rangerob

iTrader: (1)

My friend told me to call this shop and they said that they would port and polish my heads for 3 or $400. Is this a good deal, and should i get it done? I know nothing about porting and polishing. I just got a ZO6 cam for Xmas and im puting that in myself on thurs. How agressive should i get them ported?
(2002camaro Z28, 326.8hp, 333.6tq) thanks.

ZoDDy

Well i recommend you NOT to polish the inlets.. This is an old thing.. no pro engine builder polish the inlets today. Rough is good.. the air will not stick to the walls... and helps the air/fuel to mix better and stay away from the inlet walls!

And if somebody recommend you to polish iīm starting to wonder what company doing this today? It will make everything more worse

Porting the heads is also a thing you should be very careful about.
Enlarging the inlets might destroy everything. Itīs not about the flow...
Itīs about the airspeed too.. the velocity in one direction. Not the other way (backpuls)

The performance in your engine/heads depends om what type of port you have.. The flow structure in the cylinder is matched with the design of your heads and ports.. In other words again, how the air/fuel enter into the cylinder. In what speed and direction. The type of flow structures has differen't names.

Swirl and tumbling.. is two of them. Swirl is a vortex effect usually happen in 2 valve engines.. (not always) and in 4 valve engines tumbling is very common coz it's almost impossible to get the vortex effect with 2 inlet valves so close to eachother.

Lotīs of ppl want your money, but i bet the original flow in the LS1 heads will take you very far. The ppl that's behind the chevy engine is no idiots.
Lotīs of research and testing made this engine from scratch. The thing is that the tolerances can't be kept in the massproduction so there is some possibility to do some touchup in the end. But you must know that ya doing!!

goober35

iTrader: (1)

Zoddy have you seen any of the ls1/ls6 port and polish jobs. They all have smouthed out inlets.

here is a site for you.
http://www.absolutespeedls1.net/

BergerMan

Goober, he is talking about smoothing and polishing the intake runnners which is NOT what you want. The surface must be a little rough from the porting or cnc tool to help mix & atomize the air/fuel charge. Now on the other hand, smoothing and polishing the exhaust port and the combustion chambers is a different story. Having those smoothed out will help keep carbon from building up.

ZoDDy

Bergerman is right, I meant the suface, not the shape of the inlet runner.. The shape and the smoothness inside the runner can improve the flow and airspeed. One very critical point for the flow and airspeed is the choke point and the bowl just inside the inlet valve.

On all V8's it's very important 2 do a good port job, everything is times 8.
2 poor runners is bad... but 8 poor runners really sux.. The total power loss will be very big.

I've done some testing trough the years.. And i found out what lot's of stuff that ppl do like portmatching can make things more worse too. I got a real good experiance with a strange testing i did a couple of years ago.

I got a head from a friend, it was overported & really hopeless.. the engine felt very weak.. It's hard to describe but the engine felt dead. The same feeling like you have too little ignition advance

I tested lot's of things but no go until i tried the unported original inletmanifold. The inlet was suited for DCOE Weber carbs and has lot's smaller runners.

I got a big step between the inlet runner and the inletmanifold (the inlet was bigger and inletmanifold was smaller)... Guess what?, the engine woke up... and the difference was huge.. the pickup from the low end was very good all the way up to the redline.

This time i had no idea why this happend.. today i know! The big inlet runner also flowed backward.. the pumping loss was huge and the step between inlet and inlet manifold probably stopped it or slowed it down a little.
I still use this technique, but i prefere to have a smaller inlet and aim for a runner without any deadspots..

High flowing ports can flow very high backward too, if they are not correctly ported! I can't tell if this work's on all heads, impossible! But i'm trying, i have now started to buy heads from all manufactures in the world.. One head from every car, traktor, aeroplane and bike that ever been made..
From A-Ford, all the European cars, Japs and the US muscle heads you name it!! I think i need to build a bigger garage