head gasket question

[anakin3197]

I have a 1990 turbo laser. I blew the head gasket, and had to have the head shaved. The machineist said that i should take it easy ### the head was past its limit.

Well i installed a fel pro head gasket, with new head bolts, and decided to use the head, instead of getting a new head. Well I got everything installed, tonight and it was running like a charm. I took it down the road and let it boost a few times, needless to say on the way i blew the head gasket again.

So the question I have is, im going to to get a different head gasket and try to get a new head. I need to get something better than a fel pror, and I was looking at the cometic mls head gasket. Is this a pretty good one? Also when selecting which gasket to get they have a 1.3 and a 1.6 mm gasket with different size bore options. I dont know what i should get or what bore size i need to get. Can anyone help with this?

 

[GIRman67]

Well the bores size is talking about the piston size so if your laser is stock engine then you just need standard bore as for the different thicknesses I have no clue which one you'd need I'd venture to guess that since you had the head shaved you might want the 1.6mm

 

[2g 6 bolt swap]

Mls head gasket is def a good choice. May I ask if you checked the block to see if it was warped? If you decide to go with the mls metal head gasket,
the block and head need to be resurfaced in order to get a proper seal.

 

[anakin3197]

It is stock bore size, but i dont know what that is. They offer 85.5,86, or 87 bore size options. And yes i had to have the head shaved. the machineist said that it was as far as it could go, and that i should try to find a new head, which is what im going to do.

the block wasnt warped

 

[2g 6 bolt swap]

Is your motor the non turbo 4g63?

 

[anakin3197]

no its turbo

 

[RT-AWD]

What did you torque your head bolts to? If they are arp you need to torque them to the spec they tell you. also did you use oil or molly lube when installing the studs?

 

[2g 6 bolt swap]

Since it is turbo. Get some arp head studs and a metal head gasket. Go onto Modern Automotive Performance: Your source for turbocharged sport compact performance! and check the head gaskets out. Oh and if I remember right our bore size is 85mm. The mls I have is the metal 4 layer one. My motor is bored .20 over and I used a standard size headgasket. When you blew the hg the second time,did you just slap the head on and go rip on it. If so,theres the problem. I always re-torque my head after 100 miles.

 

[95gst16g]

I use a stock composite gasket with copper spray.Works fine for me.Just make sure the block is clean before putting the HG on it.Use something like a brass wire wheel on a drill and do it at low speed.Then buy a can of brake cleaner and spray it on the block and wipe it with a clean rag.TQ the studs in proper sequence to a proper TQ.Use a 3 step tq process for example 30,60,85.

 

[anakin3197]

I used oem head bolts with oil on them. i torqued to spec in the correct order. I forget what i used, but i know that it wasnt copper spray. And i made sure the that block was real clean when i installed. I think that it was jus the head it self. Thats why im gonna get another head, but i wasnt sure about using another felpro gasket, and didnt know what was best or the correct bore size that i needed to get

 

[BogusSVO]

how was the head surfaced? that would be my first thing to check
with a HG fail that soon after a replacement, I bet it was belt surfaced.

http://www.dsmtuners.com/forums/cyl...0613-why-not-let-your-head-belt-surfaced.html
the surface finish should look about like this
http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html
he said it was past the limit.. how far past? did he measure before and after the re surface?
toy need to measure from the valve cover rail to the head gasket surface of the head at 4 points
new head thickness is 5.200 with a min thickness of 5.185 (area spec) mitsu alows for a combined total of .008 from head and block

I doubt the felpro gasket was the cause of the failure, serach around on the board, you will see that there are some running 25 psi w/ARP head steds and either a fel-pro or mitsu composite head gasket

unless you have both the block and head milled properly, I would advoid the use of a MLS head gasket, Mitsu or cometic

also if the head needs milled, before that is done .. do this oil mod.
http://www.dsmtuners.com/forums/newbie-forum/341028-4g63t-head-oil-port-mod.html

 

[anakin3197]

im not sure if it was belt surfaced or not, i wouldnt be suprised if it was. when i went to pick the head up from the shop, the head guy wasnt there and i talked to the block guy, and he didnt say much, other than it was on its las leg, and that i should be very very easy with it, and try not to run any boost on it. it blew on 9 psi. is it possible that the gasket blew because the head wasnt surfaced good, or that it was jus in so bad of shape?

was i wrong to torque them to spec using motor oil?

i found was reading this post and this is what it said.
Their torque value is actually typically 75% of the yield strength. But ARP's torque recommendations are usually a little on the conservative side, so you can usually exceed their recommendations by a little bit, but not much. If 80 ft/lbs is 75% of it's yield strength, then 100% would put it at around 107 ft/lbs. That's why it pains me to see guys torquing standard ARPs to 105 ft/lbs (with moly) thinking that it's better.

The reason for the higher value with motor oil is due to friction. The threads will drag and create friction and that will "inflate" the torque value. 120 ft/lbs with motor oil is basically 80 ft/lbs of torque and 40 ft/lbs of friction drag. In the end, the nut will be equally tight with either method, but using moly lube will yield a more accurate clamp force across the board.