HP gains after porting heads

[Broosedamoose]

How much HP do you think porting/polishing a set of aluminum heads yields? Is it worth pulling the heads? My engine is in and running but while I'm waiting for other stuff to be completed (exhaust, wiring, etc.) I was considering pulling the heads back off and sending them to the machine shop.

 

[Blmpkn]

What heads/what motor? There's a ton of variables that come into play. If the guy porting your heads sucks then your gonna lose power. If its a carbed motor your not going to want to polish, just port. Where are you looking for gains in the rpm range? Whats the compression ratio going to be? What are the specs on the cam?

There isn't a good answer to your question without a mountain of more details.

 

[gaz]

Broosedamoose,

If you have 5.0L, then you could make a noticable15-50 additional Hp, depending on the porting method, Porter and the rest of your set-up.

 

[Junglejoe]

My twisted wedge heads and explorer uppwr and lower i take has all been ported and.port matched. Now, I haven't fired it up yet or taken it to the dyno to be tuned.. it should be an an easy 35-40 hp over stock twisted wedge heads and intake

 

[RonD]

Its a percentage increase not an actual number in HP unless its measured on same engine before and after

i.e. a 200hp engine might show 220HP after just porting, so 10%
A 350HP engine might show 385HP after so 10%
But one is 20HP increase and the other 35HP increase
But 10% is probably a little high, lol

It also matters on how well the intake matches the head ports now, same for exhaust ports, they can be ported as well, but exhaust ports have thinner walls to coolant passages so you need to be careful

Porting is done to remove air turbulence from mismatched intake to head transition, so air movement is not slowed
So can be a big improvement if there is a big mismatch, or a little improvement if there's not, but ALWAYS an improvement

Not a fan of polishing, I think a bit of roughness on the surface at the edge of the air flow(boundary layer) keeps the fuel off that surface, so most of the fuel makes it into where you want it

 

[Ramcharger90]

All depends on the setup. I used port matched and polished gt40p heads I might be making 300-350hp im not sure I have some other things I have to do before tuning.

 

[Ramcharger90]

Weren't you the one who was having trouble with over heating after the aluminium heads were put on?

If so I would pull them and see if the small holes of the head gasket were towards the front of the block or the rear they need to be on the front of the block. I was looking for the original thread but couldn't find it.

 

[Junglejoe]

No.. haven't even started mine yet

 

[Junglejoe]

Porting also opens the whole system up to flow more air..

More air and fuel in and out..the more power it makes

 

[gw33gp]

Porting is more than just opening it up. You can actually go too far in opening it up which slows the velocity of the air flow and can make less power. I have seen this happen in races cars. Fortunately, it was my competition, not me.

I have my race car heads flowed by a professional that really knows how to do it. He maintains he can get more dynamic compression ratio by flowing the heads properly. He takes all things into consideration when flowing heads. He wants to know the specifics on the cam, lift, intake flow, static compression ratio, header style, etc. With all that has been done to my normally aspirated race car engine, it is over 100% increase in horsepower over stock. There is even more that I can do, but reliability become more of an issue.

Getting more power out of an engine usually requires more than changing just one thing. If you port it to get more flow, you may need more lift or larger valves to take advantage of that increased flow potential. Exhaust may need to be changed also.

 

[RonD]

"There is no replacement for displacement"

"Port" a 302 to a 390, then port the 390 to a 460

Joking............but "There is still no replacement for displacement"

 

[gw33gp]

Actually, there is a replacement for displacement. It is called light weight. My 1100CC, 1450 lb Austin Healey Sprite was beating up on some V8 powered Corvettes at a track I was at recently.

 

[Junglejoe]

You guy are correct. You can't just hog everything out.. it ALL has to be matched to cam, exhaust, compression.. ect..

 

[RonD]

Actually, there is a replacement for displacement. It is called light weight. My 1100CC, 1450 lb Austin Healey Sprite was beating up on some V8 powered Corvettes at a track I was at recently.

I think that would fall into the power to weight ratio category, lol

 

[Junglejoe]

I'll add to this..
Depending on if the pocket is ported and how much, you will lose some compression.
Then you need to mill the heads. Then if you mill the heads, sometimes you have to mill the intake also.
Its ok to "polish" on the exhaust side, but doing that on the intake side can cause things to puddle up and you don't want that happening