in my quest to rid myself of the infamous 288 heads. i found a set of 441 castings with screw in studs, guide plates and ported. 1.94 in 1.6 ex valves. they have some surface rust so i disassembled them and they are at the machine shop being crack checked and cleaned. now for my questions. when removing the valves each spring had different thickness spacers under them .06, .03 ect. what are their purpuse and when i reassemble how do i go about determining what to use ? springs are 2.16 tall and 1.22 round. also can someone post a picture or drawing of valve guide bosses that have been machined for positive type seals ? pardon my ignorance but im just getting into head mods.

 

The shims are typically installed to correct machining variations when fitting valves and springs. They are there to adjust for correct spring installed height.

This shows a typical factory guide before sizing for positive seals (in the process of stud boss cutting):



This shows guide that have been cut for positive seals:



Sorry for the blur

FWIW, you can get factory positive vlave guide seals that fit the factory guide bosses in many cases. They are OEM on LT1 and LT4 engines. Most aftermarket positive seals are slightly smaller diameter and require the machining. The smaller seals allow for a wider range of valve spring combinations and clearances.

 

thanks vader. looks like my heads are cut for positive seals. i have been reading alot lately and still havent found how to check for proper spring height. know of any good books or links that explain this procedure? also not sure if heads have been shaved. is there a way to measure this ? i have most measureing tools, used to work in non auto machine shop. im trying to do as much of the work my self.

 

The guide size for the later style of heads with the factory positive seals is about .625" OD. The seals are realtively thick and rubbery though, and have a wire band clamp around them; so they'll fit a rather wide range.

For "real" positive seals, i.e. Teflon ones, the guide OD needs to be either .501", or .531". The larger of those 2 sizes is the more common one. Far greater precision is required to use these. However, they work FAR better, and last practically forever; whereas the various rubber varieties such as nitrile and Viton, deteriorate fairly rapidly from heat and age.

I know of no good way to determine how much has been cut off the deck of heads. They are too imprecise to begin with. That is, there's no feature that's sufficiently "standard", to measure off of.

A better piece of knowledge to obtain than "how much ahs been milled off", would be the chamber volume as it now exists; which you can get pretty close on, with a medicine cup like for Nyquil or something, and a CD, and some grease or Vaseline on the valve seat and deck to seal the valve to the seat and the CD to the deck, and some antifreeze as your measuring fluid.

You check for proper spring height with a spring height micrometer. http://store.summitracing.com/partde...art=CCA%2D4929 You put the valve in the head, put the mic on the head, put the retainer and keepers on, unscrew the height mic until it takes the slack out of everything, subtract the desired spring height (found in the spring mfr's catalog) from this measurement, and stack that much shim on the head before you put the spring in.

You can get guide boss cutting tools from Comp, Crane, Isky, and others. Use them at your own risk; the results aren't always what's hoped for.

 

thanks sofa.
heads came back from shop with no cracks and looking all shiney !
guide bosses are .530 so im good there.
decks have been milled you can see the tooling marks.
ill have to get that tool for measuring spring height, and some spacers.
will also cc the combustion chamber, i have seen some good info on this procedure in my books.