why does no one bore?

[yota-runner]

I always see people asking how to get more HP and it seems the SC is the go to option, but why do i never see anyone on here bore their cylinders. I wouldn't think this would make your vehicle any less reliable than a SC would. But what do i know? I'm not a doctor.

 

[TheeMikeB]

I always see people asking how to get more HP and it seems the SC is the go to option, but why do i never see anyone on here bore their cylinders. I wouldn't think this would make your vehicle any less reliable than a SC would. But what do i know? I'm not a doctor.

My first thought is that a SC is bolt on HP, boring cylinders is a major rebuild.

 

[yota-runner]

My first thought is that a SC is bolt on HP, boring cylinders is a major rebuild.

This is true. Although to properly supercharge shouldn't you upgrade internals anyway?

 

[Whitson Metalworks]

Boring won't get you far either, MAYBE to 3.6 liters, and that would include a lot of machine shop billzz and buying new over sized pistons.

 

[SCRunner12]

This is true. Although to properly supercharge shouldn't you upgrade internals anyway?

Injectors and new spark plugs, but most people leave the heads, pistons and such alone. It mostly additional bolt on items or tuning that adds the extra horsepower with a supercharger.

Pretty much as others said it's a lot of work for not that great of a $ to HP gain. One member matt starr bored out his 3.4 a long time ago, but I can't remember how much extra hp he got, but I remember reading he did say there was a noticeable power gain. I'll look for it.

EDIT: Here's one thread, but I thought there was another. This one doesn't give many details on what was actually done. http://www.toyota-4runner.org/3rd-gen-t4rs/48407-dream-project-might-coming-true.html

 

[chimpy]

:snacker:

 

[BigFishAllDay]

I would think that porting & polishing the heads and lower intake manifold would make a bigger difference for less money, while not requiring a full rebuild. I guess if you were having the engine rebuilt, then why not go for it, and check into some cams, too. Also, I wouldn't be surprised if I learned that there was limited room/material thickness available to bore out a 5VZ block.

I'd be looking at the options if I were doing a re-build, but for someone starting out with a healthy motor, the answer is simple...

$$$$ : benefit ratio.

BTW, edit:

This is true. Although to properly supercharge shouldn't you upgrade internals anyway?

No. Plenty of us are "properly" supercharged, and still running stock internals.

 

[yota-runner]

Injectors and new spark plugs, but most people leave the heads, pistons and such alone. It mostly additional bolt on items or tuning that adds the extra horsepower with a supercharger.

Pretty much as others said it's a lot of work for not that great of a $ to HP gain. One member matt starr bored out his 3.4 a long time ago, but I can't remember how much extra hp he got, but I remember reading he did say there was a noticeable power gain. I'll look for it.

cool I'd like to see that

 

[yota-runner]

I would think that porting & polishing the heads and lower intake manifold would make a bigger difference for less money, while not requiring a full rebuild. I guess if you were having the engine rebuilt, then why not go for it, and check into some cams, too. Also, I wouldn't be surprised if I learned that there was limited room/material thickness available to bore out a 5VZ block.

I'd be looking at the options if I were doing a re-build, but for someone starting out with a healthy motor, the answer is simple...

$$$$ : benefit ratio.

BTW, edit:



No. Plenty of us are "properly" supercharged, and still running stock internals.

I see, and wasn't trying to imply that you or anyone else here did it wrong. I just remember a buddy of mine having to do all the internals before he SCed his car. Then again he was working with 800+ HP.

 

[hoe_nah]

pretty much comes down to $$$...if I were to bore out my motor add pistons, I'd add everything to my build from cams to os valves etc etc etc. then on top of that add the s/c lol.

ps, I'm actually looking to find a spare motor to do this hahaha

 

[PitbullRescuer]

Boring = thinner cylinder walls = hotter running engine = less reliable. (Not to mention hitter running engine produce less power).

I get what you were after here and in theory you're right. But the Toyota engineers did a good job on this motor as is. Unless you need to bore for a cylinder wall issue, it's just isn't worth it on these things.


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[mikebontoft]

which is where you install a lower temp thermostat and reprogram fans to come on earlier... but still, it has thinner walls.

 

[Skidmarcx]

I'd rather drop an LS motor and switch out the axles than bore this motor... SC is easier bolt on power

 

[Dous]

LC Engineering built a 5vz-FE a few months ago that made 300 HP N/A

"300 HP 320 Torque, naturally aspirated 5VZEF V6 built at LC Engineering, bored .20 over, 12 to 1 compression ratio, chromoly I beam connecting rods, forged crankshaft, Ported and polished heads and intake."

 

[the great him]

^^^ it also needs 102 octane fuel nbd


LCE used to make a pro street version of this motor, that could run on pump gas, but i guess they stopped making that, cause at $12k no one bought one, i was going to after my up coming deployment but... ill probably just buy a used one, tear it down, rebuild it using LCE stuff like heads ect and then put an SC on it along with doug thorley headers and a larger throttle body and have the ECU tuned by LCE for the larger intake...

i probably wont bore it, cause as stated the cylinder wall thickness becomes an issue and so does the long term durability and reliability. what LCE did there with that motor is great for a race motor even in an endurance setting but its not a motor that anyone is planning on putting 100k+ miles on with out rebuilding. and thats something that i want

 

[snivilous]

Boring = thinner cylinder walls = hotter running engine = less reliable. (Not to mention hitter running engine produce less power).

Why does thinner walls means it runs hotter?

 

[the great him]

metal helps dissipate heat, and also with thinner walls the heat will have a much easier time warping the walls

 

[JayRolla]

Really??? run hotter?? I have seen many cars with bored blocks with zero temp change. My talon had .40 over pistons. You guys do relize when you bore its .20 up too usually .60 larger pistons. That is not much at all, not enough to really cause the motor to run hotter and cause a weaker side wall.

Most of the time people bore because there is scoring in the cylinder wall and its too much for just a honing job. They need to bore over to get a good cylinder wall for the pistons rings too seal correctly.

If you want to make more power from a rebuild you will get way more gains from more static compression bye replacing the pistons with dome top style pistons, higher lift cams and better flowing heads. Boring does really nothing compared too those other parts.

 

[the great him]

Really??? run hotter?? I have seen many cars with bored blocks with zero temp change. My talon had .40 over pistons. You guys do relize when you bore its .20 up too usually .60 larger pistons. That is not much at all, not enough to really cause the motor to run hotter and cause a weaker side wall.

Most of the time people bore because there is scoring in the cylinder wall and its too much for just a honing job. They need to bore over to get a good cylinder wall for the pistons rings too seal correctly.

If you want to make more power from a rebuild you will get way more gains from more static compression bye replacing the pistons with dome top style pistons, higher lift cams and better flowing heads. Boring does really nothing compared too those other parts.

yes but boring to increase displacement means at least .80 over and more... doing that can cause issues, thats why when engine builders build big displacement motors they will use high strength sleeves like titanium for cylinder walls they fight heat build up hold up better to abuse and are just all around better for high power and high stress. also with increasing piston size your are increasing the rotating mass and with thinner stock walls this can become an issue. -again that is all from going with a bore that will yield noticeable gains... like you said though your typical bore to clean up the cylinders will not give you anything noticeable even to a dyno. i dont see boring a really effective way of increasing power, id rather put the money into a longer throw crank if it is possible to give me more torque

 

[Swimmerboy2112]

For what it's worth. Both my Tacoma and 4Runner are supercharged. I've never had it dyno'd but i'm willing to bet the Taco is somewhere in the 300hp range and both of them are on factory internals. One at 86K, the other at 142K.