lifter pre-load?

-
That's a little tight for my personal taste, but yes, that will work fine. I also agree though, they should be the same.
 
jeff schwarz said:
it is what my engine builder told me, the valve tips are all at the same height.
Click to expand...

If you're running the stock rockers, there's your difference. They're pretty crappy as far as being the same, but they are very reliable up to a point with valve spring pressure.
 
Wyrmrider said:
reground cam?
Click to expand...


Must be. If the stem heights are all the same, the lifters should have the same preload. If it's a new cam and the base circles are different I'd get another cam. If it's reground, you'll have to live with it. And it's ok, I just wanted to know why they aren't the same.
 
Confused... Are you actually finding out that the preload is .035 on intake and .055 on exhaust? Or is this what the builder is finding? Or is this what he is telling you to shoot for?

If the valve tips are truly all at the same height, you are still going to find variations in preload. But it makes no sense that they would all be one distinct number on the exhausts and another number on the intakes...unless the cam indeed has a different base circle exhaust vs. intake. ( I can't say I have ever looked for that....) They ought to randomly vary around an average. The variations would mainly be due to the rockers, the pushrod lengths, machined slopes on the decks and heads, and the lifters themselves.
 
jeff schwarz said:
It's a mopar performance cam 268/272 450/455 and the rockers are mopar performance heavy duty stamped steel, the cam recommended install is 108 and with a 2 degree offset cam key it installed at 107&1/2.
Click to expand...
That cam, with the right springs will rev to the moon. If you have a manual trans, and you have NOT modified your oiling system, then I recommend to get a rev-limiter, and set it to about 5800, probably no more than 6000.
 
AJ/FormS said:
That cam, with the right springs will rev to the moon. If you have a manual trans, and you have NOT modified your oiling system, then I recommend to get a rev-limiter, and set it to about 5800, probably no more than 6000.
Click to expand...
901 Comps?
 
the intake and exhaust number the builder gave me are averages, and that is what they are the engine is finished, the springs and retainers are mopar performance, I forgot the number, they are the red ones for the cam good for 500" lift, and as far as mopar performances quality goes, when he degreed the cam it came with in 1/2 of a degree, I think that's as good as anyone, I was thinking that the difference between the intake and exhaust may be from the cam being a split pattern.
 
Roger.... Without the actual numbers on each valve, hard to know exactly what those averages mean. (Could be 1 or 2 valves of each type that are far off enough from the rest to move the averages apart.)

If none of the lifter preloads look too far off from the rest, then go for it. Those 2 averages are well within in the normal range.
 
Last edited:
The Mopar FTH cam 268/272 is
PN 4452761 with specs of 268/272/110 , lifts of .450/.455 and .050s of 228/231; springs are P4120249
This cam is usually installed at +4 degrees or in at 106 but you have a couple of degrees wiggle room either way depending on your cylinder pressure and/or useage.
If the block is perfectly square decked, and if the heads are perfectly machined,and if the valve stems are all at the same height, and if the rocker arms were identical in their pad heights and ratios,and if the pushrods were all the same length and straight,
THEN, the ONLY thing that could altar the preloads would be the lobe base circles. That's a lotta ifs.

You know that there are left and right rockers ,right?
And that 340 rockers are beefier than all others,right?
 
Does ur builder know that the rocker shafts have to be put on a certain way? Pass side notch to the left and down. Driver side notch to the left and down also. That won’t make ur lifter preload any different, but will screw up the oiling if not right. Kim
 
Even the heavy duty paddle rockers are not very accurate as far as geometry. Also, look at the slop in the holes where the shaft goes through. "Heavy duty" or not, they're still just stamped formed steel rockers. They AIN'T real accurate. If the lifter preload bothers you that much, you should get adjustable rockers and be done with it. You can zero in on it much better then anyway.
 
oldkimmer said:
Does ur builder know that the rocker shafts have to be put on a certain way? Pass side notch to the left and down. Driver side notch to the left and down also. That won’t make ur lifter preload any different, but will screw up the oiling if not right. Kim
Click to expand...
Unless you get a pair of shafts (from Comp Cams) that are incorrectly marked. I was looking at the oil holes vs the "notch" markings and luckily noticed that the oil holes were 180° off.
 
The shafts that I have are mopar performance hard chrome shafts made for stamped rockers, they do not have the notches on one end, you just have to put them on with the off set oil holes down and to the side of the valves. as far as the preload goes, I am ok with the difference I just wanted to know if .035 to .055 was ok.
 
go for it Jeff
meticulous is good
lots of good points in this thread which you may have known already
but others will find it later with a search
so post back how it comes out
tks
 
You must log in or register to reply here.
-

Back
Top