Polishing my heads...

[Lifted79CJ7]

OK, so I am about to finally drop some coin and get my machine work done on my 401. My question is should I even bother polishing my heads? Will I really see any increase in HP or TQ from doing this? I am gong to be running the stock 1978 heads (same as 360's). I will be running an edelbrock 600 cfm carb, performer intake, performer cam, ~9.5:1 or 10:1 CR, stock manifolds till $$ is available for edelbrock headers, and MSD BlasterII coil. Just wondering if I should waste my time. I will keep this thing under 5500 rpm and it will be a weekend vehilce/trail vehicle.
Thanks!
Jack

[73hornut]

Just smoothing out the rough casting in the ports and gasket matching the ports will help quite a bit.

[tufcj]

Yep, it made a noticable difference on my 360. Nothing radical, just smoothing bowls and removing the casting flash. Definitely worth it.

Bob
tufcj

[Lifted79CJ7]

Alright, this is what I like to hear!
:lo1l:
So what about 3 angle valve jobs? Anyone able to notice a difference with that upgrade?
Jack

[Rogue Racer]

Yes. The valve job is more critical to air flow than the porting.

[fuzz401]

take the sharp edges out of the intake runners under the bowl and the same for the ex side

[Mudrat]

Jack,
Still have bench space/vacuum and air-compressor available- you buy the sanding/grinding kit. My pneumatic grinder bit the big one so I need to replace it.

Mudrat
(ps I told you it was worth it :? sorry couldn't resisit :wink: )

[Penguin]

I bought the Summit kit. I like it . I did the I-6 that I might have just wrecked with it. Used my die grinder to do it.
Was that wrong?

[Mudrat]

I bought the Summit kit. I like it . I did the I-6 that I might have just wrecked with it. Used my die grinder to do it.
Was that wrong?
For using a die grinder? I hope it wasn't wrong!!! :shock: I did the samething with stones and paper rolls on the Dremel, and mine runs fine (in the shop) ;-) I did grind and polish before I sent it to the shop for a boil and valve job with replacement seals and polished seats :lo1l:

Mudrat

[shimniok]

I've heard that polishing should only be done on the exhaust side. The rough casting on the intake prevents fuel from puddling better than a smooth surface would. I'd be curious to hear others' thoughts.

Also FWIW, playing with desktop dyno, it seems port & polish has the biggest gains above 4500rpm on race motors with big breathing requirements... *shrug*

Michael

[Mudrat]

I've heard that polishing should only be done on the exhaust side. The rough casting on the intake prevents fuel from puddling better than a smooth surface would. I'd be curious to hear others' thoughts.

Also FWIW, playing with desktop dyno, it seems port & polish has the biggest gains above 4500rpm on race motors with big breathing requirements... *shrug*

Michael
Polishing to a high shine yes, it starts to be a detriment on the intake. You want some roughness that will allow the air/fuel to keep mixing, not a mirror polish. What you need to do is port match (if your racing or looking for big gains) and deburr the intake to keep the air flow unobstructed. Get rid of the casting flash and sharp corners (especially around the valve seals) that will create a vortex (vacuum) but still allow swirling and mixing.
The exhaust side - smooth and polish it. But remember that the engine needs some back pressure to function right. Some shops do not port match the exhaust to help that. Others use a smaller diameter exhaust tube to keep the back pressure up. How much BP depends on the engine and application and I don't know how to figure that.
On the 258 I port matched the intake and just polished the exhaust without changing port size, but the 6 is a lower RPM grunt machine :idea:

A pretty good write up is HERE (http://www.sa-motorsports.com/diyport.shtm) Kits, abrasives yada, yada, yada can be purchased lots of places like Summit or Jegs.

That help any??
Mudrat

[Penguin]

Lots of help. Thanks. I think I did pretty good for my first time.

[fuzz401]

here a set that I started but never finished
http://img.photobucket.com/albums/v153/fuzzgremlin/IMG_0549.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/IMG_0548.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/IMG_0545.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/IMG_0546.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/IMG_0544.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/IMG_0543.jpg
they have been siting for a while but it gives a idel on what to do