Has anyone shaved off their VG heads a bit to increase the compression ratio? I am aiming for a compression ratio of 10:1 (It's 9:1 Standard).

 

shaving heads is not recommended at all. i especially wouldn't do it due to the engine being an interference engine but the biggest reason is it will mess with the timing part of it (the timing belt might be too slack or many other things).

for higher compression your best bet is to just get custom pistons made for higher compression... but even then, you won't get much power out of an n/a vg. maybe the vg33e with Q pistons but personally, you'd be better off putting the time and money into a turbo setup.

not trying to shoot down your idea at all, just trying to point out it might be more work and/or money that its worth to stay n/a.

 

VE compression is more than VG's 8.5. What is the main difference from compression point of view: crank, pistons, gasket, head (4v)...??

 

8.5 to 1 compression ratio is for the twin turbo Z32, VG30DETT motor. Ours is the VG30E, plain old motor, used in max, and Z31 single turbo (VG30ET). Our specific motor has 9.0 to 1 compression according to the book here. You'd have to shave a crapload off the heads to get 10 to 1. You'll need high comp pistons to get that.

 

The two main factors that determine compression are the piston profile (dish, flat, dome) and the combustion chamber shape and volume (measured in cc's).

 

use rods and pistons from a VE or from a VG30DE. problem solved.

 

 

You may want to search online for options for an all-motor VG. Remember, VG's are in all kinds of Nissan cars and your definitely not the first person to try to build an all-motor VG. Check the 300zx forums, possibly even some Pathfinder forums, or even magazine articles online (I think I remember seeing a built VG33 in a pathfinder)

Edit: Just found this http://www.club-s12.org/board/archiv...hp/t-6231.html very high hp and tq with mostly Nissan parts.

 

after doing some calculations using the VG30DE rods and pistons in a VG30E would give you a compression ratio of roughly... 9:1. that is if the deck height and gasket thicknesses are the same. most of the compression gain in the VG30DE seems to be from the 44-46 cc combustion chamber compared to the VG30E's 55 cc or so.

if the VE has a larger combustion chamber volume like the VG does then you should have the same compression ratio as the VE using VE rods and pistons in the VG. however if its less like the VG-DE's then you probably won't notice many gains.


powerful all motor VG:
www.hekimianracing.com/nissan3lna.html

very, very, very expensive and doesn't produce too much torque. a stock VG30ET nearly pulls as much torque as that engine does.

 

I can't afford to do any of that. I'm getting my heads overhauled and the heads get resurfaced in the process and it doesn't cost any more to get more taken off. As somebody mentioned before, the combustion chamber has more volume in the E than the DE. I'm trying to counteract that by shaving some off. If I would have to shave a crapload off to get 10:1, the question is, how much can I shave off before the valves become dangerously close to the pistons?

 

Sir. Have you read anything that was posted? If you shave too much, you risk the valves hitting and risk ruining the cam timing. Anything more than the slightest cut just to true up the heads will change the above. And since you want to raise the compression by 1 point that's quite a bit of material. (as stated)

You could have material ADDED to the combustion chamber but you don't have the $ for that.

If you DON'T have the money to do it right, fix the car correctly and search for power with the traditional bolt ons. Your machine shop will know how much can SAFELY be cut w/o damage.

 

truthfully, by asking this you are telling us 2 things:
1. You do not have the money for a shop to build the engine for you.
2. You do not have the knowledge to properly build the motor, and need to have a shop do it for you.

Another problem with adding material to the combustion chamber is now you are messing with the airflow, you are more susceptible to hot spots, etc.

 

When I suggested adding material, it implies that it's done right. And used to improve airflow if possible. Not to arbitrarily add material where ever.

 

Here is an articles to help you understand. Again as stated, costly
http://www.fordmuscle.com/archives/2...arch/index.php

 

OK, so 10:1 is out of the question. What I'm saying is that I can have the heads shaved for FREE. If you had that offered to you, would you not try and find out how much can be shaved off? I guess I'll have a bit of a look when i take the heads off. Are you guys telling me that it would be a bad idea to shave 0.7 - 0.9mm off my heads? Surely, the valves wouldn't hit the pistons then.

 

you can not just throw rods and pistons from a VG30DE into a VG30E you have to do some modifying of the domed part of the pistons to make it work. otherwise the pistons will hit the bottom of the heads. I dont know if it is true but I dont think that the E heads have more volume than the DE heads due to the fact the VG heads are only 2 valves and the DE are 4. now because of that the DE pistons will hit the E heads without modifications. I should know I've done it. Kinda sucks when you have no instructions or advise to go on. You also have to modify the 2 lower bolts of the baffles taht sit above the crank, so that the corner of the rod does not hit them.

 

I think I'll go with an 0.5mm head shave which will give me 9.5:1 compression ratio. Nissan MUST have room for error with the distance from the valves to the pistons because when people blow head gaskets, they should get the heads resurfaced and there MUST be room to have that done.

 

Uh...yeah let us know how that turns out for you. \

 

have fun man..
when you break it, let me know. I have two spare engines in the shop.

 

I would love to see the shipping $$ on that....

 

Now we get into the real business, exact measures, (my question was not if pistons have rings or crayonwings, BUT exact measured difference VG-VE.)

VG: one cyl, 500cc compressed to 55 means 9:1
VE: one cyl, 500cc compressed to 45 means 11:1
---> Based on that, VE must have different piston with 5cc volume lowering compression. Again, asking ONLY facts, as I have not had these pistons on my carage table for measurin.


-94 FSM EM-97, compression ratio, says (lol) funny things:

VE: 10:0 'must mean' -->10.0:1 pressure 12.9kg/cm2
(VG: 9.0 'must mean' --> 9.0:1pressure 12.2kg/cm2)

Bore and stroke the same, so crank must be the same.

 

not necessarily...you could have 2 crank and rod combos that yield the same stroke. having the same bore and stoke just tells u the discplacement is the same... just ask old ford guys what the differences are between a stroked 302, 351W, 351C, 351W, 351M, 351HO, 351CJ and a 351BOSS

 

Geometrically piston movement (lenght) is defined only with crank (rotation diameter). Rod end (=piston) moves always exactly the same distance regardless of rod lenght.

Shorter rod, places piston 'lower'. Compression will follow, be less. This possibly is the VE rod -case if head cc is so much smaller than VG. Smbdy with actual measured numbers, VE vs VG?

 

I just checked my handy FSM. The resurfacing limit for the VG30 and the VE is .008" or .2 mm. The .008 includes what you may remove from the block. Generally, you won't need to "deck" a cast iron Nissan block so let's assume the maximum that Nissan allows to come off the head is .008" You may could get away with a little more but not by much. The car will never run because once you go out of the limits you won't even be able to get the slack out of the timing belt. I rebuilt a Mazda B2200 engine last year. I had to buy a reman head from a reputable head service because the original was toast, anyway they had milled the head .006" over the limit which I discovered when the timing belt was not even close to fitting. This was incovenient to me and my customer as well as the cost associated for that shop to get me a good head. I've done this for a living and I'm sure some of these others have. You should take the advice. Buy a Y pipe and enjoy the gains from that.

 

Has any body put vg30de pistons in a ve? What were the results? Better top/bottom end?

 

they're just designed differently due to using two extra valves. the VG30E has a sort of hemispherical head and that design makes it hard to get many valves in it. if you compare the E head to the DE head you'll see that the DE head is quite a bit flat where the valves are which makes it much easier to fit more valves in there.

Here's your standard VG30E head:



(from: http://www.redz31.com/pages/headwork.html)

A VG30DETT head:



(from: http://www.sportcompactcarweb.com/pr...scc_proj300zx/)

 

Have u got pics of piston heads, VG/VE?

 

VE heads. pics of the pistons of both are in the autozone link in the STICKIES.

 

Hate the place. Spend night lookin for pis-tons

found VE flats, = not what i wanted

 

I am finishing my VE30DE build today and used VG30DE pistons. I have pics if anyone is interested. I will post how she runs once I am done. Generally, raising compression will raise power across the board provided you don't go overkill and everything else is right. The VE30DE chamber is a "pentroof" design which is probably the most detonation resistant. An American wedge chamber would be more detonation prone. Pentroof heads are more forgiving when raising compression than other designs. The same shape is in the SR20DE head. People bore the SR20DE from 86mm to 87mm for the VG30DE piston and get 11.0 to 1 CR. This is a common mod on the N/A SR20 cars.

 

Pls yall ppl get the 3gen engine types right. Kinda hard to follow...

VG 30 E ------- 9.0:1

VE 30 DE ----- 10.0:1

 

I'm definitely inerested in seeing the results of your project. I'm going to do the same thing with the blown VE in my car right now.. it's just a matter of money.
one block is damaged from a broken rod... one has already been bored to 87.5mm.. one was overheated horribly... which one to rebuild? ugh.

but umm yeah.. I'd love to see the numbers and any issues you ran into with the pistons. I figure they shouldn't have a problem with the dome on the piston since the heads of both VE and VG30DE look almost identical around the combustion chambers.. I haven't measured, but I will when I get a chance.

 

yeah it is probably a lot easier to put the DE pistons in the VE maxima engine than the VG. the only thing is I wonder how much of a difference it would be? some dyno testing would be pretty handy right now. I was planning on doing some pulls with my car till the T-belt snapped, hopefully I'll get it put back together this weekend and see if it still has compression.

 

if it snapped while it was running, I guarantee you have a bunch of bent valves. don't even both putting it back together.

 

I never thought of the fact that the timing belt would get slacker! Thanks for pointing that out! I guess the inlet manifold wouldn't line up properly either if i took too much off. I'll talk to the guy at the rebuilding place and see what he thinks.

 

what do the heads/pistons from the mercury version of the VG30E look like, cause ford made nissan modify it so it was no longer an interference engine for those right, could we use any of those parts?

 

They have cavities for valves -if- both piston and valves out at same time. Takes pwr out as compression is less.

Cannot figure out how belt would be slack shavin heads only millimeter fractions.

 

It doesn't take much...

 

it doesnt' make the belt slack because the tensioner will simply pull it up.. but what happens is it changes the cam timing since there is physically less distance.
it's not much, but even a half degree can make a measureable difference in power. more losses than gains.

now if you had adjustable cam gears (which nobody makes for these cars), you could negate those issues.

you will also run into clearance problems with the lower intake manifold and the bolt holes and etc no lining up.

 

I am very interested! The only reason I haven't done it yet is because I was worried about clearance and timing issues. And I need my car on a daily basis. Now that someone has finally done something I can figure out if it's worth doing.