Oversize valve guides?
01-07-2003, 09:03 PM
#1
Racer
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Oversize valve guides?
I recently pulled the head on my car due to an exhaust leak, and I plan to have it cleaned up while out of the car.
Planned work includes:
- new valve seals
- new valve guides
- new valve seats (reground)
I am in the process of ordering parts, and I received a few questions back.
1. They said that the valve guides (944-104-328-51) are "oversize" and that "some machine shops don't like them." Exactly which part of the guide is oversize? I'm guessing outside diameter which would require additional drilling in the head to make them fit. What other options are out there or do most people use the oversize parts?
2. The parts staff also asked if I was planning to have the head resurfaced where it mounts to the block. I'm guessing they are asking because I would need a thicker headgasket in that case. Is warpage of the head surface something that I should expect after 145k miles? I will plan to ask the machine shop to check the surface.
Planned work includes:
- new valve seals
- new valve guides
- new valve seats (reground)
I am in the process of ordering parts, and I received a few questions back.
1. They said that the valve guides (944-104-328-51) are "oversize" and that "some machine shops don't like them." Exactly which part of the guide is oversize? I'm guessing outside diameter which would require additional drilling in the head to make them fit. What other options are out there or do most people use the oversize parts?
2. The parts staff also asked if I was planning to have the head resurfaced where it mounts to the block. I'm guessing they are asking because I would need a thicker headgasket in that case. Is warpage of the head surface something that I should expect after 145k miles? I will plan to ask the machine shop to check the surface.
01-08-2003, 01:27 PM
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I would have the machine shop doing the work supply the valve guides as they may actually have a better price as well as know what they have had good luck with. Plus if there was a problem they supplied everything. In general OS guides have a larger outside (OD) then standard.
As to surfacing the head, have them take a clean up cut so you have a good surface or have them take it down to raise compression. I usually just have a .005 clean up cut taken and would prefer to have both sides done so everything is nice and flat when it bolts up. The gasket does not have to be thicker, but use a good quality gasket.
Good luck
As to surfacing the head, have them take a clean up cut so you have a good surface or have them take it down to raise compression. I usually just have a .005 clean up cut taken and would prefer to have both sides done so everything is nice and flat when it bolts up. The gasket does not have to be thicker, but use a good quality gasket.
Good luck
01-08-2003, 02:07 PM
#5
Three Wheelin'
Don't mean to leech TT9714..... 
</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by thomschoon:
<strong>take it down to raise compression. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Do you have experience with this? I am currently shopping for a Euro spec engine which already has 164Hp(compared to 143hp in the US version). If I find a nice used one I am considering getting this done since the engine will be apart. Do you know how high the compression can be raised and still be safe? I don't mind doing some minor fuel and ignition upgrades.
</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by thomschoon:
<strong>take it down to raise compression. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Do you have experience with this? I am currently shopping for a Euro spec engine which already has 164Hp(compared to 143hp in the US version). If I find a nice used one I am considering getting this done since the engine will be apart. Do you know how high the compression can be raised and still be safe? I don't mind doing some minor fuel and ignition upgrades.
01-08-2003, 02:58 PM
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I would check with some of the spec racing folks for how much they took off. If I remember correctly they allow an increase to 11 to 1 by machining the head.
01-15-2003, 02:40 PM
#7
Three Wheelin'
</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by thomschoon:
<strong>I would check with some of the spec racing folks for how much they took off. If I remember correctly they allow an increase to 11 to 1 by machining the head.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Is this on race gas? I would think 93oct would be safe for a 11.0 to 1 in a 2.5 N/A
Opinions??
<strong>I would check with some of the spec racing folks for how much they took off. If I remember correctly they allow an increase to 11 to 1 by machining the head.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Is this on race gas? I would think 93oct would be safe for a 11.0 to 1 in a 2.5 N/A
Opinions??
