120" off the length to accomodate my now shorter head. So, smart me, to help the machine shop I shot a couple of Xrays of the rod ends to see how long the ends extend into the tubes. I had to shoot these at about 10X the power that I would normally shoot a tooth with to get some penetration. The machine shop will either think I am crazy or be very appreciative. Kinda like when an LBC fanatic goes to a regular paint guy and expects his car to be sprayed to concours condition on a Maaco budget. Is this part of my OCD disorder?
Xray.jpg


Sorry for the fuzzy quality of the film but you can see that the ends of the push rods extend only about 1/4" into the hollow rod. The machine shop will have to "peel" off the outer layer of the rod right at the end, then shove the end into the now-shorter hollow rod. Question: are these rods hollow all the way down like a tube or hollow on the ends only. The Xray seems to suggest hollow on the ends only. Guess the machine shop will know. Now on to more important things.....

Bill
 
Geez Bill -- I going to find out what my dentist would charge to x-ray a few parts for me.

I know next to nothing on this subject, but... have you considered shimming the pedestals rather than shortening the push rods? I recall that one has to be cognizant of how this affects the geometry of the rocker but if it would work it would be simpler and preserve the integrity of the rod ends.
 
I think that pushrods are hollow. The machine shop will just cut the outer layer of the end to the width that you want them shortened (.150" if I remember your post correctly). Then the end can then be tapped into the hollow tube to give the corrected length. Some ends are welded on so they may also need to do this too.
 
Bill, the rods should be hollow all the way. Hence the term "tubular pushrods."
George, I believe Bill took off about .120" from the head. This much shim under a rocker pedestal would throw the geometry out the window.
On my 1500, I had to not only have pushrods made to the exact length required, I had to cut .125" off the pedestals to maintain proper geometry.
It can be a fiddle to determine the correct pushrod length, which is why I didn't get into it on Bills previous thread.
Jeff
 
Bill, just a suggestion but Ted Schumaker sells custom length chrome moly pushrods (that you wouldn't have to cut) tsimportedautomotive.com nfi PeterK
 
Peter, you are a lifesaver. I have been tryng to find someone that sells custom length push rods for the longest. Will give Ted a call in the morning. Will return these to TRF (and save half the monies). Thanks again. Now, if I can only turn my Xray up high enough to zap my differential.....

Bill
 
Hello Bill,

I suppose you know that Triumph already made short pushrods for 9.5:1 heads. Not tubular of course. And I agree with Jeff, shimmming is not an answer in any form, as that upsets the rocker geometry.

Alec
 
Hi Alec,
I was aware that Triumph made the shorter push rod for the UK TR6PI with the 150bhp engine. I would love to get my hand on a set of these but, alas, haven't had any luck.
Unless you have a special inside connection to Rimmer or the likes on your side of the pond.

Bill
 
Hi Bill,

Nice photo of the pushrods! Not many of us have X-rays in our restoration scrapbooks. Next, maybe an ultrasound? /ubbthreads/images/graemlins/wink.gif

Yes, the usual method is to make up a cutter the right thickness and slip the pushrod in a lathe, carefully "peel" the correct amount off the tube, then push the end down into the shortened pushrod tube.

Seriously tho, there are pushrod measuring devices... essentially just an adjustable pushrod, that makes for the best method of measuring after modifications like you've had done. I guess there is some potential for variation from the pushrod being shortened exactly the same amount the head was shaved. For one, using a different head gasket, in combination with the head modification, would change the perfect pushrod length. The adjustable "dummy" pushrod is installed and the valve gear bolted on, the pushrod is adjusted to give the best possible lift, then removed and measured. I'm still looking into doing this and don't have all the details, but wanted to mention it as an option.
 
Bill,

Are you using Goodparts roller rockers? Richard cut my heads for 10:1 and he said this to me in an email after I asked him about this very same thing:

[ QUOTE ]
You should not need shorter push rods, especially with the roller rockers. If we need more room we can shim the rocker pedestals. The ideal height for the roller rocker shaft is a bit higher than normal anyway. If you do replace your push rods I would recommend tubular ones just because the new "stock" ones I have seen recently are junk. The cups are very rough inside.

[/ QUOTE ]

I think the push rod galleys were opened up a tad, but that's the extent of my push rod mods. Been running great now for 2000 miles.
 
Alan, I do my engines using an adjustable pushrod, and machinists layout blue, to determine the proper "wipe" of the rocker across the valve stem. Then, I have Crane make my pushrods to the optimum length. Strangely enough, the last set I had made, for a 1500, was cheaper from Crane than buying a set of shorter pushrods from the usual suppliers.
Jeff
 
I just ordered a new set from Schumacher and his being familiar with the GoodParts cam, roller rockers and the amount I had shaved, suggested I get a set custom made that were a tad longer than the .120" cutoff I suggested. I didn't argue the geometry with him, just accepted is vast knowledge compared to mine. I, too, was told by Richard Good to just shim the pedastels wince he sent me a set of shims. I couldn't even fit the stock length rods inside the rockers (they are still set at my original setting). So, shims don't work. I am satisfied that I have now made the right choice. Thanks for all the great imput. Hope to be cranking soon!!!

If something goes "pop" when I crank the engine for the first time, I may well need an MRI for the whole thing....

Bill
 
hey,forget the originals.get a custom set from previously mentioned supplier or british frame and engine (you can find them on the web) or any other triumph specialist, cambridge motorsports,racetorations(i like these guys, they build and develope their own engines,great advise also). measure EXACTLY what you need to put the rocker end (on the valve)in the exact correct position. head skim dimension does not necessarily = push rod lenght correction. camshaft has a major bearing on this. you want the sweep across the end of the valve to be correct.talk to a tr expert like racetorations.(not me)
 
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