Port and polish

[Matthieu]

I was wondering If you port and polish a head for a b230ft. would it make a big difference in peformance. I thought if you run the same amount of boost the the engine would breath the same as if it was factory specs. just thinking technical . also if you port and polish would you use the same gaskets as stock.
thanks
Matt
1989 740wagon

[Captain Bondo]

imagine your ports were the size of drinking straws. You would need a lot of boost to make the same about of air go through them. The opposite is also true, making a port less restrictive will let it flow more air at the same pressure. However, it's definitely far more complicated than just "MAKE IT BIGGER!". I would read the whole "squish vs. quench" thread and linked article therein for a better view of the bigger picture. Also, I came across a book called "Modern Engine Tuning" that is good for people newer to the game. Should be able to snag it at the library.

But do read that thread and then post questions if you can, as it'd be cool to get the response from a newer person- might help compile an FAQ or something.

[Oskari]

Is that "modern engine tuning" written by Graham Bell?
If so, there is a lot of good points, but also information that has gone old,
part of the information is from 1988. if this is the same book we´re talking about.

[Captain Bondo]

Ya same one. Definitely some stuff in there that is out of date, but it helps with some of the general concepts as far as what happens inside the port and combustion chamber, etc. Just in my opinion. Really I don't think there is any book that contains 100% all info that everyone will agree on, but I think it is an ok place to start.

[Oskari]

I agree and after that one should read "Maximum boost" by Corky Bell, just bought that recently, i only wish that í had read it about 5 years ago, would have save me from a lot of trouble.

[qwkswede]

And while we are talking about books. The two mentioned above are very good. Also, Turbochargers by Hugh Macinnes is quite goood. It is a bit dated and some of the turbo models aren't even around anymore, but the technical information and theory is pretty good and can be applied still today. I have a collection of books like this. Its a good place to start when you are a beginner.

[mikep]

Just read anything/everything technical you can find. Some small details may have changed, but not the major concepts.
The best part about doing mods for me is knowing I did them, even if they don't make the earth shift off axis every time I launch.

[EricF]

Between reading Corky Bell's and Hugh MacInnes's books a few times, I feel like I could write a book of my own... Very good stuff.

[Boosted2003]

IM getting comptech to port and polish and put all new parts in my head with stiffer sprigns and 5angle valve job

[Captain Bondo]

"even if they don't make the earth shift off axis every time I launch."

LOL, I thought that said "sh*t off axis" first i read. Fell off my chair laughing. I was going to say, I do a mod and the earth doesn't **** off axis, I tear it off, burn it, urinate it, and start over. lol.

Anyways ya what everyone else said....
also,
www.theoldone.com has some really great (more advanced though) articles as well.

[Magnum TE]

AFAIK no one has dot any scientific tests with port and polishing a b230ft. What i mean by that is a base line dyno before doing the PnP and redynoing under the same conditions afterwords. If someone has done it, they havent talked about it, or posted any data.



Will it help? probably. How much? probably not that much on an otherwise stock moter. Correct me if I'm way off, but the results of a PnP will show up better on a higher tuned moter (big cam & turbo, higher CR) than an stock one.

From what I've seen the exahust side needs the most work (anyone else want to express their opinion on this), if you dont want to rip into the head- at least work the exahust manifold some. Port match, and get rid of as much of those bumps as you can reach... Header anyone?

.02

[Oskari]

AFAIK no one has dot any scientific tests with port and polishing a b230ft. What i mean by that is a base line dyno before doing the PnP and redynoing under the same conditions afterwords. If someone has done it, they havent talked about it, or posted any data.



Will it help? probably. How much? probably not that much on an otherwise stock moter. Correct me if I'm way off, but the results of a PnP will show up better on a higher tuned moter (big cam & turbo, higher CR) than an stock one.

From what I've seen the exahust side needs the most work (anyone else want to express their opinion on this), if you dont want to rip into the head- at least work the exahust manifold some. Port match, and get rid of as much of those bumps as you can reach... Header anyone?

.02

well i had 240hp, in my 2,3 liter with 9cr and @ 1 bar, stock 531 and a cam, chipped motronic injection.

new engine was 275hp 2,1 liter with 7,2cr and @ 1bar, group a head and cam, + carbs

turbo and exhaust side were same on both constructions.

Somebody wiser can calculate how much i gave power away with lower cr and displacement.

[mikep]

I am still collecting bits for a dyno flog. I have no clue when it will happen.

You could always claim that porting falls under Feng Shui mechanics.

I have not seen any back to back comparisons for a Volvo 2.1/2.3 8V. People often do the headwork along with other projects, and in those cases, its hard to seperate the headwork from the other changes.

I think its safe to say that a multiangle valve job is the best deal for the money, if you head is off and has to be rebuilt anyway. The next best deal for the money is a cam, because it will lift the valves open further and hold them open longer.

After that, you get into labor intensive headwork, and labor costs money. The gain per dollar goes down, but there remain extensive gains to be had. Any serious headwork will be accompanied by before and after flow testing, so if you can find people who have had serious headwork done, they will be able to provide you with numbers that show gains in CFM at a certain amount of water (vacuum) at various lift points for the valves, for both intake and exhaust. Peak numbers alone do not tell the whole story. You want to see gains all along the way, but at the same time, you do not want to "really open everything up" because you will lose gas speed at lower flow levels -- this is where the balancing act comes in. You can get good flow numbers from a fully worked "big valve" head, but the low end will suffer and that is not good if you spend a lot of time driving between 1000 and 3000 rpm. But above about that point, the car will be pretty entertaining -- fine if you have a 7000 rpm limit but if your limit is 6000 rpm then you just narrowed your power band considerably.

10% to 20% in CFM at 28 inches of water is reasonable to expect from moderate headwork. If the shop is doing just a port and polish, it probably is not flow testing (since that will cost more money) and is not doing anything radical due to the risk of having uneven ports or going through a water jacket, and the gains would be towards the bottom of that range. I don't have a formula for converting CFM improvement into horsepower gain, but roughly the power gain might be 2/3 of the CFM. I am not sure.

The good news is that whatever flow gains you get, and you should get some unless the work is done incompetently, the gains will be leveraged by the turbo. The turbo theoretically doubles airflow at about 15 psi, so the 10 hp you gain from the cam as tested on a non turbo motor or based on calculations derived from duration and lift improvements becomes 20 hp. And the 15 cfm or 10 hp you gained from the multi angle valve job becomes 20 hp.

The testing we did showed that the exhaust flow was valve limited. A bigger valve will make the head more efficient for higher boost levels. However, the Group A 240T used stock valve sizes and made great power from these heads (but I think that the heads were worked over even though the valve sizes were stock). Since you do not have Group A restraints, you can do better if you are having your head worked over significantly. Most experts seem to agree that for turbo use, the exhaust flow should be closer to the intake flow than for non turbo use. On the stock head you might see peak exhaust flow of about 115 CFM and peak intake flow of about 135 CFM. This is not a bad ratio -- in the range of 85%. The 531 head has the same exhaust flow, but significantly better intake flow -- maybe about 165 CFM, so the ratio goes down. This is not ideal for a turbo motor, but will make more power. If you could increase the exhaust valve size and do port work on the exhaust to restore the 85% ratio, the motor would be more efficient and might last longer and make more power. The other trick people do is to use an asymetrical cam that favors the exhaust. I am not sure if any stock or aftermarket Volvo cams fit this profile. The VX3 goes the other way -- it is asymetrical but favors the intake.

My recommendations are to invest in a better cam, do inexpensive light clean up work in the ports and chambers (like removing casting irregularities), have a multi angle valve job done, and leave it at that. If you have a little more to spend, ask about installing larger exhaust valves and porting the exhaust. If you have yet more to spend, lightly port the intake. If you have even more money, flow test everything so that the port work matches up.

Philip Bradley

[MikeSr.]

Makes sense to me to leave the work to a minimum in the turbo motor.
The name of the game is to improve volumetric efficiency-while extensive port work will improve n/a airflow, the turbo is cramming the air in, thus improvements that will allow better knock management and cylinder sealing would produce more gains/$
How about: O-ring head/block or Cutting Edge head gasket

Electronic engine management with knock sensor and boost/timing optimization, wideband o2 sensor. (Ultramegasquirt)

Water injection for high boost.

Allowing 20-25 lbs boost with these type of mods would push hp to 400+ on a typical 2.3 redblock
The Ford 2.3 guys seem to have found the solutions and frequently run boost levels this high

[Oskari]

Pbomsalb:

You are right, it all depends what you are lookin for about the engine,
theres no point to go all out with one part of it, and leave others stock,
big picture counts.


" I am not sure if any stock or aftermarket Volvo cams fit this profile."


Atleast kg trimming sells unsymmetrical cams for turbo use.

I sold just yesterday a grinded 280 degree cam with 10,5mm lift on the intake and 11,9mm exhaust side.

[mikep]

Pressurized air is thicker, and has a harder time getting past gross imperfections in a conduit.