Lifter pre-load, school me!

[hypermite]

OK, I've been running my 440 Duster around for a couple of years now, Whatever I try to do to tune it, it just wont rev past about 5200 rpm. combo is: 10.2 to 1 440, untouched Edelbrock RPM heads, Lunati 10230703 "Voodoo" cam, old # 60303, Edelbrock dual quad manifold with 2 600cfm Eddy carbs. & Schumaker tri-y headers. It ran 12.20 @ 111 mph at the local track shifting at 5K, and letting off well before the finish line, (with a stock converter & 3.91 gears it's over 6K before the E.T traps) Car pulls super hard in each gear, & just takes a nose dive right around 5-5200rpm. When I set the lifter pre-load I tightened the adjuster on the rocker till I felt the pushrod just start to drag, & then gave it a 1/4 turn & locked it down. & did this on the compression stroke with both valves fully closed, on each cylinder. Did I miss something, should I be closer to a full turn?

 

[OldmanRick]

I think your lifter preload at 1/4 turn is just about spot on for my liking.

My first thought was that the Eddy springs are giving up the ghost, but that cam is not really radical. Not that it still couldn't be the issue?

How's the fuel supply? Pump, lines, tank, pickup, etc.

 

[RustyRatRod]

I agree. Sounds like it needs more valve spring.

 

[moper]

If you have the 71977 (recommended for that cam) then you can go more or less to find out what it likes. Those are factory type lifter so preload should be anywhere from .020-.050+. If the lifter bores are a little loose more preload may help the acheivable rpm. You need to know the thread pitch of the adjuster of the rockers you have, then determine where you are now. Also - it can be difficult to find when they are both closed... I will do the intake when the exh is at full lift, and vice versa to make sure the one I'm working on is on the base circle.

 

[rumblefish360]

Lifter preload is the amount of the lifter top compressible plunger is depressed down. The unuseable range according to Ma MoPar is the first .010 depressed and the last .010 at the bottom of the plungers travel.
I don go that far down myself and different lifter manufacturers tha e different specs of what is OK.

The less depressed the plunger, the more the lifters compressible range is used. The same only in reverse for the more depressed it is. The lifter pumps up sooner when it is depressed further. Less, the more time it takes to pump up. More time or less the plunger is depressed, the longer the lifter stays in pumped and the cam acts smaller.

Now your combo as listed should have the matching springs as per Lunati. I do not know there rates or what it is vs. Edelbrocks. The spring pressures have a lot to do with the rpm ceiling. Or lack there off possibly.

In addition to fuel pressure, check distributor timing and see if enriching the fuel mix helps the top end. 1 change at a time to see if THAT change worked.

 

[oldkimmer]

..............I always go with the minimum lash on a hyd cam.......I like .006 thou kim........

 

[hypermite]

Thanks for the replies guys. As far as the fuel system goes,( you guys are gonna fillet me for this) it's all the stock 318 stuff the car came with, 5/16th lines & pickup. that being said, since it falls off at a specific RPM in each gear, i figured it was either spark, or valvetrain. I had the distributor checked, but the old SUN machine only spun up to 5K, but spark was real strong up to that point.

 

[rbdart]

Improve your fuel system and the prob will likely dissapear..eddy springs should be plenty good enough but chk them anyway

 

[IQ52]

Here's my take on it. Comp says for their standard lifter (822-16) .030"-.040" preload and for the Pro Magnum & race hydraulic lifters .000"-.010".

They further state that for the 822-16, if the preload is less the lifter could be noisy and if the prelod is too much you may damage the hydraulics of the lifter.

So, if it 'mght' be noisy, so what? I was running the standard lifter and the engine would fall off around 5400 rpm. I put in adjustable pushrods, set them for zero lash and the engine would pull to 6200 rpm. This was back in 1976 so maybe it won't work in 2013. But maybe, just maybe...............

 

[451Cuda]

Fuel starvation.

 

[Bakerlite]

It seems these days lifters must be built with tiny little brains in them so they know how much plunger depression they have...

 

[Bakerlite]

Fuel starvation.

Fuel recovery from a drop in RPM and G force as the engine lays over. If not an issue now, then it sure will be soon.

 

[Bakerlite]

Comp says for their standard lifter (822-16) .030"-.040" preload and for the Pro Magnum & race hydraulic lifters .000"-.010".

Why do you think there is a difference in settings for the lifters?

 

[IQ52]

Why do you think there is a difference in settings for the lifters?

Minor correction here, depending on where you read on Comp's website you are told, zero to 1/8 turn or .002"-.004" preload hot.

Why do I "think" they use a different preload? I think they are designed differently. The Pro Magnum is a high performance, short travel, anti-pumpup lifter. Short travel being, less plunger travel and hydraulic volume inside the lifter body. That's what I think, I don't really know.

Man I hope I'm right, maybe I could design lifters!

 

[RustyRatRod]

Yup. The anti pump up lifters, some manufacturers even recommend up to .002" lash.

 

[oldkimmer]

.........yup, I've been there b4 rusty.......002 lash.........................kim.......

 

[GEO]

http://www.harlandsharp.com/tech_tips.html

 

[dano]

Get the correct springs. I have the same issues and know for a fact I have the wrong springs (stock 340 springs). This was years ago "the great cam flattening era" and the machinist was tiring to band aid an issues that was all ready resolved. Anyway, mine wont rev part 4500 and I've read the Edelbrock springs are not up to the task of that fast rams the VooDoo cams have. You need the correct springs.

 

[Bakerlite]

.........yup, I've been there b4 rusty.......002 lash.........................kim.......

Yeah, hard to pump up a lifter with 0.002 lash. Anti pump ups.. a total farce.
You know Vizard did some Dyno testing on the Rhoads lifters about 20 years ago and found that they never showed the full events of cam timing even when they had so called "pumped up" under higher RPM..

 

[RustyRatRod]

Yeah, hard to pump up a lifter with 0.002 lash. Anti pump ups.. a total farce.
You know Vizard did some Dyno testing on the Rhoads lifters about 20 years ago and found that they never showed the full events of cam timing even when they had so called "pumped up" under higher RPM..

Not that I doubt you, but I would like to see that if you have a link or can find it. They don't actually "pump up" it's the RPM that's supposed to make them realize full cam specs, not oil pressure. Do you think the Vizard information also holds true for the new VMax line from Rhoads as well? They are supposedly cutting edge.

 

[Bakerlite]

Wow, you made me think here where I had read it. If you have his first "How to build Horsepower book from 1990 and look at the start of page 56 , you will see what he's says about them. The problem with these sort of lifters is that they assume all engines are the same. Ie, different spring rates and valve size( weight) will have an effect on the lifter.. see where I'm coming from. All you need is a good quality lifter and the correct valve spring ( within limits)to control the valve train... job done.

 

[RustyRatRod]

I usually alleviate the problem altogether. Run solids.

 

[Bakerlite]

http://speedtalk.com/forum/viewtopic.php?f=1&t=22176
Pay attention to what Camking says..

 

[RustyRatRod]

Thanks for the link and the book info. That's one I don't have.