New motor, loose rocker...

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flyfish

flyfish

C8H18+N2O = :-D
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Quick back story (sorry, this might be long). I just built this 408 in the late summer last year, did the cam break in like normal (took ALL precautions to keep a solid flat tappet cam alive), after putting the inner valve springs back in and taking a short trip to the gas station and back (~1.5 miles round trip) checked the rockers. All were fine except 1 (#8 exhaust). It was really loose…..like I had crank the adjuster down a couple revolutions to get it re-adjusted…


Here is my problem….All of my rocker adjusters are showing ~1/2 a thread except the #8 exhaust, which now shows ~2.5-3 threads when properly adjusted. This makes me nervous, like that lobe is going flat. But here is the weird part, I freaked out & measured the lobe (from the push rod) and the lobe looks fine. I compared it to others and it was about the same. I checked the oil and it looked OK (although a little hard to tell since it is a new motor), but no metal shavings. I have had a flat cam many years ago, so I know what they look like, but this one really doesn’t “look” bad as far as I can tell.


The motor literally has ~ 3 miles on it + cam break in time, and I’m in the process of pulling it to fix a rear main seal leak (first motor I ever built that leaked...Grrrr!). I’m debating a few options while I have the motor out, here is where I need help:

1. Scrap this cam & lifters and get a new one (probably the same one, Hughes STL6468AS-8).

2. Put my old small solid roller back in (248/254 @ 0.050, ~0.575 lift). My reservations with doing this is, will it work OK with my 13:1 compression and e85? My old motor that used this cam only had 10.8:1 compression. This option will also slow my car down a little….

3. Leave it and see what happens (I’m not really comfortable with this one, probably won’t happen).

Motor specs if needed:

360 block, 4” forged Scat crank & rods, Icon pistons, 13:1 compression

Ported Edelbrocks, Victor intake, Hughes STL6468AS-8 cam, Howards direct lube lifters, “750” e85 carb built by me.

Thanks in advance
 
Measure the length of the adjuster screw compared to the others.

Measure pushrod length too.

If it loosened up 2 turns worth of wear in 3 miles....... and the cam is what’s going away....... it won’t take long to figure it out.
I’d relash and drive it 15-20 miles and then check it again.
 
PRH said:
Measure the length of the adjuster screw compared to the others.

Measure pushrod length too......
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The rockers and push rods I used in the previous motor, they are all the same when compared to the others.
 
I like the above I mean it should take you a half hour to get another 15 to 20 miles on the car and then you'll know. Obviously you'll measure the cam if you're taking it out to put a different one in. And then you'll know.
And when it comes to cams I always say call Ken at Oregon cam grinding (personally I like an old guy who's been there and done that and owns his own shop is willing to talk to a guy for free) who is standing in a machine shop with thousands of Cam surrounding him and that's all he does and he races many of them. Unlike Hughes who does not manufacturer cams. Likely most that just have a tech line with people reading off their graphs given your specs..
I'm sure you already know that though...
 
Pull that lifter out. You can pull it thru the distributor hole. Use a magnet to get it out. Check cam lobe and bottom of the lifter. In doing so you will have the pushrod out check that its not bent and the cup is not mushrooming out the tube. also possible to deform the rocker. Thats a aggressive cam and needs lots of spring pressure so.....
 
My point on measuring the adjuster and pushrod lengths was to confirm those weren’t the pieces that are wearing instead of the cam/lifters.
 
mod5v said:
Pull that lifter out. You can pull it thru the distributor hole. Use a magnet to get it out. Check cam lobe and bottom of the lifter. In doing so you will have the pushrod out check that its not bent and the cup is not mushrooming out the tube. also possible to deform the rocker. Thats a aggressive cam and needs lots of spring pressure so.....
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I forgot to add, in preparation for pulling the motor, I already pulled the intake and visually inspected the cam & lifter...both look fine. I also swapped the lifter out with the intake lifter right next to it just to confirm the lifter is not the issue...no dice (measured the same on lash). Push rod is good as well.

Motor is coming out this weekend to replace the rear main seal.
 
flyfish said:
I forgot to add, in preparation for pulling the motor, I already pulled the intake and visually inspected the cam & lifter...both look fine. I also swapped the lifter out with the intake lifter right next to it just to confirm the lifter is not the issue...no dice (measured the same on lash). Push rod is good as well.

Motor is coming out this weekend to replace the rear main seal.
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I'm still at take it for a drive for 15 or 20 miles for a half hour before you pull the motor. I assume it's not leaking that bad? Then you'll have a few miles on it and see if anything's going wrong..
 
j par said:
I'm still at take it for a drive for 15 or 20 miles for a half hour before you pull the motor. I assume it's not leaking that bad? Then you'll have a few miles on it and see if anything's going wrong..
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Yeah....can't really do that...the only thing left to do before pulling it is converter bolts and bell housing bolts...everything else is unbolted.
 
j par said:
Oh yeah your committed LOL..
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Well, I WAS trying to make it to the track next weekend for a 3 day race....probably won't happen, but there is hope. If all I had to do was the rear main seal I think I would be OK, but not if I have to fart around with a cam swap....just not enough hours in the 1 day I have to work on it.
 
Just a thought but is there a chance the hardware holding the rocker shaft down is the problem and under load it's lifting the rocker shaft by pulling the threads in the head ? Just a guess. Good luck on making the race
 
If the cam lobe and lifter are both fine..... why are you changing them?

It’s either failing or it’s fine.
 
That's my dilemma...my gut says its failing, but I can't find any proof other than the fact that it is the only rocker with more than 1/2 a thread showing.....I hate new motors, they make me a nervous wreck, lol.
 
Cut your oil filter open, see if there is a bunch of extra Black Residue in there from the cam wear, even look for steel in there too. Take a magnet to the paper part of the filter after you cut the tin off the filter, this will easily pick up any steel that is coming through your oiling system and getting caught in the paper element.

Lot easier to change the oil filter, than it is to change a cam and lifters and find out they are good.
 
George Jets said:
Cut your oil filter open, see if there is a bunch of extra Black Residue in there from the cam wear, even look for steel in there too. Take a magnet to the paper part of the filter after you cut the tin off the filter, this will easily pick up any steel that is coming through your oiling system and getting caught in the paper element.

Lot easier to change the oil filter, than it is to change a cam and lifters and find out they are good.
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There was a fair amount of "black residue" in the oil, but I could not tell if that was from the motor being new and all the assembly lube and such. Nothing shiny in the oil (I strained the oil through a paper towel while shining a light on it).

I still have the filter, I set it aside to cut open if needed....but its a pain, so I have not yet.
 
I had a fresh engine lose it's rocker adjustment. Thought it was the cam. It was the pushrod tips eating themselves. New better quality pushrods, and all good. Look at the tips.
 
You will want to actually cut that filter open, the racers do it all the time to check their engines. I usually drill a 3/8" hole down 1" from the thread base on the filter (or punch a hole in it with a scratch awl and open that up to 3/8" with another punch so as to not get loose filings into the filter), then take one of these 3 legged Air Sheers and put the center finger of it into the 3/8" hole and zip around the filter quick.

Can do the same thing with and Air Hammer and the 3 fingered Body Panel cutter bit, zip around it till the can falls off.

This is the area that will actually be catching all of the nasty debris, take a magnet to that paper filter, this will tell you the whole story, and see what pours out of the tin can part of the filter too.

Most of that black residue in the pan is probably the cast iron from the cylinder walls from the rings breaking in. You can take a magnet and swish it around in the bottom of the drain oil pan of the oil you just drained out and see what you pick up there too.

airsheer.jpg
 
George Jets said:
You will want to actually cut that filter open, the racers do it all the time to check their engines. I usually drill a 3/8" hole down 1" from the thread base on the filter (or punch a hole in it with a scratch awl and open that up to 3/8" with another punch so as to not get loose filings into the filter), then take one of these 3 legged Air Sheers and put the center finger of it into the 3/8" hole and zip around the filter quick.

Can do the same thing with and Air Hammer and the 3 fingered Body Panel cutter bit, zip around it till the can falls off.

This is the area that will actually be catching all of the nasty debris, take a magnet to that paper filter, this will tell you the whole story, and see what pours out of the tin can part of the filter too.

Most of that black residue in the pan is probably the cast iron from the cylinder walls from the rings breaking in. You can take a magnet and swish it around in the bottom of the drain oil pan of the oil you just drained out and see what you pick up there too.

View attachment 1715332478
Click to expand...

Yep , this right here, the power tool he is speaking of is called Nibblers , this could save a lot labor and parts ,{possibly }
 
Was the valve job different on one valve? Take the rockers off and lay straight edge across the top of the valves. the kind of difference you are talking about should be seen, very easily.
 
What was the rocker brand again? Have you moved the suspect rocker to another cylinder/valve and checked it? And as mentioned, checked the valves with a strait edge? Tried a different rocker arm etc on that particular cylinder/valve? I'd suspect either the rocker arm is slightly off or the valve if everything else matches up.
 
Update: Found the problem, and it is NOT the cam or lifters. I feel like an idiot for not seeing this the first time….I looked at the pushrods and compared them from the exterior, but I didn’t look in the cup. The inside of the pushrod cup is 0.065” deeper than the others….apparently it got crushed.


Then it dawned on me….when my engine blew a few years back, the piston hit 1 valve hard enough to bend it. These are the same push rods that were in that motor (face palm)…..this is apparently the pushrod that was on that valve….I’m a doof.


Sometimes the problem is right in front of you and you don’t see it. Thanks to everyone that chimed in and helped me figure this out. You guys are awesome!! Now I just need to make a quick call to Smith Brothers to get a couple more pushrods (always good to have a few spares).


Here is a pic, the one on the left is the bad one….

IMG_3469.JPG
 
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