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Advice for rebuilding 400 Pontiac Engine rookie rebuilder Rate Topic: -----

#1 User is offline   Madvarga 

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Posted 25 July 2011 - 12:16 PM

I recently purchased a Pontiac 400 engine that was born Oct. 13th, 1973. My plan is to rebuild this engine myself and would like the end result to have anywhere from 350-400 HP for street use.

I have been researching as much as possible about how to go about doing this and the actual physical labor part of breaking the engine down and building it back up is not my worry.

My worry is when I look into rebuild kits, purchasing new head, a cam, etc. I feel I am reading a foreign language when it comes to all the specs.

Can any of you savvy Pontiac Firebird folks give me some advice as to what parts I should purchase? I.E. - Reliable rebuild kits, compatible heads, cams, mainfold, carbs.

I am a newbie at this and I would hate to rebuild an engine with incompatible parts that would ultimately require me to do it all over due to my lack of knowledge.

Any and all advice is greatly appreciated!


1980 Pontiac Trans-Am rebuild project
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#2 User is offline   joeq 

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Posted 25 July 2011 - 01:21 PM

Chris
If you're new to Pontiacs, you got to pick up Jim Hands book "How to rebuild Pontiac V-8s (SA designs). Great book for "current info". Your goal of 350-400 HP is very sensible and realistic, and is easily obtainable, even on todays "crap gas." I'm sure you'll get lots of advice on which way you could go with your build. Just be honest with yourself on what you "really" want and need, compared to what you can really afford.You want to have fun, and going broke is none of that. Good luck with it.
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#3 User is offline   TransAmer99 

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Posted 25 July 2011 - 01:49 PM

If you are referring to the 'kits' like PAW (Performance Automotive Wholesale, Warehouse or something like that), I would steer away from them. They're 'all-in-one' mentality appears to group together components they can acquire cheaply and package them for a price that seems affordable. But if you do your own due-diligence and carefully select the components yourself, you get much better quality for about the same price. But you need to do your own research.

To built a powerful, but reliable motor, you need a stout bottom end. Usually you can get away with the factory crank if the engine shows no obvious signs of fatigue. But you will want to invest in some good forged rods and pistons. Geno (a.k.a. 72blackbird) can get a little more specific than I can. Same with bearings and rings - cheaper is not better. Also, pay careful attention during assembly. Inadvertantly blocking an oil passage or improperly gapping the rings will spell an early death to the motor. Head gaskets should be specified to get you the proper compression ratio. On the top end, cam selection and valvesprings/rockers will depend on the heads you use. Aluminum heads are expensive - minimum $2200 a set - but you can spend almost as much machining iron heads and doing valve work. I only recommend Rochester Quadrajet carbs. While there are many Holley afficianados out there, nothing can compare to a properly-tuned Q-Jet with those huge secondaries.

Above all, consult Jim Hand's book. It is 'the bible' for Pontiac enthusiasts.
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#4 User is offline   Birdman1970 

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Posted 25 July 2011 - 02:08 PM

I will say one thing I wish I had done on my rebuild was to put in ARP bolts for the connecting rods. The factory bolts are the weak point in all poncho blocks but most go all out and get forged connecting rods. As for cam selection, i'm guessing you want a 'lil extra kick from that 400. Just remember, Pontiac's don't need a high lift cam b/c they would lose all that low end torque. I couldn't tell you an exact cam for a 400 but i've heard good things about the factory Ram Air IV. As for the intake manifold, the best ones are either the stock iron manifold or the Edelbrock Performer (which is the exact same design as stock, just made from aluminum).
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#5 User is offline   76ta 

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Posted 03 August 2011 - 06:44 PM

what is the motor going in would help for manifold choice . and northern auto part's sell a whole rebuild kit for around $650 but they give 8 brow piston's which will give you slightly less compression . and the cam would only be stock but they do let you upgrade there kit's for a little more money depending on what you are upgrading . i would go with some 6x head's and have them milled and ported try to get at least a 9.1 compression ratio but not more than 9.5 or you may not be able to run on pump gas.
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#6 User is offline   72 blackbird 

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Posted 04 August 2011 - 06:46 AM

Chris,
Building a 350-400 hp 400 isn't rocket science, but you're not gonna luck out and put together the right combo w/o good advice from an experienced Pontiac builder. I see alot of good advice posted so far- forged pistons and rods are so inexpensive these days it would be foolish not to include them in your build. Stainless forged 1-piece valves are also affordable and superior to the stock 2-piece spin welded OEM valves, so be sure to use those when you heads are rebuilt as well. I do piece together my parts list for engine builds because each build is a little different and built to suit a customer's needs, but I also shop for parts athe the usual sources, like Summit racing and Jegs. I also buy alot of parts from Pacific Performance Racing- they are exclusively Pontiac and have all the parts to assemble an engine from scratch.

Any good Pontiac builder will ask you a few questions first to help you get a better Idea of how you can put together a parts list to achieve your hp goals. We know you want 350-400 hp from your 400, but what we need to know is what kind of budget do you have, the no. of the heads that are on the 400, do you prefer a smooth or choppy idle, and what you plan to do with the car once the engine is installed. You also mentioned you plan to assemble the engine yourself- please tell us what kind of experience you have building engines and what engine tools you have to accomplish this task.

Geno
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#7 User is offline   Madvarga 

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Posted 04 August 2011 - 11:04 AM

I do not have any experience with this assembly other than the literature I am acquiring and the information I receive from here. My budget is pretty flexible and with the HP / Torque I am looking at I dont think the cost should exceed $4k. I would prefer a smooth ride and plan on using it as a weekend driver and to show off occasionally. As far as tools go I am compiling a list of the ones I need. Once I get the engine broken down (this weekend) I will be taking it to a local machine / performance engine shop and plan on sitting down with the owner and get advice from him as well.

Thanks you all for all your advice. I will post some before and after pics when it is all done.

Ultimately, if I have to pay to have this done then I will, but I would like to see if this is something I can accomplish for the experience and the challenge.



View Post72 blackbird, on 04 August 2011 - 06:46 AM, said:

Chris,
Building a 350-400 hp 400 isn't rocket science, but you're not gonna luck out and put together the right combo w/o good advice from an experienced Pontiac builder. I see alot of good advice posted so far- forged pistons and rods are so inexpensive these days it would be foolish not to include them in your build. Stainless forged 1-piece valves are also affordable and superior to the stock 2-piece spin welded OEM valves, so be sure to use those when you heads are rebuilt as well. I do piece together my parts list for engine builds because each build is a little different and built to suit a customer's needs, but I also shop for parts athe the usual sources, like Summit racing and Jegs. I also buy alot of parts from Pacific Performance Racing- they are exclusively Pontiac and have all the parts to assemble an engine from scratch.

Any good Pontiac builder will ask you a few questions first to help you get a better Idea of how you can put together a parts list to achieve your hp goals. We know you want 350-400 hp from your 400, but what we need to know is what kind of budget do you have, the no. of the heads that are on the 400, do you prefer a smooth or choppy idle, and what you plan to do with the car once the engine is installed. You also mentioned you plan to assemble the engine yourself- please tell us what kind of experience you have building engines and what engine tools you have to accomplish this task.

Geno





It is going into a 1980 Trans Am

View Post76ta, on 03 August 2011 - 06:44 PM, said:

what is the motor going in would help for manifold choice . and northern auto part's sell a whole rebuild kit for around $650 but they give 8 brow piston's which will give you slightly less compression . and the cam would only be stock but they do let you upgrade there kit's for a little more money depending on what you are upgrading . i would go with some 6x head's and have them milled and ported try to get at least a 9.1 compression ratio but not more than 9.5 or you may not be able to run on pump gas.





Since I am going from a 301 engine to a 400 what should I change the rear gear to?
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#8 User is offline   72 blackbird 

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Posted 04 August 2011 - 05:52 PM

Chris,
I hate to burst your bubble, but getting 350-400 hp from a 400 with a $4k budget is a bit overoptimistic for a first timer w/no engine building skills. The hp output you seek from a 400 isn't impossible, but will require ported 72cc iron heads, and most head porters typically charge around $500-700 for this mod. Pontiac heads cannot be ported like Chevy heads- an improper porting job can actually decrease flow, so only a well known Pontiac builder should be used to do the port job. Increased port flow in the 240-250 cfm range, combined w/ a 9-9:5:1 static compression ratio with the right cam and induction usually results in a 375-400 hp output in a 400. You'll also need dished pistons to keep the compression at 9.5:1 or less. Flat top pistons w/ these 72cc heads results in a 10:1 compression- too high for pump gas- despite what some so-called experts will tell you, doing so will hammer your bearings w/ detonation and result in eventual engine failure (rod or bearing knock).

To get 350-400 hp from a 400 also requires complete machining of the block, crank, and heads- no shortcuts anywhere. The block will have to be cleaned and magged, line honed,decked, bored and honed w/a torque plate, the crank turned, balanced and polished, the cylinder heads surfaced, 3-angle valve job done, new valve springs, retainers, keepers and bronze guides installed. All of this machine work isn't cheap- be prepared to spend at least $800-1000 in machine work and at least $1500-2000 in new parts. How do I know much it costs to do all of this and what parts will work together to make that power? I've been building Pontiac V-8's and other Detroit engines for over 20 years, and when it comes to Pontiacs it's safe to say I know them well.

I don't know how proficient your mechanical skills are, but putting together a Pontiac V-8 for the first time should be done under the watchful eyes of an auto tech instructor or experienced mechanic- you don't want to screw something up after spending over $3k in parts and machine work. I've gotten more than one rebuild from so-called internet-taught Pontiac owners who thought it would be a snap to rebuild their engine by themselves and ended up damaging some internal parts. My customers have little hesitation paying me to assemble their engines- they know it will be done correctly the first time and will run well.

Feel free ask me any questions you have about proven 400 combos- I'm more than happy to share my findings w/ you.

Geno
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#9 User is offline   Madvarga 

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Posted 04 August 2011 - 06:22 PM

I definitely dont expect it to be a snap. It would be a great accomplishment to achieve a goal like that but I have to be realistic in the fact that I will require professional help. I should have went into mechanical engineering instead of Petroleum. So what I will probably do is have it built properly, but I will have fun taking it apart at least. :B):

Since you are willing to share your expertise with me I would love to hear of one of your favorite 400HP proven combos with this engine. $4k was just a number I threw up there, if it costs more then so be it. This engine will be the heart and soul of my 1980 Trans Am resto so there is no room to cut corners. After calling around and talking to numerous mechanics in my area I found someone that is willing to meet with me and discuss my plans and he says he has plenty of experience with Pontiacs. In fact he kind of sounds similar to how you speak about them. Hopefully our meeting goes well. If I can give him a list of parts that I am interested in using then I can also see how he reacts and share my experience with all my Pontiac lovers on here.

Thanks Geno, you rock!

View Post72 blackbird, on 04 August 2011 - 05:52 PM, said:

Chris,
I hate to burst your bubble, but getting 350-400 hp from a 400 with a $4k budget is a bit overoptimistic for a first timer w/no engine building skills. The hp output you seek from a 400 isn't impossible, but will require ported 72cc iron heads, and most head porters typically charge around $500-700 for this mod. Pontiac heads cannot be ported like Chevy heads- an improper porting job can actually decrease flow, so only a well known Pontiac builder should be used to do the port job. Increased port flow in the 240-250 cfm range, combined w/ a 9-9:5:1 static compression ratio with the right cam and induction usually results in a 375-400 hp output in a 400. You'll also need dished pistons to keep the compression at 9.5:1 or less. Flat top pistons w/ these 72cc heads results in a 10:1 compression- too high for pump gas- despite what some so-called experts will tell you, doing so will hammer your bearings w/ detonation and result in eventual engine failure (rod or bearing knock).

To get 350-400 hp from a 400 also requires complete machining of the block, crank, and heads- no shortcuts anywhere. The block will have to be cleaned and magged, line honed,decked, bored and honed w/a torque plate, the crank turned, balanced and polished, the cylinder heads surfaced, 3-angle valve job done, new valve springs, retainers, keepers and bronze guides installed. All of this machine work isn't cheap- be prepared to spend at least $800-1000 in machine work and at least $1500-2000 in new parts. How do I know much it costs to do all of this and what parts will work together to make that power? I've been building Pontiac V-8's and other Detroit engines for over 20 years, and when it comes to Pontiacs it's safe to say I know them well.

I don't know how proficient your mechanical skills are, but putting together a Pontiac V-8 for the first time should be done under the watchful eyes of an auto tech instructor or experienced mechanic- you don't want to screw something up after spending over $3k in parts and machine work. I've gotten more than one rebuild from so-called internet-taught Pontiac owners who thought it would be a snap to rebuild their engine by themselves and ended up damaging some internal parts. My customers have little hesitation paying me to assemble their engines- they know it will be done correctly the first time and will run well.

Feel free ask me any questions you have about proven 400 combos- I'm more than happy to share my findings w/ you.

Geno

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#10 User is offline   72 blackbird 

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Posted 04 August 2011 - 07:26 PM

Chris,
You never told me what heads you plan to use- that will have alot to do with getting the hp you want. And I'll be happy to compare notes w/ you once your builder reveals his parts list-I like to see if my peers are keeping up w/ the best parts.

Geno

PS- thanks for the praise. If you don't throw money, give me positive feedback-lol!
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