Port and polish

Hi guys only been on here a few times so i hope you all dont mind helping me out.I would like to polish the intake and exhust runners on my 340 J heads,my 360 is being rebuilt right now and I have some time on my hands this winter.So were to start and is it realy wortth it.My build is a mopar 360,30 over,280 474 purple cam 340 J heads 202 intakes single plane intake with 750 3310 holly going in my 69 Dart.I will try to upload a pic of the Dart.thanks all.

 

Modern thing to do is polish the ex ports only, you want some turbulence on the intake side to help keep the mix atomized.

 

I used a kit from eastwood when I did mine a few years back.

 

thanks guys for the quick replys back.waiting for a cal from eastwood for pricing on there kit ,still would like some does and donts.

 

No need to wait for a call, the price is on the website and there is a how to video online. Try this http://www.eastwood.com/engine-porting-kit.html

 

Twice I've used the porting template kit from Mopar Performance on factory heads fro my 440s, I think there is also a kit for the SB heads. The best bang for the buck of any mods I've done to it, just be prepared to spend some time, say 10-12 hours. As stated, no power gains to be had from polishing intake runners, just blend and polish the bowls, and polish the hell out of the exhaust side.

 

Are you a member of www.forabodiesonly.com? If you aren't, you should be. There's a 4 or 5 page thread over there on head porting. Your '69 Dart will fit right in over there.

 

Thanks sound like a plan.

 

Ya I am a member over there my name there is snake.I dont like to belong to one site.i think all sites are great.

 

Yes, I did some old Dart Iron Eagles. They are the 230cc's. They flowed 250cfm pre and 280cfm post. I did it at my local community college. I'm not big on grinding but for a half ass job I think I did pretty good. I probably could've got them to flow 300 if I worked the short side a little more.

If you're going to do this you need some tools.
First, you need a makita geo600 grinder. This is a great tool to have around. It's like a dremil on roids. I paid $110 for mine after some haggleing at grainger with some ebay print outs. You can use an air grinder but you need a large compressor to run it.

I got my carbides from a swap meet. Or you can pick them up from Joe Mondelo. Get the long shank ones with the 2 flute for iron and one flute for alum. after you carbide the ports you need to stone (not on alum) them and sand roll them. Only use the 80 grit on the intake but you can polish the exhaust if you want. My exhaust work didn't really do a whole lot. Get the sand roll kit from jegs or the like.

Don't forget the gasket match on the intake either. Get some dykum die and a skribe. O and it's nice to have a HD valve spring compressor on hand.

Since you did all this work, might as well farm out the seat work, buy some ss vavles, some HD springs and run a soild roller.

I got 490hp out of a sbc385

 

Here's my porting thoughts, if you don't have access to a flow bench and aren't well versed in porting, port match everything and smooth up the ports without changing shape and leave em alone otherwise. Have fun! Lippy

 

Mondello sells various kits for heads also...

edit= Didn't see the post above until it was to late...

 

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The theory on polishing seems to be best suited for FI or some kind of forced induction. Leaving the heads rough causes a desireable swirl for the intake charge. Bowl blending and gasket matching would give you the best bank for time spent. On a SBC 1/2" to max of 3/4" into port. You have to be careful, sometimes you might hurt performance if not extremely careful. Consult someone that ports heads for a living that might be willing to advise you...........good luck.

 

I suggest following the guidelines in one of the older Mopar Performance engine handbooks. They spent many millions of dollars over the years doing all of the research for us.

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I just handed my cylinder head guy a couple of $100 bills and told him to impress me. He took that personally and really pulled out all the stops, but as said before, not a bit went into the intake side. He removed a casting flaw that is on the same intake port of every casting, cut the seats, then blended the bowls, and put a nice 220 grit polish on the exhaust after some minor port matching to a standard gasket. The visible difference is amazing. I'll report back on the performance in the spring.