7M build advise please

[Dan_Gyoba]

Okay, after replacing the clutch last year (ACT stage 3), I got some issues, which seem to fit with a walked crank, or at the very least, rod knock.

I've got another 7M-GTE lined up, and should be here before the weekend, which I want to get ready to drop in.

In preparation for this, I've ordered a MHG (Titan 1.4mm), ARP head studs, and a complete gasket kit. My hope is that I can get the head resurfaced and lap the block to install the MHG and be good to go. Is it realistic to expect to be able to lap the block (Assuming that the block surface is good with a straightedge) with the pistons in and get a MHG to seal? I'll replace the manifold gaskets, valve cover gaskets, front and rear main seals, oil pump drive seal, and whatever other gaskets I see when I pull things apart.

Also on the way is a new timing belt and oil pump. I'm picking up a DM oil pump hose locally, too. I'll be re-using the alternator, starter, turbo, injectors, AFPR, wiring harness and a few other things from my current engine when this is ready to go in.

I don't think that I have the budget to be replacing bearings and getting associated machining done, which is why I had thought that a different block would be a good place to start. I also plan to eventually repair the block that is in the car now, but that's likely to take some time. It'll be on my engine stand for a long time, I think.

Anyway, given that I'm putting this engine together on a tight budget, is there anything else that I should do while I've got it open?

 

[IBoughtASupra]

Are you sure it is crank walk? Does the crank move when the clutch pedal is pressed?

 

[suprarx7nut]

If you can't afford to have the machine work done I would VERY strongly suggest you use an OEM head gasket. MHG should only be done when you can assure the block surface is prepped correctly. A good machinist will laugh in your face if you tell them you're going to prep the block by hand with a lapping plate for any serious HP.

Having the block work done shouldn't be that much. Bearings are $60 for an entire set. Piston rings are maybe $100. The labor for machining a bare block shouldn't be over a few hundred $.

I'm putting in a very firm vote for OEM composite head gasket in your scenario. Exchange the Titan MHG for a regualr Toyota HG, buy bearings, rings and oil pump. If you want to go MHG, you have to do the prep. That means professional machining. If you can't afford the professional machining, you can't afford the MHG. Plain and simple.

I've said it a thousand times and I'll keep saying it. Stock HG's can handle decent power and a ~350 whp 7M is always better than a poorly prepped 7M making double the power, but that could explode at any moment.

 

[Dan_Gyoba]

No, I'm not sure that it's crank walk, but it is an unpleasant hammering sound at ~2k RPM which seems very much consistent with rod knock at the very least.

I will only consider the MHG if the block surface is already very good, or yeah, I'll suck it up and take it in for machining work. Regardless, the head will get decked professionally. I have a factory gasket in there now, and the complete gasket set that I bought has an OEM HG in it, so I'll use that with the ARP studs if I can't get something from the block that I can have confidence in. The block surface should be good, as this engine does not have a blown head gasket. Last time I went with the OEM HG because I knew that I couldn't afford the machining, and the surface wasn't as good as it could have been.

I'm sure that the stock HG is fine at the power levels that I'm currently running, with the Lex/550s and the 60-1 turbo at ~15 lbs. I'm not looking for much more than that in the end either, since then I'd just start breaking other stuff.

Well, I'll look at bearings and rings, since I don't want to be looking at doing this again any time soon either.

 

[suprarx7nut]

If the block surface has been used for anything more than a couple hundred miles I wouldn't even consider it. In all seriousness, mhgs are NOT intended to seal anything other than a freshly machined, low ra finish block. Some machinists don't even have the equipment to machine the block to the required smoothness.

Nevermind a used block with hand prep...

Especially if your power goals aren't anything beyond what you listed, that mhg might be a big gamble with no added benefit anyways.

Sent from my ADR6400L using Tapatalk

 

[Another MkIII]

Get it machined or use an OEM head gasket. Otherwise you will join the never ending cycle of BHG > JZ Swap > This car is a piece of junk > Part out.
-AM3

 

[Backlash2032]

Just because the engine doesn't have a BHG doesn't mean the block surface is perfect.

My late block 7M with 100k miles and no BHG had to be decked 20 thou to clean up. And there was still some discoloration between the coolant holes.

Deck the block and head or run an oem gasket. Simple as that.

Sent from my HTC Rezound

 

[505turboman]

Get it machined or use an OEM head gasket. Otherwise you will join the never ending cycle of BHG > JZ Swap > This car is a piece of junk > Part out.
-AM3

LMFAO!!!! I second that! I just finished my second build on the same engine cause I used an HKS 1.3mm bead type head gasket on my 7mgte and thought "I should be good I'm within spec on the tsrm and my head machined...." NOPE! Dead wrong leaked compression on cylinders 2,3, and 4 wish I was on this site having these guys telling me the correct route to take.

 

[Dan_Gyoba]

Well, this is why I asked. I guess I'll just have to grit my teeth and live on rice and beans for a couple extra weeks.

In many ways this car is living on borrowed time as is, the chassis is well into the "miled out" age and condition, and really, this build is more about me being stubborn than smart. Still, like I said, I don't plan on doing this again anytime soon, since I need to start saving money to get the rest of the car to where I want it to be. The more stuff I have to fix AGAIN, the less likely that is to happen.

In other words, this isn't going to get to the "JZ Swap -> This car is a piece of crap" stages in that cycle, if this build fails, it's going into the part-out category, though most likely the first in line for parts will be me, into whatever A7 chassis I buy to replace it. (I've got some nice parts, which I'm sure that I'll want to keep.)

Okay, so deck the block it is.

So, does that mean replace main bearings for sure? Should the rod bearings be okay? Wrist pins etc? If the pistons are coming out, I'll shoot a hone down the bores and replace the rings at the very least.

For the main bearings, do I measure the crank journals and buy bearings to suit? (Never liked plastigauge much though. Don't have a lot of confidence in it.)

A new Toyota shortblock for $2,400 is starting to sound like an attractive option...

 

[suprarx7nut]

Well, this is why I asked. I guess I'll just have to grit my teeth and live on rice and beans for a couple extra weeks.

In many ways this car is living on borrowed time as is, the chassis is well into the "miled out" age and condition, and really, this build is more about me being stubborn than smart. Still, like I said, I don't plan on doing this again anytime soon, since I need to start saving money to get the rest of the car to where I want it to be. The more stuff I have to fix AGAIN, the less likely that is to happen.

In other words, this isn't going to get to the "JZ Swap -> This car is a piece of crap" stages in that cycle, if this build fails, it's going into the part-out category, though most likely the first in line for parts will be me, into whatever A7 chassis I buy to replace it. (I've got some nice parts, which I'm sure that I'll want to keep.)

Okay, so deck the block it is.

So, does that mean replace main bearings for sure? Should the rod bearings be okay? Wrist pins etc? If the pistons are coming out, I'll shoot a hone down the bores and replace the rings at the very least.

For the main bearings, do I measure the crank journals and buy bearings to suit? (Never liked plastigauge much though. Don't have a lot of confidence in it.)

A new Toyota shortblock for $2,400 is starting to sound like an attractive option...

Glad to see some others chiming in with personal experience. And glad to see you making the right decision.

You should plan on replacing all bearings. Mains, rods, thrusts. Wrist pins might not be needed. I've never replaced those on my builds. You will need to have the crank polished (~$60) and the machinist can tell you what size bearings you can use. If you have a micrometer, or access to one, and you dont mind doing some basic data recording, you can use Toyota select-fit bearings which should get you the best size possible. I got away with using "Standard" size generic bearings on my last two engines and had no problems.

a quick hone to "deglaze" the cylinder walls is a good idea. The machinist should know exactly what to do.

The Toyota shortblock still leaves you with a hell of a shopping list. If your block is good, aka, not cracked or warped, you should be just fine to re-use it.

Happy building!

 

[Turbo Habanero]

Well i can tell you that OEM head gasket will last you about as long as the the OEM pistons will last you....

I'm sure if you hit detonation good enough to deform the head gasket you can also kiss the piston goodbye as well.

I am around 360-380whp on a 60-1 turbo @ 14psi with a stock block and rebuilt head OEM toyota gasket from driftmotion with ARP headstuds @ 90 FT LBS

I have always made sure i'm on the rich side of 11.5 AFR'S and so far my motor has been strong and good to me

My car see's redline everyday for the past 2years. It's made many Drag passes and track days 7 in a row one day time!

 

[Dan_Gyoba]

Well, after some shopping, thinking, more shopping and more thinking...

Basically, I'm going to tear the thing down. New timing belt, bearings, rings, oil pump. Got a line on a nice micropolished crank, and some shotpeened balanced rods. Keep the pistons. (Though the Probe forged pistons are tempting. We'll see what happens before this is done.)

Will deck the block w/ timing cover.

Pull the valve train from the head, get that decked, too. Get the valves and seats done. (Considered 1mm oversize, but probably not in the budget. Considered port and polish, too, but again, budget...)

Titan MHG. I've ordered the 1.4mm, but will reconsider depending on what gets shaved from the head and block. I figure that a bit higher compression isn't necessarily a bad thing, as a small amount isn't likely to be a limiting factor. I already have a set of ARP studs, but I'll get another set, since I want to have this block assembled before I pull the one that's currently in the car.

Keep current turbo, wiring harness, injectors and Aeromotive AFPR.

Hopefully this will result in a nice, solid 7M which will last me a while.

I wasn't worried about the stock HG in my current engine, and if it hadn't started making nasty noises I'd have been happy to keep it as is. But... If I've got to rebuild, then I might as well do it the best that I can.

 

[suprarx7nut]

Sounds good. I wouldn't worry about oversized valves unless you are really planning on some big power. The stock head can apparently handle plenty of flow for ~500+ hp.

Sounds like you've got a good idea what you want. Should be a good build!

 

[harley1985]

little off the subject, my engine is solid completely stock, no problems at all. im going to be doing some upgrades. looking for around 375 to 400 hp. now ive got my arps, and fixin to order my MHG. can i pull the engine and give the block and head to the machine shop with the internals still in the bottom end?

 

[supraguy@aol]

Yes, they can disassemble it for you.
It'll just cost a bit more in labor. Make sure that the shop you go to has the ability to create the proper surface on the head and block, for your head gasket; not all shops do.

 

[Dan_Gyoba]

Yeah, the question right now is if I have the extra for the forged pistons. at $425, the Probe pistons seem like a good deal, and considering that I need at least rings for the stockers, it's not THAT much more... but still more, and not needed for my power goals. Just that I know that my goals tend to change, once I reach them.

 

[harley1985]

Yes, they can disassemble it for you.
It'll just cost a bit more in labor. Make sure that the shop you go to has the ability to create the proper surface on the head and block, for your head gasket; not all shops do.

i dont want to disassemble it lol. its perfectly good, i just want to get it machined down so i can put a MHG in it.

 

[IJ.]

i dont want to disassemble it lol. its perfectly good, i just want to get it machined down so i can put a MHG in it.

Can't think of any shop that would take the halfassed approach you're suggesting...

There's no way to be sure of not getting swarf in critical areas.

 

[Another MkIII]

i dont want to disassemble it lol. its perfectly good, i just want to get it machined down so i can put a MHG in it.

Well somebody doesn't know how machining works...
-AM3

 

[harley1985]

hmm if i wanted a douche bag answer then i suppose i went to the rite place. a simple yes or no would suffice. it is not a half ass approach. the bottom end is new, less than 30k in it. like i said before the engine is in perfect running condition. there is no need to open the bottom end. all i want to do is get it machined so i can put a MHG on it. thanks anyhow, now go beat your dog.