The motor has less than 5k since complete rebuild with all new parts from hot heads. I was driving it easy when it went. Just cruising at about 50 mph. Engine specs are 1956 hemi 354 iron block and heads hydraulic cam - 280@108 (.485 lift, 238 Dur .050, 108 ls) non-adjustable rockers adjustable pushrods I pulled the passenger valve cover off and found number 6 had intake and exhaust bent and 4 had exhaust bent. I ordered replacement adjustable pushrods from hot heads to match. After pulling the rocker and installing the new pushrods, I bent the new #4 exhaust push rod while turning the motor over by hand during the valve lash adjustment. I read so many different ways to adjust the valves but the way I went with was from http://www.centuryperformance.com/valve-adjustment-procedure.html Write the first half of the firing order over the second half. 1843 6572 Rotate engine (clockwise if standing in front of radiator looking at motor) - watch #6 rocker - when intake is fully open adjust intake valve on #1. adjust to zero lash (cant spin pushrod between fingers) the added 1/3 turn for preload. Rotate engine - Repeat through firing order - I did the intakes first then exhausts for #1, #3, #5, #7 the did the same for #2, #4, #6 #8 Does anyone have any ideas of what I should try next? or should I just drop it off at a mechanic to have it done. I checked the rocker arms when I had it off and they didnt seam oval. All the valve springs seem OK. The exhaust push rods seem to be too short. Im almost maxed out on the adjustment. The intakes are fine. (Id have to measure them to be sure but it seemed like the #2,#4,#6,#8 needed to be adjusted about a 1/4" more than the #1,#3,#5, #7.) Could it be a stuck lifter? can I just pull it out with a magnet and replace it. any help would be appreciated.
For some reason it sounds like your not on the base circle or heel of the cam when adjusting. I would do all zero lash settings when the engine is hot and I mostly do it while it's running with cutout rocker covers. While the engine is running back off the adj. nut and then back in the nut till the clicking noise stops then pre-load the hyd, lifters to spec. as per your camshaft/lifter instructions. Pre-load is crucial. You could possibly have bad lifter or your lifters are bleeding out and when you set your pre-load you are actually opening a valve which in turn bends push rods when the cam reached full lobe contact.
Pushrods bend due to mechanical interference. To bend both intake and exhaust on a Hemi engine at the same time on the same cylinder can indicate possible valve to valve contact. Possibly sticking valves or as was mentioned before, stuck lifter. For it to be fine for 5K miles and then all of the sudden have this happen would make me want to do a teardown of the top end before going any further with trying to replace more pushrods. Check for bent valves also.
Flow test your suspect cylinder since a compression test is out f the question due to bent push rods, pressurize the cylinder with a air blow gun with a rubber tip to seal the spark plug hole. Apply full air press and listen for air either coming out of the exhaust or intake, Do this with the push rods removed so valves are fully closed. I you can keep pressure in the cylinder and cannot here a hiss out of the intake or exhaust you should be ok. You could have had some valve to piston contact, overspeeds, high rpm's
Thanks for the help. I'll check to see if it holds air. Sounds like my problem may be beyond my skill set. I'll post back what I find out.
You'll get a thousand different opinions on how to adjust valves and a million on which procedure to use. That procedure in that link is way too complicated for me to even contemplate. Here's the way I do it and never have a problem. Start with your firing order and with # 1 coming up on compression stroke ( it will blow your finger off and tgere are whisltlers ) adjust both valves. Next in firing order and on around. Never any trouble, your certain that the lifters are on base circle and there is zero confusion. If the phone rings or you gotta pee There's no fuck ups. Maybe you need to rotate the engine a few more times but that is a good thing !!!! Your hemi should be 0.030 preload with hydraulic lifters. The easiest and most accurate way is to have the intake off and measure , see, touch, feel the plunger come down off the clip 0.030. Especially since you are breaking shit.
Man that is unusual with a hemi and such a small cam. I would definetly pull the head and check it out. Hemis stuff is way too expensive to tear up. Check, check, check and make sure. Good louck.
Check for coil bind, I like a least .035 between 3 coils at full lift. Or guide to retainer clearance.
When I bent a pushrod on my Y-block it was because a valve was sticking. The valve didn't want to move, the cam pushed, something had to give. See if the valves move freely. Mart.
Like 31Vicky said, ask 10 people and you'll get 12 different answers... IMHO, it would be prudent to remove the heads and have a good/proper look-see on the bench. Sticky valves could do the bending but so could coil bind...yeah I know, 5000 trouble free miles... What are the valve spring specifications? Installed height? I am most troubled by your description of the pushrods being different lengths...that is a real concern. As to adjusting the preload, a cold engine is fine as the hyd part of the hydraulic lifter does take up slack for hot parts. I use a preload of .050". Remember that adjustable pushrods have 32tpi so for each full turn you get 0.032" longer or shorter. One turn might be ok, 2 turns is too much. .
If you adjust the valve when not on the base circle they would be to loose not to tight. When you turn it over by hand are the valves with the bent pushrods moving? 108 is a pretty tight lobe center could the valves be hitting each other on overlap?
I definitely have a bent exhaust valve too. I pulled the rocker and the #4 valve is stuck open. I agree it's weird that the exhaust push rods are different lengths on each side. The 1,3,5,7 cylinders had averaged about 0.20" of thread showing between the adjustment nuts. On the opposite side where the valve is stuck they average 0.35" of thread showing. I'm guessing the guy that rebuilt this motor before I got it didn't know what he was doing. I'm going to take it to a friends shop and pull the heads this weekend. He has 62 nova that does 10's and has built 15 motors this year. I'd rather have it done right then having the satisfaction of doing it myself.
The valve may not be bent, just stuck. I may be being over optimistic, I'm not a hemi guy. On my sticking valve y-block I was able to free the valve up without removing the head. I fed rope down the plug hole and used the piston to push the valve up, (gently). I'd tap the valve down a bit with a small hammer, and push it back up with the piston, helped by the spring. It still was a bit tight so I used the piston and rope to hold the valve up and removed the spring. I was then able to drench the stem with oil. With the spring removed, I was able to rotate it with a battery drill and stroke it back and forth while it was going round, all the time drenching it with oil. In the end it was whizzing up and down freely and clacking shut nicely. My problem was caused by using some old gas. Mart.
Hemi exhaust will run with more stem clearance because the guide does not run down hill and no seals. Some hemi have an oil hole on the top side of the guide.
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