ported heads vs HP

will porting a set of heads on a good running factory stock engine that had decent flowing stock heads make any HP when putting the ported heads back on the stock engine without any other modifications on the stock engine ?. let's say the ported heads flowed 10% - 15% better.

 

Yes. move as much air efficiently as possible through the engine will make mo power.

 

Sold a nicely ported set of stage 1 valves heads to a board member years ago......he swapped out his stk heads and no other change.....if I recall he reported either a .4 second or .6 second gain in the quarter mile. He did have a small cam......but he had that b4. But sure it proves your question.....your gains might be less with stk cam and not changing valve size.......but ifbthe portingnis done right u will gain.

If done right.......had large valves put into a good set of port small valve heads on my own car once and I slowed down .5 cause they destroyed the short turn with the bowl hog when doing the valves.

So if ported correct yes

 

would you say the gain in power would come mostly at the upper rpms or across the board ?

 

My first thought, Larry, is how much effort it takes just for 1 second of E.T.

 

Heads are the key to making HP in all engines. Increased HP comes from high numbers at at the torque peak, and then the ability of the engine to breath at higher rpm, to hang onto that torque. Remember HP is just a math equation. Power is all about producing, and then sustaining torque over a larger rpm range than stock.

Even on a budget stock type build, the heads are the place to spend your money. Great return on investment, in performance with driveablity.

Good heads don't need a big cam to make power. To illustrate that, I offer this:

HP/intake duration at .050.. HP/intake dur is a stat I use to judge efficiency of a combination.

Larry Hymowitz's motor was an early lesson on this. That 600 HP engine has a 231 @. duration 050 camshaft.

It made 2.60HP per degree of intake duration @.050- That's exceptional. A good High Performance pump gas Buick BB engine, with no tuning or combo mistakes and "good" aluminum heads is closer to 2.3-2.4 HP per degree of duration.

That engine's HP/intake dur was only recently surpassed, by an engine identical to Larry's, save for 3 things:

• Fully ported Stage 2 SE heads flowing 361/254 cfm at .600
• a 222* @.050 camshaft
• it was a touch bigger-- 482 vs Larry's 470

It made 595TQ/595 HP and I recall being surprised, although I had built so many engines and worked on so many other from the time I degreed that cam, until we actually dynoed it, I could not exactly recall how big the cam was. It was slated to have one of my 237/245* roller cams in it, for a 600+ HP build. But after waiting almost 5 years, due to the supply chain/roller cam core shortage, we finally just built it with whatever roller cam I could come up with.

When I called my dyno operator to tell him how big the cam was, his response was "is that even possible?".

Here is the sheet on that new HP/intake duration/pump gas King engine.

It made 2.68 HP/intake dur.



I wish the customer did not live in New Hampshire, I sure would like to drive this engine. With my 3200 stall converter in it, this one is gonna flatten your eyeballs from the hit of the throttle till you let off.. assuming he can get it to hook.

The small cam made great torque at lower rpm, yet the free breathing intake/exhaust tracts allow the engine to continue to perform at high rpm.

And to top it all off, this engine will idle at 600-650 rpm in gear, with 15" of vacuum, and virtually no lope. Just enough to know it has a cam in it. Low speed, every day driving is very easy to get along with.. you could drive it to work in traffic every day if you wanted.

I would..

JW

 

Jim, what is the LSA on that cam?
Do you prefer a tighter 108, a wider 114, or something in between for a smaller cam?

 

Wow. 590 tq @ 3500. Better get some tire under that one. That is impressive all the way through range, Jim.

 

i know that sean that used to be a member here had a 350 that was making right at 300 hp just by head porting. So id say its worth it.

 

Walt,
Generally speaking, smaller cams can have a tighter lobe center.. the my experience says that in a 455 based Buick, you need to get that intake close *.050 number at about 42* ABDC, for a stock "sounding" engine.. very mild lope.. and frankly, the sooner the better.. this one's IVC is at 36*..

This one's actual LCS is 109.75, and it's installed at 105*.

JW

 

Hi Jim,
Looking forward to getting it back in the car soon (just got it picked up and unpacked yesterday) and giving feedback on the drivability on it. If you are ever find your way out to NH you can find out for yourself!

I am glad to see that the Stg II heads performed really well. I had CFM Performance in Indy do a full race port on them when I bought the heads about 8 years ago. I was happy with them on the last build but this is really letting them breathe.

 

Thanks Jim. I'll be trying a 108* LSA in my '66 401.
Solid lifter 224/230 @.050 duration, (262/270 @ adv. duration) Intake close @ 40 ABDC. Close to your 482 cam.
I figure a smaller cam will like a little more overlap (11* @ .050), and it's not so much as to have negative effects. I don't mind some lope.
The early closing intake does put my dynamic compression up to 8.32. I'll likely install it straight up.

My theory on ported heads is that a good valve job and bowl blend helps low lift flow significantly, and will help at all rpm ranges.
Next step would be reducing the valve guide obstructions.
Then for more high rpm power, open up the port where it's restricted.
Sure wish I had a flow bench to document the different stages of mods.