ive been digging around and haven’t really found any good discussions about porting the 392 heads, yeah I know the 555s are better but I don’t have a set. The hemi tech thread had a little discussion but the head cutaway images died with photobucket. So Before intake the die grinder to my intake ports, I’d like to go over what I’ve gathered that I should be looking at. My current plan of attack is to port match with an emphasis on the sides of the port while not going to far as to bust through to the pushrod channel, and forming a cone to help velocity.. From here... I’ve got the idea that I should leave the port floor as cast to help keep some turbulence for fuel suspension. I’ll be working around the guide to clean up casting lines and to open up flow past it. On the exhaust side I’m mainly cleaning up and smoothing the casting. I have started on that but have not removed much material. Any opinions on how I should be doing this? Motor won’t see more than 5700-6k. 221-230ish @.050 and 470ish lift on the Cam.
You need to talk to Gary (member name 73RR). I'm sure he's been down this path many times and would be a good resource. - EM
Here's a HR magazine refresh, 408hp @ 5,500rpm and 463.6ft lb torque @ 3,300rpm, or 431hp @ 5,500rpm with 489.2 ft lbs torque @ 3,700rpm; that's 23hp and 25.6lb ft torque increase. I've heard the term thin wall casting applied to early Hemi heads due to core shift. Smithberg Racing (I've no affiliation) also work with Hemis, however it comes at a price. There are a few photos of finished ports on their Facebook page
I looked at a lot of 392 intake ports and even cut up one broken head ported from a nostalgia Top Fuel engine. I did all of this before porting a set for a friend of mines 392 that was originally going to be a fun type 40 Willys pickup, (now sold). Maybe it'll go into his Austin someday..! Anyway, the best thing to do is make the side walls 90 degrees and "straight", from the intake gasket surface, all the way to the bowl. YES...remove the restriction of the head bolt bosses. I ground a flat on one boss, then checked the thickness with my sonic tester. Plenty of material. I even did a slight reverse cone effect so the flow doesn't have a large cross section change (slows the fuel speed) when the air/fuel get to the much larger bowl. Even if you are concerned (don't need to be) about breaking thru... An OLD small Chevy head trick is to press a sleeve into the bolt hole to seal it. Like I say, I ground a larger cross section near the bowl, than at the manifold end. Again, still over .150" wall thickness with all of my material removal. Don't need to do much to the exhaust, just get rid of all the sharp corners / edges. Have a good quality 3 angle seat ground on the head and two angles on the valves. Note: Per the note above, as verified by my sonic tester, the thinnest wall in these heads is about .130", and that was near the short turn radius, where I did very little grinding. Mike
Welllll looks like we lost some tips from @402BOSSMAN in the crash... so I’ll reupdate the thread. I’ve been working on the roof of the ports, taking it slow because there is water up there, things are looking much much better! I still need the guides removed so I can finish my work in the bowl/guide bump area. Per his advice I will be having my machinist do a 30 degree back cut on the intake valve (only, not the exhaust) when I have the seats done. I’ve got the heads setup in a way that’s allowing me to move from port to port, performing the same operation, IE doing all of the roofs in a row, then moving to the sides/floor. I’ll be doing the bowls like that as well. I’m doing them like this in an attempt to be more consistent. I’m excited for these to be done! I maaaaaaaay just have access to a superflow to see how well I did. Still working on that access though.
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