porting and polishing...

[exilous]

Is there a significant benfit to porting and polishing your heads and such? I did some research on the net and couldnt find definitive answers. I might give it a go on my heads that I'm putting on my dad has all the tools to do the job I was just wondering if it is like a substantial difference or not.

[Chevalade]

Now the porting being beneficial depends on many factors. You can hurt performance if you do the wrong porting. Polishing is always good especially in a high compression motor.

[eventhorizon66]

If you have good game plan, you can improve power with porting.  The trick is to stay conservative and try to "augment" the port's current shape rather than change it completely.  Polishing an intake port is not advisable as it can contribute to fuel "riding" on the walls rather than staying in suspension.  Besides, flow is in the shape not the finish.  Polishing the exhaust port can be beneficial for two reasons: reduced heat transfer and reduced carbon buildup (which could affect flow if it gets too heavy).

If we are talking about porting out a set of "square chamber" 882-type heads, don't waste your time.  Have you ever heard the expression "polishing a turd".

Check out these two books for some awesome guidance on porting SBC heads:

http://www.amazon.com/Build-Performance-Blocks-Budget-Design/dp/1884089348/ref=sr_1_1?ie=UTF8&s=books&qid=1242968969&sr=8-1 (I've read this one about a hundred times)

http://www.amazon.com/Chevrolet-Small-Block-Cylinder-Motorbooks-Workshop/dp/0879385472/ref=sr_1_5?ie=UTF8&s=books&qid=1242969024&sr=1-5

[VileZambonie]

Port alignment, and porting is a lot of work but well worth it.  Making a tighter radius and getting rid of casting flash is the easy part. Creating an increase in velocity and getting more air in and out increases volumetric efficiency. Atomization is important but remember the purpose of porting is to increase flow and volume. To acheive good combustion you do need a homogenous mix. I wouldn't worry about negatives as the positives outweigh the neagtives. Do some reading as event suggested and be careful.

[HAULIN IT]

I would like to know more about the engine these heads are going on & the truck the engine is in before opinion/advise is given. You did use the word "significant" in your question. Lorne

[eventhorizon66]

Here's another good source also written by David Vizard (the same guy who authored those books I posted earlier).

http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/index.html

[exilous]

Well I was just surfing the net reading up on some stuff and I came across it a few times and was wondering what the benefits were whether they were significant or not thats all...as for if I do it or not who knows. but if i do it on my engine it is a 350 4 bolt main bored 60 over stock heads, with a torguey kind of cam. Not going to be a huge horsepower maker by any means, but if it would make any difference I figure while im here I might as well give it a shot. I figure its a learning experience for me as it is. and if i screw it up I have a few other sets of heads in case i do something wrong.