Feel free to move this--didn't know where to put it. Anyway, I'm lead to believe that lighter valve train components, including valves, retainers, springs, prs, etc, contribute to better performance, etc. It usually says that lighter components allow higher revs. So my question is, do lighter components make any difference if you do not intend to rev over 7 grand, and....exactly from a technical standpoint, in layman's language, how does a lighter valve train get these results, and which components are the keys to this phenomenon?

Thanks.

 

BUBBA:
There is an interesting high-speed video of the gyrations valve springs can go through while trying to keep lifters, pushrods, rockers and valve in contact with each other as Gm intended them to be. Seems reasonable to assume lighter weight will reduce the work load on the springs ... however in the interest of reliability ... FWIW 7.2" stock LT1 pushrods are ~44 grams each and Trick Flow 7.2" .080 wall 4130 Chromemoly pushrods are ~51 grams.

 

Thanks for your info NJ. I guess if you dissected each component and its movement you could make a good case for the proclaimed benefits. E.g. if the prs are lighter, the the cam and crank don't have to work as hard to push them up and the lighter the pr the less pressure on the cam lobes resulting in less wear. The lighter valves, esp. on the intake side allow faster opening (which is more important than faster opening of the exhaust) A lighter retainer is easier on the spring as it decompresses upward resulting in less wear on the spring, etc.

I'm just curious. Although the Lt4 came with sodium filled prs to make them lighter and cooler, I wonder why more attention and focus is not given to lighter components based on each components contribution based on its weight and strength. Given the prohibitive cost of titanium retainers (even though this metal is one of the most common metal on this planet) I wonder if there is any concrete proof that they offer any advantages, aside from strength, especially for an engine that will never see the north side of 7 grand.

 

Now you understand why LS1 uses thinner 8mm valves stems.

 

To back this up in real world experience I'll fill you in a little bit on my new set up.

I built a stout 355 with the goal of all light weight. My heads are a copy of AFR's new eliminators and were the inspiration for them. They are stock castings that were originally LE2's. My engine builder (famous 70's drag racer) worked his magic on them and went through them putting LS1 sized valves in them for the thinner shafts at a size of 2.02/1.60. They alone were 40% lighter than the ones that were in them. All titanium hardware was used as well as 918 behives. He used comp 1.60 promagnums as well. Pushrods were engine pro.

Now on the other side of this is the bottom end. He went against the norm and chose eagle rods @ 6.125" long with Mahle Powerpack pistons. Everything is forged. To give you an idea of how light the rotating assembly is, balancing the assembly required only 1400 grams to simulate 2 piston, 2 rods, 2 sets of rings, 2 pins and bearings. If you don't understand how this all works, it is a ton less than most out there and is the 2nd lightest assembly he has ever done in 40 years.

Now what does this all mean?

1- lighter top end equals less mass, equals higher revs to eliminate valve float, giving you a very stable easy working valve train with less wear and tear on parts.

2- lighter weight bottom end equals extremly fast rise in rpm thus getting you in your HP/TQ power faster and pull through the power faster. If you were to see how fast my set up spins up you wouldn't believe it.

3- side note, longer rods puts less stress on the pistons and side wall of the cylinders.

4- end result... my little old 355 made 491 rwhp NA.

Now there are some other things done to my intake and some other tricks that I will not let public out of respect for my builder. But I will say, the build exceeded all our goals and put a big smile on our faces.

My suggestion to you if you are planning on doing anything to the valve train, buy the best, strongest, lightest parts you can. You will not regret it. You will only gain over it's matching heavier parts.

 

In addition to RPM, you also have to consider gross lift, and how aggressive the lobe ramps are. The faster you try and move the valve train components, the more important inertia becomes. First the cam has to accelerate all the parts in the valve train, and then something has to stop all the parts, and allow them to reverse direction. The less the parts weigh, the easier it is to control their motion, and the less energy is required to accelerate them and stop them.

 

x 2

 

IMHO the area not to skimp on weight wise is the pushrod. Go for the stiffest one that will fit. You don't want the pushrod to act like a pole vault.

 

I agree. But one can also achieve a rapid spin up with a billet light weight flywheel like SLPs that dropped about 8lbs off the roating assembly

Impressive indeed.

Good advice

 

I'm using Manley Race-Flo 2" /1.56" w/ undercut stems. Wt+ int. 109 grams, exhaust 91 grams. CRower 1.6 SA RRs, Crane 99893 springs w/ the retainer and locks with my baby crane cam 210/224. I see that the LT4 stock valves are alot lighter. Probably should have gone with them or something else. Don't know. I seem to have good throttle response and the cam is a 6 grand cam, so I guess I will be ok. I understand where you are coming from re lighter components, but I guess I missed the boat on that one.

Thx.

 

Weight on the valve side is more important than on the lifter side due to the multiplying effect of the rocker arm. You only start to need exotic components when the revs get very high. There's too many variables to say "above x rpm you need y parts". But I have seen plenty of motors running 7,500+ without resorting to anything special except the right springs.

Rich

 

What is the concensus here on a steel pro-mag rocker vs. an aluminum rocker as it relates to this discussion?

 

I've used both on street and race cars.Never had problems with either. The aluminum looks cooler, so that is what I have settled on.

Rich