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Old 09-25-2005, 18:30   #1 (permalink)
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What caused these guide plates to break?

My valve train started makin some really loud clicking noises. It started about a week ago, but very very soft. Just figured that I had a rocker that was getting a tad loose, so I didn't worry about. Well, it got REALLY bad. So yesterday I pulled the valve covers off and found that 3 of the guide plates on each side broke. What could cause this? The only thing I can think of is that the pushrod was too tight up against guideplate and made it rock real slightly and it broke. So I had 6 pieces total break off, they all look the same. Here are some pics:


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Old 09-25-2005, 19:47   #2 (permalink)
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Re: What caused these guide plates to break?

Looks like the rockers been inpacting it pretty hard. Is the pushrod straight? I know it annoying having to pull a pushrod and then redo the rr adjustment. If the pushrod was impacting the guide and is straight. It means you have a geometry issue. The pushrod maybe too short or too long. Check the pattern on the valve tip. I usually color the valvetip in with a permanent marker and manual turn the engine over. The rr bearing will wipe off the permanent marker where it contacts. It should contact as close to the centre as possible and be as narrow as possible.
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Old 09-25-2005, 20:49   #3 (permalink)
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Re: What caused these guide plates to break?

Do not know if it is related but the dyno run of yours i downloaded, the first one i think where the guy seemed to load it for so long on there, that can't be good for vavle train component's. But for now do what brenx suggest's with the pushrod's.
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Old 09-25-2005, 21:38   #4 (permalink)
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Re: What caused these guide plates to break?

The geometry is spot on. Had a custom pushrod length checker and at 8.050", it had the best pattern on top of the valve and it was super thin. Can't i just notch the guideplate a tad bit so the pushrods don't touch the inside of the fork?
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1982 F100 2wd-408c CHI 3V 225cc Heads, 3v Intake, Pro Systems 1000+HP carb, 260/266@0.050 w/ 0.694/0.697" lift solid roller, JPT Rollerized c6 and 5000 rpm converter, 4.86 gears and S&W Ladder Bar kit with QA1's all the way around.
7.976@89.90 mph 1/8 mile with lots of bounce - with old engine and suspension(should be greatly improved)
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Old 09-25-2005, 21:43   #5 (permalink)
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Re: What caused these guide plates to break?

If thats spot on. Notching the guide plate and head if needed is they next best bet. Either that or Crane style guides which are flat.
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Old 09-25-2005, 22:10   #6 (permalink)
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Re: What caused these guide plates to break?

Quote:
Originally Posted by brenx
If thats spot on. Notching the guide plate and head if needed is they next best bet. Either that or Crane style guides which are flat.
I'd love to go with the flat ones, but I can't find any in 3/8" pushrod size.
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7.976@89.90 mph 1/8 mile with lots of bounce - with old engine and suspension(should be greatly improved)
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Old 09-26-2005, 01:21   #7 (permalink)
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Re: What caused these guide plates to break?

Hey dustin the pushrods are fouling the plates from the middle pic and that I will put money on this as your problem! The plates are hardened and as such wont putup with any bending at all.

Go ahead and notch em but im not too sure why you need 3/8 as the trend brand 5/16? (stock size?) in the 80th wall would be easier to deal with and the Crane plates can be used! The trends would be a lighter rod and easier on the rest of the valve train.
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Old 09-26-2005, 01:51   #8 (permalink)
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Re: What caused these guide plates to break?

I doubt the rocker has touched the guide plate. I cant see why you couldnt grind a bit of the plate, but i also doubt the pushrod has rubbed hard enought to damage the plate. You would have BIG problems elswhere if the pushrod was thrushting the plate that hard. I recon its your studs, or something there. Do you have to hit the socket on to tighten stud, or do you use a open spanner? It looks like the hex part of the studs as you do them up are rubbing hard up against the plates where they are on the flat of the head. It looks like it in the picture anyhow. Could this be loading up the plate all the time, then finally fatiguing it?
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Old 09-26-2005, 07:28   #9 (permalink)
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Re: What caused these guide plates to break?

Here is a really poor theory but i thought i would add it anyway...
Since the fracture surface exhibits no permenant plastic deformation (permenant bending) this indicates a highly brittle material.
With brittle materials, fatigue is a major source of failure since minor surface imperfections concentrate stress allowing tiny cracks to develop which in turn create a fracture over time and repeated stress cycles. As xyfmtjoe said
"The plates are hardened and as such wont put up with any bending at all"

It MIGHT be possible that the hardening/heat treatment/carbon content or another quality of the steel was incorrect for the application. Were the guide plates a reputeble brand? Do you know of anyone else who has used them? Does the supplier admit to anyone else having the same problem?

Steel expands when hot. The head and guideplate probably do not expand equally (different material and dimensions). This causes stress in the steel. The repeated heat/stress cycles MIGHT have fatigued the poor brittle steel or combined with the other factors mentioned or had nothing to do with it!

Just as an example of brittle iron, we've all hears of cast iron barbies cracking if you quench them with water (localised cooling = contraction = stress = crack)
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Old 09-26-2005, 08:46   #10 (permalink)
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Re: What caused these guide plates to break?

Quote:
Originally Posted by F100cleveland
My valve train started makin some really loud clicking noises. It started about a week ago, but very very soft. Just figured that I had a rocker that was getting a tad loose, so I didn't worry about. Well, it got REALLY bad. So yesterday I pulled the valve covers off and found that 3 of the guide plates on each side broke. What could cause this? The only thing I can think of is that the pushrod was too tight up against guideplate and made it rock real slightly and it broke. So I had 6 pieces total break off, they all look the same.
You don't mention whether the 6 pieces that broke off were all intakes or not. The photo shows an intake guideplate that is broken. 8.050" sounds waaaaaaay too short, are you using standard length rocker studs? I generally use +.100" longer studs to gain more clearance and better rockerarm geometry at the valve tip. My "Cleveland & BBF" pushrod length checker has a minimum length of 8.350".

The photo clearly shows the impression made by the meeting of the pushrod and the guideplate. This undoubtedly occured during the opening of the valves. If they are all on the intake side, then I'd start by looking at the one that isn't broken. Take a look and see if it is fracturing.

I'd check to ensure that your pushrods are not contacting any material in the cylinder head, too. Checking to ensure that they are straight, is a good idea, too.

You may want to consider posting a bit more information about your valvetrain. EG: camshaft lift, lifter type.

I can't imagine using a set of 3/8ths inch pushrods with a modest camshaft and hydraulic flat tappet lifters, so something tells me that you've gone to the upper limits in off-the-shelf cams or possibly even a high lift custom grind. If that is the case, then you probably should be using taller rocker arm studs. Your installed spring height could also be a factor with a standard length stud. Do you know your installed spring height? Did you assemble your cylinder heads yourself?

There is very clearly a clearance problem. It should have been resolved during assembly, and if it was, then as previously mentioned, you may have bent pushrods. A bent pushrod could take up any otherwise available clearance. It is very easy to check for bent pushrods. If they are straight, you could buy new (I'd replace all of 8 them!) guideplates, notch them and try again. Going to longer rocker arm studs will mean new pushrods, probably not a bad idea if they are worn.

It is fairly tough to make any real recommendation without the details of your valvetrain. Even your deck height plays a role in it...but 8.050" sounds completely wrong. 8.408" is a stocking length for a 351C by Comp, 8.500" is a stocking length by Crane. You're nearly a half inch short, if your measurement is accurate. It sounds like you used a pushrod length checker for a 351W/BBC. You need to use one for a BBF/351C or tall deck BBC.


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