Ported and polished?

[Ribz80]

It doesnt matter if its a 2.8 or 3.1 since the parts are the exact same.....atleast when it comes to anything other then the internals.    THe goal for porting and polishing is to go about 2" down into the runners.  Thats as far as you can get without shelling out big bucks for the extrune hone process.

[Chris88CL]

With a "pencil" attachment on a dremel you should be able to reach significantly further into the plenum to clean up rough casting if you go through the throttle body opening tho.

Chris
ICQ: 10833817
AIM: Chris88CL
lezarch@Hotmail.com

[Guest]

Alright lemme try to throw some info on here to clarify some things.

GEN II 2.8L 87-89 (89+ is Speed Density not Mass Air Flow)

GEN II 3.1L 90-93 (Differerences between this and the 2.8 are piston height and stroke, stroke went from 2.99" to 3.3122" which is the same as a 3.4.  Another minor difference was the eletronic EGR and some other small changes)

GEN III 3.1L 94-96 (Like 90% a different engine but, some parts are still interchangeable)


The intake setup on a Multiport Fuel-Injection system like ours is simple.  Air first travels in through the Throttle Body, which has a 52MM opening to let air through.  Then, it goes into the intake plenum (which is the part that says 2.8/3.1 or 310SFI on it).  The plenum holds a certain volume of air for the engine and also divides up the cylinders (air flow-wise).

On engines like ours, the intake runners begin in the plenum.  An intake runner is just the imple air tube that goes from the open area of the plenum to the opening on the car's head (which is where the air will be entering the cylinder afterwards).

Intake Runners are a certain set length and size if they are tuned on that engine.  If you look at the bottomside of one of the 2.8/3.1 Intake plenum's you will see how poorly the engine's runners are designed Out of tune,the 3100 has all the same length runners which makes the engine more in tune.

The purpose of tuned intake runners is because when the intake valve closes, the air is moving so fast it reverses and travels back up the runner.  Ifhe intake valve opened again when the air came back the runner would be in tune and the engine would be getting somewhat of a supercharging effect as it is easier for it to breathe.

An intake runner is tuned based upon the speed of sound I believe.  the air travels at a certain rate through the runner at a certain RPM.  So, you can make the runner long enough so the air travels back in the intake valve when it comes back down the runner.  Intake runners are not the full length they need to be for the air to only travel once down the runner and back so, you divide the calcualted length until it is a real world number and you can use it.  In other words, the air may just travel up and down the runner 8 times or however many it need be to be divided from the calculated full length.

Now what was I getting at, oh, more useless information.

The GEN II and III do NOT have any interchangeable (easily) top end parts above the heads.

Which means you cant mix and match unless you get crazy with some parts.

GEN II motors are not going to see the power gain from porting and polishing that a GEN III motor will.  The GEN II motor also needs MUCH more exhaust manifold and head port flow to run better.

The GEN II Plenum is a work of FART.  It purely sucks.  it is probably the worst design they could make.  Do not use it if you want to make nice power.  You can NEVER get all the cylinders perfect with it.  You are much better off starting out with the GEN III parts.

Back to P & P though.  If you get the Throttle Body first, don't put it on till you get the plenum done.  Don't get the plenum and intake manifold done seperately, you would be best off doing them exactly at the same time so the ports match up correctly.  But, if the lower ports on the intake manifold get ported you gotta port the heads aswell now.

And if you ported the Intake Manifold and Plenum, you gotta get a larger Throttle body.  So, NO, YOU CAN'T WIN!  Pretty much the best way is to just do the whole engine at once, every performance mod you need, that's what my rebuild will entail, hehehehe.

So basically what your best bet is.  If you have a GEN II do the exhaust side of the heads at least and the exhaust manifolds.  You will propbably see 5HP for now from that I bet.  But, it is like all those health people say about Marijuana, it is the gateway drug.  Just do the exhaust and you'll be getting into much heavier stuff after that.  You'll be addicted after a while, hehe.  (it's all just in your head though)

if you have a GEN III I'd probably say to go with the plenum and intake manifold.  Then afterwards pick up a 56mm or 60mm Throttle body (make sure you got the plenum bored coorrectly for the TB you will use, stock is 52MM).


Is that enough crapformation (information from Dave about cars) for you guys?

P.S. NONE OF THIS STUFF IS EASY TO DO WHATSOEVER.  If you can't tell me off the top of your head umm, hmm, what size mains you have or what size the wrist pins are you probably don't know enough.  (2.64" and .9052")  Or alright, what is the rod journal size?  (Everyone should know this one,
it's the same as a pre-68 Small Journal 327/350 motor.  Let's just say, the large journal is 2.1" and it's a little smaller.)


-Dave

[Canada]

What about those of use that are on a budget? I can't swing ported plenum and a TB at the same time.

[Chris88CL]

Quote (CoRpSe @ April 05 2002,02:31).......
GEN II 3.1L 90-93 (Differerences between this and the 2.8 are piston height and stroke, stroke went from 2.99" to 3.3122" which is the same as a 3.4.  Another minor difference was the eletronic EGR and some other small changes)
......

......
GEN II motors are not going to see the power gain from porting and polishing that a GEN III motor will.  The GEN II motor also needs MUCH more exhaust manifold and head port flow to run better.
......
The GEN II Plenum is a work of FART.  It purely sucks.  it is probably the worst design they could make.  Do not use it if you want to make nice power.  You can NEVER get all the cylinders perfect with it.  You are much better off starting out with the GEN III parts.
......
P.S. NONE OF THIS STUFF IS EASY TO DO WHATSOEVER.  If you can't tell me off the top of your head umm, hmm, what size mains you have or what size the wrist pins are you probably don't know enough.  (2.64" and .9052")  Or alright, what is the rod journal size?  (Everyone should know this one,
it's the same as a pre-68 Small Journal 327/350 motor.  Let's just say, the large journal is 2.1" and it's a little smaller.)
.......

-Dave
The electronic EGR was available on 2.8L's aswell before 90.  I know because my 89 2.9L had it which made it alot easier to switch to the 93 3.1L engine thats currently in my car.

And the Gen III motor already flows much better (what are the #'s, 17% better on intake and 39% better on exhaust due to the D shaped exhaust ports?) so Id be inclined to thinking that the gen II top end would benefit much more from the porting and polishing.  With the end results the Gen III might flow high numbers, but the Gen II would surely have the greatest increase.

And theres a difference between useful and useless information  Not everyone needs to use that information in their everday life which makes it useless to 90% of the people here.  Your not going to try and tell me that because I dont know what size the rod journals are in my engine that I dont know enough to port and polish an intake plenum.

Chris
ICQ: 10833817
AIM: Chris88CL
lezarch@hotmail.com

[MAJ28]

what are rod journals and what do they have to do with anything?  

[Guest]

If you want serious power from your gen2 mpfi. This is what I would do. (actaully I've been thinking about getting a 3.1 gen2 5speed beretta and doing this)

Put on the newest 3100 heads and intakes. This will require swaping some other parts and doing something about the EGR. Port and polish them before you put them on. Put in a nice cam shaft, good pistons & rods (high comp, or lower if going w/boost). I'd get an aluminum fly wheel and the pulley set. 62mm tb. You couldn't get steve hamms' headers though now because you'd have gen3 heads. If going turbo you'd have to have custom manifolds anyways. Or get the newest 3x00 manifolds, the rear one has a bit more tuned "runners" on it, but that would be for n/a or supercharged only.

But if you just want some more power for low cost, I'd say port and polish your upper/lower manifolds and buy a 62mm tb from franz. If you have more money get some headwork done.. if not then don't have the lower ports of the lower manifold ported as you don't want a big opening and then the air hitting a smaller opening where there would be a lip or ledge of the smaller opening on the heads...

As far as p&p'ing on the upper manifold is kind of pointless. As if you do the runners then you will run into the deal of the air hitting a restriction again when it goes into the lower manifold. And you gotta take off the upper manifold to port it for a tb, so might as well do the runners and then do the lower manifold as well.

Hmm. I really do like the idea of a project beretta. Hmmm. I need garage space though it would be fun though.

[Chris88CL]

Its great until you run out of money.  Trust me

Chris
ICQ: 10833817
AIM: Chris88CL
lezarch@hotmail.com

[Guest]

"With the end results the Gen III might flow high numbers, but the Gen II would surely have the greatest increase."

It would have a greater increase in potential due to inferior factory design.  As you may have noticed, the 3x00 motors have much better flow in the stock air intake setup then the older setup.  Which means, you are starting with a better base to work with.

If you stay with the Gen II setup you might see a greater increase in HP but, it will still never surpass the flow of the 3x00 top end.  And, it will also be out of tune in comparison with the 3x00 parts.

The reason why I mention such costly things that most people cannot afford is this;  if you modify one of the GEN II engines you will be spending much more money per HP as opposed to one of the 3x00 engines.  If you were to change over from the heads up to the 3x00 setup on an older GEN II engine you would be helping out the engine greatly.  It may be costly but, it is not that expensive in the grand scheme of things.

I could get the heads up off a 3100 for less then it would cost for the intake manifold and plenum to be done.  But, instead I would also be enlarging the exhaust ports, adding roller rockers, and also a much better flowing top end.

You would have a "hybrid" engine.  Some of the best of both worlds.

But, the way I see it, this would be the most cost effective but, the most addictive.

Next thing you know you will want the bottom end rebuilt while you are down there...  

One thing to note though is in doing all this you increased HP but also you will have fresh new stock parts to port out.  So, you paid as much as the porting job probably, but, you can still get that done and get a bigger increase in HP once again.


Just the way I see things.


I am poor too, so none of you can really complain, most of us ride the same boat, some of us are just more willing to make sacrifices.  (Who needs car insurance??  hehehe)

-Dave

[Chris88CL]

Thats if you can find Gen III engines in your local JY.  There arent ANY around here.  And theres only one yard here that might sometime stand a tiny chance of getting one and they'd charge me a hell of alot of money for the parts.
So if it comes down to porting the manifolds myself or spending $500+ (cdn funds) on a 3100/3400 top end I'll choose porting myself.  You'd need the exhaust manifolds aswell, and the 3100 downpipe is restrictive as hell.  Which means either screwing with that yourself or else paying for a mantapart unit.  Theres more money.  All when you can spend $100 total on a dremel (if you dont already own one) and do some minor porting and polishing of your intake manifolds.  Sure you might only see a 10-15 hp increase if your lucky, but its CHEAP and you dont spend forever looking for parts that are hard to find (around here anyways).
Thats just my opinion tho.  Your right.  If you have the resources then the Gen III top end is the best way to start your project if your serious about it.

Chris
ICQ: 10833817
AIM: Chris88CL
lezarch@hotmail.com

[MAJ28]

So corpse what you are saying is that I should convert the upper to a 3100 upper?  The way I read it, I would also need 3100 heads(for best results)?  And what is the difference between the heads?  How difficult is it to change the heads?  Wouldn't that also involve changing the springs?  Aren't the springs in the heads?  

Jason

[Guest]

Where can i find that gell for porting???

[Guest]

Do you have to convert anything if you get the 3100 heads and intake and put on a 2.8 im really curious about doing this...Im in the process of rebuilding a 2.8 and putting a high performance cam in it and flat top pistons...anything that is not tooooo expensive would be great...

[MAJ28]

I think the "gel" is some sort of super strong acid is the way I took it.  I personally would wanna try doing that at my house, playing with acids can be really dangerous, especially the ones that can eat metal.

Jason

I think I'll just port mine with my dremel...

[Guest]

What about a plenum from an older HO 2.8 with a distributor they where all equal length runners.  

Dan