'87 7M-GTE teardown/rebuild.

[Dan_Gyoba]

Okay, after swapping in a 7M-GTE which had been sitting for an unknown period of time, and had (Surprise surprise) a BHG, got rod knock.

Bought another 7M-GTE which had been pulled, and disassembly started for $250, which I was originally just going to swap in. Well, currently I'm glad that I didn't do that. Next the idea was to do the same as what I did last time, pull the head off and replace all of the gaskets and seals. The addition this time was to also change out the oil pump which I did not do last time.

Asked around here, and... Well, it's going to be a larger project than that. New rings and bearings, MHG, ARP studs... Well, a pretty complete build, really. My power goals are not extravagant, but I'd like to be able to make more than 400WHP without having to open the block again, so obvious weak points should be avoided.

I can't afford to just take the engine to a builder and say "Make it so" so, will be doing what I can by myself.

Anyway, started with tear down today.

Timing cover, waterpump removed

Head gasket, Cyl 1&2

Cyl 3&4

Cyl 5&6. Oh look, what a surprise, the HG was going out at #6.

The head on blocks.

Turn the engine over, remove pan

Otherwise, removed a few other pieces here and there from the engine, the water neck, heater core pipes, and other misc bits and pieces as opportunity presented itself. Things look pretty grubby in there, but the head bolts came out looking nice and clean. Surprisingly so, actually. One head bolt was a bit troublesome. At least none of them were loose.

 

[Dan_Gyoba]

I think that this may be a later block. I've been told that the engine came out of an '87T, and the wiring harness and ECU back this up, but looking at the Early vs. Late GTE blocks sticky, I think that this looks much more like a later block.

In this photo, the ribs going to the mains looks a lot more like the wider ones in the sticky than the "light" block. Also the pan rail appears to be the thicker one with the bolt holes not centered int he rail. I don't have great pics but I think that the extra ribs on the side of the cylinders are also present. I'll be able to see the front of the block better when I get the PS bracket off to see if the extra ribs are there, too.

One other potential telltale that the engine may not be original is that there is no block heater. I am 100% confident that no Supra would have been sold in Canada without a block heater. I'm going to go out on a limb and guess that the block was swapped for a JDM "low mileage" block at some point in the car's history. One thing that I also note is that the picture here clearly shows that the crank is indeed a 6M crank without the large counterweights on #2 and #5.

Hope that this doesn't mean bad things later on, but in part, this makes me just a bit happier about the decision to build this block, since it's "stronger" (I expect that it makes zero difference for my power goals anyway.)

Head gasket was a stock Toyota type composite with copper rings around the coolant passages, just starting to go on #6. Head bolts were also stock Toyota ones, so there's a possibility that the block hasn't been machined down, and that whomever rebuilt it to install in the '87T just installed a stock gasket on a cleaned up mating surface. I think that the head bolts might have been torqued down better, or at least re-torqued, since all of them were tight when I removed the head.

I'll have to take a closer look at the head casting, to see what I've got there.

 

[Dan_Gyoba]

Well, 100% certain that this is a newer block now.

Can't get the crank pulley bolt off. Put a 7' fence post on the end of the breaker bar, reefed on that, no good. Hit the bolt and pulley with a propane torch, still no good.

Anyway, while puttering around the block, I removed the oil pump, and remaining accessories and confirmed that it is a newer block casting.

 

[Dan_Gyoba]

Wow. I am so glad that I didn't even try to just swap in this block.

Finally got the pulley bolt off. The pulley bolt holes appear to be rusted up too badly to allow me to actually put a bolt into 'em though, so I haven't actually removed the pulley. Red thread-lock compound is NOT what I'd call a good idea, but I guess that the pulley wan't in danger of coming loose...

Pulled the pistons. Holy crap!

#1 looks okay, but one of the bearing tabs was broken. #2, mushroomed a bit on the piston side. The cap doesn't want to fit back on the rod when I place it aside. #3 is mushroomed a lot. #4 is just... Gone. There is nothing left in there that resembles a separate bearing piece at all, just some yellowish streaks in the grooves in the crank journal and con rod. #5 is also mushroomed, while #6 still looks good. It and #1 are the only ones that I can still put the bearing caps on the con rods easily.

Cylinder bores look good. A tiny bit of a ridge at the tops of the cylinders is all.

Anyway, pics.

Overall shot of the block, pistons out.

#5 (bottom) and #6 journals

#1 (bottom) and #2 journals

#4 con rod. Stick a fork in it...

#3 and #4 (left) journals

 

[IBoughtASupra]

So you are saying there was no bearing in the number 4 rod or did I misread that?

 

[Dan_Gyoba]

I believe that there had been a bearing in the #4 rod, but that it was/is most likely a bunch of metal shavings in the oil filter. I've got to say that I'm somewhat concerned about the state of the wrist pins as well. Maybe the Probe pistons will end up happening after all, since they're not that much more when you factor in that they include rings and wrist pins.

Fortunately, I was planning to replace the crank and rods already. I have one that's been polished and balanced lined up.

 

[IBoughtASupra]

You can get a set of NPR pistons for cheap. Devin used them for a while without issues.

 

[Dan_Gyoba]

Yeah, for some reason, I thought that I'd need to buy rings separate with the NPR set, making the price difference between the Probes and the NPR somewhat lower.

At Driftmotion, the Probes are $425 for pistons, rings and pins, the NPRs are $120 for the same. (I thought that I'd need to also buy the $65 piston ring set) The difference is a bit over $300,

I'm going to talk to the machine shop about the bores, in case I need to go with an 83.5mm bore for example. I'm not sure that I trust the wrist pins given the condition that the crank bearings were in, there had to be metal shavings in the oil hitting the wrist pins, too. I REALLY don't want to have to open the block again. If a bit of a hone would do the trick, then the "standard size" Probes being a couple thou over makes for a nice option, and maybe worth the extra $$$.

So long as the NPRs are at least as good as stock, I've got no problems with that, and I would be happy to keep a bit of extra coin in my pocket.

 

[IBoughtASupra]

So 400 HP is your power goal. That's doable on the NPR but for a little insurance the probes won't hurt but I like CP over anything.

Have you read about the stuff needed to be done to the probes before use? In short, the tops are rough and need to be smooth down.

 

[Dan_Gyoba]

I'll have to take a closer look, and do more reading. I don't want to step into a lot of unnecessary work.

If the NPRs are as good as stock, then my power goals are attainable on them, as I would have been happy to keep the stock pistons. If the Probes need additional work, particularly if they need to be addressed by a machine shop, then that's not desirable at all.

 

[Dan_Gyoba]

Block is ready for the shop.

The main journals all looked good, except #3, which had a score down the middle of it in the cap bearing. (Block side is grooved, with no apparent damage)

I have the front timing cover bolted back on so that it can be machined with the block.

Now I have to decide what I'm doing about pistons. I guess I can have the shop measure the bores and make recommendations, but at this point I'm thinking that a .020 overbore is probably in the cards. Maybe I'll just buy the pistons now, and have them work with that. I'm going to ask about having them assemble the shortblock, too.

 

[Dan_Gyoba]

Pistons arrived today. Dropped them off at the machine shop (Though I guess all they really need is the paper with the specs on it for bore size, since they aren't installing them for me.)

I was a bit surprised by this last. I was expecting stock compression ratio. Well, I'm not planning to really push the upper boundaries of boost, so this should just mean a bit better off-boost performance, and I should keep it to 15 lbs instead of 18 lbs.

 

[suprakidd]

i like what im seeing, keep it up..

 

[supraguy@aol]

LOL.
You're mulling it over between NPR's and Probes...and then you go and buy some Arias. Nice.
I also did not know that Arias came with slightly higher compression, how much did they cost?

 

[IBoughtASupra]

They need the actual piston to make sure the clearance from piston to bore is correct. Each piston is not the same, they all are .020 over but still different from each other when you measure them.

 

[Dan_Gyoba]

The Arias pistons were $680 USD. Not absolutely convinced about the 9:1 compression, but I don't think that it'll pose a problem. I'm pretty sure that it's not going to limit me under 400WHP.

Everything is (finally) done at the shop. They have bearings for the crank at .020 under for mains and .030 under for rods. Thing there is that the crank was at that size already from a working pull. Car it was in had JE pistons, one of which was melted, which was the reason for the pull. All the shop did was polish it. Given that information, it pretty much has to be hard enough. Anyway, they found bearings to fit it, so I'm going to keep it for the engine which is currently in the car with rod knock.

The other crank is .010 under both mains and rods. The bearings are coming from Driftmotion for these, and that's what I plan to use.

I've seen the gasket surface for the head. I can see the machining marks in it, so I was worried, but I can't feel them at all with my finger/fingernail. Machine shop says that they're at better than 20 RA, which is good enough. The head is very shiny. They painted it "aluminum" colour.

The block is a semi-gloss black. Haven't removed the shrink wrap from it yet. Took a peek at the cranks, which look great.