Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> Pontiac 400 vs. Pontiac 455
User Name
Password
lost password?   |   register now

Thread: Pontiac 400 vs. Pontiac 455 Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
03-19-2011 07:31 PM
WDCreech
Quote:
Originally Posted by chevypower1
the 455 is a much better engine that the 400 and the 421. You should be happy with it.
I've been running Pontiacs for almost fifty years and I've had all sizes. The 455 is no better than the 421/428 or 400. As a matter of fact, the 400 block is stronger because of it has 3 inch mains vs the 3.25" mains of the 421/428 and 455. I know because I've had one start to split. For the horsepower needed for a healthy street engine, the 455 would be the best choice because it has plenty of torque without replacing any internal components, even though I would change to forged rods and pistons.

Bill
03-19-2011 06:24 PM
Thumpin455 It should be obvious which one I prefer, but I still like the 400. All the 455 really needs is a cam, some headers, and maybe a set of heads depending on which ones it has on it now. Get us a pic of the center exhaust ports, there should be a number cast into it like 6H, 6S, 6X, 4X or 7H1.. We can tell what heads it has then and if you should swap them or not.

Otherwise use the heads from the 400, they will increase the compression a little and bolt right on. You wont have any problems getting the pulleys and accessories to line up then. Or like Creech said if you can get the stuff that came with the 455 use that, because the water pump pulley is a different size to slow down the pump speed. It will still work with the 400 pulley if you cant get the 455 pulley, just a different diameter, and they should all have the same offsets unless someone swapped in a 67 earlier era front cover.

350, 400 and 455 use the same balancer and flexplate, so no worries there. They are internally balanced and most flex plates are drilled for both large and small pattern torque converters.


The F body mounts from 70-76 wont work on the 77-81 cars, but the 455 should have the bosses to use the brackets the 77-81 cars use to mount the engine. You cant find those mounts in stores, they are stamped steel and all you can get is the frame mount, so dont lose them. Just use the ones you have since most 455s have both mounting bosses. This is what the mounts look like on the 77-81 cars with Pontiac engines. I can get a pic of the 72 455 mounts if you like, they are different.

03-19-2011 05:19 PM
chevypower1
400 verus 455

the 455 is a much better engine that the 400 and the 421. You should be happy with it.
04-01-2006 11:52 PM
Grusome Goat One thing you may encounter is motor mounts as ones for a 455 are slightly different than the 400, these are readily available, get ones for a 71-76 as some were factory equipped with a 455. The 455 is a torque engine so keep the rpm's under 5500 with stock parts. Otherwise it's bolt in.
04-01-2006 11:45 PM
WDCreech To make the installation easier, try to get the pulleys and accessory brackets that are on the 455. It may save you from looking for ones that will work, but most of the stuff from the 400 should work, if you use all of it.

Bill
04-01-2006 03:51 AM
madamstn
2 cents worth

jeffs right, many times the boss is there but not bored and tapped. use a block plate. More ci mean more power al else being the same. The common mistake is all else being the same. If for example your volumetric efficiency is 95 percent in one it has to be the same in the other. And that is a function of many things.NEVER SIMPLE ANSWERS. M
06-07-2002 05:34 PM
jeff of nc should drop right in, only thing you might want to check on is your accesory bolt holes. if the 455 is older it may not have all the bolts holes on the heads. not sure about the flyweel or balancer.
06-06-2002 08:25 PM
chevyelc81
Pontiac 400 vs. Pontiac 455

I just bought a 78' Pontiac trans am that has the 400 engine in it. I found that the block is cracked. The machine shop said they could repair it for $250 but I have a friend with a running pontiac 455 that i can pick up dirt cheap. Does the 455 perform better than the 400? Im not to familiar with pontiac and I was wondering if the 455 would just drop right in. Let me know if theres any kind of little things i need to change such as pullys or flywheels, or should I just spend the extra bucks on fixing the 400 block. The car is going to be built for street/strip.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 12:34 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.