Lifters losing ther prime

[jap901]

I have a dodge 318 with A 268 xtreme cam and I have valve train noise and im only holding 6in lb of vacuum at idle. Iv read that the xtreme cams are know for valve train noise but my power brakes are hard to push is what got me to check my vacuum and iv also read that if ur lifters are not holding its prime it will cause low vacuum, valve train noise, and rough idle, so i removed my valve covers and turn the engine over to where the valve was open and u can watch the rocker move up because lifters are losing ther prime and both lifters on cyl 2 i can push down with my hand. I soaked the liftes for a week b4 installing them. Im lost to why there lifters are doing this unless ther just a bad batch of lifters. Whats ur imput on my issue. THANkS IN ADVANCE.

 

[sgtpontiac]

this is on the Comp site for Chrysler tech.....

Rocker Arm Adjustment/Lifter Preload
All but a few Chrysler engines were equipped at the factory with non-adjustable rocker arms. Anytime a solid lifter camshaft (either roller or flat tappet) is used, you must also use the adjustable rocker arms and appropriate pushrods.

When installing any high performance hydraulic camshaft, the lifter preload is something which must be considered. Too little preload will result in a noisy valve train, and too much preload will result in tight valves and a poor running engine. Either condition can result in less than expected performance or engine failure. After the cam, lifters and rocker arms are installed and prior to installing the intake manifold, you must check the plunger depression in the lifter. With the cam on the base circle (valve closed) the plunger in the lifter should be depressed .040”-.060”. With nonadjustable rocker arms, you must change pushrod lengths to obtain proper lifter preload. This is a delicate and time consuming process, so if you have any questions, contact the CAM HELP® line at 1-800-999-0853.

Not sure if that helps but seems that this step is important.....might be the reason so many Chrysler sites show Comp cams wiping lobes and noisey valve train issues....????

 

[Studebaker]

Rocker Arm Adjustment/Lifter Preload
All but a few Chrysler engines were equipped at the factory with non-adjustable rocker arms. Anytime a solid lifter camshaft (either roller or flat tappet) is used, you must also use the adjustable rocker arms and appropriate pushrods.

When installing any high performance hydraulic camshaft, the lifter preload is something which must be considered. Too little preload will result in a noisy valve train, and too much preload will result in tight valves and a poor running engine. Either condition can result in less than expected performance or engine failure. After the cam, lifters and rocker arms are installed and prior to installing the intake manifold, you must check the plunger depression in the lifter. With the cam on the base circle (valve closed) the plunger in the lifter should be depressed .040”-.060”. With nonadjustable rocker arms, you must change pushrod lengths to obtain proper lifter preload. This is a delicate and time consuming process, so if you have any questions, contact the CAM HELP® line at 1-800-999-0853.

Not sure if that helps but seems that this step is important.....might be the reason so many Chrysler sites show Comp cams wiping lobes and noisey valve train issues....????

Pretty much sums it up. If at first u dont succeed read the directions

 

[jap901]

Thanks sgpontiac. This is a 87 model engine. I done had the engines cam b4 i knew this engine had a roller cam so i also had to get longer pushrods 7.500 for none adjustable hyd flat valve train i been thinking of making it a adjustable but thats not going to keep the the lifters from bleeding down. like i said i can watch the rock move as the lifter loses its prime all 16 of them.

 

[sgtpontiac]

I could see maybe one or two lifters being bad....

Thanks sgpontiac. This is a 87 model engine. I done had the engines cam b4 i knew this engine had a roller cam so i also had to get longer pushrods 7.500 for none adjustable hyd flat valve train i been thinking of making it a adjustable but thats not going to keep the the lifters from bleeding down. like i said i can watch the rock move as the lifter loses its prime all 16 of them.

but it seems a real stretch that all of them would be bad....if you can see the lifters bleed off, it makes me think that the lifter is preloaded too much as explained on the comp site....are you sure that the pushrods you got are the correct length? Maybe the valve train is noisy due to the rockers coming off the valve tip or running really close to the edge instead of in the middle as they should be...easy to check...use some prusion blue on valve stem and then cycle the rockers by turning the engine over....should have an impression of the rocker about dead center on the valve stem...but honestly, I'd start from the beginning and do it like you were just installing the cam...that low vacuum concerns me...almost like the valves aren't closing all the way...that 268 cam doesn't have that much overlap to cause that low a vacuum reading.....unless the intake is leaking somewhere or there is another vacuum leak.....6" is extremely low...JMHO

 

[jap901]

I have check the pushrod lenght many times by The Book And Parts store its 7.500 but what ur saying about the pushrod being to long and holding the valve open makes sence, that will explane why it sounds like it lopes harder than it should for a 268 and would also explan why I dont have much vacuum. I can run the engine up tell the vacuum gauge reads 14in and I Can hold it there and I can hear the engine sound like its trying to stall and it will drop to 10in vacuum and pop up to 20in vacuum just like IF Iv rav the engind up but i did.

 

[sgtpontiac]

At that low of vacuum if it's carb'd

I have check the pushrod lenght many times by The Book And Parts store its 7.500 but what ur saying about the pushrod being to long and holding the valve open makes sence, that will explane why it sounds like it lopes harder than it should for a 268 and would also explan why I dont have much vacuum. I can run the engine up tell the vacuum gauge reads 14in and I Can hold it there and I can hear the engine sound like its trying to stall and it will drop to 10in vacuum and pop up to 20in vacuum just like IF Iv rav the engind up but i did.

the power valve is open the engine is flooding and probably can't clear itself under all the fuel...another thought....could you maybe have the timing off by a tooth on the cam and crank??..But as i said, I'd start right from the beginning and go back and check all the install stuff....might entail pulling it down and checking the cam timing and then work your way back up.....good luck and let us know what you find.....might help somebody else down the road...

 

[jap901]

Thanks for all the help and I Will let u all know what I find. I did find that both intake and exh valve lifters on #1 cyl are very spongy and will not build up and get hard the others build up but bleed down, so checking the preload on the lifters want be right, so I plan on replacing the lefters changing pushrods and going to adjustable valve train. I did check and the rockers are running in the middle.

 

[jap901]

Got A friend to check out my problem, mopar is all he deals with and he said it looks that I got a bad run of lifters he said that he ran a lot bigger cams than I got using the same stock none adjustable valve train with the same leight 7.5 '' pushrods. He gave me a free set of lifters and intake gaskets he had sn I'll chang them today if I the time and let U all know how it goes.

 

[jap901]

Update: I tryed to check the preload on the driver side bank and I have no preload at all the pushrod likes bettween .015 to .025 b4 the rocker arm and push rod come in contact with the valves closed. That explaines why I had alot of valve train noise but still dont explain the really low vacuum. I started to order pushrods .050 longer to get the .020 to .040 preload but desided to spend a extra 70 and just go adjustable valve train and be done with it. The reason for all the trouble is because comp cams grind the cam on A smaller base circle.

 

[jap901]

I Got it all back together and it runs great with no valvetrain rattling any more. I still don have but 6lbs of vacum at idle. The cam sounds no bigger than a comp 280 cam. This cam was new a open box 268 extrem cam that was sold from a parts store that was closing its doors. So im thinking its not a 268 extreme cam but my buddys 350 with a 280 cam pulls 15lbs vacum at idle so I would think mine should but its not.

 

[sgtpontiac]

I'm assuming that you went with the adjustable valve train?

I Got it all back together and it runs great with no valvetrain rattling any more. I still don have but 6lbs of vacum at idle. The cam sounds no bigger than a comp 280 cam. This cam was new a open box 268 extrem cam that was sold from a parts store that was closing its doors. So im thinking its not a 268 extreme cam but my buddys 350 with a 280 cam pulls 15lbs vacum at idle so I would think mine should but its not.

6 inchs of vacuum is really low....unless you have a significant amount of overlap on that cam....(shouldn't if it's the cam you believe it is) I'm assuming you put intake gaskets on it if you put in new lifter with this valve train??...15 inches of vacuum would / should be about normal with that type of cam.....6 inches is way low....JMHO....

 

[jap901]

Yes I did. I could of keep it none adjustable but I would have had to order a diff lenght pushrod for each valve.

 

[sgtpontiac]

Just a thought....

I'm sure you've got the timing set up right...but is it possible that the damper has spun? Happens to GM's at time.....maybe the damper is actually got the timing retarded....even if it looks good with the light...have you tried moving the timing around to see if the vacuum comes up??? Just a thought...

 

[zzrodder]

Thanks sgpontiac. This is a 87 model engine. I done had the engines cam b4 i knew this engine had a roller cam so i also had to get longer pushrods 7.500 for none adjustable hyd flat valve train i been thinking of making it a adjustable but thats not going to keep the the lifters from bleeding down. like i said i can watch the rock move as the lifter loses its prime all 16 of them.

I'm no Mopar expert, but you mentioned that this motor came with a roller cam and now you are using a flat tappet cam. Is it possible that the engine is not compatible with flat tappets? The oil passages may not be lining up correctly with the different style lifters, causing the bleed down? Another thought is that the smaller base circle cam will put the lifters farther down in the bore and causing the same problem. Just reaching for a reason...
With such low vacuum, it sounds like the valve lash is way too tight...

 

[sgtpontiac]

I agree

I'm no Mopar expert, but you mentioned that this motor came with a roller cam and now you are using a flat tappet cam. Is it possible that the engine is not compatible with flat tappets? The oil passages may not be lining up correctly with the different style lifters, causing the bleed down? Another thought is that the smaller base circle cam will put the lifters farther down in the bore and causing the same problem. Just reaching for a reason...
With such low vacuum, it sounds like the valve lash is way too tight...

We are missing something here....I'm no mopar expert either but something just an Kosher..... I've got a few friends that dig mopars, maybe they can shed some light...[S