# Difference between 1972 455 and 455 HO



## gotyorgoat (Jun 19, 2011)

Can anyone tell me the difference between the 455 and the 455 HO? I can not find any good info online.

Are there any castings that indicate which model of pontiac an engine came out of?

Thanks


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## 05GTO (Oct 6, 2004)

The 72 455 HO used 7F6 heads which had round ports, 2.11/1.77 valves, a CR of 8.4 and 111cc chambers, the HO used the 068 cam.

Part of the original car's vin was stamped on the front of the block next to the timing chain cover.


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## BearGFR (Aug 25, 2008)

:agree The main differences performance-wise were the heads and cam.
Generally, you can identify any "late" (62 and later) Pontiac block by starting with the 4 character date code near the distributor hole to identify the model year (remembering a block cast after about July or so is probably for the "next" model year), then once you know the model year you can use the 2 character block code (YC in your case) to figure out which car(s) it was used in. The reason that date code is so important is that there are instances of the same 2-character block code being used in several different model years with very different meanings.
Also, later on Pontiac began stamping a portion of the VIN into the blocks as well - down low, next to the timing cover. On a "numbers matching" car, this number will match the serial number portion of the VIN.

Cylinder heads also carry a 4-character date code, either on the outside just below the valve cover or inside underneath the valve cover. The process for identifying a head is the same: start with the date code to identify the year, then use the casting code on top of the center exhaust ports (or in a few cases on top of one of the end exhaust ports) to identify it.

Then, to the Interwebs Batman!!
(Caveat: always check several sites to cross check your findings, there are some mistakes out there)
How to identify your Pontiac engine
Pontiac Engine Codes
Pontiac Engine Codes
Wallace Racing's Pontiac Engine Search
Pontiac Cylinder Head Search
http://www.wallaceracing.com/intakesearch.htm
Pontiac Power

Bear


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