Which Head Gasket

[MR2Mania]

Hi Chris,

I am reading a great book at the moment (maximum boost by cork bell) I found a paragraph that sums it up….

“What is the best compression ratio for a turbocharged engine?
There is no such thing as the best or ideal compression ratio. The simple fundaments are:

The lower the compression ratio, the easier it is to produce a lot of boost with no detonation.

The higher the compression ratio, the greater the fuel efficiently and non-boosted response.”

Corky's book is a good book to have, but some of the content and ideas are quite a bit out of date (it's not a new book!). For a start, this is the man that says "Water Injection is a band aid", etc. However, there's quite a bit of content in there that at least sets one off on the right path.

I am not going too disagreed with the proven facts behind squish / quench area, from what I have read 0.04” or 0.1mm is the max you want. The 3sgte has far more than this standard as you have the head gasket + deck height.

It's actually 1.0mm that they talk of being the max for squish - which just so happens to coincide with what the Rev3 runs! Nice that!!!

Just out of interest do you know if the rev3 has the same deck height as a rev1/2 (I never measured it).

I don't mate, no. We didn't even measure the deck height on my engine, because in working out the CR, we used a burette to measure the volume above the piston with the piston installed in the block and at TDC. I then calculated the volume of the HG holes and the combustion chambers, so I didn't really need to know the deck height. Interesting question, though!

Rev3 has 1.2mm head gasket standard (0.2mm more than rev1/2) so that combined with same deck height would mean a rev3 has a larger squish volume?

I don't know in terms of squish volume (I just made sure that my squish height was right). The thing is, the combustion chambers on the Rev3 engine have a larger volume than on the Rev1/2. I think this volume and the HG thickness are the main differences, so probably deck height is the same for both engines. Does anyone have any stock REv1/2 pistons sitting about, so we can see if there's a noticeable difference between those and the Rev3 ones??

[gtschris.com]

Corky's book is a good book to have, but some of the content and ideas are quite a bit out of date (it's not a new book!). For a start, this is the man that says "Water Injection is a band aid", etc. However, there's quite a bit of content in there that at least sets one off on the right path.

Lets have a seprated debate over the Merits of water injection, i'll start a thread in mods section soon.

It's actually 1.0mm that they talk of being the max for squish - which just so happens to coincide with what the Rev3 runs! Nice that!!!

Whoop slip of the keyboard, i ment to say 1mm. but does the rev3 have 1mm squish? isn't the squish band volume h/g + deck height off the top of my head i would say the deck height on a 3sgte is min 7or8mm + 1.2mm h/g.

I don't know in terms of squish volume (I just made sure that my squish height was right). The thing is, the combustion chambers on the Rev3 engine have a larger volume than on the Rev1/2. I think this volume and the HG thickness are the main differences, so probably deck height is the same for both engines. Does anyone have any stock REv1/2 pistons sitting about, so we can see if there's a noticeable difference between those and the Rev3 ones??

I am fairly sure the rev3 get is is reduction in c/r via the 1.2mm stock h/g vs 1.0mm rev1/2 and the rev3 pistons have a greater dish volume.

[gtschris.com]

Chris,
Are these gaskets available in thicknesses below 1mm?

The reason I ask...
Some USA 'off the shelf' pistons come in fairly low CR's EG, Arias - designed to give a 8.5CR on a Rev1/2, so if used on a Rev3, the ratio will end up even lower - especially if any material has been removed from the combustion chambers during head work.

Seeing as these pistons are usually designed to be compatible with over-size valves, could the resulting CR be raised slightly again by using a thinner gasket without worrying about valve clearance.

Thoughts Chris / Dino??

As an example, Dino, What was your resultant CR compared to what the piston manufacturer suggested for a R1/2 engine?

Paul

Interesting idea, i am not sure how much much the rev3 loose c/r in its extra piston dish compared to rev1/2 if you sit piston next to piston rev1/2 vs rev3 you can see the difference.

I am sure 1.0mm is the smallest MSL cosmetic make for the 3sgte (noting smaller listed in my Catalog anyway)

[MR2Mania]

Oops, completely missed this post by you Chris!

Hey, Dino never realise it was you till I check out your website didn’t know web development was your career, thought you work for Owens Development ? (nice site by the way)

Yeah, I *did* work for OD, but things ended sourly (don't ask, LOOOONG story!), so I've gone back to my "normal" career.

I've been in web dev from 1996, and have been fortunate to work on and lead some HUGE projects, but when things were looking a bit bad in IT, I decided to put my degree to good use (I'm a B Eng Mechanical Engineer), and work in the tuning game. However, it's so cut-throat, it makes IT look like a UN peace-keeping force!

Thanks for the nice comments on my site, though, mate!

[MR2Mania]

Chris,
Are these gaskets available in thicknesses below 1mm?

The reason I ask...
Some USA 'off the shelf' pistons come in fairly low CR's EG, Arias - designed to give a 8.5CR on a Rev1/2, so if used on a Rev3, the ratio will end up even lower - especially if any material has been removed from the combustion chambers during head work.

Seeing as these pistons are usually designed to be compatible with over-size valves, could the resulting CR be raised slightly again by using a thinner gasket without worrying about valve clearance.

Thoughts Chris / Dino??

As an example, Dino, What was your resultant CR compared to what the piston manufacturer suggested for a R1/2 engine?

Paul

Hi Paul,

You've raised a very good point there, as the quoted CRs by US piston suppliers are based on fitting them to a US Gen1 engine which has a CR of 8.5:1 as standard. However, you can't even compare that to the JDM Rev3 because that's got a different head, HG, pistons, etc.

It did worry me when I was ordering my pistons though. However, I think the figures they quote are for a "drop in" scenario for the US Gen1. So if you were going to do head work, fit a thicker HG, etc, you'd get a lower CR.

In comparison to other piston suppliers, Ross seem to give a considerably lower CR, however I wouldn't consider ever using these anyway.

With regards to how the CR panned out in *my* engine, I can't tell you the exact CR, because I'd have to shoot you (I told you people are secretive of their CR! ), but it's slightly more than the stock JDM Rev3. I settled for a stock Rev3 HG (1.05mm uncompressed, 1.0mm compressed), and had the combustion chambers enlarged accordingly.

You're right, though, Toyota do offer different thicknesses of HG, but I don't know what they are. ISTR though that there are options for THINNER than stock.

[Edited to say that I'm using "9.0:1" CP pistons]

[paul port]

Well I suppose you could always skim a little off the head / deck - which may be beneficial anyway (to guarantee a flat surface)

Paul

[MR2Mania]

Well I suppose you could always skim a little off the head / deck - which may be beneficial anyway (to guarantee a flat surface)

Paul

Yeah, I think really you should always do this, to guarantee a good seal. This was the final procedure in my headwork, so that we could get the combustion chamber volumes just right.

[Paul R]

Guys. You seem to have lost track of the thread.

Just to put you back on track......

now you have discussed, which gasket should I go for for my rev1 tubby..

Bearing in mind it has a CT20 turbo and de-cat pipe on it. I'll be running 1 bar boost.

Cheer,

Paul.

[MR2Mania]

Guys. You seem to have lost track of the thread.

Just to put you back on track......

now you have discussed, which gasket should I go for for my rev1 tubby..

Bearing in mind it has a CT20 turbo and de-cat pipe on it. I'll be running 1 bar boost.

Cheer,

Paul.

IMHO, TTE 1.2mm.

[Paul R]

What about a Cometic one?

[MR2Mania]

What about a Cometic one?

I don't know what the Cometic ones for the 3SGTE are like, but I do know that some Evo boys are running a Cometic gasket, and not heard any issues. I should hope they're a damn sight cheaper than the HKS equivalent. I've compared the stock Rev3 HG against the HKS offering, and I sure as hell can't see a difference that is worth spending an extra £170 on, and nor can some informed experts.

The TTE 1.2mm HG for the Rev1/2 is as good quality as the stock Rev3 one, but cost a little bit more (but they're a pain to get hold of).

[JJ]

For cost effective reasons and reliability, I like to think the Rev 3 toyota gasket is the best for all worlds. I've fitted quite a few to Rev 1/2's and to be honest yeilds drivability ( as expected ) for the driver that wants that bit more responce and reliability, from a recent head gasket failure.

The drilling of the gasket is not an issue unless you've got a blunt drill bit and your crap at diy.

When it comes to refitting my engine back together, I will still use the toyota stock gasket... No I'm not being cheap I havent had one fail on me yet and I've chucked nitrous and high boost at it. Obviously HG failure is down to conditions of use... when i say high boost, I say 1.5 bar ... jonnos is destined to run more than 2 bar... so I cant speak for them boosts. So many other factors involved including clamping down forces, movement of the head ( headbolts ), surrounding coolant temperatures, in cylinder temperatures etc etc. I'm only intending to run 1.5 bar in the future... so is suffice for my needs.

As for getting the most out of the engine, I like to think the tuner or my meddleing hands sort that out.

Over and out ! Nothing too complicated in that reply !