|
06-21-2017, 10:02 PM | #31 |
Member
Join Date: Nov 2005
Location: Waldorf Md
Posts: 222
Likes: 10
Liked 26 Times in 15 Posts
|
Re: cometic head gaskets
You have to be careful with this as most MLS gaskets have a coating on them from the manufacturer that is there to help them seal. Putting another coating on them might actually make it worse. I prefer to go with whatever the gasket manufacturer recommends.
__________________
Bill Koustenis |
06-21-2017, 10:23 PM | #32 | |
Member
Join Date: Feb 2007
Location: NORTHEAST
Posts: 287
Likes: 1
Liked 18 Times in 10 Posts
|
Re: cometic head gaskets
Quote:
I have always sprayed my Cometic head gaskets with Copper head gasket spray with no problems to date. I have seen quite a few old Cup engines that have used cometic gaskets that were sprayed with Copper head gasket spray. If they are using it that's good enough for me. |
|
06-22-2017, 08:08 AM | #33 |
Member
Join Date: Sep 2006
Location: Moncton, N.B.
Posts: 276
Likes: 24
Liked 24 Times in 13 Posts
|
Re: cometic head gaskets
Rick, are you going to be ready for the Miramichi NHRA races???
Terry K |
06-22-2017, 01:04 PM | #34 |
Junior Member
Join Date: Mar 2003
Location: Detroit,MI
Posts: 75
Likes: 25
Liked 24 Times in 11 Posts
|
Re: cometic head gaskets
OEM head gaskets require a "smoother" surface finish to seal coolant and oil passages. The "rubbery paint" is there to provide a micro-seal against leaks. OEM head gaskets are beaded to provide an effective sealing load around these passages and the chamber.
A torque wrench measures torque, not friction as someone stated earlier. Torque = friction coefficient x tension x thread diameter (for elastic region bolts). Friction coefficient is generally 0.1 ~ 0.3. Adding oil or other lubricant will increase the bolt tension over a dry or unlubricated condition. Something a friend and I did at work years ago with a strain gauged bolt to see for ourselves. Last edited by RonP; 06-26-2017 at 11:08 AM. |
06-22-2017, 03:25 PM | #35 |
VIP Member
Join Date: Feb 2003
Location: Glendale, Arizona
Posts: 2,991
Likes: 693
Liked 1,457 Times in 543 Posts
|
Re: cometic head gaskets
In lieu of the Copper head gasket spray I would recommend Hylomar spray.
Do not use the Permatex/Loctite Hylomar sold at most auto stores; it's a watered down version of Hylomar. The best Hylomar is the Yellow can industrial version. |
06-22-2017, 03:42 PM | #36 | |
Member
Join Date: Nov 2005
Location: Waldorf Md
Posts: 222
Likes: 10
Liked 26 Times in 15 Posts
|
Re: cometic head gaskets
Quote:
That is correct and what I was trying to get at was the fact that the friction will significantly affect the preload on the fastener for a given torque. My choice of words were not the best
__________________
Bill Koustenis |
|
06-22-2017, 08:22 PM | #37 |
VIP Member
Join Date: Jun 2007
Location: Northern New Jersey suburbs
Posts: 2,275
Likes: 25
Liked 510 Times in 200 Posts
|
Re: cometic head gaskets
I have used Cometics with zero issues for at least 5 years. I have reused the same gaskets 3 times with no additional coatings and also another set 2 times with copper coat spray. This is a 15-1 compression engine and with or without the copper coat there was no leaks. Pretty smooth finished block and heads. I generally block sand the heads if they are off with wet 400 paper in a wash tank. Cometics work very well for me.
__________________
Rich Biebel S/C 1479 |
06-22-2017, 10:18 PM | #38 |
Junior Member
Join Date: Jun 2007
Posts: 64
Likes: 0
Liked 0 Times in 0 Posts
|
Re: cometic head gaskets
Thanks for all your comments guys, the block is just machined too rough for those gaskets
|
06-23-2017, 02:18 PM | #39 |
Veteran Member
Join Date: Mar 2005
Location: Sand Springs, OK
Posts: 8,132
Likes: 896
Liked 389 Times in 168 Posts
|
Re: cometic head gaskets
Listen to Rich.
__________________
Ed Wright 4156 SS/JA |
07-05-2017, 08:29 PM | #40 |
Junior Member
Join Date: Jul 2016
Posts: 55
Likes: 11
Liked 46 Times in 19 Posts
|
Re: cometic head gaskets
Something else to consider on a SBC is the size of the dowel pins. The OE dowel pins are .309" diameter. If .3125" (5/16") pins are used the head can bind on the pins. This will prevent the head from clamping properly to the block in the lower corners. Several companies sell SB dowel pins that are actually 5/16" roll pins.
|
|
|