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Originally Posted by Steve Weiner-Rennsport Systems
You have to machine the heads to accept a gasket. Further, we also machine the tops of the cylinders a little to aid sealing when this modification is done.
Can anyone with experience tell me what setup these heads are machined for?
That's a twin plug 930 head for a 1985 Turbo or 3.2 Carrera.
Note the narrower cylinder head stud spacing and 2 bolt intake port. Running the studs closer to the bores reduces the bending stresses of these heads, which is why the Carrera 3.2 does not suffer from the same issue as the early 964.
That's a twin plug 930 head for a 1985 Turbo or 3.2 Carrera.
Note the narrower cylinder head stud spacing and 2 bolt intake port. Running the studs closer to the bores reduces the bending stresses of these heads, which is why the Carrera 3.2 does not suffer from the same issue as the early 964.
EDIT: Got my motor back and the heads look exactly like post 27.
I find this very interesting as I’m looking at purchasing 964 and would like to understand more. Does anyone have a picture of the cylinder side after machining to accept the metal gasket, which can mate with heads (post machining) in post#27? That picture in post#27 seems to flatten a bigger area on the heads to accept the other side. Is there actually new grooves cut to allow insert of gasket, or just milling out both sides to make bigger flatter contact? Thanks for the details...
Bubbling this back up - so confusing, everyone has a different way
3 scenarios that I'd like to hit on
#1 - If someone uses LNs that don't have the groove machined - and heads that also do not have the groove machined, but are updated by machining to mate with the barrel as above from @Super90 - that's all that's needed if you want to rely on the original no gasket strategy. It's flat on flat and done.
#2 - If you have LNs with the machined groove and heads same as above - adding the "fire ring" (is that right?) in the groove will fully compress into the barrel and against the head but does not increase deck height (technically the deck height is the deck height...guess we are talking about squish at that point)
#3 - LN barrels machined in groove and heads machined as above WITH the machined in groove as well - which "ring" is used here and I'm guessing still no addition to squish.
Sidebar - is there a bore size where you can no longer machine the groove into the barrel? I've seen it for 3.8..but at 104-105mm, is it too close to the edge? Are most fire rings custom machined? Who has the largest selection?
I have an early '90's car that had the original cylinder heads. When I did my rebuild I bought a set of updated pistons, cylinders, and connecting rods from a later car that went to Singer (they don't use anything but the block). A couple
years ago the entire setup was about $600. The machine shop did the heads to match and everything went back together quite nicely. I guess you could call it option 4.
PS - also, what ring is used on new nickies with 102 or even 105mm bore? Seems like the margin could get too small to use the OE ring on these 3.8 and up motors?
PS - also, what ring is used on new nickies with 102 or even 105mm bore? Seems like the margin could get too small to use the OE ring on these 3.8 and up motors?
Typically most customer don't run a sealing ring or head gasket with any of our Nickies cylinders. We've been doing them that way for 20 years now.
We do have the specs on file for the stock sealing ring grooves and we can put them into cylinders with the stock bore sizes, but when you go bigger, there is less real estate on the cylinder sealing surface and it is my opinion that you are weakening the cylinder and making it more likely to have a failure by putting in a sealing ring groove area.
Where we do see a benefit is if you are running 8:1 or higher compression ratio and running a bar or more of boost. That's where using a flame ring is beneficial, but the heads and cylinders must both be machined to match. Another place where we see them called out is really high rpm and high compression ratio race engines. Here are rings we use:
We're also in the process of evaluating gas filed o-rings (aerospace stuff) that grow with the parts to ensure positive seal but they are very costly as a possible alternative to flame ringing.
Thanks Charles! That does make sense and I was starting to get the understanding that the larger bores could be an issue but this really helps drive it home. So with nickies and fresh heads, 11.5 NA applications for 3.8 should just go flat to flat. I'm good with that
Lots of confusion between the changes made during OE production and the current aftermarket offerings of machining one or both sides.
05-02-2017, 12:01 AM
