I have some head questions relating to my ’70 Chrysler 300 convertible with 440 TNT (HP) motor. A previous owner had this motor rebuilt about 12 years ago.

- Bored .030 over.
- Flat top pistons – Assuming stock compression. Piston TDC .080 below deck.
- 906 heads with std 2.08 intake and 1.74 exhaust
- Heads were surfaced but still around 83 cc but not sure if deck was
- According to Summits compression ratio calculator its at 9.1:1
- CompCAM 21-306-4 hydraulic cam
http://www.compcams.com/Company/CC/c...?csid=700&sb=2
- Added ’70 6-Pack setup with iron manifold

It has been running rough so I checked compression and found 3 cylinders low. Tore the heads off and it turns out the hardened valve seats were not installed during the rebuild and the exhaust valves are sunk in the head. One of the bad ones already had a repair seat (crushed down as well) and bushed guide. Two more are sunk so far that it broke down a portion of the port roof. I'm sure that a replacement seat will cover it though.

Bottom line is that the heads will need lots of work. Is this the time to switch to aluminum heads? This is just a street machine so I want to stay on the inexpensive side (Edelbrock 75 cc E-Street, 440 Source Stealth, or ???) A 75 cc chamber head should but me at 9.6:1. Will that still be OK for pump gas?

Or will I cause myself more issues from loosing the manifold heat cross over? What are my choke options if I loose the manifold heat. Am I just better off fixing up what I have instead?

What would you recommend?

Thank You
Dean

 

Get some heads from a 400/440 motor home that are not trashed and have them rebuilt.
75cc Aluminum head would be fine also

 

dont know if this will help but i just priced some head work on a set of 906s installing new hard seats and a 3 angle valve job it was less that $350