Cylinder head work question. EDITED!!
08-10-2005, 03:32 PM
#1
Rennlist Member
Thread Starter
Cylinder head work question. EDITED!!
I just got off the phone with Scott Gomes at Under Pressure. Why didn't I just call him first?
I received this e-mail from a recommended machine shop. I get the feeling he is trying to talk down other shops at the same time he is trying to talk up his own.
It seems that any decent shop familiar with Porsches should be good.
What's your take on how he describes the work involved?
I received this e-mail from a recommended machine shop. I get the feeling he is trying to talk down other shops at the same time he is trying to talk up his own.
It seems that any decent shop familiar with Porsches should be good.
What's your take on how he describes the work involved?
Understand, our customers told us we cost more not because we overcharge,
but because our material and process to do precision work takes longer, then
your general “production” machine-shops.
Take something as simple as installing valve guides.... there is a lot of
technique involve, ifin most production shop press the old guide out and
press the new guide in.... you WILL broached the valve guide hole in the
head (pulling aluminum). Therefore now, the valve guide hole in the head
does not have a smooth-polish surface to completely grip the new valve guide
being install. Thus, this decrease heat transfer, in addition, the fit
between valve guide hole and valve guide is also decrease (since the hole is
broached-enlarged) Aftermarket valve guide have 1-2 oversize (no half
sizes); therefore, if a stock diameter guide is install into a broached
hole, the fit is too loose, if a oversize (too much fit) guide is installed,
it is likely it will crack the ceramic in the 944 turbo exhaust when the
head heats up.
When we install guide, we do not use a Press (HMR developed techniques), and
we size each valve guide to the exact diameter of the guide-bore in your
cylinder head for correct fit.
We see a lot of bad-valve jobs, and try to paint you a small picture of what
we do for what you are paying for.... (we have not even talk about how to
establish a true ID bore and finish between your valve stem diameter and the
ID of the valve guide)....
but because our material and process to do precision work takes longer, then
your general “production” machine-shops.
Take something as simple as installing valve guides.... there is a lot of
technique involve, ifin most production shop press the old guide out and
press the new guide in.... you WILL broached the valve guide hole in the
head (pulling aluminum). Therefore now, the valve guide hole in the head
does not have a smooth-polish surface to completely grip the new valve guide
being install. Thus, this decrease heat transfer, in addition, the fit
between valve guide hole and valve guide is also decrease (since the hole is
broached-enlarged) Aftermarket valve guide have 1-2 oversize (no half
sizes); therefore, if a stock diameter guide is install into a broached
hole, the fit is too loose, if a oversize (too much fit) guide is installed,
it is likely it will crack the ceramic in the 944 turbo exhaust when the
head heats up.
When we install guide, we do not use a Press (HMR developed techniques), and
we size each valve guide to the exact diameter of the guide-bore in your
cylinder head for correct fit.
We see a lot of bad-valve jobs, and try to paint you a small picture of what
we do for what you are paying for.... (we have not even talk about how to
establish a true ID bore and finish between your valve stem diameter and the
ID of the valve guide)....
Last edited by streckfu's951; 08-10-2005 at 06:38 PM.
08-10-2005, 03:51 PM
#2
Addict
Rennlist Member
Rennlist Member
I recall the FSM procedure for doing the valve guides is a lot more involved than pressing the old ones out, new ones in, reaming and grinding. The factory does expect you to lathe the new guide to size and not just heat up the head, chill the guide and whack it in. Never occurred to me that the guide might help crack the exhaust port liner. You probably get the quick n' dirty procedure for less money at production shops. How much more is this quote?
-Joel.
-Joel.
08-10-2005, 05:27 PM
#6
Rennlist Member
Thread Starter
I have no doubt they do great work. $850 before decking is way out of budget right now. I can swing about $4-500 if I want to get this back on the road before the appocolypse.
Trending Topics
08-11-2005, 11:42 AM
#8
Addict
Rennlist Member
Rennlist Member
Originally Posted by streckfu's951
I just got off the phone with Scott Gomes at Under Pressure. Why didn't I just call him first?
HMR are pretty damn good too. Nice thing about Scott is that he does all his machining in-house. Total accountability.
08-11-2005, 11:54 AM
#9
Rennlist Member
Thread Starter
Originally Posted by Ken D
Scott's terrific. I spent quite a bit of time speaking with him during the purchase of my 951. He'll talk turbos all day long if you let him. HMR are pretty damn good too.
Nice thing about Scott is that he does all his machining in-house. Total accountability.
HMR are pretty damn good too. Nice thing about Scott is that he does all his machining in-house. Total accountability.
About half way through that conversation, the clouds parted, the sun shined, and I swear I heared angel singing.
He went into great detail about their process, valve and seat grinds, and why I don't need a 5 angle or radius grind with stock or slightly larger turbo (however, he said that if I insisted, he'd be happy to take the money anyway...
).And he beat HMR's quote by $400.....
08-11-2005, 12:14 PM
#10
Race Director
Scott's a good guy. I spent an afternoon with him 2.5 years ago at his shop.
I was just looking him up because of Ted Wright's thread about going to the cape, but couldn't locate him on the web anymore. I thought his company was Under Pressure Development and his web site was area951 but I found Under Pressure Performance in another location from where he was an there was no mention of Scott on my glance through the site.
Is he still in the same place?
I was just looking him up because of Ted Wright's thread about going to the cape, but couldn't locate him on the web anymore. I thought his company was Under Pressure Development and his web site was area951 but I found Under Pressure Performance in another location from where he was an there was no mention of Scott on my glance through the site.
Is he still in the same place?
