headgasket

[idahotuner]

i am planing on up grading my turbo to a 2871 but i was wondering if i really need ot replace the head gasket. becasue the motor has super good compression. why replace soemthing if it is still good right, buti read soem where that when you replace cams and retainers that you mgith as well just pull the head and replace the gasket. so what i am asking is it really important to replace it? the motor has about 60,xxx miles on it

[ILikeMy240sx]

you do not need to pull the head to replace retainers. All you need is compressed air that you can force into the combustion chamber so that the valves dont drop.

Anyways, some people say stock HG will hold even with 2871r pushing 20 psi or so. Some people have done it and swear by it.

For me, I wouldnt feel safe doing it. I recommend Apexi HG with ARP head studs. This is what I have in mine and its been strong for 1.5 years even with the HG being reused like 5 times.

The thing I have learned with cars... is that if you go cheap then you pay later.

[95silvia14]

aint that the truth

[idahotuner]

what would be the worst thing that could happen if i didnt replace the headgasket, and just waited until it actually needed to be replaced and then do head gasket and studs?

[95silvia14]

it could leak oil in your antifreeze and vice a versa, you not knwo and wonder why you spun a bearing

[ILikeMy240sx]

It is 2 AM in the morning, you are coming back from your friends house after a long night of party.. You are sobered up but just want to go home and sleep... You are on the highway with no lights... just you and the dark... its January and its below 30 degrees outside...

You start to feel that your car is not doing well... you feel it losing power, misfiring sometimes.. its just acting really weird... You decide to look at your temperature gauge and the needle is pegged at H...

You pull over and wait 20 mins for it to cool down. You drive again and after 10 mins, it starts to over heat again...

FU*K you say to your self... You are about 20 mins away from your house and all you want to do is just get home... "I hate this car" you say to your self...

You call the towing place and after waiting 30 mins in the freezing cold, they finally show up. They take another 20 mins to load your car and drive it home.

You get home at 4 in the morning and you realize that you have work tomorrow morning.

"I should have listened to ILikeMy240sx".... is the last thing you say before you get ready for your 2 hour sleep.

[idahotuner]

It is 2 AM in the morning, you are coming back from your friends house after a long night of party.. You are sobered up but just want to go home and sleep... You are on the highway with no lights... just you and the dark... its January and its below 30 degrees outside...

You start to feel that your car is not doing well... you feel it losing power, misfiring sometimes.. its just acting really weird... You decide to look at your temperature gauge and the needle is pegged at H...

You pull over and wait 20 mins for it to cool down. You drive again and after 10 mins, it starts to over heat again...

FU*K you say to your self... You are about 20 mins away from your house and all you want to do is just get home... "I hate this car" you say to your self...

You call the towing place and after waiting 30 mins in the freezing cold, they finally show up. They take another 20 mins to load your car and drive it home.

You get home at 4 in the morning and you realize that you have work tomorrow morning.

"I should have listened to ILikeMy240sx".... is the last thing you say before you get ready for your 2 hour sleep.

LOL scary story,

But it still didnt answer my question will it hurt my motor any or cause any damage that is not repalce able. and wont i notice the loss of compresion?

[95silvia14]

if your going to take the head off at least do it right and and replace the headgasket it will bring you a piece of mind, and please dont get a cometic ive had three in the last year and have blown them all i should have just got an apexi in the first place

[silvia tech]

I recommend replacing the head gasket as Ilikemy240sx said. ARP studs and a reputable headgasket manufacturer, Apex, Tomei, HKS. I had a customer that blew a headgasket, I determined this by the white smoke bellowing out of the exhaust and the coolant smell from the exhaust. I told him to leave it and replace the head gasket and studs. He decided to drive it home. about 10 minutes after he left I recieved a phone call asking me to get the truck and trailer. We got the car back to the shop did a compression test and it was all over like 170, 30, 75, 200. I pulled the head off and noticed the cylinder walls. the coolant and oil mixed giving poor lubrication and the walls done for. To anwer you question it will more than likely cause damage minimum new studs gasket and sending you head and block out to machine shop to get decked. If you were my customer it was more cost effective to drop in a ned long block than to pay for that kind of machine work and bottom end parts. It is nothing that you cant replace as you said but it is your money a gasket and headstuds are cheap now. How cheap will it be if the headgasket blows out and you are looking at motor and a headgasket and studs or even machine shop work. Fix it right the first time, do the headgasket and studs now.

[idahotuner]

wow. this answered my question, thanks guys, i guess i will take the safe route and do the headgasket and studs.

[idahotuner]

so what headgasket should i get, i can get a stock thick on, of can get one that lowers the compression a little bit. it says for higher turbo models. this is the one i was looking at http://www.240sxmotoring.com/apsrhega.html the stock think on at .8 mm or 1.1mm or 1.5mm even up to 1.8 what one should i get?

[idahotuner]

why should i replace the head studs. i am only going to be using the .64 gt2871r so why is it recomended to replace them, cause if i dotn have to it could save a little bit of money for me.

[Hijacker]

headstuds clamp better than headbolts. they help even the clamping load across the mating surfaces. also, you have two sides clamped in place with threads instead of just one. The only thing headbolts have over head studs is cost.

Corky Bell said it best "headbolts are an accountant's decision. headstuds are an engineer's decision."

[idahotuner]

so what thicknes should i use for the head gasket, .8 mm or 1.1mm or 1.5mm even up to 1.8 what one should i get?

[Rosco]

and please dont get a cometic ive had three in the last year and have blown them all i should have just got an apexi in the first place

Why the hell does nearly everyone say this?? Jeff at 240sx motoring swears by them......He's said the only problems they had where faulty installations by customers (ie...not getting the head and block decked and polished). The reason I ask is because I have a cometic and I have yet to put it on. So if you didn't follow proper installation procedure please don't blame Cometic. If you did then please post your experiences with them so I can put my Cometic on eBay and buy an Apexi...

[Hijacker]

ie...not getting the head and block decked and polished)

Those are the only reasons I've seen cometics fail.

I found on Enthalpy's website some excel spreadsheets that can help you determine what thickness headgasket you'll need.

http://www.rs-enthalpy.com/info.htm

Scroll down a little ways and you'll see the heading SR Compression Ratio calculator. All the variables are already inputted for a stock setup, all you have to do is just change the variables for whatever piston you're using. And you can find that info on the manufacturer's website. After you input the piston data with the stock HG thickness you can get an idea of what you're dealing with and then you can start playing with HG thicknesses to give you an idea of what you need.

I'd like to do the calculations myself, but my spreadsheet viewer is read only.

[idahotuner]

ok guys i ordered my apex head gasket, now i got a few questions. and arp head studs

is ther anything special i should have done to the head when i change head gaskets?decked?shaved?how much does it cost to have this done generally?

just need to know cause i am planning on taking my head of probably tonight since my gasket will be here tomorrow.

[ILikeMy240sx]

Ideally, you want to have both the block and the head decked so its nice and flat but you can get away by just getting the head decked. Just make sure your block surface is super clean.

The machine shop I go to charges 45 dollars to hot tank and deck the head. basically 1 hr labor. Not too bad for a head that will look spanking new.

Im really glad you decided apexi and ARP. You just cant go wrong with that combo.

[idahotuner]

Ideally, you want to have both the block and the head decked so its nice and flat but you can get away by just getting the head decked. Just make sure your block surface is super clean.

The machine shop I go to charges 45 dollars to hot tank and deck the head. basically 1 hr labor. Not too bad for a head that will look spanking new.

Im really glad you decided apexi and ARP. You just cant go wrong with that combo.

thanks,

yeah i decided to be safe rather then sorry. i only want ot do this part once, and iwant ot get it over with.

one more question though. i saw on another forum that to seal it off they recomended this http://lambretta.net/shop/shopexd.asp?id=4136

or does it matter. can i just have everything super clean then bolt it down, with out any other materials?

[Hijacker]

With metal headgaskets, you really should get both the head and block decked. Uneven mating surfaces are the achilles heel of metal heagaskets.

[idahotuner]

that would mean i would have to pull my whole motor, which would be a PITA.

so if ILikeMy240sx head gasket has lasted this long and that is all he did then i think that is what i will do.

this part of the build is just getting more and more complicated lol. cant wait tell it is over, so the n ican do bolt on goodies so what about that spray stuff i posted up there

[ILikeMy240sx]

I swear by the copper spray. Ive used it every single time my head came off. Ive been using the same apexi HG with the copper spray for about 4~5 times now. Meaning they were torqued down, ran for some period of time, then was taken off about 4~5 times.

Some people will say no but the spray does fill in all the little imperfections on the surfaces. I have had no ill effects from using it.

The only downside is that... when you take off the HG after its been torqued down... it does get messy and harder to take off the head as that copper spray is very sticky.

As he said above, ideally, I would recommend getting both the head and the block decked as this creates the best sealing condition. However, if that's not feasible just deck the head and make sure the surface on your block is super clean. Absolutely no residue from the previous carbon HG.

Oh and make sure stuff doesnt fall down the oil/coolant holes on your block during your cleaning.

[idahotuner]

does it takea special hot tank to hot tank and aluminum head. or does it matter. when they deck they head will they hot tank it to, or will that be more do you think, i stopped by the maching shop today and it was closed so i will have to call them tomorrow and see if they are open.

[ILikeMy240sx]

usually hot taking the head takes very little time and the machine shop SHOULD hot tank your head after re-surfacing to remove the metal shavings that might have found its way into the head.

But, make sure you tell him to hot tank it anyways. Two operations should fall with in one pricing i.e. 1 hour of labor.

[idahotuner]

ok sweet thanks.

[idahotuner]

when i take the head to the machine shop to have it decked and hot takned, do i need to take everything off of it, like the valve springs retainers valves and stuff.

becasue my dad use to rebuild old hot rods but he doesnt know much about the new cars. he said i will want to replace the valve seals? so that means taking eveything out.

i thought i could take my cams and stuff out and leave valve springs and retaners and rocker arms in? who is right. because if i really have to take all that stuff off i might as well build a head to rev to 9000rpm but i didnt want to do that. so any information would be good

[ILikeMy240sx]

your dad is correct in that if your head is out of the motor, you might as well as replace the valve stem seals. I ALWAYS do if the head is off the block.

However, it is not necessary. Im not too sure if the hot tank process will ruin the valve seals tho... You might want to ask the machinist.

Taking the springs out is a PITA if you do not have the right tool (aka Snap-On valve spring compressor) see my article for more info. But its all up to you. Just know that, if you do not replace it and the seals are bad later, you will hate your self for it.

[idahotuner]

do i have to order special valve seals too, or can i get those at napa?

so i pull everything off rocker arms and valves and everything before i hot tank it, then put everything back together after i get it back?

[ILikeMy240sx]

well things like rocker arms and shims and rocker guides all have to come off regardless.

Make sure you keep those suckers in order. If they come off the left valve on #1 cylinder then thats where they go back.

Intake valve stem seals are the same as SE-R seals.

Exhaust valve stem seals are the same as KA-DE

Just look at my article. It should answer all your questions regarding valvetrain.

[idahotuner]

hey will i have my head all apart and at the machine shop. would it be worth it to get a port and polish? would it be a very noticable difference? how much do they normally cost to have done?

oh ILikeMy240sx i read you article and am going to to follow it when taking ever thing apart. but i think the hard part will be gettign it back together. RIGHT