Head Gasket question???

[Paul Smith]

Ok i've been having a think about the head gasket. How much power can the standard head gasket with stand?

Also another thought would be if i used a standard head gasket and maybe over torqued it by 10 torques whether it'd seal better and for longer?

Thoughts?

 

[frank]

mine are always overtorqued paul, (but thats only because they are re-used tho :wasntme
and its probably more the boost than hp that blows them imo

 

[Paul Smith]

ha thats a fair shout, what sort of torques do you use?

 

[frank]

ha thats a fair shout, what sort of torques do you use?

dunno paul, probably 120 nm ? but i always pull them down and then leave it to compress (ideally overnight) then i back them off 1 full turn then pull them back down again (one at a time)
doing it that way, the bolts will go another 30 deg or more

 

[Paul Smith]

I think my sensible option is probably to wait and see if i can pick a copper one up from somwhere. Then torque it as above. Anyone got any ideas who or where to try?

 

[Low Rider]

If you want a metal gasket talk to Mike Tanski at Ferriday Engineering. He already has a patern for the CGA3 engine and can make one any thickness you like I expect.

 

[Antony]

torques?.... i am assuming you have been watching too much top gear / jeremy clarkson?
it is torque, Lbs f/inches, lbs f/feet, Newton meters etc etc.
sorry. but the dumbing down on engineering terminology has bitten my arris one too many times..

and if you over torque your cylinder head bolts the only thing you will do is apply a torsion and tensile stress point to happen along the shaft of the cylinder head bolt. you can over torque a stud and nut system as the torque is loaded through the nut and not through twisting the shaft of the bolt.
the stock headgasket (a genuine nissan one) that is brand new should be good for AROUND 7psi with correct fueling on a turbo setup. but as far as other bhp figures go. you will struggle to get much more over 110bhp with the stock compression ratio anyway, so you will need either a decked/skimmed head, high C/R pistons or a thinner head gasket.
what are you planning on doing?

 

[frank]

and if you over torque your cylinder head bolts the only thing you will do is apply a torsion and tensile stress point to happen along the shaft of the cylinder head bolt. you can over torque a stud and nut system as the torque is loaded through the nut and not through twisting the shaft of the bolt.

so you,re saying it wont increase the pressure on the headgasket then ant fwn

 

[capri v8]

nissan gaskets are NOT designed to be "backed off" then re torqued! they release a sealent when tightend and this should not be desturbed once tight .

 

[Low Rider]

That's not strictly true seeing as the gasket tightening sequence is a 2-stage initial torque-up, slacken off, pre-torque then finish off with a final angle torque-up.

 

[martinb]

Anthony- kristian made 163 @ 10psi on stock compression??????

Where does 110bhp come from?

Skimming the head would also be wrong as you wouldn't want higher compression ratio would you?

The ideal solution Paul would be low compression forged pistons but its at a big cost unfortunately

Paul I'm in the same situation now mate, either I get it mapped at 10 psi by Ed, or source a low mileage auto block go see Frankenstein with it in the boot and pay him to fit a 2mm head gasket

Haven't got the money to go forged pistons

I'm not trying to brake records or race everything in sight but would like to get as much as safely possible on a stock engine with stock compression

 

[Antony]

110bhp naturally aspirated lol

 

[Low Rider]

110bhp naturally aspirated lol

Unless you fit throttlebodies eh

 

[Paul Smith]

Hi sorry for the lack of response, i have been watching and reading but my boy has chicken pox so i have trying to keep him busy so not had a chance to reply.

I can see why maybe using a stock head gasket could be bad so I think on this occassion that is out. As for the compression it will be slightly higher although not as extreme as a 2mm skim, it is running an auto block whick will help with strength. She lasted a couple of years on the first stock gasket and about a year on another stock gasket so need something more substancial.

Not to sure on the 110 BHP being the max but 128.9BHP is to much obviously. As for kristians 163 BHP at 10 PSI that is very good but how long will the gasket hold out. Also remember I use the car a lot so it needs to be able to take the strain whether i drive calmly or have a little fun (living 1 mile from the Pod).

Thanks for everything so far. Is Ferriday the only gasket maker used or are there others people have used?

Thanks

Oh also yep she is running throttle bodies :wasntme:

 

[Low Rider]

CGA auto blocks are open deck, so there's no rigidity benefits like CG1 series blocks with semi closed decks.

There may well be other companies, but Mike happens to have done some in the past, as well as MA & CR engines, so has the design already. I expect if you want one from anyone else you'll be either sending them a cad drawing or gasket to copy before they will make one up.

Interesting that the gasket let go. We're making 6bhp less from the CG13 and have no problems, the car gets tracked quite a bit and is never driven without plenty of gusto Must be a case of bad luck?

Good luck with the build anyway!

 

[Paul Smith]

Hi

sorry to be a little dim, can you explain the open decks for me please?

I think your right i think the last gasket was just bad luck if i'm brutally honest, but i don't think i wanna chance it again.

 

[Jim-GR]

thats an open deck block

iam sure you can understand the difference now

 

[Low Rider]

And this is a CG1x series closed deck from an auto.

 

[baguete]

Im lucky to get 2 of these closed deck blocks until now... :grinning:

 

[Low Rider]

Im lucky to get 2 of these closed deck blocks until now... :grinning:

Same here, both low mileage CG13's all with Grade 2 bores. One for the next N/A build which should be making power to 8000rpm. The other will be shelved and kept for the turbo which will be built from my old N/A run about GX 4-door since the chassis is practically corrosion free.

 

[martinb]

WHat about 2 x oem Nissan ones, stani runs them with no probs??

 

[baguete]

Same here, both low mileage CG13's all with Grade 2 bores. One for the next N/A build which should be making power to 8000rpm. The other will be shelved and kept for the turbo which will be built from my old N/A run about GX 4-door since the chassis is practically corrosion free.

All the CG engines that i opened have Grade 2 bores/pistons/rings, could it be the "STD" value?

 

[Low Rider]

Bags - Yes I think so, I have never seen an engine with Grade 1 pistons in it. I have seen a few with 3x Grade 2 and 1x Grade 3 pistons in it plenty of times but it does seem as though Grade 2's make a common appearance.

Martin - I realise the subject of things 'working' gets a lot of people's tempers frayed on here when people offer alternative opinions, particularly when money is a factor and people are told that they are wrong. While I am choosing to avoid stating such things, what I will say it by using 2 gaskets you introduce additional limitations into the system. One such limitation, for example, would be that you would now have 3 possibilities for a possible leak path compared to 2 for using a single gasket.

When switching to a charged engine, the headgasket is a very important area to consider.

 

[Noddie]

What do you guys mean when you talk about bore and piston grade?

 

[frank]

What do you guys mean when you talk about bore and piston grade?

the bores and pistons are graded at the factory ed, so that if the piston is fractionally undersize (but still within spec) it will be fitted to a bore that is fractionally undersize too, and the clearance is still bang-on if a grade 2 piston is fitted into a grade 2 bore

 

[Noddie]

Thought it was something like that... so grade to is in the middle of tolerance? and 1 and 3 are either side?

 

[frank]

Thought it was something like that... so grade to is in the middle of tolerance? and 1 and 3 are either side?

0 to 3 apparently mate, so the toolsetter strives for 1 or 2 ideally eh

 

[martinb]

Bags - Yes I think so, I have never seen an engine with Grade 1 pistons in it. I have seen a few with 3x Grade 2 and 1x Grade 3 pistons in it plenty of times but it does seem as though Grade 2's make a common appearance.

Martin - I realise the subject of things 'working' gets a lot of people's tempers frayed on here when people offer alternative opinions, particularly when money is a factor and people are told that they are wrong. While I am choosing to avoid stating such things, what I will say it by using 2 gaskets you introduce additional limitations into the system. One such limitation, for example, would be that you would now have 3 possibilities for a possible leak path compared to 2 for using a single gasket.

When switching to a charged engine, the headgasket is a very important area to consider.

Cheers for reply, I appreciate your view and to be fair everything I'm reading about it from people with other cars who have done the same agree... It's not ideal and can become a weak point

I can't afford a forged setup, but I can afford a 2mm spacer at a later date with saving

Would a 2mm copper head gasket be sufficeant to safely run more than 10 psi on stock internals? Nistune from Ed with correct fuelling and ignition timing adjusted

Thanks in advance

 

[Paul Smith]

Hi

Its now settled I will go for the bi metal head gasket from mike at ferriday.

The next question, when fitting the head gasket does any one have any tips to ensure a good fitment, such as torque the head bolts up leaving them for x amount of time before backing them off again anything like that really?

Thanks for all the info so far.

Thanks

paul

 

[superls]

paul, are you going turbo of sticking with NA? what thickness gasket have you gone for and importantly how much?

 

[Paul Smith]

Hi the engine is NA at the moment on throttlebodies and possibly will progress to the supercharger at a later date. Not sure about the ideal thickness was gonna discuss this further with ferriday. The price is £158 plus postage

 

[Noddie]

Youl have to decide whether you want to go forced or not really eh. If your sticking with TB's then you want high C/R which is no good for forced, but if you lower the C/R for forced then it wont be great for an NA setup.

 

[Paul Smith]

Hi

The desicion is to have both, now as of the effectiveness of throttlebodies on a supercharger has yet to be decided but 1 thing is for certain it will be far better than the standard throttlebody.

 

[Paul Smith]

The next question, when fitting the head gasket does any one have any tips to ensure a good fitment, such as torque the head bolts up leaving them for x amount of time before backing them off again anything like that really?

Thanks for all the info so far.

Thanks

paul

 

[Paul Smith]

Any suggestions on a good thickness as i'm having one made?

Thanks

 

[frank]

Any suggestions on a good thickness as i'm having one made?

Thanks

that depends on how much boost you intend to run paul

 

[martinb]

10 mm lol

I'd be keen to find out this

Frank what's perfect c/r for turbo?

For instance polly ps setup with forged pistons, would be equal to a 2 or 3mm gasket etc

I know it's a bad comparison but I'd like to know similar compression ratios

Many thanks

 

[frank]

10 mm lol

I'd be keen to find out this

Frank what's perfect c/r for turbo?

For instance polly ps setup with forged pistons, would be equal to a 2 or 3mm gasket etc

I know it's a bad comparison but I'd like to know similar compression ratios

Many thanks

i would guess pauls dishes were about equal to a 2mm decompression plate martin and i dont think you will get a consensus about what c/r to run, jim gr want more than stock iirc, and i agree with him (for low boost)