Lifter preload...more or less?

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Mojoe9955

Mojoe9955

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I rebuilt my stock 318, rings bearings. Resurfaced the heads, Mr Gasket .025 head gasket, Comp .990 springs and 258 Voodoo cam. I broke it all in using the stock pushrods and some shims as I was concerned the pushrods would be to long. All seemed good after the break in but the valve train was pretty noisy on the passenger side. I took the shims out of that side and it quited down with no ticking on either side. Still not knowing what actual pushrod I really need and want to get the best performance, I got a pushrod checker, removed all the shims and checking 4 corners I come up with an average length pushrod of 7.375. To tha Lunati recommends adding 0.020/0.060 preload, I'm an average gut so I'm thinking 0.040. On the shelf I can find 7.400 which gives 0.025 or 7.425 which gives 0.050...I'm impatient and want to drive.
If I use the stock 7.500 rod I get .125 which seems excessive, but the motor runs pretty good and the spark plugs look nice.
Of course there are other factors to consider, but I'm most interested in hearing the best cases for more or less.
Thanks
 
You have 0.125" of preload? Are you sure about the measured pushrod length? How much came off the heads? The Mancini shim kit come with 0.030,0.015 and 0.010" but its too much to shim in my opinion. I would be buying the shorter pushrods and shimming possibly. Of course adjustable rockers would help too.
 
When I was at this stage, I got this great explanation about preload from member @Bewy and I quote..........

"The reason for such a short pre-load of say 010 is in case the hyd lifters pump up at high rpm. If the preload was, say, 080, that would mean the valve can theoretically increase max lift by 0.120" with 1.5 rockers.....& the valve could hit the piston.
If you have adequate valve spring tension, you will not get get lifter pump up. Internal lifter travel is typically at least 0.150" & you set the pre load anywhere within that range. If not sure of the available preload, compress a lifter in the vise [ slowly if it has oil in it ]."
 
I’d run the shorter pushrod. But don’t over think it and loose sleep over it.
 
I'm saying I've been a carpenter over 50 years and can accurately measure using all manner of instruments. Using an approved adjustable push rod and approved methods in 4 locations my pushrod length is 7 3/8" or 7.375 as a decimal against a stock rod of 7.5" the difference between the 2 is .125 or 1/8 inch which using the stock rod in the valve trains current situation would theoretically would give double the Lunati recommended recommended preload of 0.060.
I had shims and the stock rods but it was very noisy. Upon removing the shims and with the stock rods it sound better/normal.
 
At 7.375 there is no preload. I was thinking adjustable rockers but am really not interested aside from new pushrods spending extra money at this point. I also thought of a little longer pushrods and shims, but it's too complicated. My springs are considered an upgrade/stonger. Keeping that in mind I'm back to new push rods, one gives .0250, the other 0.050 preload. I also as a carpenter find it hard to believe that 1/16 - 1/8 makes that much of a difference.
 
I set hydraulic preload at the minimal , just off the retainer.
Less likely to pump up
 
Mojoe9955 said:
I also as a carpenter find it hard to believe that 1/16 - 1/8 makes that much of a difference
Click to expand...
I have a saying...

Close enough for concrete. (+/- 1")

And along with that goes

Close enough for wood (+/- 1/16")

And

Close enough for metal (+/- 0.002")

(Just numbers I use for example)

What I'm getting at is in the concrete world close is perfect.

In the wood world really close is perfect.

But in the metal world you better be dead nuts on or you will have problems.

Imagine if you used your 0.125" for bearing clearance!

Also just like everything else, metal grows when it gets hot and in an engine it gets much hotter than wood or concrete.

My 273 has mechanical lifters and if the gap is set too loose the lifters rattle. Too tight and valves will not be sealing when the engine heats up. The engineers spent decades learning how to compensate for all the growth that happens in the engine.

So yes a few thousandths makes a big difference.

With hydraulic lifters and not particularly high rpm you can get away with pretty close.


But as pointed out if the lifter pumps up and the lifter piston is too far compressed... Piston meet valve.

Just my 2 cents
 
Mopar hydraulic camshafts came from the factory set at 0 lash, just say'n.
 
If you use a buncha pre-load, a lobe can wear a looong way before some noise makes you aware .
A small amount of pre-load makes you aware very quickly of a bent pushrod, any loose fastener/adjuster, rocker/lifter failure, or any lobe/shaft/parts wear in a timely manner to avoid a buncha contamination thru-out the engine.
Experience .
 
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Why is the valve train noisy? Taking the shims (rocker shaft shims I assume) out adds to the preload. If you already have 0.125" preload I don't see how adding more preload would quiet things down. I could see it if you had zero or less preload to start.
 
1MeanA said:
Why is the valve train noisy? Taking the shims (rocker shaft shims I assume) out adds to the preload. If you already have 0.125" preload I don't see how adding more preload would quiet things down. I could see it if you had zero or less preload to start.
Click to expand...
I probably had very little lash with the shims.
As far as .125 preload that is a figure based upon the difference between the 7.375 rod and the stock 7.500 rod.
I think I have it worked out now.
 
Make sure the stamped rocker arms are not banging on the retainers! This is a common problem when upgrading the springs.
IMO, with stock stamped rockers Your preload should be about .020. Too much less and you will be going back in, in a few weeks as things move around.
More will work, but the risk is valve to piston contact, as the springs lose control with rpm. I highly recommend adjustable rocker arms.

Post #3 for the win.
CFD244 said:
quoting Bewy
"The reason for such a short pre-load of say 010 is in case the hyd lifters pump up at high rpm. If the preload was, say, 080, that would mean the valve can theoretically increase max lift by 0.120" with 1.5 rockers.....& the valve could hit the piston.
Click to expand...
 
Sealed Power made anti pump up lifters.....& std lifters. HT-2011R & HT-2011 respectively for the SBM. They are identical except for the circlip design.
This is what it says: 'A special high strength steel retainer is used in place of the spring clip to precisely limit the travel of the plunger...'

The hot lash with these is set at 000/002". I have seen these pop the circlip.
The purpose of these lifters is to limit pump up [ hence: anti p/up ]. The problem is that the circlip is gets pounded as the lifter tries to pump up.....& stronger though they are, they can & do pop out.
Majority of hyd lifters have about 0.150" internal travel/pre-load. Setting pre-load anywhere within this range [ 0-0.150"] will provide the same engine performance & there is ZERO benefit setting lash with 010" gap to the circlip, & to do so will almost guarantee popping the paper clip type circlip used with stock lifters...& the possibility of lifter bits through the engine. The proper way to limit lifter pump up is to keep rpm below the start of pump, use stronger valve springs or use sol lifters that are tight lashed.
No car company, including Chrys, used zero lash from the factory because of the above danger.
 
Call Smith Brothers in Oregon. Tell them what you have, ask their advice and get them to make a set of push rods that are just where you want them (where they say they should be). It doesn't take them long. I just got a set for my 340, took less than 2 weeks, price wasn't bad and I know I have the best.
 
I like .040 for Comp lifters. I have set the as loose as .010 with no increase in performance. They were noisy at idle with .010 preload and 5w-30 oil. Tightening up to .040 preload lessened the noise tremendously. Running 10w-40 made it go away completely.

I agree with others on calling Smith Bros.
 
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