Gaskets sealer on head?

[2fast4y0u]

ok, so im doing a headgasket swap...

i have a cometic 1.01mm metal gasket. what(if any) gasket sealer should i use? i read some where that i should be using some just incase i have scratches or something else like that.

also, i have the long block assembled and sitting there. i checked the piston to bore tolerance because i was just curious. i have it bored 20 over, so what should the tolerance be. i checked the manufacture of the pistons and also the FSM but im not sure its going to be the same. the manu. didnt give tolerance specs.

one more thing, is there a usdm replacement thermostat for the sr redtop? like sentra se-r or something like that? the one thats in my motot now i dont think its working. its set for a 170ish degrees


Jay

[LigouriRd]

Originally Posted by Cometic Gasket, Inc(<link)

What surface finish is required to use an MLS head gasket?
A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design.

50 Ra equates to a having a scratch more than .002" deep...that is about thickness of a hair. Pretty much if you can feel the scratches with your fingernail then you need to get the block and head re-surfaced or almost polished for it to seal properly. After that my engine builder recommended a light coat of permatex spray copper on all the block and head sealing surfaces just to be sure of a good seal.

Someone else can chime in on the Pistons clearances and thermostat.

[IRN]

I always like to use some rtv when doing the head gasket. I mainly put it on the front of the engine on the timing cover surface. and copper spray is always a plus.

[NemeGuero]

I've heard of copper spray but mostly for RE-USING a metal headgasket, not just for first time installing.

RTV? really? I don't think I like that idea much. At least not for the head.

and whoever did your block work should be able to give you tolerances.

[IIIXziuR]

I have heard that some cats like using some sealer sparingly.
I don't see it being too necessary but I guess its personal preference.

A few years back, I remember reading an article about an SR20 build/assemble and the engine builder from Signal Auto was using gasket sealer on everything, including the head gasket.

[Jlee]

so if you don't have any thick or huge scratches then gasket sealer isn't required?

Jon

[2fast4y0u]

good deal...i got the engine put back together and everything went well. im leaving at the end of the week and wont be back until May 1st, but i will let u guys know how the re-build went after i get back get to start it.

Thanks for the help, much appreciated
Jay

[NemeGuero]

You should post up your tolerances and answers to your questions so your thread is complete.

[Harris]

I will add a little something to this thread from personal experience.

I finished doing a complete rebuild of my motor last November (2007). Most of the rebuild was OEM replacement, but I did go with 300ZX TT pistons with the block. With regards to the head, I went with a Cometic head gasket along with a custom sheet metal intake manifold. I made one mistake which I think has led to issues I've been dealing with since the rebuild.

I reused the OEM head bolts, which I feel didn't hold up to the same boost I was pushing prior to the rebuild. I ended up leaking motor oil from the area between the front cover and the head, and I think now I'm dealing with a blown head gasket altogether as I keep seeing my coolant reservoir getting filled up with coolant. There's no oil/coolant mix, although I do see that the coolant has some black gritty particles in it, which could be carbon deposits from the combustion chamber. I'm betting one of my pistons is going to look really clean due to the involuntary coolant going into the combustion chamber.

Lessons learned: don't ever reuse the head bolts, use gasket sealer between the front cover and the head to avoid motor oil leaks, and never EVER go with Cometic head gaskets again.

Having said all this, I'm going back to the OEM head gasket as the old one never leaked before. I'm ordering ARP headstuds, and for now I'm going back to my OEM intake manifold as the one I have isn't meant for my hp goals (400hp max). This time, RTV sealant will definitely be used, as well as copper spray.

I know the main reason for all this could be from the fact that I haven't been able to mill the head. However, it never gave me an issue before at all, so I don't see how the head could ever get warped in the time that it took me to rebuild the motor. I did see some pitting on the squish pads and the pistons, so I know there was detonation, but that's got more to do with the 91 cow-piss we get here. Fix for that is E85. The pitting on the squish pads were fixed by gently filing the pits down to where it was all smooth. That was the only area that I saw issues with on the head. So, in essence, the head will stay the way it is. I'm not about to trust anyone out here in the middle of nowhere to work on my motor. I hate being where I am right now (I've head people call this area V8-land), and I'm not about to let someone mess with something I can tell they're not really sure about.

Just my two cents.

[HalveBlue]

Permatex.

I asked the machine shop what, if any, gasket sealant they recommend. The guys at the shop swore by Permatex.

I gave it a shot and went with their advice. Just got back from road trip to Salt Lake (like 20 minutes ago, literally) and I don't have a single leak. The engine now has around 1,500 miles on it.

Make of that what you will.

[IRN]

I use it on the front timing cover because I've had bad experiences of it leaking due to an uneven surface. the timing cover had a lower surface then the head so the gasket didn't seal properly so it leak oil out the front of the engine. as for the copper spray, its main purpose is to prevent hot spots and not to seal. it fills in fine imperfections but the spray is not a replacement for liquid gasket.

[ManoNegra]

Following the advice of old car head with plenty of engine building experience, friend and I used a bit on the hg of the KA we just rebuilt. The block and head had been decked aswell. OEM rebuilt w/ re-used bolts. I'm ~100 miles into breaking it in and running smooth.

[2fast4y0u]

well, i hoping for the best. i did use a little on the front cover area just in case. also, the mechanic that i had before i became some what knowledgable with engine did a lot a shady shit. he didnt put the front 2 (sub bolts) in the head, the 2 outside corner head bolts that are out sid ethe head, and the head gasket was slightly crooked and didnt ever deal properly.
so, i decided to tear it down and do it my self.

i dont have the actual tolerances on the piston to bore clearance(i just moved with my hands), but i was curious to what people had found. unfortunetly i cant get a hold of who did all the machine work because i am no longer speaking to the HACK mechanic that worked on this project before.

also, i tested the thermostat that i have and it should be fine. it opened and closed smoothly with hot water and cold water.

[ManoNegra]

Originally Posted by 2fast4y0u

well, i hoping for the best. i did use a little on the front cover area just in case. also, the mechanic that i had before i became some what knowledgable with engine did a lot a shady shit. he didnt put the front 2 (sub bolts) in the head, the 2 outside corner head bolts that are out sid ethe head, and the head gasket was slightly crooked and didnt ever deal properly.

If that's the case then I doubt he followed proper torque procedures aswell. I've seen plenty of people re-use bolts on OEM re-builds with no problem.

[2fast4y0u]

he probably didnt follow torque specs or pattern

i bought arp studs for him to install, and i am re-using those of course

[Z U L8R]

copper gasket spray ftmfw

Dave =]

[2fast4y0u]

umm....im not down with the web abbreviations . i dont know what ftmfw means

[OBEEWON]

FSM says use a thin continuouse bead. That what I do with permatex everytime Im making a motor sammich. But of course I polish to a mirror shine anyway.


I re-use head bolts also but only if they are not streched within the lower tolerances of the FSM, if they are extended more than a few mm's I toss them. Ran 22 psi on old head bolts no probs.

[Jlee]

when you guys say "permatex" are you guys refering to their gasket sealant spray the copper one? or the high temp 1372 form a gasket?

Jon