Topic: wy 400 engine block with 6x small chamber heads or Yh 455 with 62 heads

[va bandit 78]

i bought a 79 ta for the 4 speed to convert mine over, the owner said it had a 301 , but after i picked it up i found out it was a wy 400, which i believe is a ram III block 366 hp , but i had already bought a YH 455, which according to year one is aram IV 365 hpmotor, i know the 455 has the better heads to give more comp. Havent decided which way to go any ideas would be greatly appreciated. and whats the goin rate for these motors

[va bandit 78]

62 heads on 455, and 6x small chamber on 400

[72blackbird]

No. 62's on a 455 will give you over 11:1 CR, too high for pump gas. The 6x-4's on a 400 yield about 8:1 CR, should even run on 89 octane. You could swap heads (put the no.62's on the 400 and 6x-4's on the 455) which would give you about 9.4:1 on the 455 and about 10.3:1 on the 400- you'd need to open up the chambers on the no.62's to bring the CR down on those for pump gas.

Geno

[Mr. P-Body]

Dude...

   WHERE are you getting these "numbers"? There is no such thing as a Ram Air IV 455.  "62s" were not used on "Ram Air" engines of any description, including the 366 HP version of the 400. A '69 model had "48s". '70 had "12s". Those were the only two years of the 366 horse engine. Both of those heads were used on other engines, as well (350 horse 400s).  455 heads are essentially the same as 400 heads of the same year, EXCEPT the combustioin chamber, which is LARGER on the 455, making the compression LOWER.

   I'm not taking "shots", I'm trying to clarify (there's that word again...). I highly recommend you get Jim Hand's book "How to Build Max-performance Pontiac V8s", published by SA Designs.  Get "educated" on the Pontiac, so you can make good decisions.  Listening to bench-racing buddies is fun, but rarely the "path to success" regarding a Pontiac "build".

Jim

[rad400]

X2 on both comments from Geno and Jim.