383 HP Build! Please Help!

[NewRevNorton]

I recently bought a 1967 Coronet with the 383 HP engine. The previous owner told me that the disassembled engine included was original and after looking at the heads the casting numbers were 2406516-8 and 2406516-6. I took the engine to the machine shop and found that it was already cut .040 over and I did not feel comfortable building a street car at .055 or .060 over so I only left the heads to be worked and started searching for another block. So I tracked down another block in Indiana that was already complete and fresh from the machine shop. The block is dated 1970 and is .030 over with Keith Black floating flat top pistons and the owner claimed it has a forged crank and rods from a 67 HP engine. He also threw in a set of heads which are both casting number 2780915-1 which he claimed came from the same HP engine that the crank and rods came out of. Now the questions... The set of heads I am having done that came with the car had a different last number on the castings as stated earlier and are a different font size. Are these still a matching set? And if so, which heads would be best for this build... the 516 heads I am having worked or the set of 915s I got with the fresh block? I am also curious to know what kind of compression this new build will achieve.I know that the 1967 HP engines were 10:1 but wasnt sure if the 1970 block with the 1967 HP internals would change the ratio. Any help is greatly appreciated. This is my first Mopar restoration.

 

[fatecaptured]

From what I've read (don't take this to heart). The 383's could be bored .0060 without danger of making the cylinder walls too thin. But everyone recommends sonic checking the walls before going that far. But that would be the last time you could bore without sleeving the block.

The 516's are a 64-67 361-383 head. The 915's are a 67 440 high performance head.
Now from what i've read, I would use the 915's. They have a larger exhaust valve as tock. But as far as the rest idk. Here's a link of the head castings you can see the differences between the years:http://www.cowtownmopars.com/CastingNumbers.html

 

[Garys1969RR]

Hi New Rev, well your in the right place. Ok the 67 heads casting # 2780915 have the better port contours out of the factory. That is the only year they made that head, so its a rare one. Many racers want that head and they hard to find. I have used them many times, and they work real well especially with the proper porting work. Some had 1.60" ex valves, and the Hi Po 440 in 67 had that head with the larger 1.74 ex valves. As far as C/R goes, need to know head cc, cyl bore diameter, head gasket thickness, stroke, and piston to deck clearance. Plug these into the KB piston compression ratio calculator and it will give you the C/R for that combination. And the 915 heads would be a better choice for your build. And would be a correct head for a 67 year model car. But Im not sure if that head came on any 383 s, or just the 440. Maybe some one else would know. Good luck!

 

[Meep-Meep]

Consider the 915 heads a bonus! Use them! The 516's have the same chamber but the intake port is inferior to the 915. The 915's did come out in 66 but were used on Chryslers and I have even seen a 66 383 with them. So really two year production for the 915 heads but they are still pretty hard to find. FYI - The factory HP 915's (1.74" exhaust valves) had an "HP" stamped on the alternator mounting pad but you can take any 915 and have it cut for the bigger valve, thus bringing it to the HP spec. I have run the closed chamber heads on a 383 and a 440 with .040" of piston top clearance with no issues.

The compression increase on a 383 is not quite as much as on a 440. You can expect about a half point on a 440 from open chamber heads to closed chamber and on a 383 a bit less. Depending on your piston deck height you can also run the steel shim gasket to get a bit more squeeze.

 

[RustyRatRod]

The 915s were also made with the smaller 1.6 exhaust valve. So make sure you measure the exhaust valves. If they are 1.74 then they are the 67 only HP casting. As to whether the non HP 915 heads with the smaller exhaust valve has the same port configuration, I do not know, but I would suspect that since they carry the same casting number that they would. To me, either way, the 915s would be the ones to use.

Here is a chart for reference.

http://www.mymopar.com/headcastnumb.htm

 

[69 roadrunner]

Rusty did you find rods sorry didnt get back to you had death in family if you still need some I have a set that are redone with arp bolts will let go cheap call me at 530 926 0500 or pm me if you pmed me over weekend i cleared it while tring to get to it on iphone sorry but back in town so if you still need a set let me know Thanks steve

 

[RustyRatRod]

Rusty did you find rods sorry didnt get back to you had death in family if you still need some I have a set that are redone with arp bolts will let go cheap call me at 530 926 0500 or pm me if you pmed me over weekend i cleared it while tring to get to it on iphone sorry but back in town so if you still need a set let me know Thanks steve

Thanks. I sent you a PM.

 

[NewRevNorton]

Any tricks to determine if the crank in the new block I got is forged or cast? The previous owner claimed it was steel but it looks much more dull than the steel HP crank from my original block.

Now time to hunt down a power steering pump bracket, door panels, and bumpers to get the ole coronet on the road. I'll be going with the 484 lift / 284 duration Mopar performance purple cam I think. Any experience with this cam?

Thanks for all this help. At least I ended up with some extra 67 close chamber heads, an HP block, virgin HP steel crank, and some HP rods. Good swap meet items to sell and trade!

 

[Garys1969RR]

I always look at the front balancer to see what crank it has. The steel crank has a balancer about 1 inch wide. While the cast crank ones are closer to 2 inch in width. They also have" use with 440 cast crank only " cast into the front. In either 440 or 400 size designation. Not sure if the 383 ever came with a cast crank, don't think so. But the 383 and 400 both have the same stroke of 3.38" Ok C Ya