[NeonElixir]

Hi. I'm new here and I figured I would try asking for a little assistance. I've been searching the forum about what head gasket size to get, and it's been debated so many times that I wanted to see what people might have to say about my specific situation.

I bought a 88 Turbo in non-running condition with intentions of installing a JDM engine. It was (and still is at the moment) completely stock. Plans changed to simply changing the head gasket after advice from a local Supra loving friend. I had the head milled at a machine shop that primarily works on racing engines. .006 inches were removed from the head. I didn't have any work done on the block. So what size head gasket should I get? I was figuring the HKS 1.2 mm bead, but I want to make sure. Trent from MVP told me that stock was 1.2 mm and to get the 2.0 mm, but the guys at SupraStore.com said the stock was 1.0 mm and I only need 1.2 mm. I called the Toyota dealership by me and they have no clue what size it is, HKS wasn't much help either.

What size gasket do I need? Do I need to make any other special preperations (sealants or anything)? Finally, what torque should I use if I'm getting ARP head studs?

Thanks so much for your help.

-Brett

 

[bgrieger]

1.2 should be fine. There was so little removed as to not be worth worrying about. Stock is 1.2 uncompressed, around 1 compressed. You tool off .15mm, you won't see enough change in CR to matter. Should be like stock when done.

Did the shop prepare the head surface for a metal gasket or composite? How about the block deck? If composite, or not specifically for metal, then forget the metal idea, or get them done. Don't kid yourself into believing 'close enough'. If it was not specifically machined for it, you stand perhaps a 60-40 chance of doing it again in 6 months...not worth the savings IMO.

HKS, Greddy, Cometic...whoever's gasket floats your boat. They're all about the same.

70-72ft-lbs is the semi agreed standard torque for ARP or stock bolts. The metal is the sealant. Nothing but a blob of RTV or Toyota FIPG to seal the front of the block as per the TSRM/Haynes manual. Don't bother with anything else if all surfaces are preped.

 

[NeonElixir]

I called the machine shop just now and he told me that what he put on there was the smoothest he could get it without lapping it. I guess he ran the machine at the slowest speed. If I got you a closeup picture of the head do you think you could tell? He told me that he's only used composite gaskets and that I should probably call HKS and check to see if maybe I needed to spray it with something.

Wouldn't a composite gasket just be prone to blowing again?

 

[NeonElixir]

Does it make any difference in torque that I'm using ARP head STUDS rather than bolts?

 

[bgrieger]

Composites are fine depending on a couple of things.


1) torque the head bolts to 70-75 foot lbs. Reg Reimer (supra race car owner and Sonic pres) took the bolts to a metalurgist to determine the appropriate torque. Once the torque is set, and checked at about 5000km, they hold up quite well.

2) Careful with the boost. They don't tolerate detonation well, and high combustion chamber pressures will cause failures as well. Keep boost to factory fuel cut or less and all goes quite well. I've had mine in for 3 years with slightly elevated boost and it's been quite happyPass through 12 lbs and expect to do this again in the not so distant future.

Torque is probably listed as being per manufacturer specs. Studs are a more positive lock than bolts, but should have the same torque values. If you're working with a composite gasket (I recommend Toyota ONLY...others can be poor quality), stock bolts are fine. ARP are high quality replacements, but really are overkill unless the price matches new Toyota ones.

BTW, never reuse a head bolt...


Bob

 

[NeonElixir]

I ordered a 1.2 mm HKS bead gasket today and I already bought ARP studs on eBay. If you really think I should get the Toyota gasket then I may reconsider. My friend who's helping me and actually knows the car very well says it should be fine, but he hasn't yet looked at the head. I'm not planning to go all crazy with performance mods, but somewhere down the line I plan to add some stuff.

 

[bgrieger]

Trust your machinist. If he said composite, then it's probably a good idea. You can try the metal, but don't say you weren't warned. If he never does metal gasket surface preps, he may not have a machine capable of milling that finely. Lapping may be his only alternative to get it where it needs to be.

HKS says dry install last I checked...so do the others.

If you insist on the metal, take the head and block back to be lapped if your machinist thinks it best. I haven't seen the surface, he has. To be perfectly honest, it should feel much like the surface of a new brake rotor. The ra values (should he have a profilometer) will need to fall in under 20 ra, with ideal being somewhere around 12-15. Damn smooth, but not quite mirrored. If you feel ridges from the bit working the surface, you are taking a chance you might regret. Feel provides better info than sight, so don't worry about the pics. The visual of bad and good for metal gaskets is not easily noticed on a screen.

Again, what are your goals for the car, and that determines what you need. You want big boost, you want metal done right. You want a 250-300hp daily driver with 12ish lbs of boost, you can use a composite without much risk as long as everything runs properly. Avoid detonation, tune up regularly, change fluids on time. All the basics.

Bob

 

[NeonElixir]

I just want it to be a daily driver I can have some fun with. I can't see myself going over 350hp. I'll list all the performance mods I can see myself possibly doing within the next couple years....

air intake (already bought the A'PEXi), downpipe, cat-back, BOV, and flywheel...

Do you still think composite?

Thanks for your help by the way.

 

[bgrieger]

No problem. Glad to help.

Flywheel is a bit overkill, but each to their own. You'll end up a little more free reving, but gain nothing HP wise. Couple that with an aluminium driveshaft and light weight wheels, and you should feel a lot faster than you really should be. Rotational mass consumes torque and acceleration, and the less you have, the more you put down. I'd personally spend the money elsewhere at your stage of modding, unless you are heading for some serious power (400+), but that's just me. Nothing wrong with it, but don't expect the world.

Again, if you plan on staying under fuel cut (12ish PSI) you should be fine on the composite. 350 won't happen with your mods. You can't pass fuel cut. With 12 PSI, 300 is about the upper limit (approx 11 hp per PSI, we run 6.5 stock, so there's about 60 more coming). With a cheap boost controller, your mods are 300ish at the crank. Daily drivers IMO shouldn't be heading beyond that point, as things tend to get expensive/break more frequently. Again, that's just me.

In that range, unless you plan to rag on it, or start playing with fire (aka fuel tuning), the composite is fine. Many run that all day long. As I said, 3 years now for me without fear. MHG is the nicer option for a little more "peace of mind", but most Supra owners are so scared of the dreaded BHG that they start believing the sound of the headlight motors or a rattle in the hatch is the sign of death. Hence, they believe the Toyota gasket is crap and that some fancy metal gasket will save them. In fact, it's the workmanship and preparation and following the guidelines that will...same applies to the metals. Failure to properly prep is a leading cause of metal gasket failure. Those things should never die if they're done right. Same for the composite.

If you get anything from this, take this away: If you are unsure on whether the surfaces are properly prepared for metal gaskets, get a machinist you, or plenty of others, trust in their opinion. Supra owners are knowledgable about the supra, but are not machinists...myself included. I personally would not chose the metal when in doubt. Composites were designed to seal less than perfect surfaces, and metals need near perfect surfaces to seal perfectly. With your mods, you are not in dire need of a metal in my opinion, as long as you prepare, clean install and finish the car to spec. Torque as above (low 70 ft/lb) and enjoy the car. By the time you need to look to more power, you should have the engine fully built to take it anyhow, so you can get the metal gasket then.

Bob

 

[NeonElixir]

I'll get the composite and call MVP tomorrow to remove the gasket from my order. Hell if my machinist works on race car engines and only uses composite, they must be good for somethin. I assume the CR still won't change enough to notice? My friend helping me gets 30% off Toyota stuff through work, so there's that. I probably won't do the flywheel to be honest, at least not anytime soon. I have other things to worry about like headlights and whatever other minor things the car needs. Next year I hope to get it painted. Maybe somewhere down the line after that, rims. I am however a 19 year old kid in college, so super expesive mods that do super teeny tiny things unless you go all out just won't happen here.

My friend said he had his up to 10-12 psi with some sort of wastegate shimming. He said he would do that for me and I'll probably be perfectly content with that. I imagine I should probably get a boost controller and boost gauge?

While I'm at it, any suggestions on turbo timers? I was going to get GReddy but switched and ordered the HKS Type-1 US Spec. I had also debated the Blitz DC III Dual TT though as it has a built in boost gauge.

 

[bgrieger]

I have the HKS Type 1 myself. Fine unit. If you got it for all the features, you'll likely quickly get bored of them and just use the timer side. If I had to do it again, I'd have gotten the cheaper Type 0. I never end up playing with the features anymore, and have the battery out so frequently for work that I'd have to reset it all the time and usually forget about it. Live and learn I guess.

CR should be fine. You won't notice at the levels you are looking at.

Shimming the wastegate is by far the cheapest of the boost increasing devices. You put extra washers on the wastegate bolts to tighten up the spring. It restricts the flapper door and forces the turbo to run more exhaust through it. I've done it myself, but in almost every case, a manual boost controller would be a better choice. Again, live and learn. Shimming will stress the spring, and can result in boost creep as the wastegate can't open wide enough anymore. Dawe's devices ones are fine, and cheap. They are a ball and spring controller. Until the controller pops at the setting, the wastegate stays closed and releases rather suddenly. Allows slightly quicker spool and run to peak as the wastegate does not slowly open as the pressure heads to the preset (the way stock ones do), but pops off at the desired setting. They can have spiking side effects, but that's not all that common.

With the list you have of things to do, you'll be to engine rebuild time long before the gasket fails so you can run some big power down the road (kinda assuming you keep it that long).

Best of luck,

Bob

 

[NeonElixir]

I bought the HKS a little for the extra features, I found it for $25 more so I was like eh what the heck.

We're talking about a manual boost controller right? Is something like this (http://www.geocities.com/chmwatson/FAQs/mbc.html) adequate or should I buy one? Also, would you suggest I get a better boost gauge than the factory then?

 

[bgrieger]

That's basically the boost controller. A boost gauge is nice, but fuel cut will tell you if you went too far (an an abrupt and pants filling moment of panic as the dash freaks out and the car begins to feel like you are repetitively running into a wall)

I just use a cheap mechanical one for now to tell me where I am.

Bob

 

[NeonElixir]

Yeah, uh, I don't like the sound of the pants filling deal. Mind showing me what kind of gauge you use?

 

[bgrieger]

Sunpro...same kind you've been able to get cheaply since the 50's. 2 1/4 inch mechanical 20 PSI gauge. I've mounted it in a little autometer metal gauge cup beside the steering column. I'll take a pic later.

Bob

 

[NeonElixir]

Never heard of it. I was thinking about getting one of those 2 gauge A-pillar things. I saw some cups that go above the steering collumn that I kinda liked, but they were an awkward size.

What's the difference between these mechanical and electronic gauges? I'm guessing they all have the same kind of sensors and then the actual conversion to gauge readout is somehow different to be more precise. No?

 

[VVT-i Owns]

Great Thread, Very Informative I enjoyed the read!

 

[bgrieger]

Electronic gauges have a sensor located close to the source and wires that run back to the passenger compartment mounted gauge. Mechanical gauges run a pipe or capillary tube to carry the source measured to the location of the gauge (aka, a little plastic tube that runs from the manifold to the gauge, or a capillary tube for fuel or other liquid).

Mechanical tend to be less accurate due to the long runs, but the tiny bit they are off is not of concern, and most people wouldn't notice the difference unless 2 were side by side.

I think the colum mounts work alright...

Bob

 

[NeonElixir]

Hmm that's pretty interesting. Know where I can get a gauge and a pod like that? I was kinda considering getting the GReddy Boost Controller since it has a built in digital gauge. On eBay it's like $250 which would almost be the same price as getting a manual boost controller and a nice gauge.

Today I took care of like everything I need to buy. Oil, battery, coolant, thermostat, couple hoses, my friend ordered the gaskets and some other small stuff from Toyota, and my intake and timer should be shipped today. The ARP studs should be in the mail already. So we're getting there. Hopefully I can get this thing running before school!