need advice on my crank situation

[wh0wants2know]

I recently had a little problem with my crank pulley flying off while I was driving down the freeway. As a result, the keyway on my crankshaft is all fucked up. I have decided to rebuild my engine as a result, but I have heard a lot of conflicting information on this through the judicious use of the search feature of this forum and a certain other forum that's also about supras. Anyway, here's the situation:

The crank needs to have the keyway repaired but as far as I can tell it is in otherwise good condition. I have not mic'd it yet (more on this later) but it ran fine up until the pulley fell off. My current goals with this car is about 400hp or so and it is not a daily driver, although I do intend for it to be street driven and occasionally taken down the track. I understand that if I want more power, I'll need to go forged internals and stuff, so if I decide to go that route later then I will be doing another rebuild.

Also, I am not one of those broke-ass mkIII owners that has to do this on the cheap in like three days. I have plenty of time and plenty of money, however I do not want to spend money on anything that I don't have to have in order for the car to run, but I'm willing to spend what I need to in order to have this done correctly so that it will last. I am also capable of doing most of the repair work myself.

Anyway, I have read that the optimal clearance for our bearings is .0015" although the tsrm states a range between .0008 and .0021 is adequate (http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=69). So this is the first problem: I own a set of calipers but it only measures to 3 decimal places. The mic set that harbor freight sells also measures to 3 decimal places. Will this be "close enough" (If I see it's between .001 and .002 it's right) or do I need a set of mics that can go to 4 decimal places and if so, where can I find them because no place around me seems to sell them and the interwebz have failed me. I could also trust the machinist who measures it, but I'd rather not do that after reading some of the threads on here.

Next question, should I just get a new crank or repair my crank? The dude at NAPA said that they sell a 6m crank that is reground to a standard size bearing and includes the bearings. Naturally, my first instinct is not to trust this, but I could always measure the crank and get thicker bearings. I could also have them check my current crank and see how close it is and maybe have it reground or polished or something and get thicker toyota bearings. Again, I want this done correctly, but I would prefer to go the cheaper route of either fixing my crank correctly or buying a new crank. Also, if there are any other recommendations for where I can get a new crank, please let me know.

Final question, what bearings should I use? I'll be using stock main bolts and ARP rod studs in this rebuild (I recall that stock main bolts are reusable since they don't stretch, please correct me if I'm wrong). I know toyota bearings are good and they're available in like 5 sizes. I've heard good things about clevite bearings, but I also heard that they just repackage them these days and they are actually crappy unless they were made more than 10 years ago, is this true? Are there any other good bearings out there? Again, I don't need bearings rated to 100000hp or anything but I don't want crap either, I'm willing to pay for decent quality.

I know this was a bit long-winded but hopefully the next person who asks about this and uses search can find this thread and it will have good information. Thanks in advance

 

[suprarich]

The crank can be repaired. A peice of carbon is used to mock the key. The crank is repair welded around the carbon faux key. Then the carbon is knocked out leaving a new key way. Then the snout will need to be reground. In most cases, if your damper came off, the entire snout will now be undersize. The snout may need welded and reground to bring the diameter back to spec. Doing all of this can bend the crank, which can be straightend by grinding the mains or with heat in the right place and some pressure. If using the stock toyota bolts for the mains, use new ones. Clevite bearings are fine, just not what they used to be, but are still very good bearings.

Repairing your old crank and refurbishing it will run you in the 325-400 range. Not sure what NAPA was going to sell you one for.

 

[bowsercake]

Might be better to get a crank from someone else used, or from the junkyard.

 

[MmmBoost]

suprarich is 100% right about how much it will cost to get the work done. in my honest opinion, you should buy a reman'd one or a known good used one.

also, a caliper is used for measuring stuff when accuracy doesnt matter. (not in the case of a crank). you need a micrometer to properly measure the crank.

also, to have it last a good amount of time, a good machinist will require you to give him your block, front cover, tensioner, crank, rods, pistons, and a torque plate, along with any new bolts and bearings you will be using. the rods should be re-ground to make sure that with the new bearings the clearances are within specs, and the block needs to be line honed along the main journals to make them perfectly straight (were talking 0.003mm from one side of the block to the other) and to set the clearances with the new bearings and assure that the proper crush is applied.

honestly, i bought a reman'd crank from autozone (the website) on my old car. it was like $350 after the core refund. it came with clevite 66 bearings, and was in perfect condition. i took my rods and block to the machine shop and had them worked. it lasted a very long time.

 

[Adjuster]

A new crank is less than fixing yours correctly, and you run the risk of adding more problems with the heat induced warping of the crank. So, I agree with buying another one. Junkyard, NAPA or whatever.

Bearings are bearings in my opinion. You only really need them when you don't have oil, and the mains are not a problem on the 7M, but the rod bearings are problematic if you don't have proper oil.

There are aluminium ones, clevite's and the Toyota ones that they buy from someone else, and also I've heard some fancy F1 spec bearings with microscopic triangles on them.. Very cool.

For an everyday build, just get the clearance right, and run an extra quart of oil over stock on your new shimmed oil pump, and you should be fine. (And ditch the stock oil cooler! It's like having a high pressure leak, just when you do NOT want a leak to happen.)

Go for the tight end of the spec for the bearings. This motor seems to run best when set up that way.

I checked mine with plasti gauge to check them, and took the word of the machinist on what sizes to buy. (It worked out fine, just tell them you want to shoot for the tight end of the specs, even on a "race" motor, it's best for this motor.

Some tips.
1) Pull the plugs on your crank, and replace them with new ones loctited into place. While they are out, clean the crank out a few times with solvent and compressed air. You will not belive how much crap is hiding down in those oil passeges, just waiting to become embedded into your bearings, and cause wear and problems.

2) Shim your new Asin oil pump with one 10mm nut. (This is about 5mm thick, and will raise your oil pressure slightly.) You can add Arz's oil crossover tube if you want, but really, for a stock build, the stock stuff is probably fine. (But it's easy to do the tube if your are there, and hard to go back and do it later..)

3) Get rid of the stock oil filter mount and oil cooler port. This is another "bypass" point for your oil. It's supposed to open about 40psi, and dumps excess oil out via the cooler, and then dumps it back into the oil pan.. Totally not what you want when your engine is under high rpm stress. Go to a spin on adapter, remote filter and cooler with a thermostat, and your engine will last much longer, and filter and cool better than ever. (Especially if you go with a quality depth type filter, like those from Canton/Mecca. They are full flow, no bypass, and filter to 8 microns. Most people agree that particles over 10 microns cause wear, and most spin on filters only trap stuff down to about 20 microns at best, so you decide...) Also the Canton filter flows more "dirty" than your brand new paper media spin on filter does.. So you decide.. LOL

4) The stock main bolts are not a common 7M failure point. I do not see any reason to replace them unless your going to build a 500hp or more capable engine. ARP rod bolts are an excellent upgrade, and so are the head studs, but replacing the stock main bolts is a waste of your good money in my NSHO.

5) Same goes for the line bore. I do reccomend using a tourqe plate when boring for your new pistons, but the mains are not often off on the 7M in my experiance. As stated by others, make sure they machine your deck with the front cover in place, and use a tourqe plate when you do the pistons! (We found as much as 3K worth of flex and variation.. so it's worth it.) Someone also reminded me to make sure your cam belt tensioner bolt is in place when you do this too, it flexes the block as well..
So, in short. front cover, tourqe plate and all front bolts in place that go into the block... you could also put the engine mounts on, and other stuff to simulate what the engine would be like installed, but somewhere, you have to draw the line as you can't cut the bores with the head on there now can you...

Ok, good luck, and read up on assembly tips and other stuff. There are some easy oil mods you can do if you want. (See my post on how to avoid using an adapter if you just plug up the oil hole from the rail fitting, to the filter boss, and then use the NA cooler port as your "out" fitting to the oil filter etc... and a standard AN fitting in the middle to return oil to the main galley. It's cheaper than a quality spin on adapter, and actually makes it easy to plumb your remote filter/thermostat/cooler setup.)

One last thing. Do the Comp Cams valve springs.. Cheap, and easy for new springs that are better pressure wise than even the stockers... Besides, did I mention they are less money for better springs?

 

[wh0wants2know]

Thanks for all the advice. I've decided to go with the crankshaft from NAPA, although I need to talk to the machinist in more detail to determine exactly what he's going to need me to bring and what work I want done. I figured while the block is out I may as well have it cleaned, have the freeze plugs replaced, and have them check the head/block surface for MHG (it had one on it but I want to know what thickness to buy for the new one and verify that it's still smooth enough, I trust nothing about the engine at this point) and anything else that the machinist recommends to keep this thing good. I'm hoping to be able to keep this all under $1500 for parts and machine work (I can do everything else myself) but I have no problem spending more if I need to in order to get this done right. I'll look into the oil system mods mentioned, sounds like a cheap and easy way to improve lubrication, which is always good. Thanks

 

[Motofool]

if you want to know what tolerances you are working with do not buy your instruments from harbor freight. there are other in expensive tools of much higher quality from a local machinist shop. or ENCO, MSC and many other large tool companies

you need a micrometer that measures to .0001 for engine work.

now there is something else to think about if you dont use the same micrometer you will have variances so when you measure it at the machine shop with one tool and go home with another tool your bound to have different measurements. and this is because of calibration and tolerances an average calibration tolerance is plus or minus .0002 " this was in an aerospace coatings facility where i managed the calibration of 3000 instruments.

i would recommend getting a new or used crank so you dont end up with a warped freshly repaired crank =)

i would also recommend arp rod bolts and new stock main bolts or arps its not a problem area on our blocks but i like to have the piece of mind that i left no chances for failure in a performance application that you will take the motor beyond its stock power rating.

would also recommend new oil pump while it is out and every other hard to get to item while you have it tore down.

best of luck on the crank search it can be a fun road

 

[suprarich]

i would recommend getting a new or used crank so you dont end up with a warped freshly repaired crank =)

A repaired crank will be straighter than any used or even a new crank. If it is not, then you should slap the guy who ground your repaired crank. A repaired crank from me will be within .00005 of a zero run out.

 

[wh0wants2know]

I called the local machine shop at the Napa near my house and the machinist said he has worked on 7M's before. I told him my situation and he sounds like he knows what he's talking about. He said that the best thing for me to do is not to take apart the bottom end and just bring it in and let them take it apart. He said that he'd be able to get a better idea of the condition of all the parts that way. Once he's gone over everything, he can give me an accurate estimate of what it'll cost for me to get everything, but it's looking like a maximum of about $1100 to disassemble, clean, replace freeze plugs, replace oil pump drive shaft bearings, measure crank/rods/caps/bearings/etc and tell me what size to buy (or they'll order for me, either way). He'll also check the cylinders and bore if needed (it'll be less if he doesn't have to and he said he has a torque plate). He'll also check the head and block to determine flatness and smoothness and then fix it so that it's smooth enough for a MHG. he said he's done this before several times and I mentioned an RA of 15 or less and he said no problem. I also mentioned the line hone and and he said that he'd check it but he's never seen one that needed it yet. He'll also install everything including pistons, rods, bearings, etc. and balance the whole thing. He said that price was probably the most it would cost if he had to do a lot of work on it. Does this sound reasonable? I think it's probably fine (and I'm ok with paying that) but I just want to run this by you guys to make sure it sounds right as i haven't had this much machine work done to an engine all at once before. Thanks