MKIIIarpus;1760102 said:
I understand, I just hate that the composite gaskets aren't good for over 35x whp. It seems everywhere you look somebody has a different opinion or made this or that work. Even as most said, most machine shops can't even get that surface. Hard to dicyfer what is hype, what isn't, and what is actually working for everyone. I'm thinking if disassembly of a block is required to replace a head gasket then maybe the supra wasn't the car for me. lol
I agree that there are a dozen different opinions flying around and it's tough to find the truth. You're new to the mkiii world, (from the sounds of it) and we just want to make sure you dont make a quick mistake now that you'll regret down the road. These engines take more than the average tuner attention and will quickly punish you for any shortcuts.
Keep in mind that Sonic page was written when 7M blocks were 5-15 years newer than they are now. The average Supra was much closer to new than it is today.
I'm sure there are plenty who have made a poorly prepped engine hold 500 whp for much longer than most of us would expect, but the bottom line is that there is a clearly defined, published method to a successful MHG install and it *always* involves fresh *high quality* machine work. Anything short of that and you are asking for trouble. The inline 4's (EVO, STI, Neon, Civic, Integra...etc.) and V6 motors have a substantially smaller surface area. That makes it MUCH easier to do prep work on the motor in car. You can easily get a lapping plate that covers the entire block and you just have a smaller space to mess things up. The inline 6 is LOOOONG and gives you plenty of opportunity for catastrophic error that you wont even notice while doing the prep work. You can finish lapping it and see a "perfectly flat, mirror finish" when in reality, there are 3 low spots and 200,000 grains of cast iron and diamond paste floating in your oil passages waiting for the first start up to start tearing at your bearings while the low spots gradually cause a BHG.
HKS makes a special note with their gaskets (even the Stopper) stating that the gasket provides NO protection against any imperfections in the deck material of the block or head and it should only be used on a fresh, flat, smooth surface. Their gasket is designed to be used on a perfect block and perfect head. Nothing else. Same goes for any other MHG. They were never meant to just be thrown on a used engine and deliver better results than the composites.
In the end it's your choice and I wont be hoping for your demise if you choose to lap it in car and go MHG. IJ's opinion is worth 10x more than mine anyways so I'd heed his warning much more than my own. Good luck either way.
suprajztwenty;1760165 said:
if the motor is "fresh", why not pull it out and verify the bottom end? a bhg would be the least of my worries (especially after 6k miles), but mostly because the previous owner already lied once...i mean how many miles do you think are on it??? only way to estimate is to pull the bottom end, measure and inspect.
on top of all that, with a bare block you wont have to worry about the compound getting down into the rings when you try and lap the surface.
i can see why you wouldnt want to buy the tools to pull the motor, like a hoist or a stand...but you can pick them up for maybe 150 used. if all checks out as normal, put it back together and call it a day, or like you said, upgrade to forged pistons.
seeing that its had a rebuild i just wouldnt take the change in investing the money in head work, gaskets and time involved without making sure the bottom end is tip top.
These are also very valid points. So far you have a motor that, for all you know, is on stock bottom end components about to fail even if the head gasket issue goes smoothly. There is a TON to gain from a full engine rebuild. Pulling the motor for even just a crank polish, professional block surfacing/lapping, head work, new bearings, rings, (pistons if you choose), etc... All that can even be done cheaply if you keep it simple.
My engine hoist and stand put me back a whole $120 from craigslist/harbor freight and were two of the best investments I've made.
