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Old 04-22-2012, 05:02 PM
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Pontiac 455 Engine Build Help

Perhaps I'm in over my head... but I have faith in myself and my project. I have a 1978 Trans Am. I bought it with no motor. I am putting a 455 in it. I am getting a th350 built for it, its being built into a bop transmission housing. I need to get the motor ready while I wait on the transmission. Its a Pontiac 455, right now its just a short block, basically just the block, crank and pistons. Its all been machined and is assembled up to this point. I don't have a whole lot of experience in a lower end of an engine and even less experience inside a Pontiac. Basically I just could use some basic step by step help installing the cam and timing gears in a way that I know I won't have any serious problems. Here is a link to the cam I am buying. http://www.summitracing.com/parts/CCA-SK51-241-4/ it should be fairly easy, the engine is on an engine stand and ready to work on. I had a lot of help on this motor but I moved and have no one around me anymore so I figured I would attempt to finish it up myself. Thank you in advance for any help. K.c. I'm sure I'll have lots more questions as the project moves along, but I cant wait to complete it!!

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Old 04-22-2012, 06:15 PM
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Quote:
Originally Posted by kcscott6329
Perhaps I'm in over my head... but I have faith in myself and my project. I have a 1978 Trans Am. I bought it with no motor. I am putting a 455 in it. I am getting a th350 built for it, its being built into a bop transmission housing. I need to get the motor ready while I wait on the transmission. Its a Pontiac 455, right now its just a short block, basically just the block, crank and pistons. Its all been machined and is assembled up to this point. I don't have a whole lot of experience in a lower end of an engine and even less experience inside a Pontiac. Basically I just could use some basic step by step help installing the cam and timing gears in a way that I know I won't have any serious problems. Here is a link to the cam I am buying. http://www.summitracing.com/parts/CCA-SK51-241-4/ it should be fairly easy, the engine is on an engine stand and ready to work on. I had a lot of help on this motor but I moved and have no one around me anymore so I figured I would attempt to finish it up myself. Thank you in advance for any help. K.c. I'm sure I'll have lots more questions as the project moves along, but I cant wait to complete it!!
On this page under Pontiac books there's a book by Rocky Rotella on rebuilding Pontiac engines. Also the book by Jim Hand may help.

That is a LOT of cam, I hope you know the ramifications of using such a grind. Gonna take better rods, compression, good flowing heads, single plane intake (might get by w/a RPM intake, but I wouldn't), large diameter headers, higher stall torque converter lower rear gears, etc. to let that cam work, else you could end up w/a radical sounding stone.

It's going to need to spin to make power- something that the large journal 55 Pontiac crank like yours sometimes takes expensive exception to. This is one reason that guys often use a 400 block to build high RPM Pontiac engines from because they have a smaller main journal diameter, so has slower bearing speeds.

In any event, I'm sure there will be other opinions on this. Good luck.
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Old 04-22-2012, 06:47 PM
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Cobalt is correct here about everything(as usual ) LOL
but seriously , your build probably has cast pistons on factory rods,which isnt a bad thing, not bad thing at all. These motors are built to make torque at low rpm and have a long steady torque curve through all rpm.
A stock build on a 455 is only safe to rev to 5250 rpms.The cam you chose there starts making peak power at 3000 rpm, not leavig much range for use, not to mention it will need a lot of stall converter Like 2500-2800 to even be able to wrk right.
First thing to consider when deciding to build, is to decide what the purpose for the engine/car is going to serve.
You want street? street/strip? full out drag?
Chances are you are building a street machine, which makes the 455 the best choice because its a lot of cubic inches.
For stock 455 street build I would put in a comp cams XE 262, those cams "make" compression for low compression engines and give good performance.
Lunati 60902 also would be a good choice for a stock build 455 for the street.
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Old 04-22-2012, 08:32 PM
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I didnt look at the specifics of your cam choice. But one thing to think about, If your valvetrain is the stock non adjustable rocker type. Be careful that you dont stack the valve springs solid. Stock Pontiac heads cant handle a lot of lift in a cam. Just food for thought.
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Old 04-23-2012, 07:09 AM
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That cam is an old "Magnum" grind, obsolete for more than 15 years now. Comp still offers them because people still buy them. MUCH better cams available for the ol' Injun today. The Magnum series are ALL "single pattern" (both lobes are the "same"). Pontiacs, from the "factory", were ALL "dual pattern", where the exhaust had more duration. Magnum was never a "good' choice for a Pontiac.

Also, the "K" kits leave much to be desired. They come with the 'cheesy" timing set (2112) instead of the "true roller" (3112). They also come with old-style Teflon valve stem seals. IMO, ypou're MUCH better off dealing with Pontiac specialists rather than Summit or Jeg's. It will prevent you fromm having a pile of mis-matched componenets, a common problem when a "newbie" is trying to build a Pontiac. Always remember: This is NOT a Chevy. It runs differently, makes power at different points, and has a completely different set of "strengths" and "weaknesses".

Jim Hand's book is the most current study of performance and the ol' Injun. This book is "aimewd" at street engines, but has some good tips and info about the engine family as a "whole". It IS 8 years old now, and the "re-write" has left out many of the original contributors. Certasin aspects f the Pontiac "hobby" have become very polarized and "brand loyalty" has threatened to kill the progress we've made over the last few years.

If all you have is a block, pistons and a crank, how is the short block assembled? Does it still have the stock cast connecting rods? They have GOT to "go". That is the biggest weakness of the design. Good forgings completely "cures" it. Also, if you see a 400 block "go by" (casting 557 excepted), grab it! 400 blocks are tougher than 455s... (:-

Jim
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