Boring motor.

[Doc2012]

Here's my dilemma.

My #3 cylinder has some obvious issues with it.

When I blew the HG in August, [MENTION=59542]Singtoe[/MENTION] and I noticed some scoring on the walls when we took her apart.

I've been debating on doing a V8 swap, but don't have the time, patience to deal with the wiring, or the money to do so. At least not right now.

I can get a 3.4 from a guy I know for about 600. Swap that one in, then rebuild this one slowly.

My question is, at what point is the boring of the cylinder too much? I've read up on this on TTORA, and some other sites. I'm not talking about going .030 over, just enough to smooth out the cylinder. These motors don't have very thick cylinder walls to begin with, so there's not a snow balls chance in hell that I would go more than .020.

I won't be adding a turbo or a SC, just leaving it NA. Not looking for massive power gains, but while I'm doing rebuilding the motor, I might as well have some head work and such done to it, just to get a little more out of it.

What say ye fellows of T4R?

 

[Swimmerboy2112]

Here's my dilemma.

My #3 cylinder has some obvious issues with it.

When I blew the HG in August, [MENTION=59542]Singtoe[/MENTION] and I noticed some scoring on the walls when we took her apart.

I've been debating on doing a V8 swap, but don't have the time, patience to deal with the wiring, or the money to do so. At least not right now.

I can get a 3.4 from a guy I know for about 600. Swap that one in, then rebuild this one slowly.

My question is, at what point is the boring of the cylinder too much? I've read up on this on TTORA, and some other sites. I'm not talking about going .030 over, just enough to smooth out the cylinder. These motors don't have very thick cylinder walls to begin with, so there's not a snow balls chance in hell that I would go more than .020.

I won't be adding a turbo or a SC, just leaving it NA. Not looking for massive power gains, but while I'm doing rebuilding the motor, I might as well have some head work and such done to it, just to get a little more out of it.

What say ye fellows of T4R?

$600 for a running motor is a good deal in my neck of the woods.

Regarding boring the motor, I have read over on CustomTacos that .040 is the max you could bring it out to, although I would be hesitant to go more than .020 over.

Regarding bringing out the power, look into the 3VZ-FE cams in the 3.4, supposedly they up the hp and torque and bring it into a more useable range although I can't confirm anyone doing the swap.

Other than that, if you can swing it, headers are best to be done when the motor is out of the vehicle although you won't see much hp & tq gain on a N/A setup.

 

[nor_cal51501]

Glad to hear you ask this, I'm hoping to eventually build a motor myself and want to hear the info. As a side note, its important to know which cylinder bore you have stock. These 3.4l came with three different stock bores and are marked on the cylinder. Here is the info for you. Keep us posted. View attachment Cylinder Bore differences FSM.pdf

 

[Whitson Metalworks]

Boring is going to add a lot of cost for extremely minimal gains. Price a set of oversized pistons, ouch. I don't think you'd see or feel any appreciable power with what little you can bore a 3.4. Head work on the other hand could be great, if the guy knows what he's doing...

 

[KidVermicious]

What say ye fellows of T4R?

I like the idea of swapping in a used motor to buy time, but I'd suggest you hear it run first. I made the mistake of swapping an unknown motor into the Bastard, and it turned out to be worse than the one I took out. Then, I'd strip down the block you have now and take it into the machinist. They can check the cylinders and tell you exactly what needs to happen or whether a repair is feasible at all, and then you can make an informed decision. Once you find out how bad it is, you might decide it's worth your money and effort to find another block for your slow rebuild.

Also, I read the thread title "boring motor" and I thought to myself "Doc's engine must not be very exciting, maybe he needs a little strange". If you know you're not happy with the 3.4, get the damned 1UZ swap going already. Dumping money into a rebuild when you don't like the motor in the first place is waste of money IMO.

 

[TheKorstjens]

Is it minor enough you could just hone it and use factory sized pistons a rings?

 

[shadyluke]

I would swap in the $600 motor and be done. If you really want to build a motor build an LS for it. Way more options.

 

[nissanh]

Rebuilt toyota engines won't last as long as a good used toyota engine.
If you can get OEM toyota standard sleeves and pistons/rings, then you might build a good engine.

 

[Singtoe]

I agree, the 5vz-fe is a boring motor.


Use the money and get that Sequoia motor from Hickory...:guitar3:

 

[txclimber]

I have bored out every engine I've rebuilt and I see no reason yours should be different. It's not a matter of seeking increased power, but rather restoring a perfectly round shape without loosing compression.

After 200k miles or whatever you have, your cylinders will be slightly oval shaped. No amount of polishing will get rid of this. Round rings/pistons in an oval shaped cylinder won't fit as well as they could, losing compression.

If you're going through all the trouble of a rebuild, don't you want the result to be that of a tight, fresh engine?

Also, you can't just bore it over "a little". It has to be at a set measurement so you can buy the appropriate pistons at that same set size.

Best practice is to take block and crankshaft into machine shop. They'll put the mic on it and tell you how much they have to bore out the block to make it right. They'll also check your crank to see if it's out of round. They will then tell you if it can be bored out or if the wear is "too much" (your original question).

Then they will tell you what size pistons and rings to go buy. That's really the only way to get a rebuild that is worth the time/trouble.

The machine shop guy is your best friend here, and the only one with the proper tools and setup to answer these questions.