273 valvetrain question

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bigrobsRT

bigrobsRT

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In the 67 barracuda I had some lifter noise and lots of oil leaks so I thought I would change the intake and valve cover gaskets. The motor has the commando valve covers and came with the commando air cleaner. Well I took the valve covers off and it had stamped steel rockers. That's odd. I look up the head casting numbers and they turn out to be 318 fast burn heads. OK, also the lifters are hydraulic, so I assume at some point it had the cam and heads, intake (Weiand Stealth) changed out. The block casting is 273 so that matches the car. I put new hydraulic lifters in it and put everything back together. It sounds like people describe a "sewing machine" now, much louder than before. Could the guy have left in the solid roller cam and put in hydraulic lifters? Is this going to break something? I can take a video and upload it if needed.

Any advice would be appreciated.
 
I'd pull the thing apart and see exactly what you have . Set up right a 273 is a good little motor but not with 318 crap in it.
 
Sounds more like you put the rocker shafts on wrong or mixed the left and right up. The original cam in a 67 273 is a solid and won't work with non adjustable rockers. You replaced the lifters? Post a couple pictures of what you took out so we know for sure.
 
toolmanmike said:
Sounds more like you put the rocker shafts on wrong or mixed the left and right up. The original cam in a 67 273 is a solid and won't work with non adjustable rockers. You replaced the lifters? Post a couple pictures of what you took out so we know for sure.
Click to expand...

This is what came out.
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IMG_20161029_165638_01.jpg
 
OK, looks like hydraulics. I wonder what pushrod was used. You say it rattled before and after the new lifters? I hope the pushrods are for hydraulic cams and the correct length. They are shorter than the solid ones. They should be 7. 510" in length with a ball on both ends and are the same that say a 1970 318 would use. The rocker shafts being installed wrong could cause a oiling problem and clatter also but it looks like the engine has been together and running for a while. I'ts so hard to diagnose problems like this over the internet.
 
Here is a video of the noise. Not sure what the whistling is. That started as I was taking the video.
 
I'm going to let someone else take over here possibly a technical editor. I have a nasty headache and I am going to go take it easy. I'll check the thread tomorrow. Use the search engine and find posts about hydraulic pushrod lengths and rocker shaft orientation. I think that might be your issue.
 
Some of the lifter faces don't look great. I'll second the wiped lobe concern. Pushrod length is next on the list as others have said.
 
With the lighting as it is, it is hard to tell if any of the lifter faces are worn badly, or if it is just the lighting. I would suggest that if anyone thinks they see any oddly worn lifter faces, they try to ID them by their position in the lowest photo so the OP can zero in on them.

I would start with a compression test on all 8 cylinders. The video is only so helpful; the sounds get distorted by the tiny microphones. The sounds do not strike me as mere valvetrain noises. It does sound like an intake or carb leak whistle there near the end.... or the fuse on the bomb inside the engine running down!

And as said, the pushrod length is suspect with the valvetrain changeout. They obviously cannot be the originals with the different rockers.
 
Several of the lifters that came out are worn on the face and if you look on the back half of the cam, several lobes are worn on it as well. I'm not to familar on how much damage is ok, i'm guessing none. Also, none of the lifters were functioning when I took them out, they were all stuck with no movement on the plunger.
Like I said, these heads are not the original heads as I looked up the casting number and they are from 85-86 318. I'm guessing the rockers are from the same. I just have no idea if the previous owner left a mechanical lifter cam in and threw hydraulic lifters on it. Looks like I will be swapping the cam, there is a first time for everyone! ha
 
those are hydros, and match up with the stamped rockers. Put a dial indicator on the cam lobe and cycle it one revolution. The solids have a slow ramp up then the lift, the hydros have none. Id put a dial indicator on each pushrod and see if all the lobes are uniform, then look at your header gasket.
 
The cam should show no grooves in the lobes, and one side of the cam nose should be discolored to let you know it was/is getting the contact with the lifter. If its the same color across the nose, ie gold, then the cam is shot, the lifters are not turning and its time for a new cam kit. Those heads are not bad at all for the 273. They have hardened seats for unleaded and about the same chamber shape and size, actually a little smaller for more compression.
 
What some of the guys are alluding to is called lifter preload. If the pushrods are too short, then they do not depress the little cups at the top of the lifters. In effect then the hydros become solids, and if the lash is excessive, they clatter; like yours .
The lifters you took out may have been pumped right full of oil, and then they appear to be locked up solid. You can submerge them in a solvent overnight, and then maybe they will be easier to bleed down. You can chuck a pushrod in a drill press and use it to apply a steady pressure as the oil slowly moves out the port.After the oil is out, you should see the cups pop back up to the top when you remove the pressure. Or you can just take them apart.
But yeah, the rocker shafts must be installed a specific orientation. On the end of each tube is a notch; it is oriented to the left and down. That is to say; on the drivers side(left side of car), the notch on the left is near the rad, while on the passenger side(right side of car), the notch on the left is now up against the firewall. Notches down means closest to the head. Installed this way, the oil is able to enter the tubes from the rocker stands as the factory intended. This oil lubes the rocker arms, the pushrod upper tips and the cools the springs.
But that clatter is most likely lack of lifter pre-load or lack of oil-pressure into the lifters, or oil-pressure loss out of the lifters around their perimeters, due to oversize lifterbores. Since the rods don't appear to be knocking,that kindof eliminates oil-pressure loss into the lifters;kindof.
I have run hydros on a well-used solid 273 cam and not had this issue. I have also run used solids on a used teener cam,lucky me, with no issues. I wouldn't try that with todays oils tho.....
Lifter preload is checked with the lifter on the cam's base circle, so it's best to do this with the VC off so you can see what you are doing. With the amount of noise I am hearing,I would check them all.Unless the very first 4 you check are faulty, then you can pretty much figure that they are all bad.
On the off chance that the preload is good, then you will have to check for oversize lifterbores. It seems to me there is supposed to be a coded mark above the engine number at the front of the engine on the pad there,if it left the factory with o/s bores. It mighta bin a small diamond, or an A. Anyone?
 
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Some circular wear marks on the lifters are perfectly normal. The question is if the lifters are dished out on the contact surface. If you place a good straight edge across a new lifter face, you will see that it is slightly convex; they will normally wear to slightly concave over a long period of time. Severely concave, or with deeply dished and an irregularly grooved surface indicates bad wear. In your last picture above, the lifter that is 2nd from the right in the back row looks like it has wear in the center but the lighting makes it hard to say from the photo.

Badly wearing lobes often show an irregular shape on the lobes, with flat areas across the lobe in spots when viewed in profile, and breaks in what should normally be a continuously smoothly curved surface.

Stuck with no plunger movement may well mean that the check valves are good and the lifters are holding oil and are thus not compressible. If this is the case, one would expect a bit of movement if the lifter preload was right. But short pushrods would make the lifter preload little to none. So this symptom is unclear in this case.

BTW, what motor oil and weight have you been running? If the ZDDP content is too low, that could lead to excessive cam/lifter wear.
 
I haven't. Bought the car, been fixing things on it when I've had time and money since July. Needed interior stuff and motor just had a light tick before but massive oil leaks from valve covers and intake bolts. Probably should have left it alone.
 
No,that clatter is gonna get expensive. It's good that you caught it now.

Those lifters (pst#4) look worn concave. I know it's hard to read on this side of the screen, but if they are, then the cam is similarly worn, and it is toast as well. New lifters on the old lobe will mean a short life for them as the old lobes beat the iron to death. There is also a slim possibility that the base circles are worn, and that will reduce the lifter preload as well. The worn lobes smacking the lifters cannot be controlled by the low-performance springs. And so it clatters.
So check the lifter bases.They are supposed to be ever so slightly convex, that is, high in the center, that is; take another lifter and lay it sideways across the base of the first, to form a TEE. When new, it will have a slight rocking action to it. When they go concave, that is dished, then both the lifters and the cam are worn out.
 
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Lifters look like garbage, cam will be also. New cam/lifter time for sure.
 
So I finally had time to open it back up and I had the rocker shaft upside down on the driver side. passenger side was in there correctly. All the pushrods were 7.4X I dont have a large enough caliper but definitely shorter than 7.5 by the tape measure. I'm going to change out out the cam, lifters again, pushrods, and new timing set. Time to order some parts. Will This summit racing cam work? "SUM-1789 - Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 272/272, Lift .454/.454, Chrysler, Small Block"
 
I would think that is too much duration for a Low compression 273. Your Dynamic compression will fall into lawnmower country, and acceleration below 2800rpm will be measured with a sun-dial,lol. And further, the ramps on that stick are horribly slow. The 050 numbers are 216*on a 110LDA.
OK so that's harsh. What compression ratio are you currently running, and what Rear gear ratio, and what TC-stall? Got headers, dual exhaust and free-flowing mufflers?
All these are very important to a sweet combo.
 
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I would assume its stock compression for 273 commando but who knows after finding these heads aren't stock. It has long tube headers and dual glass packs. Has a 8.75 rear end but dont know the ratio. Don't know the stall either.
 
Well, you kindof need to know those things to build a successful combo, the heart of which is the cam.There is no sense putting a 6000rpm cam into as 5000rpm combo.And especially into a completely unknown combo.
The operating range of the engine, more or less dictated by the cam,is usually selected before the engine ever goes together, and then, the rest of the combo is built around it.
But in your case, the combo already exists, so, now, the cam has to be chosen to make it the best that it can be.To do otherwise, invites a re-engineering of the combo, which usually leads to a lot of money being spent.
 
The Static compression ratio can really only be determined by actually measuring the chamber size; which is done before the heads go on. This ratio can be reasonably back-inferred by measuring the cranking cylinder pressure, and knowing the cam specs. In your case the cam is probably going to lie to you, and not knowing the pre-lobeloss cylinder pressure, it will be a little tough to select a cam without knowing a little about how well the current combo was performing,how well it suited your driving habits, and what the current combo actually is.
Measuring the current cylinder pressure is the first step in determining where to go. Hopefully there will be at least a couple of lobes left to give an indication of how to proceed.
The TC stallspeed is also very helpful, and ditto the rear gear.
I highly recommend to know those things before stabbing in the wrong cam, and being horribly disappointed.
If the cam is already out of the engine, obviously the cylinder pressure cannot be determined, and so,selecting a cam will be very tough indeed. In this case I would recommend to go middle of the road,cuz too small could be just as bad or worse than too big. Too big just leads to a "doughy"(I love that descriptor) bottom end, while too small can lead to detonation which can destroy an engine pretty quick. If the cam is out and it has at least a couple of good lobes, it can be fingerprinted, but this is not something every body can do. Second best idea is to calculate the lobe-lift of at least one good intake lobe, and one good exhaust lobe, if you have any that are still good. Because it's a 273, the range of possible cam sizes is pretty limited. Again, knowing the stall speed and rear gear, and your comments as to how well the combo was worked out, will help in figuring out what the previous installer mightabin thinking; and thus reduce the cam selection process.
 
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