ticking at high rpm

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furydan

furydan

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My freshly rebuilt 318 started a lifter tick at hihgway speeds that goes away when at city street cruising speed. It takes about 30 to 40 seconds for the ticking to subside after the rpms drop.. I checked oil pressure yesterday and was reading about 25 at idle and 35-40 peak when at high rpm. dont have a tach..
Bad lifter? Oil pump? any thoughts?
The motor runs with a lumpy idle, but not sure if it is supposed to. I have a comp 268 cam and 10.5 to 1 pistons with the block decked and 302 heads. Cylinders bored 40 over.
Dan
 
hydraulic lifters = will pump up and cause valve float starting at around 6000 or 6500 rpms. this is normal.

if you are going to run high rpms... 6500, 7000, 7500 etc you should have solid lifters flat tappets or roller it doesnt matter, they should be solids for high rpms.
 
Did you make sure the rocker shafts are on correctly and the rockers are positioned correctly regarding the pushrod cup offset?

Also, almost every single performance cam is ground on a reduced base circle as compared to stock and will usually require a longer pushrod. This is why it is so important to get pushrod length right. I always consider every MoPar I build using custom length pushrods.
 
Preload is to tight and the plunger comes down below the hole in the lifter when cruising. And the lifters go dry. Set the preload by shimming the rocker shafts , getting shorter push rods or getting adjustable rockers. This was caused by heads shaved or block decked. common problem with mopars. The Preload should be no more then 1/4 turn down after zero lash for a street car with a after market larger cam with adjustable rockers. Zero on a race car.

Many times guys don't run into this with a large cam after decking or shaving. This is because larger cams have a smaller base circle not a larger lobe this make up for the the difference in the shaving/decking and guys get lucky.

Check the preload and correct the setting. This will cure your problem. Steve
 
furydan said:
Yes...I've been running the car for over a year and this problem just developed within the last 4 times out...last month or so..
Guess it's time to puill valve covers...
Click to expand...

if you find that you are not losing a cam lobe , I would suspect you have a lifter going bad. in the past, I have lost brand new lifters with 20 minutes of run time on them
 
Well i took off a valve cover and ran the motor till hot..The thing sounded like all the lifters were ticking a little, but when at the high rpm...4500..I start hearing 1 loud tick above all others.. Plenty of oil coming out of the pushrods so I assume it is going through the lifters properly..I guess maybe the shorter pushrods might be the answer?
I probably should go ahead and take off the intake and look at the cam though.
 
What I would recommend would be to get an adjustable checking pushrod. Install it on one intake and one exhaust and record the lengths with it adjusted to the correct preload and see what you have. Simple, effective, cheap and will leave NO room for doubt.
 
Plenty of oil coming out of the pushrods? Is this a Magnum engine? If so, hard to put 273 rockers on a Magnum.
 
RustyRatRod said:
What I would recommend would be to get an adjustable checking pushrod. Install it on one intake and one exhaust and record the lengths with it adjusted to the correct preload and see what you have. Simple, effective, cheap and will leave NO room for doubt.
Click to expand...

I guess I didnt know that hydraulic lifters need a preload set ever..That was the whole point of being able to "pump up" to meet the push rods at whatever temp the motor is running. I mean all you do is bolt the rocker shaft down...right?
 
IQ52 said:
Plenty of oil coming out of the pushrods? Is this a Magnum engine? If so, hard to put 273 rockers on a Magnum.
Click to expand...

not a magnum..72 block 318... can i just swap the rocker arm assembly or do I need the 273 push rods as well? How do you preload a hydraulic lifter/rocker arm assembly?
 
It's not a magnum, but you're oiling through the pushrods, is there any advantage to that?
 
Louie70Dart said:
It's not a magnum, but you're oiling through the pushrods, is there any advantage to that?
Click to expand...

How else does it get oil? I am confused..I am re using the rocker arms and pushrods that were in the motor when i rebuilt it.. I ran the motor without valve covers and it looked like oil is coming out of the rocker arms where the pushrods are..Isn't that normal for an LA small block?
 
from a 273 you need the pushrods, rockers, shafts, everything. the pushrods have a cup on the upper end, rounded on the lower end. the pushrods you have now for stamped rockers are rounded on both ends.

try to keep the shafts assembled it will be easier later if you dont mix everything up.

the pushrods will probably fit unless you have had lots of millwork done.

but like Rob said, you can get a special one that you can adjust and measure with. then you can buy a set of cut-to-fit pushrods from mancini or wherever and get them cut / pressed together for your length
 
furydan said:
How else does it get oil? I am confused..I am re using the rocker arms and pushrods that were in the motor when i rebuilt it.. I ran the motor without valve covers and it looked like oil is coming out of the rocker arms where the pushrods are..Isn't that normal for an LA small block?
Click to expand...


yes oil comes through the rockers shaft
 

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So is there a procedure to follow to set the preload on hydraulic lifters when using the 273 rockers and pushrods and shafts? I have the complete rocker arm assemblies and cupped pushrods..
 
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