Head porting, pocket porting,...is it worth it to me? School me

I like big hp numbers as much as the next guy.  But let's face it, usually they are achieved at high rpm.  Nothing wrong with high rpm at all.  On a race track or in a race.  I like to make power at much lower rpm.  In other words I'm a torque fiend.  Most of my stuff is or will be off road or towing oriented.  Not SCORE or desert racing off road but expedition type stuff.  Bigger tires, adventure trailer with dirt bikes in tow, mountains, that sort of thing.  I wish every engine had the same characteristics as a TDI.  I'm one for an RV cam and maybe even one that's just a hair advanced.  So my question is this:

will I benefit from pocket porting, full porting, or should I just leave the heads as cast?  I'm referring to garden variety domestic gasoline engines - both V8 and I6.  

Thanks.

I think you want to check out OldSkewlToy's THE Porting Thread.

I am no professional, but my philosophies are:

An engine is an air pump - make it easy for the engine to pump that air in and out. 

Make where the air goes SMOOTH.  A smooth waterslide is funner than a not smooth fat boy waterslide.

SMOOTH is more important than BIG. The exiting exhaust helps scavenge the cylinder AND help draw in the intake air; if the ports are too big, scavenging is less effective at lower speeds.

You likely spend 99% of your driving below 5000rpm, so don't worry so much about big port volume.

You want to watch this: Cylinder Head Games–How Big Is Too Big - Engine Masters Ep. 28

And (not porting related) advance your cam for more low-end torque, not retard it.

I also like TIGHT lobe separation - they tend to scavenge better, but they take away from the idle and the top end and give you a peaky torque cruve.  Keep duration in the RPM range you want to run, and tight lobe separation to maximize torque. But that's -my-opinion.

Advance: my bad

Seems that a good bit of 'THE Porting Thread' got destroyed by the photobucket fiasco.

That engine masters episode answers everything. With a mild motor, just do mild mods. Clean up the ports, a traffic friendly cam. IHE and call it good. 

I did just a minor hand clean up of the ports on a Ford 3.8.  Just rounded any sharp edges and got rid of slag and a little port matching to the intake and the exaust (far from perfect) and then had the heads skimmed/trued and my but dyno noticed an improvement. 

Smooth slippery holes are always better.

This is just butt-dyno anecdotal evidence so take it for what it's worth.

One of the engines I have loved the most out of all the small block variants from various manufacturers that I have driven was the Buick 350.

That little motor felt like it had gobs of low-end grunt. Far more than any Chevy or Ford offering in similar displacements.

I've been told that it was because they used smaller intake valves and ports to keep the air velocity up at lower rpm. That makes sense considering everything was done by 4500rpm.

That engine is what made me give up on high horsepower number and start looking at big flat torque curves that start at 2000rpm or less. That's where all the fun is.

Trans_Maro said:

This is just butt-dyno anecdotal evidence so take it for what it's worth.

One of the engines I have loved the most out of all the small block variants from various manufacturers that I have driven was the Buick 350.

That little motor felt like it had gobs of low-end grunt. Far more than any Chevy or Ford offering in similar displacements.

I've been told that it was because they used smaller intake valves and ports to keep the air velocity up at lower rpm. That makes sense considering everything was done by 4500rpm.

That engine is what made me give up on high horsepower number and start looking at big flat torque curves that start at 2000rpm or less. That's where all the fun is.

My grandpa had a '74 Century with a Buick "350" in it back in the '80's.  He bragged and bragged about it.  He talked about how it was much stronger than any Chevy or Ford of that size because it was a "Buick".  Then it developed a rod knock.  No problem.  He took it down to a local shade tree mechanic we knew.  Said mechanic pulls the engine and finds 455 stamped on it.  You can't easily tell them apart.

In reply to A 401 CJ :

Well, adding displacement surely helps. 

This was absolutely a 350, they are different engine families.

Nothing interchanges between them except the oil filter and possibly the distributor.

Pontiac has had (almost) one block size for the whole run, the 301 and 265 are short-deck motors.

In reply to Trans_Maro :

Maybe.  But many have been fooled.  From the Wiki (which is always the final arbiter right? )

"Of all the GM 350 cu in (5.7 L)s, the Buick has the longest piston stroke. This design characteristic made the engine significantly wider than the others — essentially the same as the Buick big-blocks, which have the shortest stroke of the GM big-blocks. The 350s over-sized intake manifold and conventionally-angled valve covers resembling those of the big block allow it to be superficially mistaken for larger engine."

A 401 CJ said:

In reply to Trans_Maro :

Maybe.  But many have been fooled.  From the Wiki (which is always the final arbiter right? )

 

"Of all the GM 350 cu in (5.7 L)s, the Buick has the longest piston stroke. This design characteristic made the engine significantly wider than the others — essentially the same as the Buick big-blocks, which have the shortest stroke of the GM big-blocks. The 350s over-sized intake manifold and conventionally-angled valve covers resembling those of the big block allow it to be superficially mistaken for larger engine."

ThaThaTha That's All Folks................. Buicks were My Fav.   10 yrs back I had built a car for the Challenge using a 455 It was a Hell Of a Car In the Mountains 

So I popped the valves out of this thing and that was a job in of itself.  Most were stuck solidly closed and had to be hammered out with a brass drift.  I'm hoping that points to having new guides and having never been run.  Again, this thing was supposedly freshly rebuilt in the early '90's and never fired.  Anyway, I couldn't believe the mess I found under there concerning the rough casting.  'Rough' is the key word.  There are barbs in here that I just cannot believe.  i can't wait to start smoothing it out.  The valves and seats look good.  I plan to lap them and just put it all back together.    

Be careful what you do.  Smooth is not neccecarily good, if you have a carburetor.  A certain amount of roughness on the intake ports creates a bit of turbulence that keeps the fuel suspended in the air flow. 

And i like Oldsmobile v8's.

Here's my 2 cents. 

Just port match, and clean up the exhaust ports. "Gasket Match" is the usual term. This was the advice I was given by the guy that taught me to wrench, and, along with a light head skimming, always gave me a noticeable butt-dyno change. People like OST can get great gains from rethinking what they did at the factory, but we mortals can screw up a lot if we start porting heads all willy nilly. Think grinding through to water jackets, reducing performance by screwing up velocity, and all other manner of other potentially bad things.

I also have to point out, someone who knows what they are doing (like OST), TESTS. He starts out with a foam cast to see what's going on, uses a flow bench to confirm he is making improvements, and hundreds of other things. 

If you're not making them BIGGER, you don't risk the water jackets.

General consensus out there (and David Vizard is a VERY good source) suggest that port matching produces minimal gains. Smoothing the bowls has huge gains.

Of course, it really matters just how bad the factory ports are to begin with.

Bare Buick 350 blocks are not what I would call "small" vs something like a Ford 302. 

Was looking at the cam card for the Comp "Baby Thumpr" for LS engines yesterday. Tight LSA, doesn't seem like insane lift, I would be curious about a similar grind for something like this motor and stated torque curve goals. 

Many moons ago I rebuilt an SR20DET after the oil pump E36 M3 the bed and munched all the bearings. While I had it apart I used some sanding flaps on a die grinder to smooth out all the rough castings and sharp edges in the head. I also did the same to the compressor housing on the stock turbo. I was very surprised how much of a difference it made in the ole butt dyno. 

I see no reason NOT to gasket match and smooth ports in anything im building.  Mass produced castings are chock full of places to make small gains that add up to moderate gains for little effort. 

^^^ I agree.

As Duster said, and have them cleaned up,new valve guides, and throw in a 3 angle valve job.

Anybody remember the mototune guy? He was a big proponent of the smaller ports camp. I remember his advice from a long time ago, make the intake ports as small as you can without reducing flow. Basically he wanted to fill in all the dead space in the port so that the entire port volume was contributing to ramming in air. He also liked having a slightly rough surface to keep the fuel/air mix evenly distributed.

freetors said:

Anybody remember the mototune guy? He was a big proponent of the smaller ports camp. I remember his advice from a long time ago, make the intake ports as small as you can without reducing flow. Basically he wanted to fill in all the dead space in the port so that the entire port volume was contributing to ramming in air. He also liked having a slightly rough surface to keep the fuel/air mix evenly distributed.

There does seem to be a school of thought that says it will flow better if left a bit rough.  That's kind of why I posed the question.  I'm not like most who are trying to gain peak hp to better their track times.  That's the end goal most are after who fock with their cylinder heads.  I'm going to clean up the bowls and see what happens.  But it might be awhile since I don't have a vehicle for this engine.  I just want to make it run so I can either use it in a Jeep or truck or sacrifice it to the List Of Craigs. 

Rough is relative. 

In David Vizard's books, he mentions that the finish left by abrasive stones are what you want. Not rough casting but not polished smooth either.

On the exhaust side, polish is desirable to prevent carbon buildup.