Re: [Amc-list] Cylinder Head Question

[Greg Taylor <amundaza@xxxxxxxxx>]

Hi Bruce,
  Thanks for your feedback.  These heads would be installed in my JEEP Grand Wagoneer, which I would never intend to fly!  It's a mostly stock reman 360 (~60,000 miles on it) and I'm tossing around the idea of using the ported 304 heads I already have had nearly done for about 12 years now.  I doubt this Jeep will ever see 4500 rpms (max if that), so you've helped to answer my question as to how they'd perform in that RPM range (low-mid).  My intake is a Holley Street Dominator, which is good up to about 5500 anyhow.
   
  I am primarily modifying the 360 for gas mileage anyways and figured that while I'm "in there" fixing the timing cover leak and replacing the components under the cover, I'll add in the heads w/roller rockers too, since I have them already and they should boost power.
   
  I am adding in a Hydrogen on demand system that supplements gasoline, as well as water injection ... both of which allow me to alter timing advance and lean out my carb considerably.  My current goal is 20 MPG in the Grand Wagoneer.  The water injection also will help with the spark knock.  As for the water injection unit, I am running the unit that some Australian car club guys have built and run down under. Pulls vacuum through the distributor vacuum advance port on the carburetor. 

The Aussie websites for H20 Injection are:

http://website.lineone.net/~da.cushman/misc/mannject.html

http://www.kuratrading.com/PDF/WaterInj.pdf

I've seen the Edelbrock heads and they are nice.  They'd cost me an additional $1500 above the $600 or so that I already have into the modified 304 heads.  As mentioned, I've already modified the 304 heads for roller rockers and the bigger Chevy Milodon Mega Flow valves.  I did this valve swap on a stock 258 head (same valves as a 304 head) and picked up GOBS of power.  I would estimate 30HP at least and more torque than that with stock bridged rockers.
   
  Thanks,
  Greg Taylor

Bruce Hevner <scramblr@xxxxxxxxxxx> wrote:
  I wouldn?t TRY to use a set of 304 heads on a 360 for performance. They
will work well for torque and MPG but the performance will suffer.
REMEMBER,,, just putting oversize valves in does not necessarily get you
better performance. I read your post and never saw THROAT SIZE (the area
under the valve seat) mentioned. There is as much or more power made in
the first ½? or so under the valve seat as the valve size itself.
The throat area on a 304 is MUCH smaller than the 360. I don?t believe
you could ever port out the bowl/throat area on a set of 304s to be the
same as a STOCK set of 360s. Even if you could what would you end up
with?? A set of heads that are the same as the 360.
First you need to determine what the vehicle is used for and what RPM
will it operate? If you REALLY want to fly look at a set of Edelbrock AMC
heads. I looked at a set at the PRI show. VERY nice quality, ports and
bowl area looked great. Yeah I know they are 12-$1500 but when you add up
what youre going to spend on your stock heads, and what you?ll end up
with,, they are not such a bad deal.
304 heads on a 360 will increase the torque and response, but they?ll be
?done? by about 4500RPM. There is no way around it, you can tune for the
bottom/midrange, or the mid-upper range. But you can?t have it BOTH ways.
If a customer asked me those questions I would recommend doing a good
competition valve job and taking maybe .020 off the 360 heads. That would
be the best all around combination.
As far as compression goes,, as a GENERAL rule you?re going to change the
compression ABOUT .1 point for every .010 you cut them. This varies with
chamber and engine size but it?s easy to figure.
If your using a stock cam be careful increasing compression. More than
180lbs running compression will be close to spark knock territory.
If you?re going to increase compression then you need to look at the cam
timing,,,,one thing leads to another,,,,
But HEY,,, that?s just ME!
Bruce Hevner
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