Quote:
Originally Posted by Jackstand Queen
Q-authority:
I did some math and measurements. And here's what I came up with
Typical valve stem diameter .2310" (both Int. and Exh.)
SI valve guide interior diameter .2362"
O.K., subtract the valve stem diameter from the Valve guide diameter and you get .0052"
So let's round that number off to 5/1000ths.
The factory clearance for valve stem to valve guide is less than 1/1000. Now double that clearance number when you apply it to my previous math (because its less than 1/1000th X'2 to account for both sides of the valve stem).
The SI valve guides appear to be out of tolerance (worn out) new, right out of the box.
The BGB recommends using a 6mm Taper Reamer to ream out the valve guide. 6mm is .2329" a reamer of this size would pass through the SI valve guide without touching the inside of the guide.
I don't mean to sound uppity, or act like a monkey with a handful of poop . . . . . but I'd reconsider the SI brand choice.
In the small town where I live, I garantee that no machine shop would be able to do a 4ag valve job. They'd run a 1/4" (.2457")drill bit through the guide and congratulate themselves on what fine work they done did.
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Okay, I'm not sure where you got your measurements from, but your inner dimateter for the oem valve guides is incorrect. The BGB lists them as .2366-.2374". I have done all the calculations, and the SI valve guides measure up just fine with either oem or aftermarket Supertech valves (as a note, I do tend to do my calculations in mm's).
The following measurements are copied directly from the BGB and from SI and Supertech published specs:
bushing inside diameter (oem valve guide): 6.010-6.030mm
SI valve guide inner diameter: 5.99948mm
valve stem diameter, intake (oem): 5.970-5.985mm
Supertech valve stem diameter, intake: 5.98mm
valve stem diameter, exhaust (oem): 5.965-5.980mm
Supertech valve stem diameter, exhaust: 5.97mm
measured valve stem oil clearance, intake (oem): .025-.60mm (.08mm max)
measured valve stem oil clearance, exhaust (oem): .030-.065mm (.10mm max)
As you can see, the SI valve guides actually have a slightly smaller inner diameter than the oem valve guides, so there should be no problem using them with oem valves.
Additionally, the Supertech valve stems diameters are just less than the largest oem valve stem diameters, and they could therefore be used with either oem or SI valve guides with no problem.