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By slick56 - 11 Years Ago
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I have done about 40 miles on my new engine, and today, while taking off from the lights, the engine started running rough.On looking in the rear view mirror, the r.h. pipe was blowing heaps of smoke, and at idle the revs were up about 200.Upon getting it home i hooked up a vacuum guage and restarted it. No smoke for a couple of minutes (then plenty) but still running rough.Pulled the pass. side valve cover and no pushrod for no.4 intake. Pushrod cup broken into 3 pieces, luckily still in the rocker area.I have installed new camshaft and all new top end; valves, springs, collets, retainers; rocker shafts, 1.54 rockers and longer pushrods. i put in longerpushrods because i kept the '56 oil trays.I have no idea why the pushrod broke, there does not appear to be anything wrong, other than lash was a bit loose, i was going to re-adjust valves when i got home today.As i do not have another long pushrod, will it be ok to run one of the slightly shorter ones that came from the engine, until i can source a new one from the USA, or should i replace them all with the shorter ones (which were a bit of a mismatch of two different styles) ??Thanks, Al.
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By PF Arcand - 11 Years Ago
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Similar problems were reported here a year or so a go. Apparently in one case, the pushrod socket was not a proper match for the ball on the adjuster. Hopefully someone will come on here with further information for you . Good luck..
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By slick56 - 11 Years Ago
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 Have just pulled out the pushrods from two engines (the rebuilt 292 and the old 312) and, including the long pushrods i got from John Mummert, there are four different types ! Effective lengths are approximate, but close.Still can't upload pics, so have added as attachment..bottom is the long one, length of 8.112", .312 dia.next up has no ball but machined insert, length of 7.982, .311 dia.next up has large ball, length of 7.975, shaft dia. of .270top one has small ball, length of 7.915, shaft dia. .3125Not a bloody set amongst them...
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By charliemccraney - 11 Years Ago
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The pushrod cup is probably too small for the adjuster screw ball.
You should use pushrods of the same length. The longest possible will yield the highest ratio at the rockers. Usually, if you do vary the length, the intake will use one and exhaust will use another. If you have enough pushrods, you can experiment with that but you probably won't notice much, if anything.
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By jonnireb - 11 Years Ago
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Check to make sure that valve isn't stuck.
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By slick56 - 11 Years Ago
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"The pushrod cup is probably too small for the adjuster screw ball." charliemccraney
These were a new set of pushrods, but i guess one out of a few hundred could be faulty..
jonnireb (6/15/2014)
Check to make sure that valve isn't stuck.
The first thing i did; put a brass drift on the valve and gave a whack with a hammer, valve moves ok.
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By charliemccraney - 11 Years Ago
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New does not necessarily mean manufactured correctly - I know because I've been there. I also would not call what you have a set. That's just a bunch of mismatched pushrods. Check them all on the ball of the rocker arm before you reinstall them.
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By 2721955meteor - 11 Years Ago
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when you pre lubed wher you getting oil to all rockers.when i bought my ranchero it had a broken push rod,Reason poor oil flow to rocker arm.Re your push rod delema ,why not remove the trays,which in efect lengthens the push rods.you may want to think about eliminating drain tubes,or at least pinch them off some.if eng. rebuilt i would guess you ar using comp head gaskets,that makes push rods shorter.push rodes are in most cases the result not the problem, good luck
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By slick56 - 11 Years Ago
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charliemccraney (6/15/2014)
New does not necessarily mean manufactured correctly - I know because I've been there. I also would not call what you have a set. That's just a bunch of mismatched pushrods.
I put in a full new set of long ones from J Mummert, it was one of those that broke the cup.
Plenty of oil to the top end, everything new including outside grooved cam bearings. Two of the reasons i put in the long ones, to make up for the thickness of the composition head gaskets, and i want to keep the trays. |
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By Ted - 11 Years Ago
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Was the fuel fresh when the new engine was fired? Old fuel will varnish the intake valve stems/guides and cause them the stick. This in turn typically bends the original style 1/4" intake pushrods but if tubular pushrods are being used, then I can see the cups taking the blunt of the force. Beyond that, the lifters are the next failure point and having pushrods fail would definitely be preferable to that.
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By slick56 - 11 Years Ago
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Ted (6/15/2014)
Was the fuel fresh when the new engine was fired? Old fuel will varnish the intake valve stems/guides and cause them the stick. This in turn typically bends the original style 1/4" intake pushrods but if tubular pushrods are being used, then I can see the cups taking the blunt of the force. Beyond that, the lifters are the next failure point and having pushrods fail would definitely be preferable to that.
Fuel was about two weeks old, and we don't have that ethanol stuff forced on us (yet).Cups on the new long pushrods are deeper than on any of the others, cam has lift of .440"
Heads have been milled .030", hardened exhaust seats, stainless valves, new valve guide inserts fitted. Running 105lb springs.Block has been decked.Previously had upper cylinder lubricant bottle installed to compensate for unleaded fuel, will hook that up again.
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By OZYRAY - 11 Years Ago
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Are you using original or aftermarket adjusters on your rocker arms, seems like the issue might be in this area, there are some slightly larger ball sizes on some of the new rocker adjusters ...something to watch out for.
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By slick56 - 11 Years Ago
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OZYRAY (6/15/2014)
Are you using original or aftermarket adjusters on your rocker arms, seems like the issue might be in this area, there are some slightly larger ball sizes on some of the new rocker adjusters ...something to watch out for.
The adjusters were on the 292, i suspect they were replacements.They are the friction type with 1/2" hex, and were very tight going into the new 1.54 rocker arms.I have a set in another engine with 7/16" hex, i will measure the ball on both and compare.
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By snowcone - 11 Years Ago
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Push rod length is determined by the position that the rocker arms move through.
If you vary the lift of the cam or the rocker ratio then you possibly move away from standard lenths.
What you need to do is view the action of the rocker from side on through a full cycle to see if the push rods are lifting the rocker too far and not enogh ie the rocker should be moving within the centre range of it's pivot.
I did have a tool years ago that fitted SBC for testing this but I haven't seen it for ages.
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By slick56 - 11 Years Ago
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OZYRAY (6/15/2014)
Are you using original or aftermarket adjusters on your rocker arms, seems like the issue might be in this area, there are some slightly larger ball sizes on some of the new rocker adjusters ...something to watch out for.
Yep, that is the problem!The ball on some of the adjusters are .0035 larger than the rest.It may not seem much, but putting the cup of a pushrod onto the smaller ball you can feel the "stiction",not so with the larger ball. The cup on the new pushrods is also deeper than the old ones.
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By OZYRAY - 11 Years Ago
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When you reckon you have the correct adjusters put a thin smear of bearing blue on the balls and fit them into the pushrod cups - give them a slight twist and check the contact area in the pushrod cup, you should have even contact right down into the cup, if they are mismatched you will see it right away.. be sure to use a very thin amount of bearing blue
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