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 400 to 455?
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beertracker
Cochise

350 Posts

Posted - 13 May 2014 :  5:12:17 PM  Show Profile  Reply with Quote
I have been thinking of getting a 455 short block and moving the 400 parts (iron heads, cam, intake, carb and headers) over to the 455. So the only difference would be 55 more cubic inches. My question is how much more torque would 55 more cubes give me? Would it be noticable in my street car?

I want a LS engine in my Pontiac

Phil
The Great White Buffalo

USA
7214 Posts

Posted - 13 May 2014 :  7:08:39 PM  Show Profile  Reply with Quote
Yes very noticeable because its mostly increased in the stroke.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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bigD
Indian Spirit

USA
643 Posts

Posted - 13 May 2014 :  7:08:48 PM  Show Profile  Reply with Quote
WOW, would it ! It's almost like night and day. 500ft lbs will burn some rubber and break some stock parts. I love the 455 ! Here's the easiest way I know of to show a simple parts list and and price estimate of what you are talkin about.

Here's a 4.25 stroke 400 block short block, to which you could add your cam, heads, etc. You can buy one of these or buy the same parts and have your competent Pontiac engine builder build it for you.

http://lenwilliamsautomachine.com/455_Short_Block.html

Or you can buy an actual 455 block motor. Here's one complete, similar to what you want. The complete engine, with Eagle crank and rods is $4500 + freight. I'm sure they would sell you this shortblock, without the other stuff, if you choose. Or if you can find a rebuildable 455 crank and block, you can have it built locally. If you decide to go this way, make sure you use a machine shop where they are very familiar and experienced with Pontiac motors.

http://lenwilliamsautomachine.com/455_Long_Block.html

Then you'll need a heavy duty tranny to withstand 500ft lbs of torque. My 1st 455 broke a PG, a TH350 and a TH400 before I finally figured out that the 455 is a torque monster that will eat trannys ! There are lots of guys out there now who can build trannys that will survive. But if you ever use any sticky tires, a stock tranny will not survive.

If you do switch to a 455, also be sure to tack weld your axle tubes to the center section, with at least 4 good tacks on each tube. I failed to do this on a 2nd gen drag car and the center section spun on the tubes sending the pinion yoke up thru the floor pan !

Edited by - bigD on 13 May 2014 7:11:35 PM
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beertracker
Cochise

350 Posts

Posted - 13 May 2014 :  9:00:25 PM  Show Profile  Reply with Quote
quote:
Originally posted by bigD

..... Then you'll need a heavy duty tranny to withstand 500ft lbs of torque. My 1st 455 broke a PG, a TH350 and a TH400 before I finally figured out that the 455 is a torque monster that will eat trannys ! There are lots of guys out there now who can build trannys that will survive. But if you ever use any sticky tires, a stock tranny will not survive.

If you do switch to a 455, also be sure to tack weld your axle tubes to the center section, with at least 4 good tacks on each tube. I failed to do this on a 2nd gen drag car and the center section spun on the tubes sending the pinion yoke up thru the floor pan !



Good info. Yep, I failed to consider a tranny upgrade; my th350 won't live long with 500 lb ft. I am not planning any sticky tires.

I want a LS engine in my Pontiac
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RayK
Cochise

USA
925 Posts

Posted - 21 May 2014 :  6:56:00 PM  Show Profile  Reply with Quote
What camshaft is going into the 455?

1969 Firebird 461, #62 iron heads, Comp roller, Performer RPM, Q-Jet Turbo 400 w/ Continental converter. GM 8.5" 10 bolt with 3:73 gears.11.50's@ 119+ MPH
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Racinrick
Tribal Scout

USA
10 Posts

Posted - 23 Oct 2014 :  09:38:09 AM  Show Profile  Reply with Quote
Hi Beertracker, it's the easiest and cheapest way to get more power from a missioned hunk of metal than any other way, especially on the street. It's an upgrade you can definitely feel in the seat of your pants. In 1972 at 18 I bought a new Grandville hardtop with a 455, mostly because I was coerced by my Dad not to have a "performance car". When trying out this car on the test drive, casually taking off from a stop light from one of the most traveled local "drags" with the radio playing Santana....I thought the car was broken....didn't move. Now mind you, my first car was a Galaxie with a 260 2spd, so I was accustomed to 1/3 throttle from a standstill to start moving....more throttle made little difference. At 1/3 throttle this Grandville was frying the right tire at the stoplight and had shifted into second and never moved....my sister's 1971 GP 400 couldn't do that unless I stomped it. My best friend had a 70 SS Nova 300 hp 350 4spd, with mods he had made..solid cam, 3.73s, EB intake, Hookers, and a Holley and it worked...and had built himself up as a contender in our hometown. From a standstill he was pretty strong, from a rolling 15 mph the Grandville would catch him and go around him by 80-90 mph...some of it was gear, but most of it was plain ole torque.
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beertracker
Cochise

350 Posts

Posted - 23 Oct 2014 :  6:57:44 PM  Show Profile  Reply with Quote
I was planning a CR of 9.3 in the 455. I think I can get by with a summit 2802 cam.

Good story on the Grandville. I remember those as big cars.

bt

I want a LS engine in my Pontiac
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 24 Oct 2014 :  12:55:16 PM  Show Profile  Reply with Quote
Sounds good, Add 1.65's if the push rod holes are altered and the heads are set op for .500 lift

Or the crane H-278 with 1.5's
http://www.summitracing.com/parts/crn-283801/overview/make/pontiac // again heads set up for quicker opening .500 lift


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 24 Oct 2014 12:56:25 PM
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DanM
Buffalo

80 Posts

Posted - 24 Feb 2017 :  11:14:55 AM  Show Profile  Reply with Quote
How did this turn out?

btw: I would have said, if you're going to upgrade from the TH350, which you'll need to do with the 455, might as well get a 200-4R with strong parts inside. Basically same cost as a TH-400 anyway and you'll have OD for the highway.

71 LeMans Sport Convertible with 310,000 miles driven year round since 1994.
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