70DusterGuy
Member
How much do I mill off the head to make 9:1 compression? I am starting stock at 8.4 compression.
/6 head
- Thread starter 70DusterGuy
- Start date
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Did they have 8:7 compression to begin with, be careful shaving your head very much, I think you will need to shave the deck (block) to get there but I am not a tech.. some one will chime in.
PanGasket
has cork sides
RustyRatRod has beefy slant head for sale right now if that strikes your interest. I'm sure he would let it go at a reasonable price
Yea :cheers: and it is already ported to I believe, I forgot about that.
There should be a thread here on shaving our /6 heads here to get to 9:1 compression or even 10:1 lbs.
805moparkid
Slant and AFX Guy
how do you know thats its 8.4:1... thats the book spec but slants can be front .125-.215 below deck. if your run the best case numbers with a 56cc chamber you get 8.89:1 and worst of 7.64:1! all over!
what you need to do is have a clean up cut done to the head so its nice and true, then cc the chambers, then measure the piston to deck height.
lastly if its a stock piston (3.4") then you can run stock head gasket of 3.4 bore by .021, there is also a steel stock style gasket at 3.510 bore with again .021 thick. now your felpro gasket will be 3.510 bore and .037 thick which kills compression BUT is easy to get, so compensate.
as Memike said off the block is miles better as your gonna get closer to quench (but never get it without pistons sticking out of the deck) but something is better than nothing!
Trust me. You aint got 8.4 compression.
My thoughts exactly :happy1:
robertob
Well-Known Member
So true. If you are just doing the head and don't feel like CCing it, or don't have the tools, take .100 off and call it a day. That should net you about 9:1 plus or minus a bit.
805moparkid
Slant and AFX Guy
maybe depending on the head gasket
robertob
Well-Known Member
If you are only taking off the head you should not use the steel (.021) headgasket, the aftermarket composition types will seal more reliably.
805moparkid
Slant and AFX Guy
bs... i use a factory steel gasket on 10:1 motor with .115 off the head and .027 off the block...
and as far as i know there is only one composite gasket which is the felpro.
70DusterGuy
Member
Alright thank you. this really helps ALOT. I will probably end up taking of .100 or so like robertob says. I have seen that number several other times here as well.
robertob
Well-Known Member
That's what I mean - your motor has fresh surfaces on both sides of the gasket. If you try that same gasket on an old crusty block you might have trouble getting it to seal.
And there are a bunch of composite gaskets - felpro, corteco, victor reinz, various australian ones (permaseal) etc...
Charrlie_S
Well-Known Member
You don't need fresh machined surfaces, for the steel gasket. Just check and make sure the surface is flat. The engines in both my race cars, are stock short blocks, with milled heads, and I run the factory steel shim gasket. Both heads are milled to 39 cc chambers, and I run nitrous. Have never had a head gasket problem.
Tread theft occurrence:
Charrlie, this is interesting, as the other board has advised me to have fresh surfaces when using a factory steel gasket. Thisfresh surface biz has always had me wondering how Chrysler serviced theseengines when in need of warrantee head work; did they use a steel gasket or aftermarket in service department?
You may recall I purchased one of these gaskets from you a few years ago, and have been holding off installing it in the quest for more compression as I didn’t want toremove block for resurfacing.
Would a Scotch pad would clean up old surface enough, and what kind of gasket treatmentwould one spray it on before installing.
Threadreturned:
70Dusterguy,you need to measure your engine’s dimensions once the head is removed, runthese measurements through a compression calculator before any surface cuttingis performed. Guessing, or pulling a cutdepth out of your hat may lead to disappointing results.
They still use steel head gaskets on newer engines. Granted they are multi layered steel(MLS), but they are not composite. The Chrysler 2.2/2.5 and 2.0/2.4 had many head gasket leak issues with composite gaskets and that was regardless of sealing surface condition. In 1999/2000 chrysler came out with the MLS head gasket for the 2.0/2.4 and when installing them on an engine that came with a composite from the factory you don't have to machine either block or head just make sure they are flat and clean.
I haven't seen any recent production engines that used a composite head gasket everyone seems to use MLS. I would use steel if you can find one.
I haven't seen any recent production engines that used a composite head gasket everyone seems to use MLS. I would use steel if you can find one.
The MLS gasket for the 2.0 L had some growing pains with it. They found out that they had to tighten the head and block surface finish and flatness specs to be able to use it.
So if you had an old block/head, it may not work with the MLS gasket if it was at the edge of the original machining specs. For service, they just threw the MLS gasket on it and hoped that it sealed - no guarantees.
805moparkid
Slant and AFX Guy
as long as its flat clean it really well and if you like use a red scotchbright disc on it...
robertob
Well-Known Member
Thanks for the advice, I was just going by what Doug& the other guys at .org said. I've used MLS gaskets in other engines plenty of times but usually with new surfaces on both.
Charrlie_S
Well-Known Member
As far as I know, there is no MLS gasket for a slant six. The steel gasket I am talkining about is the OEM steel "shim" gasket. Single layer embosed steel.
I will grant you, if possible it is best to resurface both the head and the block, but How many times have you heard of the block being machined, when replaceing the head, and/or gasket (talking engine with steel head and steel block). Many times when a head is rebuilt (ei valve job) the deck surface also gets a light cleanup, but not always.
Clean the head and top of the block really good ( I don't like power driven scotch brite pads), and check the head and block for flatness using a straight edge, and feeler gauges.
For a sealer I used to use aluminum spray paint (in the old days), or Copper Coat. Now I like to use Hylomar
I will grant you, if possible it is best to resurface both the head and the block, but How many times have you heard of the block being machined, when replaceing the head, and/or gasket (talking engine with steel head and steel block). Many times when a head is rebuilt (ei valve job) the deck surface also gets a light cleanup, but not always.
Clean the head and top of the block really good ( I don't like power driven scotch brite pads), and check the head and block for flatness using a straight edge, and feeler gauges.
For a sealer I used to use aluminum spray paint (in the old days), or Copper Coat. Now I like to use Hylomar
BillGrissom
Well-Known Member
My 1996 2.4L started leaking at 39K miles, just after the 36K warranty. A strange head gasket leak - from an oil port to the outside, which was typical. At first I assumed it was the cam seal or valve cover. I lived with the oil leak until 95K miles when I put on the MLS gasket, plus a head & ring job to be safe though I found the rings and bore barely worn. At 195K miles now, no leaks and like-new compression.
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