bushed lifter bores
 

What's the real benefit of sleeving a lifter bore? Does it provide less friction? Looking at the Engine Masters challenge rules it states: Lifter bores must retain OEM angle (+ or -1 degree) and OEM diameter (+ or - .005-inch). Lifter bores may be bushed.

How does changing the angle effect horsepower or reliabilty? It would seem that this machine work is not cheap and probably not recommended for a street motor. How much power can be found with this mod and do you suggest it?

Thanks

bores
 

Not much if any power gain.If the bores are out of line or loose it gives you a longevity factor on the rollers and less oil pressure loss to line them up and bush them, There might be a gain from lack of excessive splash on the crank,but that would be hard to record.
IF a block isn't totally worn out there is no point in doing it for less than a max effort engine.If you are going to bush the bores might as well put needle brg cam brg's in too.BRING your checkbook when you take it to get this work done.$$$$$

Re: bushed lifter bores
 

One good reason for bushing the lifter bores is that's about the only way to get them back to size after remachining them to more closely align with the camshaft. If each lifter does not run perpendicular to the cam centerline and at the exactly the correct 90 degree orientation, valve timing will be off by perhaps a few degrees, and it will vary from bank to bank.

Misplaced lifter bores are probably caused in production engines because the block is located off the main saddles and/or deck surface when lifter bores are machined, not the cam bore. To correct a block, you could locate off the cam bearing bores and the cylinder centerlines or deck surface, and remachine each lifter bore, then press in a bushing, and rebore it. This either requires some expensive jigs and fixtures and considerable machine time, or perhaps a large CNC mill, so it's costly.

If you start with a good CNC block (CNC Bowtie) or some aftermarket blocks, the lifter bores are damn close. Folks like Hendrick (Cup team) even correct them, but remember they have the need and the $ to find those last few hp.

In some engines the OEM lifter bore location gives angled pushrods. EM rules prevent you from fixing that "design flaw". The diameter rule prevents using larger diameter lifters which can give you a significant advantage in a flat lifter rule, like the EM big block competition in 2003 (or Nextel Cup, for that matter).

Sure, lifter bushings are usually some form of bronze, but the friction reduction, if any, isn't the major reason for the material choice. Remember that roller lifters can cause considerable side loads on the lifter bore, but flat lifters don't. Well, with seriously angled pushrods there is some at the top of the bore, but very little at the bottom of the bore. That's mostly from the angle on the lobe of a flat lifter cam which causes lifter rotation.

My $.02