C8AE-H

[FirstEliminator]

    Hey guys,

     Last night I counter bored for hardened exhaust seats on a set of C1AE heads. At .200 depth of cut it was paper thin under a good portion of the seat. I was comparing to a set of C8AE-H heads and I can say these C8's have a lot more material to support a hardened exhaust seat.  Also, I had a set of C4AE out for comparison. The C4 and the C1 are just about the same.  The C1 and C4 seem kinda chinsey in comparison. In the bunch there was also a C7AE. The C7 and C8 both have smaller ports than the earlier. But, not too much smaller. I've read in the past that the C8AE-H  is not a real desirable head. However, if I were to put CJ sized valves and clean up the ports, perhaps open them up similar to the C1-C4 sizes, would I have a decent flowing head? Any recommendations on where to avoid and where might need attention in the C8 heads?  It may be more work, but the C8 just looks like a more reliable casting to start with.  The engine is a mild 482 with 224/230 @.050 with 110 LS.

    thanks,
       Mark

[My427stang]

Mark, with 2.09/1.67 3/8 valves, I have seen the C8AE-H and D2TE-AA max out about 280 cfm, you could probably do a little better with 11/32 valves if you are building from scratch.  You wouldn't want to turn them into C4 shape though, what you generally want to do is keep the intake small and fast and try to match med riser dimensions, which are much closer and pretty close to the same centerline. 

That gets you much better flow and a smaller cross section than an Edelbrock out of the box, so sure, it'd run well.  I run a set of D2s like that on my 445 and it's stronger than you'd expect for what it is. 

Keep in mind though, without porting, that is a 220 cfm head, which would absolutely choke any FE worth it's salt, never mind a 482, so if you are going to port, recommend you do a serious port, a little cleaning isn't enough with a C8AE-H

However, the exhaust is pretty crappy for two reasons. 

First, the exhaust port is lower by .250-ish compared to the bolts.  Which means you need truck headers that are made for the C8/D2 or 390GT flanges from FPA or the like.  It's a roll of the dice if car headers designed for C1/C3/C4 or CJ will seal because the ports are that much lower and won't support the gasket well.  A final option is a full flange sealing header, or exhaust manifolds, the welding ring standard header will either leak, or eventually leak.

Second, the exhaust ports don't flow quite as well.  That's not a real big deal with your cam size, but it's real tough to get the low exhaust port to 75% of intake without completely changing it.  I'd say the best you'll likely get is 180 cfm-ish for closer to 65%.  If you do that, I recommend a real good exhaust behind it and a well matched header to pull hard on the port

I wouldn't let either kill the deal though if you had headers to match already, as in my case on my F100, because of course headers designed for the C8/D2 will also leak on the C1/C4, so overall, the only real reason to pick that head is if you already had headers to fit them.

[FirstEliminator]

 The headers I have are the 427 65+ cast iron. The port openings on those are quite big compared to the outlets of the C8. It's followed by dual 2 1/4 exhaust.

    A serious port job-----wish I had a sample to mimic.  A set of 11/32 valves will be going in the heads.

   Looking at the intake side, the Performer RPM isn't much bigger than the C8 port opening.   

   This engine will max out at 5500 rpm. 99% of the time it will be idling or crusing.

   thanks,
     Mark

[My427stang]

So if you are running manifolds or cast iron headers, the port location isn't an issue.

You are spot on with the RPM, it's a med riser port.  Get a 1247 gasket to use for a template and port match the heads, then with a good valve job and the throat opened up, clean the bowl up and you'll do pretty well.

The C8s could be pretty good for you, it's a fast port and I'll tell you my 445 with a 236 @ .050 solid, RPM intake, and a 1000 Holley is light switch responsive with those small ports.

I do think the 2.25 exhaust is pretty rough for a 482 though even at your RPM, not sure of the outlet size of the cast iron, haven't seen any in a while, but that engine needs mandrel bent 2.5 and even better would be 3.0 if you could open the exit of the cast headers a bit

[FirstEliminator]

Off idle and mid range will be most everything for this engine. It's like an RV or towing engine. Fuel efficiency is important, so it sounds like a high velocity port is going to be the best bet.  I will get those gaskets on the way.

  thanks,
      Mark

[My427stang]

Anytime Mark, just to clarify though, the 1247 is good for getting your port size, but I don't really like that gasket for use, it's the infamous Printoleak.  However it's easy to find and good for getting the port sizing

I prefer to run a 202S Mr Gasket when all is said and done, but it's sort of a flimsy thing that isn't quite as good when you are doing your scribing

Here is a pic of mine, sorry I don't have more.

Basically you are looking for a very mild taper in cross section (funnel, but barely) from intake face to valve throat. The problem is, you are going from square to round, so it takes a little thinking.  I have heard guys talk cross section, I like thinking in terms of area because I can calculate area of a rectangle or a circle