BenKey

iTrader: (1)

The .004-.010 is what Comp says their CompR lifters have to be set at. The internals of this lifter are much different than a stock lifter (according to them) and any more than that and you run the risk of popping out the retaining clip in the lifter. All the other lifters I know of, are a stock type lifter and get the normal pre-load setting of .040-.060, or wherever the stock preload is.

QuietTahoe

When you take one apart, I don't think you will find it much different than stock. The average difference on the clearance between the inner surface of the outer shell and the outer surface of the inner plunger is less than .00025inches, and yes, that decimal point is in the correct place!

QuietTahoe

The post above refers to the difference between a stock lifter and any high bleed rate lifter. Why don't you ask them (Comp) how they compensate for the vastly different thermal expansion rates of aluminum block and heads compared to steel pushrods and lifters. I would be real interested in that. FYI, the difference in expansion on a HD motorcycle causes .026" in thermal expansion. That is why its virtually impossible to run a solid roller in an HD on anything but a full race application. The great thing about hydraulic rollers with aluminum engine castings is that they have so much plunger travel to compensate. If you look at Comp's recommendation, it is .004-.010" preload with the engine HOT. Try to get the engine hot, get the valve covers off, change pushrod length (Comp's suggestion) to get preload correct and get the engine buttoned up before it gets much colder and the preload is off. According to Roger Vinci, every hydraulic roller lifter he has tried on every type of engine he has tried (including LS1s and Comp stuff) has worked better with the deeper preload. All I know is he has never steered me wrong, and I would submit that it's worth a try. I don't see how the snap ring could come out. There is a balance of forces between oil pressure and spring pressure that will keep the plunger centered and not allow the snapring to come loose!

marc_w

Not to change the subject, but it's real ironic that you mentioned that. I'm running into possible expansion/valvetrain problems with my old Ironhead. What's the end result after expansion, more or less lifter preload? Someone suggested that I'm getting additional preload. I haven't had a chance to get into it yet.

BenKey

iTrader: (1)

I'm not debating what anyone has done here. My post was not my words, but Comp's. You call them and talk to them, I already have. The CompR lifter is the only lifter that I am aware of that the stock preload is not recommended, but what they specify. Go to the internal engine section and read about CompRs. Many guys using them in the f-body world. I believe it is specifically made for high revving engines, 6000+. Makes no diff to me what they want them set at as long as 1) they don't fail and 2) they're quiet. I don't plan to use them. Not yet anyway.

QuietTahoe

Hi Marc, The effects of thermal expansion due to a temperature increase will usually be to decrease preload. An iron block and heads will usually expand at about the same rate as the steel valvetrain components, so preload won't change enough to have much of an affect. Aluminum, however, expands at slightly more than twice the rate of iron or steel, so it really has an affect on preload or lash (depending on what you want; it decreases preload and increases lash). This brings up all sorts of other issues. For instance, the piston to wall clearance set up at the factory or recommended by the piston manufacturers assumes an operating temp in the range of 200-215*F. This temp is necessary to boil the water vapor out of the engine oil after start up, as well as it is the best all around temp for emissions control, fuel economy, power, etc. When you take steps to increase power (more fire, pressure and heat on the piston top causing the piston to expand) and yet decrease the block temp (the block won't expand as much at 160*F and therefore, the bores are smaller); piston to wall clearance decreases and the chances of piston scuffing go up tremendously. Again, aluminum blocks change dimensionally much more than iron blocks. Especially, consider the effects of iron liners in aluminum blocks. The blocks do not heat and cool evenly, and if you run the combination at other than design temperatures, you can throw a real out of roundness issue into the cylinder as well!! This is a huge problem in the marine industry because they run high average engine speeds and loads and yet it's hard to get the blocks above 150*F. This is really a problem on all automotive engines built since about 1996. Some companies are allowing piston to wall to get as tight as .0007". Put a little nitrous in one of these engines and you have substantial piston growth and piston to wal scuffing!