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Discussion Starter #1
So I have been enjoying my last 2 days of being legal to finally drive the car on the street. Even asking the wife if there was anything we needed from the grocery or drug stores (I got to go to both today, YAY) and offered to run to the bakery for some cookies for desert. Basically been looking for any excuse to take a drive that I can. Seems I will only be able to drive the car on days when I am not in a rush because everyone wants to stop me and talk my ear off. So as of now I have 28 miles on the odometer. Fun miles at that.

So I am coming home from the bakery, stopped for some beer, and decided to take the long way around the neighborhood. I get maybe 1/8th of the way around the block when one of the neighbors stops me and wants to talk. Of course he has to show me the Jeep project he is working on. So we talk for a few minutes, him and his buddy asking questions about the car and complimenting it. When I get in the car to finish my trip around the block, he tells me to light the tires up a little. I smile and say OK. I start to leave, get to about 20 miles an hour, then give it about half throttle for about half a second. Just enough to get it a little sideways and continue home. At about the half way point, in second gear at around 2500 rpm, it all of a sudden starts popping and backfiring like hell through the carb and dies.

My first reaction is to stop and get out and look for spills. I see none, evaluate what I need to do and ponder for a minute what it could be. Obviously something in the valvetrain. So I grab my beer and my cookies and start walking the rest of the way home.

I get home just in time to fry my onion rings and pull the pork of the smoker. I get the family ready to eat and go to the garage and gather the tools I need for the top end and load them in my truck and take off.

I get there and the guy that owns the house that it died in front of is out there looking it over. Talk to him for a minute, then get to work, with beer in hand. I pull the drivers valve cover and everything looks perfect. I pull the passenger cover and find this:





So I took the girdle off and unbolted the rocker. Had to pry the rocker out a little because it was wedged, and was actually holding the valve open a little.

I don't have a car trailer, and my driveway is up hill, so trailering or pulling was out of the question, and I wasn't about to let it sit there over night without me sleeping in it. So my only other option was to drive it home. Since the exhaust rocker was the issue, I had to pull the intake rocker too so it wouldn't continue to backfire. Then my concern was leaving the lifters in. They could get beat up if the stay in, but I wouldn't have any oil pressure if I took them out, so I left them. Since I was only a 1/4 mile from home I was hoping it wouldnt be much of an issue if I kept the RPM's down. I get everything buttoned back up and get ready to fire. I got her home doing no more than 2000 RPM (not easy with a 3800 RPM stall) and had to shut it down in the driveway because the garage was closed. I didn't want to leave it running while I ran in and opened the door (I really need to get some remote openers) and didn't want to start it back up. So I pushed it back in. Ever try to push a car that has a 4 pinion traction lock unit it it? Easy if you are going straight, not so easy even in the slightest turn. Of course my garage is on the side of the house, so I almost killed myself just getting it pushed in the garage.

After my walk (with another beer in hand) back to the truck to get it home, I take the cover back off. It appears the oil pressure held the lifters in place and didn't let them drop back on the cam once they were up, so my worst fear were relieved.

So, the guide plate is broke, the rocker is a little beat up (salvagable I believe) and the pushrod is bent. So what happened first? Either the guide plate broke and caused the angles to get off and let the pushrod fall out. Or the pushrod got bent and bound up against the guide plate. Either way, I at least need a guide plate and a pushrod. I am hoping that it was a weakness in the guidplate, if it was the pushrod first then that means I need all new pushrods.

I guess this is the crap I get for playing with hot rods.
 

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As someone who has had to deal with a similar situation due to a broken guideplate in the past, you have my sympathies.
 

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Discussion Starter #3
Thanks CJ. Was yours just because of the guideplate? I am thinking that mine had to be the guideplate since it did it at low RPM. I can't imagine that the pushrod got bent at less than 4K. It didn't run any different after my romp, and was a good 45 seconds after that when it acted up. I just hope it was an isolated fluke and doesn't happen again.
 

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Yes. An "ear" on one side of a pushrod slot broke off. This was with a set of Ford Motorsport guideplates on a 351W back in the eighties. Looked over the rest of the valvetrain carefully, and found another that was starting to crack. Threw those away, and bought a set of stock SBC replacements at the parts store. Came in a TRW box, as I recall. Never had any problems with those.
 

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Ouchie Mike - I'd be checking all the PR's over for sure - no bananas. Then I'd go back to the drawing board on length agian. If the PR is flexing that much ya gotta think something is off. Especially if you were that low on RPM's....What is the pre-load on the springs? How about compressed - any chance it's binding? I'd see about getting an adjustable one and go through a few to see what you come up with. If ya gotta bore scope - see if you have any new marks on top of the piston on that cylinder!
 

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Shaft mounted rockers eliminate a lot of these problems. These are what I used on my 393 stroker.


http://www.fordmuscle.com/archives/2005/08/QuickLift/ they where made by Crane but may not be available anymore, but Jessel and Crower both make similar ones. They are a nice setup and a rock solid.
 

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I dodged a bullet by finding broken pieces of valve keepers when I pulled a valve cover. Turns out my valve retainers were stacking up on top of the valve guide (I was using stock valve guides, Crane retainers and stock oil seals. In order to use the cam I have, I needed to get new valve guides that were machined down on the top, for clearance for the retainer and PC valve seal.

None of the valves got dropped (luckily) and none of the keeper shrapnel made it thru the engine. When you discover something like that, your reaction is OMG! It was a ticking time bomb!

Did you check your valve stack-up? Not just coil bind, but retainer to valve seal at max lift?

Kevin
 

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Discussion Starter #8
I have at minimum .100 clearance on the retainers to seals, had to check, but there is room. Coil bind is not an issue either. I checked all the other pushrods and they are all straight. None of the other guideplates have any cracks in them. The geometry is spot on. The springs have 625 pounds of spring pressure over the nose of the cam, but the pushrods are rated at 700 pounds. The pushrod that is bent is just barely bent, not kinked. This is why I am thinking that the guideplate was the cause of the failure.

I have a new pushrod from Smith Brothers on the way, but am still looking for the guideplate. If I have any type of failure in the future I will just go ahead and upgrade to 3/8 pushrods. I would love to get some shaft mount rockers but they are just too expensive for the time being.
 

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Mike, I remember you had an issue with the stud position being off. Do you think this had/has anything to do with the related parts like the guide plates, the stud girdle, etc.? I'd assume that since you had the problem rememdied, that all the related parts should work as they should, since the stud position was corrected. Hate to drudge that old issue up, but was everything ship-shape with the corrected stud holes?

Kevin
 

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Discussion Starter #10
I thought of that too but if I would have any issues there then it would be in the studs. Since I have the girdles, it holds the studs in place though. They are off, but by only a tiny amount, much better than the first time around. They pull everything in nicely and all is good and straight with the girdles in place.
 

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Just wondering, is it possible that the valve stuck in the guide? I had that happen in one of my (chevy, I know ugh!) race motors years ago. Luckily the valve only slightly hit the piston and did not do too much damage aside from ruining the valve and bending the pushrod. The machinist had left one of the guides too tight. I suggest trying to push the valve down and see if it is stuck. Also it might be a good to pressurize the cylinder with the rockers backed off to make sure the valve is not bent and is seating as it should.
 

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x2 I like that thought! Maybe check the ridges on a few keepers to see if any have jumped out/in and show wear? I see Kevin's angle too though..... Look closely at the guides too....any marks where they may have rubbed it to much? I wonder if that girdle is putting a bit of pressure on any that aren't perfectly centered..? Once you crank that puppy down everything becomes as one and there isn' to much margin for error - nothing is going to give very much, which is the whole point as long as all the alignments are there. It sounds like your well within the tollerance of spring pressure so I don't think going to 3/8 PR will change anything really.

Another thought - how about checking the tips of the valves and the rollers now that you have run it a bit? --See if everything is contacting true/square. There may be enough marking to tell something - or put something on the tips to wear off and give you an opportunity to check it later....

Can you tell if the guide plate was bent up from the bottom or down from the top first? .... maybe there is a sequence you can follow to clue you in, or just a bad PR right out of the box - who knows.
 

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You can loosen the stud and move the guideplate a small amount to locate the rocker arm over the valve.

I think you have interference somewhere. Look at the rockers carefully.

Don't risk salvaging the rocker arm, buy new. Save the old one for a spare. (The rocker beside the broken one looks wedged severely). When a rocker breaks all those little needles are circulating through your motor.
 

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Discussion Starter #14
I just did a pressure test. Had to hollow out an old plug and rig up a hose to it, but did the trick. It is without a doubt holding pressure. You can hear some leak down, but I compared it to another cylinder and it was the same. It held pressure well enough that it pushed the piston all the way to the bottom of the cylinder. I also looked at the top of the piston with a mirror and a flashlight, no marks.

Everything is lined up just perfect. I spent a LOOOOONG time bolting and unbolting everything to make sure the rockers centered up just right. I am running lash caps on the valves and all of them show perfect wear. Shiny in the middle with a small strip of black left around the rims. No wear on the rockers anywhere, no eveidence of rubbing.

The leg on the guideplate looks like it was pushed over and up. Everything checks out to be just perfect. the only thing I can think of is a bad guideplate or a bad pushrod.

Like I said though, if this happens again, I will surely upgrade to 3/8 pushrods that are rated for 900 pound springs.
 

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Maybe it was just a simple misalignment on the guideplate then....? hmmm sounds like everything is where it belongs then. IDK hopefully it was just a fluke.
 

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Discussion Starter #17
I actually did find one. Turns out summit sells them by the single. I thought you could only buy them as a sell. Got it put on today, now waiting on the rest to come in so I can run her.
 

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Discussion Starter #18
Got the rest of my parts yesterday and got her put back together. Checked everything out real well once all bolted up and everything checked out good. The only thing I can figure is that either the pushrod was a little weak, or the guideplate was weak.

Took it out a couple of times since yesterday and she is running great. Took it up to not quite 7k a couple of times and everything seems to be fine. I put another 6 or so miles on it, but will see in time I guess.
 

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You may want to pull the valve covers off and check things out. Maybe do that a couple times over the next 100 or so miles. Better to find a problem in the making then after it causes more damage.
Good luck.
 
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