| Little help [message #370164] |
Thu, 21 July 2022 12:49  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Help with people, not my GMC. And, neither political nor religious so don't run 
A gentleman who posts on the GMC motorhome marketplace swears that early 425 CID rocket motors were built with a 45degree bank angle. I can think of no reason why, it would be poisonously expensive and build an inherently out of balance engine. I'm of the opinion this is just one more piece of FB misinformation. Anyone ever hear of this??
thanks,
johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
|
|
| Re: Little help [message #370168 is a reply to message #370164] |
Thu, 21 July 2022 14:27  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
I quoted him back from Wiki:
All Oldsmobile V8s use a 90° bank angle, and most share a common stroke dimension: 3.4375 in (87.31 mm) for early Rockets, 3.6875 in (93.66 mm) for later Generation 1 engines, and 3.385 in (86.0 mm) for Generation 2 starting in 1964. The 260 cu in (4.3 l), 307 cu in (5.0 l), 330 cu in (5.4 l), 350 cu in (5.7 l) and 403 cu in (6.6 l) engines are commonly called small-blocks.[1] 400 cu in (6.6 l), 425 cu in (7.0 l), and 455 cu in (7.5 l)[1] V8s have a higher deck height (10.625 in (27.0 cm) versus 9.33 in (23.7 cm)) to accommodate a 4.25 in (108 mm) stroke crank to increase displacement. These taller-deck models are commonly called "big-blocks", and are 1 in (2.5 cm) taller and 1.5 in (3.8 cm) wider than their "small-block" counterparts.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
| Re: Little help [message #370169 is a reply to message #370164] |
Thu, 21 July 2022 19:03 |
blur911
Messages: 166
Registered: December 2020
Location: Kingston, Ontario
Karma: 4
|
Senior Member |
|
|
He's talking about cam bank angles...and possibly not knowing what he's referencing.
Oldsmobile engines from 1964 onward originally used a 45 degree cam bank angle (CBA). This angle is formed by the intersection between the cam centerline and perpendicular lifter centerline. By 1968, all Olds engines were using a 39 degree CBA. In the years between, 39 degrees was used mainly on blocks found in Toronado's, and 45 degrees was being used everywhere else. The CBA also affects the pushrod hole angle in the heads.
45 degree blocks used 45 degree heads and the same for 39 degree blocks and heads. If swapping heads between 45 and 39 degree blocks, you must watch for pushrod interference at the bottom of the head. To put 45 degree heads on a (455) 39 degree block, you have to bore the push rod holes to .562" i.d. Applies to "A" heads and some "B" heads.
Burl Vibert
Kingston, Ontario
1976 GMC 26 foot, Sheridan reno, don't know original model but we call her Roxie
[Updated on: Thu, 21 July 2022 19:09] Report message to a moderator |
|
|
|
| Re: Little help [message #370173 is a reply to message #370164] |
Fri, 22 July 2022 10:27 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
That seems to 'splain it. Thanks.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
