Base gasket question

[Leftcoast leftkicker]

Getting conflicting advice on prepping base gaskets, running 2/3 with dressing (ranging from Gasgacinch to HondaBond) and 1/3 dry. Any definitive advice? I've blown 2 (thin, paper-type and 1 was dressed theh other dry).

 

[Dirtdame]

Try running a really thin coating of a high temp silicone RTV.

 

[pcnsd]

Getting conflicting advice on prepping base gaskets, running 2/3 with dressing (ranging from Gasgacinch to HondaBond) and 1/3 dry. Any definitive advice? I've blown 2 (thin, paper-type and 1 was dressed theh other dry).

Some things to consider when running thin cylinder base gaskets...
Because there is little compression available in the gasket material, it is important that the surfaces be flat, clean, parallel and without gouges or other paths or weak areas. On the one set up I had that would blow the gasket, I finally turned a few thousands off the base of the cylinder to have a known true surface and then lapped the surfaces together with course lapping compound. (Have to remove the cylinder studs) I quickly discovered a low spot where the case halves come together on the intake side. (The point of the failures.) There is little crankcase compression, typically in the 1.5:1 to 2:1 range so pressure is not usually a contributing cause. As for gasket dressings, Gasgacinch applied to both sides of the gasket and allowed to dry tack free works well for problem assemblies (for me), but is a pain to clean up on disassembly. I have also used Aviation form-a-gasket liquid with some success and it cleans up with most solvents. I am not a big fan of silicone sealants due to the high number of failures in use I have experienced. (Surface preparation must be truly immaculate.)

Hope this is useful.
PC.

Ps. I manage the corporate machine and prototype shop in my day job, If you give me your cylinder, I can clean up the base on a weekend. Takes 20 minutes. PM me and I'll give you my email address for contact, I am in San Marcos.

 

[HuskyT]

Some things to consider when running thin cylinder base gaskets...
Because there is little compression available in the gasket material, it is important that the surfaces be flat, clean, parallel and without gouges or other paths or weak areas. On the one set up I had that would blow the gasket, I finally turned a few thousands off the base of the cylinder to have a known true surface and then lapped the surfaces together with course lapping compound. (Have to remove the cylinder studs) I quickly discovered a low spot where the case halves come together on the intake side. (The point of the failures.) There is little crankcase compression, typically in the 1.5:1 to 2:1 range so pressure is not usually a contributing cause. As for gasket dressings, Gasgacinch applied to both sides of the gasket and allowed to dry tack free works well for problem assemblies (for me), but is a pain to clean up on disassembly. I have also used Aviation form-a-gasket liquid with some success and it cleans up with most solvents. I am not a big fan of silicone sealants due to the high number of failures in use I have experienced. (Surface preparation must be truly immaculate.)

Hope this is useful.
PC.

Ps. I manage the corporate machine and prototype shop in my day job, If you give me your cylinder, I can clean up the base on a weekend. Takes 20 minutes. PM me and I'll give you my email address for contact, I am in San Marcos.

Great info.... can I send you mine .. off of my 390????

T

 

[razornpc]

never put any dressing or whatever on a gasket, it will do its job just how it is.

this is how ive always done things and ive never had problems with a gasket leak afterwords.

putting silicone/yama-bond and the like will make it much more likely to smash out a gasket. not worth the risk to me. as long as you have a torque wrench there is no reason to use sealers with a gasket.

 

[Dirtdame]

I've had a base gasket squeeze out when I used gaskecinch on it, but never with RTV. I don't usually use anything unless I have a problem (usually with an older air cooled motor).

 

[Leftcoast leftkicker]

ach, now i have a headache!

 

[tommie d]

I agree with Razornpc. Dry and tight. I do put a very thin film of grease on the center case gasket but that's it.

 

[razornpc]

if youve blown 2 gaskets, and your %100 sure you installed it all right, i would make sure you dont have a warped issue going on somewhere.

on my kx and wr i put just the gaskets on with no adhesive. at work and on my own vehicles i never put anything on but the gasket. i have seen people and myself put silicone on gaskets and smash them out. i did it once nd will never do it again.

 

[pcnsd]

What a gasket does:
Gaskets provide a sealing medium at the joint formed between two mating surfaces. Depending on the design of the joint, the seal may need to resist various chemicals exposures, linear and/or rotational vibration, heat/cold cycles and extremes, dissimilar rates of thermal expansion between the sealed surfaces, etc.
The gasket is meant to fill the voids and irregularities between the sealed surfaces when compressed and survive the relevant environmental exposures. If a gasket that is properly designed for its use fails, the most probable cause is that it no longer fills the voids and irregularities present. This is typically caused by damage to the joint surface that exceeds the “fill” capacity of the gasket. (Gouges, warping, misalignment)
Solutions:
1. Rework surfaces to sealable condition with existing gasket.
2. Use a gasket designed the seal the existing condition.

What a gasket sealer does:
Gasket sealers are meant to provide a narrow range of benefits depending on the type selected. They may include one to all of the below:
1. Position fixturing and surface adhesion
2. Chemical resistance.
3. Void fill.
4. Thermal transfer.
There are valid reasons to use a gasket sealer. Most name brand gasket sealers on the market today are made to a mil-spec. A few have FSN’s or NSN’s. This implies that our government has found use for them. As a guy who has spent a life in manufacturing, I will tell you that manufacturer’s will not spend an unnecessary dime. It is the whole of the lean philosophy, but we use gasket sealers in assembly, go figure…

Regarding grease as gasket prep, works well for assemblies that are frequently disassembled, but do not provide the above-mentioned benefits.

Regards,
PC

 

[tommie d]

The reason I use a very thin film of grease is to keep the center case gasket in place during assembly.

Besides lapping the cylinder head to cylinder and the cylinder to engine cases, we also match the left and right engine cases to each other and the clutch and ignition covers to the engine cases. makes for a worry free engine when you have flat sealing surfaces.

 

[highdez1981430cr]

I have had great succes with spray on copper gasket sealant.

It goes on very thin (providing that you dont get over zealous with your nozzle finger)

Dries quickly but remains lightly tacky to aid in gasket placement and because it is copper it can take the heat and aid in thermal transfer.

Can be purched at most auto parts stores, i think the brand that i use is KW.