Valve and compression issue

oldrod40

Member
Supporting Member 1
#1
Put a new set of heads on my 348, now the valves don't seem to want to adjust properly and I have low compression in the number 4 cylinder. I have 9.5 compression the 921 Showcars Isky 488 lift cam and stock rockers. Put the heads on with new Cometic gaskets along with the other gaskets all new. Set the timing adjusted the valves and as I seasoned the new springs I had clatter. After shutting it off and cool down went back readjusted the valves again. I cranked the engine over a few times checked the pushrods and I could spin almost all of them again. Adjusted again and the same thing. Ran the engine for a bit still had ticking from what sounded like a few rockers on both sides. At this point the engine isn't idling like prior to the head swap its rough and not smoothing out. If I give it a quick hit on the gas it stumbles. The new heads (817's) had what looked like stock replacement springs. This could have be my down fall. This is what I ran initially and the valves wouldnt adjust. I changed out the springs to Showcars 3357 springs (dont know why i didnt do that in the first place). Did everything over and still i adjust the valves probably 4 times running and just turning over the engine and it seems like they loosen up. The pushrods twist so I tighten them down more crank the engine and become loose again. They do seem to be tighter then with the other springs now but a few keep loosening up even with cranking. I marked the rocker nuts and they are not backing off.

So I turn to the compression test. All cylinders appear to be good except number 4. They all have about 135-145 on crank test. Number 4 has 120. Prior to changing out the heads I did a compression test and they were all good. I loosened both rockers on #4 put a little tranny fluid in and got 190 and it held, it also held at 120. Now while i had the heads removed and just prior to installing the new ones I guess I missed the oil rag on the #4 cylinder and it had some very light rust form and I mean really light. A little WD40 and 1500 sand paper i lightly rubbed on it for a few seconds and it was gone so i dont thing that would be the issue.

So did i ruin a cam or lifters with about 10-15 minutes of run time with the unknown springs? Is my rough idle a vacuum/bad seal on a gasket? I thought maybe the #4 cylinder was from killing a cam lobe or lifter, just at a loss right now. Seemed like a pretty simple switch but now looks like I have 2-3 issues going on. I know its a lot but I'm frustrated. Time for a Pabst or 6.
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
#2
My experience with flat cam lobes is cylinder pressure goes way high, valve does not open as far/long which builds pressure. So you used the same cam and all lifters are in the same place as before, pushrods all the same also. If you adjusted the rockers correctly, lobe on the heel adjust rocker nut to remove slack then 1/2 turn or so. You would expect it to run correctly. Not sure what you mean about 'season the springs'. With a vacuum gauge connected is the reading steady? Or bouncing around? Has to be steady, otherwise valves are not sealing.
A lot can be written about valve train setup and how to do it correctly. I spend hours checking things before cylinder heads are bolted on. Just swapping out heads and not knowing what you have before you run it, usually ends in problems. Even new parts, hyd flat tappets (lifters) have recently caused me grief, big reason I suspect builders go straight to the roller cams now. But if your lifters were fine before, they should be fine now, if everything is in the same place as before, with the same cam.

'
 

tenxal

Well Known Member
#3
Hard to diagnose long distance.

But based on what you've posted, I'd go back and readjust the lifters correctly before doing anything else. Some hydraulic lifters can be very sensitive to adjustment. You need to know what style of lifter you have ie: standard travel, short travel, limited travel, etc.
 

1964SuperStocker

Well Known Member
Supporting Member 2
#6
Lifters are bad, were they soaked properly before installed? Should be able to see if the studs are moving. Not likely to be a bad cam but its possible. My money is Lifters. Way more common that most people realize. Tiny piece of dirt could put one out.
 

scott hall

Well Known Member
Supporting Member 1
#8
Is it possible you now have them to tight. If lifter was pumped up when first adjusted then you roll it over and the pushrod spins the lifter has bled down. Assuming you had the cam in the correct position when adjusted. Also pull some rockers and make sure they are not the aftermarket stamped steel and cranking at the ball area. That will cause noise when running.
 

oldrod40

Member
Supporting Member 1
#9
Thanks guys. I was getting frustrated last night and after a good nights sleep, I know I need to go back to basics, that's usually what it comes down to. The cam and lifters were in the car prior to the heads being changed and there was no issues. The engine has about 900 miles on it since a rebuild and I didn't remove the lifters during this swap. I will check the rocker studs and make sure I put the pushrods back correct and not switched an intake and exhaust. The rockers I have are original 348's and not the aftermarket stuff. I'm going to go back and adjust all the lifters after checking the above. The lifters are the high performance Isky's from Showcars. I think last time I adjusted them I went a 1/4 to 1/2 turn past once the pushrods were snug. If that all fails might have gotten something in a lifter while the engine was open some how. I don't think I'm at the point of overtightened but I feel like im close with the amount of adjustment I done. I dont have a vacuum gauge but I will get a hold of one if need be. I did mock everything up prior to install to make sure no contact with pistons and valves etc. Start fresh and go over everything again see what happens.
 

425/409ER

Well Known Member
#12
Here is what I have found over the years. A lot of shops do crappy valve jobs, I found this out when I have a BB Chevy that ran pretty poor with some of the same troubles you are having now. In the early 2000's I bought a used Souix valve & seat grinder and taught myself how to use it. I did a bunch of free valve jobs for people and I did tell people you are guinea pigs on this. After about 40 valve jobs I did my 1st 3 angle job on the race car and the way it ran afterwards was pretty amazing. I no longer have my machinist do valves for me except when I need larger valves I just have him cur the seats for me. On out 409, I know the valve job was kind of poor but we ran it anyway, the car seems to be running better after some miles are put on it. For me I think it's the fact that most non-performance shops do the interference angles which I will never do takes too long for the valves to seat in. I have also found for me anyway that all new valves I have chucked up in the machine need to be cut, every one of them and I am not lying about this. The worst performance valve job I had was from a shop that had a kid do the work, I ran the car and it was butt ass slow, when I took the engine apart for another repair I pulled the heads and decided to lap them in to see how the 45° was, you know what? he chattered every one of the intake seats. There went all the HP out the tail pipe. That for me was when I decided to pay closer attention to the valve and seats as a good valve job just makes the car run better IMO. Sorry to ramble on about this.
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
#15
In the late '70's I was trained on how to rebuild aircraft engines, and the way we were taught to do the valve job is how I do my auto engines to this day. I do not use expensive machines to get it done, in reference to the seat work. If machine shops did it my way it would take 8 hours at least to do 16 seats with no problems. How much would they charge for that? Would anyone pay for it? Ask a aircraft owner what they pay, it would surprise you. Time is money, quality is no longer a concern for most shops, it cost too much.
 

oldrod40

Member
Supporting Member 1
#16
Finally got a little time went back and checked some things. Doesnt appear any rocker studs are pulled out. Set all the valves again, check vacuum and with the idle where it is, (a little rough) i was pulling a steady 13. And that is having it advanced about 8 BTDC any closer to 0 and it gets rougher. All the pushrods were correct no damage to the rockers. Going to pull the manifold tomorrow and take a look at the lifters. I used some 3/8 fuel line to listen and sounds like i have at least 5 lifters ticking, some on each side. Thinking that small run with the unknown springs may have cost me lifters and or a cam. Or maybe a little dirt got in there while it was opened up but probably a stretch. I did some valve adjusting with the engine running but didnt get any better. I'm a little stubborn and have done my entire build myself and I'm not a mechanic so I'll keep trying to figure it out but may have to bite the bullet and have someone check it out. Thanks for all the advice, at least its cold here and I'm not missing out on cruising time.
 

Jeffrey Osstyn

Well Known Member
Supporting Member 3
#17
Try this before you pull it all apart. Get one cylinder up to TDC of compression stroke, both cam lobes will be on heel. Remove both rockers, clean the tip of the valve stem and the rocker contact pad. Get a permanent marker and paint the valve stem tip with a good coat. Assemble the rockers and adjust them. Turn the engine over a couple times, enough to get at least two full valve actuations. removing all the spark plugs will help with this. Get the cylinder back up to TDC. Remove the rockers, look at the valve tip and see where the rocker contact area is. Ideally it should be in the center 1/3 of the valve stem.
 

tenxal

Well Known Member
#18
Doubtful that you've hurt the cam or lifters with the other springs. Now that you know the adjustment is ok, you can go from there to isolate the cause of the noise.

Many new production hydraulic lifters are very sensitive to the oil being run. Older hydraulics would run quiet with anything that was slippery...not so, any more.
 

oldrod40

Member
Supporting Member 1
#19
Thanks Jeff and Tenxal. I will try the marker and see where contact is being made. That does make me think as I was going anything I may have changed that would have caused the issue. On the new springs I used the same retainers and keepers. The retainers fit just a touch loose, they sit in the spring but have a very slight play in them. I didn't figure that would cause an issue since the spring and the valve stem wouldnt move much. Maybe that could be the cause? Other than the heads themselves, I didnt change anything else on the engine during the swap. My other thought is to use the other springs etc off the old heads I switched out, see if that changes anything. I'm obviously not a mechanic by day, but I did build this engine from a short block and did a lot to this car and had it running. I'm not as sharp with the diagnostics at times, so I appreciate the suggestions and help.
 
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