400 heads
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400 heads
I just got done installing the performer cam/600 cfm carb/intake straight up double roller timing chain.
While having the valve covers off I found the casting #D5AEA2A I believe these are the 74.5 cc combustion chamber heads can anyone confirm this?
I'm also curious if the 74.5 cc heads made the 8.4 cr on the 400. I have heard there was a 8.0 to 8.4 cr ratio in these years and it would make sence if the smaller of the combustion chambers were the higher cr ratio but ford did some things that could never be explained. Like no 4 barrels on 400's!
I'm also curious of the hp now, I'm averaging 150lbs per cylinder of compression if that helps?
thanx
While having the valve covers off I found the casting #D5AEA2A I believe these are the 74.5 cc combustion chamber heads can anyone confirm this?
I'm also curious if the 74.5 cc heads made the 8.4 cr on the 400. I have heard there was a 8.0 to 8.4 cr ratio in these years and it would make sence if the smaller of the combustion chambers were the higher cr ratio but ford did some things that could never be explained. Like no 4 barrels on 400's!
I'm also curious of the hp now, I'm averaging 150lbs per cylinder of compression if that helps?
thanx
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Joined: Aug 2000
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From: (near) Denver USA
400 heads
[updated:LAST EDITED ON 01-Jul-02 AT 08:37 PM (EST)]78400mdog,
I have measured a set of D5AE-A2A cylinder heads at 74.5cc average, but I have heard other guys measured them at 77-78cc. I have personally run across some other M-block heads that had different size chambers with the same casting ID codes and made at different plants or on different dates, so I would not be surprised if that was the case with the A2A heads as well.
The maximum difference in compression ratio from the largest (78.4cc) to the smallest (74.5cc) M-block cylinder head chambers is only 0.20:1 on a stock bore 400. So if the engine had an actual 8.4:1 compression ratio with the smallest M-block chambers, it would have an actual 8.2:1 CR with the largest M-block chambers.
All truck 400s used a common truck-only piston (12.75cc dish) and were advertised as a nominal 8.4:1 compression ratio. To know the actual compression ratio of any engine, though, you'd have to disassemble it and measure everything.
If your engine is stock except the Performer cam/intake/4V carb (including stock exhaust manifolds), I'd guess it's giving 200-210hp. With headers and a good exhaust system (and re-tune the carb), you might get it up to 225hp or so.
I have measured a set of D5AE-A2A cylinder heads at 74.5cc average, but I have heard other guys measured them at 77-78cc. I have personally run across some other M-block heads that had different size chambers with the same casting ID codes and made at different plants or on different dates, so I would not be surprised if that was the case with the A2A heads as well.
The maximum difference in compression ratio from the largest (78.4cc) to the smallest (74.5cc) M-block cylinder head chambers is only 0.20:1 on a stock bore 400. So if the engine had an actual 8.4:1 compression ratio with the smallest M-block chambers, it would have an actual 8.2:1 CR with the largest M-block chambers.
All truck 400s used a common truck-only piston (12.75cc dish) and were advertised as a nominal 8.4:1 compression ratio. To know the actual compression ratio of any engine, though, you'd have to disassemble it and measure everything.
If your engine is stock except the Performer cam/intake/4V carb (including stock exhaust manifolds), I'd guess it's giving 200-210hp. With headers and a good exhaust system (and re-tune the carb), you might get it up to 225hp or so.
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