455 swap in 84 t top

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REDWOOD

Not-quite-so-new-guy
Feb 17, 2019
6
1
Hello I'm new here and currently been working on body off restoration on 84 t top cutlass supreme that I am putting a 68 455 in and need so info on what will be needed to install it as far as long or short water pump and other items that may give me clearance issues any help would be greatly appreciated
 
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oldsmobile joe

Royal Smart Person
Nov 12, 2015
1,257
113
mpls
Did you box the frame?
You might need a set of notched valve covers to clear the heaterbox.
Factory valve covers fit just fine.
I'm using a long water pump on mine. If swapping from a 307 to 455, p/s pump and brackets will work as well as the alternator and brackets, however, a spacer will need to be added where the alt and p/s meet up. R4 a/c brackets can be modified to work. Radiator hoses swap over too.
 
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REDWOOD

Not-quite-so-new-guy
Feb 17, 2019
6
1
Did you box the frame?
You might need a set of notched valve covers to clear the heaterbox.
No didn't box frame just touched everything up on it installed air ride and had powder coated. Also not sure on the valve covers I have heard I'm going to have to special order them cuz I had 1.6 roller rockers put in it right now we just have gaskets stacked up
Did you box the frame?
You might need a set of notched valve covers to clear the heaterbox.
 
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REDWOOD

Not-quite-so-new-guy
Feb 17, 2019
6
1
Factory valve covers fit just fine.
I'm using a long water pump on mine. If swapping from a 307 to 455, p/s pump and brackets will work as well as the alternator and brackets, however, a spacer will need to be added where the alt and p/s meet up. R4 a/c brackets can be modified to work. Radiator hoses swap over too.
Thanks I'm planning on running the March serpentine system that comes as complete kit with alt,power steering and ac and all brackets and hardware
 
88hurstolds

88hurstolds

Royal Smart Person
Jun 24, 2008
1,632
83
Basically treat it like a 307 with the 1.2" spacer between the alt/PS bracket and just extend your top two tabs on the AC bracket, you can use all the 307 stuff too.
Only issues are taller rocker covers and header selection, how deep are your pockets for American Racing Headers?
Otherwise just use the W/Z Thortons has out right now if you're not going all out performance.
 
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REDWOOD

Not-quite-so-new-guy
Feb 17, 2019
6
1
Basically treat it like a 307 with the 1.2" spacer between the alt/PS bracket and just extend your top two tabs on the AC bracket, you can use all the 307 stuff too.
Only issues are taller rocker covers and header selection, how deep are your pockets for American Racing Headers?
Otherwise just use the W/Z Thortons has out right now if you're not going all out performance.
Planning on using March serpentine system that comes with the ps pump,alt, ac compressor and all hardware and brackets. Do you possibly have those part #s
2, member: 18209"]Roller rockers fit under stock covers with a little modification to the baffles inside where the polylocks hit. Or, add a rail spacer....[/QUOTE]
 
olds307 and 403

olds307 and 403

Geezer
Oct 14, 2008
5,630
113
Melville,Saskatchewan
A 6" replacement water pump, the longest of the 3 water pumps used. The Milidon should be fine. Flowkooler makes a closed impeller pump which should be the best. https://www.flowkoolerwaterpumps.co...illac-chevy-gm-olds-pontiac-6-tall-water-pump You shouldn't need any brackets with there set up. The roller rockers may clear enough with just double gaskets but might need the baffles hammered on enough to clear. Thornton also makes a polished stainless shorty headers that are supposed to fit G bodies. http://rover.ebay.com/rover/1/711-5...0001&campid=5335822911&icep_item=183474943906
Also make sure you get a large two core aluminum radiator with 1" or larger tubes.
 
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