Question:
Are 918s easier on the lifters and perhaps less prone to cause lifter problems than duals? Or can stock lifters easily handle the extra load?

Would 918s be more "forgiving" to cold weather starts etc. than duals? Or is there little real world difference?

Using these two examples;
921 918
seat load 135 130
Open load 400 318
Rate 408 313

 

I am about to replace my springs and considered the duals over the singles. I have always been paranoid of the single spring breaking and dropping into the cyclinder. I purchased the PRC Duals and bought them at TSP. I talked to Zach and he said it would not be a problem. There are lots of people running these with stock lifters and I will be too.

 

I spent a lot of time looking into the lifter capability last winter. I found through searches guys having lifter problems, those with no problems and those who seemed to be on the verge of problems (occasional ticking and other things that indicated the lifters were not happy campers). I found that, although not very scientific, those who had less than 625 lbs of open load on the lifter were not having problems. So if you take your open load, multiply times your rocker ratio (stock is 1.7) to get your open lifter load, it will give you an idea if you are on the edge of having problems.

As for the springs, the beehives will run to RPM with less load than duals. TSP also just introduced what look to be very light titanium retainers for the 918's.

 

Interesting, so in my example the 918s are at 540 open load and the 921s are at 680, above the threshold for trouble.

I was thinking along the same lines - we keep hearing about ticking noises and it invariably is after some kind of spring upgrade. Preload of course has a good deal to do with it but I think there's more to it - like your research seems to be indicating.

 

A friend of mine is running 921's and a TRex cam on OEM lifters with absolutely no problems. I've had 978's for a number of years with Comp 850's, which supposedly the same as OEM, and no problems.

 

Ticking comes from too loose of a preload on lifters OR the lifters are no capable to cope with too much spring pressures OR both.

It is a common practice for a lot of poeple to run high seat pressure duals just because they fear the single will lead to disaster or just pure laziness because they do not want to check their singles on a yearly basis (or every 15K miles).

It is all a matter of properly matching setups.

It has been proven over and over that beehives have much better harmonic control than duals, especialy at high rpm where it matters.

 

Beehives also have a non-linear stiffness curve, which if you check David Vizards book on valve trains, is very desirable to eliminate harmonics and surge.

 

The same lifters that come from teh factory in an lsx engine, also come from the factory in bigblocks with almost double the ls1's spring pressure. Food for thought.

 

Pradator-z,

I noticed in a previous thread that you recommended using a longer pushrod than 7.4" with the torquer v2 cam.

I assume this is for the extra preload.

Why doesn't tsp offer a longer pushrod than 7.4"

 

Well this question has been surfacing for awhile now.
Quite a few sponsors have p-rods made for them but only in .050 increaments.
7.350-7.400-7.450
Most of the time this is too big a difference and a .050 increase would put you over the required range. So the next shortest is usualy 7.400.
To add to that is is a belief that lifters being hydraulic, they would absorb the difference with no ill effect on performance. (some even believe that lighter preload increases power output but that has yet to be verified, that I know of)
Comp Cam makes p-rods in .025 increaments which gets your preload closer to lifter stock range and can reduce noise dramaticaly.
Being a XE-R fan that I am, I found this earlier on during cam only setups when running 7.425 p-rods reduced noise.
My initial trial was with a .581 lift 224 cam, stock heads and .045 Cometic gasket. with 7.40s the valvetrain noise bothered me so, after a few calculations, i found that I could run 7.425s without going over the .100 stock preload. so i slapped a set in there and the noise was virtualy almost elliminated.
.045 gasket was .009 thinner that stock .054
add .025 to that and you get .034
The XE-R effective smaller than stock base circle radius of .045
.045-.034= .011 was still under stock range so my preload ended up .089

From my experience on stock lifters .050>.080 preload is noisy and .080> .100 is relatively quiet.