sbf valve guides

[67rcks]

I am wondering about worn valve guides. My haynes manual says side-to-side will needs to be less than 0.020" for valve lifted about 1/8" (i.e. 0.010" to one side), otherwise overhaul is recommended e.g. instalation of bronze inserts. However, when can I expect just too much of oil leaks? E.g. is 0.030-0.040" will way too much?

And what about valves, how much wear (at stems) is generally fine - also the manual does not specify it

I also received some rubber gaskets in felpro engine gasket set to install over the valve guides. Are these going to help sealing at all? please help

 

[D.Hearne]

Machineshops used to knurl the guides when slightly worn. I'm sure some still offer this. The knurling doesn't last as long as new guides, but was a cheaper alternative, especially if you're just building a weekend warrior and not a daily driver. My 1964-70 Motor Repair Manual gives valve guide clearances of .001" for the intakes and .002 to .0027 for the exhaust. It doesn't specify whether that's open or closed. more likely it's closed I'd think. Small block stem diameter is listed as .3416 to .3423 (intake) & .3406-.3413 (exhaust) I'm assuming the gaskets you're talking about are the umbrella seals, these work to a certain extent, better than nothing but less than PC type seals. The umbrellas get old and brittle at some point and find their way into the crankcase and oil pump eventually.

 

[67rcks]

Small block stem diameter is listed as .3416 to .3423 (intake) & .3406-.3413 (exhaust).

Thanks D.H. for the advice. Just wondering, are these stem diameters a factory tolerance or you mean e.g. when diameter is ,3416 valve replacement is recommended? Eg fed mogul lists stem diameter of a new valves 0,3415 (ex V1961) and 0,3420 (intake V1932) and I guess V1932 cannot wear to .3423.

On my engine ('73 302), I measured valves and they are missing 0,002" at stems, do you think I should replace them too when installing new guides? A guy who made overhaul just knurled the guides but some of them are too loose (more than 0.020") and I don't want to risk oil leaks.

Also wondering are bronze guides 2.25" long enough for old cast iron heads for which auto parts stores lists 2.5" long cast iron guides? I am thinking about using late model stock guides which are however .25" shorter.

 

[D.Hearne]

The motor book just list those specs, I'd assume that anthing smaller in diameter needs to be replaced. As for those bronze guides, new guides are usually longer than needed so they'll fit a wider variety of applications. Once they're installed the machinist can trim the tops. As for loose guides and oil consumption, that's the least that can happen. I'd be more worried about dropping a valve head with the sloppy guides.

 

[67rcks]

As for loose guides and oil consumption, that's the least that can happen. I'd be more worried about dropping a valve head with the sloppy guides.

You mean if guides are worn valves would not seat OK?

If decided to replace valves are these interchangeable with ones in EFI engines (to use regular gas without any lead substitute)? They are slightly different - .040" shorter and head angle is 45.5 vs 46 degrees. Does this make any difference that some other parts may be affected eg. springs, pushrods, etc?

 

[D.Hearne]

I don't know what heads you have but aside from the stem lengths, all the SBF 1.78/1.45 valves are interchageable as to fuel types. The Pre April 66 heads had shorter valve stems than the post april 66 heads. Then the next change was I think made in late 77 when the switch to pedestal rockers was made. Then the E6SE heads had even shorter valve stems than the E7TE's.

 

[67rcks]

thanks man