300zmax

i want to shave the heads of my vg and bring the compression to 10:1. i plan on porting the heads and running JWT stage 2 cams.

is there any other alternatives to raising compression N/A

BenStoked

iTrader: (7)

pistons, would require less machining, but could be more expensive

3g94MaxGXE

If you mean to make power...not really. I don't mean to demean you by giving this elementary response but your engine makes power out of pressure. More fuel pressure + more air pressure = more power.

You can get fancy cams, port everything and etc. and maybe make your target horsepower. If you want to go to the extreme though while still staying naturally aspirated you can try porting everything from the intake manifold up or replacing these components with parts with bigger inside diameters. Though to me this seems like a waste.

You can try ram air, it works for Pontiac! Though...ram air provides more benefit at high speeds so I would expect the butt dyno to work better than the dyno for this mod.

Now of course you can change compression ratio. I wouldn't shave the heads though, there is no replacement for displacement. If you want a high compression ratio it would be in my opinion better to find some higher compression pistons of equal or greater quality to the stock ones. You may need to bore your engine out to get the pistons you like to fit, further increasing your power through the extra displacement. You could stroke the engine possibly though I've never heard of a kit for the VG and I can imagine it would be a very difficult thing to do yourself.

I hope this post helps you, I don't quite get your question.

300zmax

for the confusion i apologize, i am planning on raising the compression on my engine to 10:1. is there anyway of doing this without out having to go as far as shaving the heads?

after increasing the compression i plan on porting the heads and install stage 2 cams.

BenStoked

iTrader: (7)

domed/less dished(dont think ours are dished, but it applies to any engine) will increase comp.
also:
using a thinner head gasket(unsure on stock thickness, but I know that using multiple/thicker gaskets will (significantly?) lower comp), of course, the shaving of the heads/block.
longer rods?

300zmax

i am rasing compression to 10:1 by shaving the heads, with additional mods

is there a better way to raise compression? while staying N/A

if i wanted to increase displacement i would drop in a vg33.

if you didnt understand before ranting, ask me to refrase the question. im bad at posting i can rewrite it

sleepyvg30e

iTrader: (1)

check out my thread on a rebuild that includes a performance engine kit that allows you to adjust compression between 8.5 and 10:1 its mainly pistons that will make a difference but if your doin this much work why not put in a turbo if youre raising compression thats gonna limit your turbo most guys say 8:1 is the best and its arguable but why spend so much on internals if your not going torbo later on?

Engine rebuild and transmission replacement

3g94MaxGXE

Ranting has a negative connotation. I was just trying to give you all the information I have relative to your plans lodged up between my ears in a timely manner.

You can basically pay attention to my third paragraph which is mostly about pistons. The reason I didn't name any displacements was because some cars come stock with forged pistons. If you could find a car with forged pistons stock a diameter that would fit in a 3-3.3 liter bored VG and provide a 10:1 CR then you can get some dirt cheap pistons in a junkyard or something. I agree with sleepy though, turbo would be better.

As far as pistons go MrGone posted a good list of piston sizes and displacements in a thread about the 3.4L 250hp VG engine. I hope he doesn't mind me borrowing it.

I found on this link that the VG33E has the following:
Bore: 91.5mm (3.602")
Stroke: 83mm (3.268")
CR: 8.9:1

I found on this site that the VH45DE has the following:
Bore: 93mm
Stroke: 82.7mm
CR: 10.2:1

The VG30E has the following:
Bore: 87mm (3.43")
Stroke: 83mm (3.27")
CR: 9:1

The VE30DE has the following:
Bore: 87mm (3.43")
Stroke: 83mm (3.27")
CR: 10:1

The VG30DE has the following:
Bore: 87mm (3.43")
Stroke: 83mm (3.27")
CR: 10.5:1

The VG30DETT has the following:
Bore: 87mm (3.43")
Stroke: 83mm (3.27")
CR: 8.5:1

I just came up with an easy answer. VG and VE pistons have the same stroke and bore and give 10:1 compression. So now all you have to do is find a VE parts car or someone parting one out, take the pistons and you should be able to expect about 175hp at the crank assuming everything else is stock.

If you want even higher compression the VG30DE from the Z32 300ZX will give you 10.5:1.

sleepyvg30e

iTrader: (1)

hey maybe he wants to run methanol instead of gasoline it would probably pay for itself eventually but if not good luck running premium dont forget to factor that cost in when compared to turbo which can actually save you gas

3g94MaxGXE

In theory it can save you gas. Most of the time when guys in turbo cars ask how they should drive people will say "avoid boost". So it doesn't always work that way. Supercharger, no debating that they will kill your gas mileage just a little bit.

jonmandude

iTrader: (1)

Let's avoid confusion with fact.

You cannot simply shave you cylinder heads to raise compression. There is not enough room for valve clearance. If you want to increase compression you will have to change the pistons.

To increase horsepower you will have to increase engine efficiency (air flow). The reason higher compression engines make more horsepower is because they squeeze more air/fuel into the combustion chamber. Doing things like polishing and porting the heads and intake, using larger diameter valves, boring the cylinders out, larger throttle bodies, larger exhaust, etc, helps the air flow more effieciently, thereby allowing you to burn more fuel creating more horsepower. Where turbo's and superchargers force the engine to flow more air (hence forced induction)

CMax03

iTrader: (3)

I wouldn't do that if I were you! You gonna screw up your cam timing! Only two options adjustable cam sprockets( if you mill the heads) or higher compression pistons!

300zmax

will i have valve clearance problems with ve pistons? i don't think the valve releafs will match. bur that is much much more helpful. and i will use z31 cam sprockets. i have a spare vg from my parts car that i want to build naturally aspirated, my buddy is a cubic inch guy, he think the vg can go past 250 with out a turbo.
thank you 3g94MaxGXE that list was a huge help!

BenStoked

iTrader: (7)

250ci... thats about... a 4 liter... biggest I have heard a vg block going safely is 3.4

300zmax

sorry i meant 250 bhp my bad. its early this morning havent woken up yet.

3g94MaxGXE

Glad to help man.

Matt93SE

iTrader: (44)

tons of aftermarket companies make higher compression pistons for the VG.

Before you do any work to it though, do some reading. There's lots of info out there on performance VG builds in the Z31 forums and even the pathfinder/frontier forums.

The other end of the coin is that rebuilding the engine, porting the heads, new aftermarket pistons (and rods), bearings, cams, and ECU will cost you in the neighborhood of $4500. do you really want to spend that much money on a $1200 car?

CapedCadaver

iTrader: (8)

if you want to possibly use the engine in another car later, then sure. like if you later on find a good z31 with no motor or something like that. or, hell, a frontier pickup

300zmax

you can have the same argument with any car really where you will kill the warranty or its blue booked at less than the mods but you point is valid, i will find the forums. thank you!

sleepyvg30e

iTrader: (1)

again check out my thread if wanna rebuild your engine if u send them the core you get a perfromance rebuild for $2400 you get all the pistons, bearings and cams you need (dont need rods stock VG rods are good for 700hp) and you can bore the block out included in that price all the way to a 3.3 or 3.4 now if you add $500 for head porting and another 400 for the ecu youre lookin at 3300

so youve got 30-40hp coming rorm the rebuild kit
you got another 30hp for head porting
if you factor in the engine bore you should hit 250hp no problem maybe even pass it throw in about $1000 in intake and exhaust mods and youll be nearing 300hp on N/A for about $4500
also dont let some of these guys discourage you most of people who sound negative about these cars have dumped way more then 5 grand into them

nismology

iTrader: (8)

Optimistic. Very optimistic. I'd love to see a monster n/a 3rd gen though.

300zmax

well cross your fingers im gonna try. i just need to prove that 250 hp can be made at the engine.

sleepyvg30e

iTrader: (1)

weel you can do it no problem if u got the mmoney and the want but remeber the transmission cant take alot of extra torque so upgrade that first cv shafts are good for 300hp but i think the rest of tranny will fail at 220tq

300zmax

i will keep that in mind if i do plan on dropping it in a car. right now i plan on it just seeing a dyno

BenStoked

iTrader: (7)

'zactly

internetautomar

iTrader: (30)

Cowl Induction is hardly worthless when designed properly. it is a VERY effective system when it is applied correctly, something that really can't be done on a FWD car.

BenStoked

iTrader: (7)

that is what I meant by "worthless"
and I still don't fully understand how the system works on a classic muscle car, but that is a different topic, for another forum (just gotta get the car...)... or I could google it, but I am too lazy.

internetautomar

iTrader: (30)

there is a low pressure front at the base of the windshield. The cowl induction system sucks that air in, which is colder and denser than the surrounding air. Colder/denser = more oxygen = moar powah.

3g94MaxGXE

I love it when you say moar for some reason. Makes sense though...in my middle school advanced academics class we did a bit of a study on airplanes as far as vortexes, drag, etc. goes and I can see how this would work.

CapedCadaver

iTrader: (8)

it's b/c on an carb'd RWD car the air filter is the ring-type, sitting right in front of the windshield. on fwd it isn't. some fwd I4's have the intake in the rear so that may work, but i have also seen some in the rear. there was a Geo i saw with the belts on the Driver side and the tranny on the Passenger side too... that was mighty weird.

so if you put on a pathfinder intake..... mebbe.... you can use a cowl effectively?

internetautomar

iTrader: (30)

you forget that the intake gets turned sideways when installed on the max, so you are back to the issue of the intake opening being off to the side.

CMax03

iTrader: (3)

I would like 2 add some positive to the negative... the lower windshield zone is a high pressure zone that helps cram the air into any intake whether carb/rwd or side mounted intake box such of ours. You can actually attach that air intake box via a flex tube to the cowl if you really want 2! Or mount a mid size intake scoop directly over the intake box with some foam you can do it...how it works in the rain is not clear to me though.

internetautomar

iTrader: (30)

oops I got pressures mixed up.
the high pressure is what also keeps the water out of the intake flow

Matt93SE

iTrader: (44)

Guys, get back to the topic of head mods or I'll have to lock this one too.
Hasn't there been enough BS around here already?

CapedCadaver

iTrader: (8)

has anyone ever successfully used RTV in lieu of a head gasket, with the purpose of slightly increasing compression? keyword 'successfully'? or is rtv's bond just simply too weak to hold the air in?

Matt93SE

iTrader: (44)

I wouldn't think of such a thing....

There's lots of better ways to increase compression than to pull something like that.

CapedCadaver

iTrader: (8)

k. i figured there was a reason i'd never heard of it..

internetautomar

iTrader: (30)

the silicone doesn't have the necessary strength to hold back 100+psi. heck it can't even hold back 15 psi.

CMax03

iTrader: (3)

This is an engine/air pump. Want more compression?...Buy yourself some Higher compression pistons...look @ raceengineering.com (website).

300zmax

Looking threw the website and all i see is wheel and moding wheels. having trouble finding high compression pistons for VG30e engine. lower compression is easy to find.

anyway took the heads from my parts car to be CC'd and flow check before i dive into cutting them up.