I am rebulding an engine in my auto class at school and was wondering how much I can bore out a VQ engine. Would it be possible to make it a 5 liter engine? I was thinking of taking pistons out a mustang and boring out my engine, then putting them in my car. Would this even be a good idea? I don't know too much about engines, I need some feedback on this one people.

-Chris

 

Dude what kind of autotech class are you taking? And no you can't really bore out a VQ that much, we got wet sleeves (or dry I don't remember the definitions, lol). Plus our motors don't have a long enought stroke to get a 5 liter, and I'm pretty sure that our pistons are just as big or bigger then a 5.0 pistons from a mustang. Last time I took one apart 3 years ago they didn't look that big.

 

1st off, that 5.0L mustang is an 8 cyl. Also meaning that if it just happened to only have 6 cylinders it would have a displacement of 5.0 * 6/8 = 3.75L which sounds very close to ford's 3.8L engine which isn't very far from a 3.0-3.5L 6cyl VQ, so the pistons probably are very close in size to ours already.

Also the VQ is an aluminum block, iron sleve setup meaning that if you go about boring the cylinders out, the iron sleeve would become thinner and thinner and would get so weak that it fractures. You could possibly push it to 3.1 or maybe 3.2 before it becomes too weak.

You'd also need to mate the pistons to the current rods or crankshaft, which would be a lot of custom work too.

Technically you could give the engine a longer stroke to attempt to increase displacement, but that would call for an different crankshaft and rods and making sure the piston sleeve is long enough. And you wouldn't be finished at just that, you'd need a newly designed, custom engineered camshaft set. And if that wasn't enough your compression is probably way too high to run on gasoline due to the longer stroke and would need to be lowered by re-engineering the cylinder head to have a slightly bigger displacement. In addition you've just increased the piston velocity at the same rpm, which would probably limit your top RPM to a lot lower value.

There are probably many other issues I left out due to my limited knowledge of auto engines.

Engines are a lot more complex than most people think, the tolerances for everything is very very tight. I'd recommend to ask your autoshop teacher or find some books on exactly this subject. Or another good place to start to learn about automotive stuff would be http://auto.howstuffworks.com/

I think it would be a lot easier just to custom bolt in a mustang 5.0 engine in your car and mate it with the FWD tranny than to re-engineer the whole engine like so. But then again, nobody ever has done that either.

 

Hoooollllyyy craaaaap.....

 

See what happens when you learn stuff =)

 

Our engines have an open-deck design so you can pretty much forget about boring it. As it is, the VQ already has a pretty large bore 93 mm IIRC

And like Drew said earlier, the only option would be to stroke the engine. But the hardest thing about that would be to get someone to custom make a new crank. Good luck finding that...

 

Wow! I didn't know that there was soo much involved. Thanks for the useful information.

 

It's not like it was never done before. Some dude bored it out to 3.2L. Someone with search capabilities find the thread for these kids.
And the dude thinking of boring it out to 5.0L, you might want to forget AUTO TECH and consider Home Economics, cooking and stuff.

 

There was a thread in offtopic a while ago. Nissan took the VQ35 and made a stroker motor for a VQ40 which will be in some models in 05 (Pathfinder Armada and something else I believe). There is some room to bore on the VQ30 and VQ35, but not much. SteVTEC went over all the details a while ago. However, comparitively, there is more room to bore and stroke a VQ than a few of the honda motors IIRC from his post.

 

Dude, that's why I was asking the question. You don't have to be an @sshole about it!

 

Supermax, Im sorry, the reason your getting bashed here is one Im not sure if you, but the legendary 5.0 was a v8 to start with. we have 6 cylinders at 3 liters. That is where a lot of the displacement came from in the stang. For you to say you wanna bore out a 3.0 to more than 2/3's it size is really radical, think about it, do you see how 3.0 to 3.2 seems more believable as compared to3.0 to 5.0. Going from 2/10ths of a liter to 2 liters is basically the additional pistons. Read up a little bit man, you are talking bout boring out blocks, but in order to do anything mechanical, knowledge is the most important tool you can bring to the shop. I'm not flaming you, just giving some insight as well as constructive criticism.

Holla.

p.s. the size of the piston is not the only factor in determining displacement, you also have to measure the stroke.

 

JUN tuning made a 3.8l vq30det making 750 whp and its sitting in a 350z right now.

 

I believe Daniel B. Martin said that teh VQ30 can be bored to a 3.3


Torgus: got a link? You sure they didn't bore teh VQ35?

 

i read it in my buddies magazine. if your really interested i can get pics and stuff...i'll scan in the artical. it was 100% definitly a vq30, thats why he showed me it...he's on the org but doesn't post often...it happens to be the same guy who has nashua's magical headers! JUN tuning did a ton of work on it. intake manifold is all knew the engine is also turned 90 degrees. and that would mean, unles i'm wrong here...that they mated it up to a rwd setup...arn't all 350's rwd?

 

Yup, 350's are RWD. THey prob used teh original VQ30DET from the cedric/gloria/cima.