[bober]

I came across a 71 455 HO with 66 heads complete with the 400 trans. Are the Ho worth more than a regular 455 ?

[Singleton]

Sounds like a regular 71 455. What makes you think its a HO?

[bober]

The last 3 engine # is the 677 and not the 428 . The 428 was to be a late HO on some info I read.

[pggto]

Whats the date and block code? YG and YC which are standard 455 use the 677 casting according to Wallace Racing page.

[Singleton]

HO block would be engine code WC, WL ,YE

[bober]

It is a YC I haven't seen the date code but I think it is possible early.

['ol Pinion head]

Originally Posted by bober

The last 3 engine # is the 677 and not the 428 . The 428 was to be a late HO on some info I read.

That's bad info & the terminology can be traced back to Pete's book, "late 455HO" gets quoted all the time on the Net.

Original '71 455 HO blocks were cast on the following Pontiac 455 block castings:

9799140, carry over casting using late '70 production 455 blocks.
such assembled engines made it in to the very earliest '71 HO car builds at all four A-body & both F-body assembly plants. Due to low production & effects of the Fall '70 UAW strike shutdown, numerous "140" casting '71 455 HO blocks made it into Norwood & Lakewood builds in late Jan of '71 after both plants finally resumed production.

483677, cast from early July of '70 through the tenth of Sept '70.
the 483677 block casting was first used for '71 model 455 Dport engine builds coded YC & YG.
As the 71 455 HO engine assembly of 4 bolt main 9799140 blocks was depleted, 4 bolt main 485428 blocks coded for the '71 455 HO engine began to appear.

485458, first cast in late Nov (K) of 1970. this casting number 455 block continued up through '74 model year w numerous early '75 production vehicles also receiving this casting number 455 block

[Baron Von Zeppelin]

Originally Posted by bober

It is a YC I haven't seen the date code but I think it is possible early.

71 YC with 66 heads is the basic 455
just to add another confirmation to what some others already stated.

About a 99% chance it is 2 bolt main caps
About 100% chance it is drilled and tapped for 4 bolt main caps.

71 HO's had the roundport 191 heads , aluminum intake , and 4 bolt caps.
Big exhaust manifolds and special carbs
Prices go way up from basic 455 pieces

[68bird400HO]

Originally Posted by 'ol Pinion head

As the 71 455 HO engine assembly of 4 bolt main 9799140 blocks was depleted, 4 bolt main 485428 blocks coded for the '71 455 HO engine began to appear.

OPH, did you mean .......9799140 blocks was depleted, 4 bolt main 483677 blocks coded for the '71 455 HO engine began to appear.

[steve25]

1971 and 72 455 HO heads are Round port Exh, the 66 casting is D port.

All 71 and 72 HO blocks where 4 bolt mains be it a manual trans car or auto.

[bober]

Thanks everyone , I thought it might have 4bolt mains as long as it wasn't the 428.

['ol Pinion head]

Originally Posted by 68bird400HO

OPH, did you mean .......9799140 blocks was depleted, 4 bolt main 483677 blocks coded for the '71 455 HO engine began to appear.

Yes, my typo. Once I typed 48, the other 4 numbers just flew off my finger tips.

On the 483677 casting blocks, I've never ran across an extremely early one that was stamped as a '71 455 HO block. The earliest 483677 casting block I've pulled was a G080 cast YG block which was machined & assembked with 4 bolt caps. It's the only 71 Dport application 455 block I've ever had, that the block should have been a 2 bolt but was misbuilt with 4 bolt caps. have had multiple dozen 71 455 Dport blocks, have only had more 73's.