Hi- new to this forum, I hang out on the 7.3 usually. I gotta question-I have a mothballed 390 that I finally can work on again. Here's what I have- FT block .030 over, Isky cam .472 lift, 270 duration, C3AE PI heads, C7AE PI cast aluminum intake, C3AE double pumper carb. My plan was to keep it as "PI original" as I can (money wise) but any guesses how many HP I can make with what I have? I'd like to get about 400, and maybe leave some room for nitrous. I'm looking for any advice at all. I fell in love with this engine when I bought my first car, a 1968 Merc Commuter Station Wagon in 1995. Gone but not forgotten!

 

How much you can make if you build it right? Lots. If you put it together like it is now? Not as much.

I think the key question here is, what pistons are in it, and if you're not using those, which pistons are you going to use? You need that to know about what compression ratio the thing will have.

There are still so many things that affect it. One, headers or no? Big difference there. What's the CFM of that carburetor? Doing any head porting? Putting in the stock valve size or bigger?

Depending on those things, could be anywhere from 314hp to 443hp.

That must be an old cam; as the Isky 270 degree cam data I have shows .510" lift.

 

DOH! you're right on the .510 lift- I don't know where the heck I came up with .472???Like I said, I haven't worked on it in a while.......Right now I have flat top cast pistons, but I'm gonna put flat top forged in it. I'm gonna go with about 10:1 comp ratio to run pump gas. I am gonna run headers, not sure what kind though as I plan on putting it in a 56 F-100. Right now the heads are dissassembled, so I'm open for suggestions on what I can reasonably do to make em flow better. I know I can make more with Edelbrock heads, but I wanna run OEM. Again thanks for the help.

 

Keeping in mind I have a truely tremendous headache right now...

So, are we talking TRW L2291's for the pistons? Good units. I dont think it'll get you 10:1 though, as they're listed at 10cc's of valve reliefs. I dont know if I believe it though.

Concerning the heads. It's actually possible, to make them flow about the same or a little better than the stock Edelbrock heads! Especially the earlier heads like you have. What you have to do, is port them. Remove all the casting roughness, take the intake to about 80 grit, and polish the exhaust port to a mirror finish. Smooth up the short side radius. Clean up any ridges in the bowl area. If your heads have an emissions bump on the top back of the exhaust port, that can be ground off. Port work goes a long way with these things. Also, you could notch the cylinder bores and put in CJ size valves.

Headers are an extremely good idea. I guess I'd start with headers for a later truck that came with an FE. If they dont work, send 'em back. If you're good with a welder you could try making a set; something I've never done. All I can say there is good luck. But if Desktop Dyno is any indication, it's well worth your while.

 

Thanks for the info Rusty- I might however send the heads out to get ported, the last set I tried YEARS ago, I opened up the water jacket uuughhhh.... I'll probably get the biggest valves I can fit in the heads without cutting into the bore, just to keep things simple.

 

Well, you can fit the CJ (2.09/1.65") valves in the stock heads with 4.050" bores, but it will be very... very..... VERY close. It's close even with a .030" overbore. Enough to impede airflow. If you dont want to notch the cylinders, you should probably leave the stock 2.02/1.55" size valves in it.

These heads really dont need to be "hogged out". They really like a good cleanup job though. You know, smooth it out, round it off. If you know a someone who knows how to port an FE head, by all means. It's a long, boring, dirty job.

 

I did my own head porting with the help of Kurt and other members, spent about 16 hours of head porting time. I invested in the head porting kit from Napa and an air rotary tool and air tool oil. Will need some sand papers (80, 120, 200, 400 and smoother sand paper of you want it really smooth and shiny). If the heads have the emission tube, remove them and plug up the holes. The heads will need to be stripped down before you start??

Here some pictures, but these are the final head porting pictures. But you get the idea.
https://www.ford-trucks.com/user_gal...=129541&width=0
https://www.ford-trucks.com/user_gal...=129542&width=0
https://www.ford-trucks.com/user_gal...=129573&width=0
https://www.ford-trucks.com/user_gal...=129574&width=0
https://www.ford-trucks.com/user_gal...=129575&width=0
https://www.ford-trucks.com/user_gal...=129576&width=0

Here the ultimate head porting finish https://www.ford-trucks.com/user_gal...=58615&width=0
https://www.ford-trucks.com/user_gal...=58593&width=0
courtesy of Kurt.