Sleeving Lifter Bores
Sleeving Lifter bores can be considered part of a complete block blueprinting, although many shops do not suggest or recommend it because they cannot do the work. Generally the only shops that do this job are hardcore Race Shops, or specialized shops. Since we are a specialized MOPAR shop we can do both small block and big blocks, including 426 type Hemis.
Photo 1 is a 440 Block set-up for lifter boring. The boring reamer is supported at both the top and bottom, note bar going through the cam bores, for maximum rigidity and accuracy.
Sleeving the lifter bores will accomplish 4 things.
1. Most importantly it corrects the alignment and position of each lifter relative to the crankshaft and each other. Photo 2 is a photo of a typical lifter bore that has the new corrected bore started. The fresh machined area shown on the top of the lifter bore is biased off to approximately the 2:00 o’clock and barely cleaning at the 8:00 o’clock position. This demonstrates how far the lifters can be out of position. This is common. The boring mandrel is supported at both the top and bottom for maximum rigidity, unlike C.N.C. set-ups which don’t support the boring mandrel on the bottom. The sleeves have a .060” wall. This original bore was off almost .060” That’s very bad!
2. The factory lifter bores can be out of position from front-to-rear which reduces lifter rotation making flat tappet cam break-in more problematic.
3. They can also be out of position circumferentially. This causes the cam timing to be off from cylinder-to-cylinder and valve-to-valve, which reduces power. Or what is really bad is if the bore is not straight. It starts off OK (or way off) and gets worse (or better) the deeper you bore. This makes everything bad. The bores can have one or a combination of all these problems.
4. The sleeving will also correct for worn and out-of-round lifter bores! This problem can be especially severe on small blocks because of their 59º lifter angle. The problem is even more common on engines that have run solid roller tappet cams.
Normally bronze sleeves are installed; however in cases where the block needs to “look stock”, for some “unknown reason”, cast iron sleeves can be installed.
The sleeves can be drilled for oil in situations needing oil to the lifters such as with hydraulic lifters.
Iron sleeving includes blending into OEM machining marks (so they can’t be noticed!
The answer to how much H.P. is it worth is answered by; how bad is the present alignment? It would vary depending on the power range you are working in and how bad they are now. In low H.P. restricted engines where everyone’s power is about equal or you have done everything else possible, sleeving becomes more important.