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Buster

400 block ID

Question

Good Morning , I'm in need of information identifying an engine block in a older firebird I purchased. it is not the original for sure.  Can  someone  help ID what exactly I have?  On the back of the block next to the distributor is stamped 75, the back of the block also has 500557 stamped. The heads are 6X. I believe this engine is from the mid 70's and I'm going to go over it and possible try and gain a few more HP without going all out. I'm told it only had 62,000 miles on it so I don't want to do a complete rebuild if not necessary. I will find out more after a thorough investigation.  Any help would be appreciated.

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The 5000557 casting was used as early as 1975 and as late as 1978. There are 54 possible configurations, according to Wallace Racing.com. All are 400 CI engines. Do you think the engine was completely removed (as a whole) from another vehicle or do you think the engine was built with bits and pieces?

There should be a 2-letter engine code on the front passenger side of the block, starting with X, Y, or Z. This will help narrow things down a bit.

Starting around 1969 Pontiac cast a 2 digit year number next to the distributor. Since you stated it read 75, this means your block was probably cast in 1975.

Now Pontiac also usually had a three or four character date cast code right next to the distributor hole. It is usually a letter (A-L which means January - December), the date, and the last digit of the year the block was cast. However, just because your block was cast in 1975, depending on when it was cast, it may have been originally installed in a 1975 or 1976 model year car. For example, a date code of B145 would mean a February 14, 1975 cast and most likely put into a 1975 model car. While a L035 would mean a December 3, 1975 cast would mean installing it in a 1976 model year car.

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Thanks Frosty, this all makes sense. I'm told the motor was pulled from a mid 70's Trans Am. I'm fairly new at this Pontiac stuff, so I am just starting to do some home work on it.  I do get the concept of the dates. I previously owed a 68 mustang. So now it's carrying over to this build. Have you had any experience with slight engine modification such as intakes carbs maybe even cam swaps without complete rebuild?  this assuming the engine and compression is all good once I go over it.  I 'm told the 6X heads are the better ones for that time frame.

 

good info thanks

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The 6X heads are the most common heads of the mid-to-late seventies era. They are well worth porting, polishing, and doing valve jobs to.

What do you want to accomplish with the motor? What is doing at the moment that you'd like to improve upon?

Just for reference, I have a '72 Lemans convertible with a 455 bored .030 over (its now a 462) with a Melling hydraulic cam and high pressure/high volume oil pump, stamped steel roller rocker arms, ARP studs and bolts all around, Eagle crank, JRW pistons (9:0 to 1) on stock rods, triple angle valve job, port matched intake & exhaust, Edelbrock performer intake, Rochester carb, Ram Air restoration HO/RAIV exhaust manifolds (factory headers), Pypes 2.5" mandrel bent exhaust.

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Well, here goes. I have a 69 Firebird completely disassembled in my garage.  Every nut, bolt seat, suspension parts,  etc.will be either replaced or gone over upon reassembly. I do not want to install the motor before giving it a good going over. In doing so I would like to be sure it is a peak performance  without breaking the bank. I do have a budget for this but need to spend it wisely . I'm sure you can imagine the cost of every small part that needs replaced. I sold my Mustang , so I have that to put back in the FB.  I'd like to keep this one because it has some family history. But again just trying to get the most bang for my buck. Any knowledge or info is definitely appreciated, what to check for or watch out for.

 

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Posted (edited)

Let me ask some basic questions then. Is this going to be a pure restoration, or a mild-performance resto-mod, or an all out performance resto-mod project (I am not assuming this is a mega dollar Steve Strope/Chip Foose build mind you but you still want it to haul butt and stop on a dime and give you 9 cents change)?

All of us on FP have tips and tricks to share, the question we need to understand is what do you want when you are done (your vision of the car) and how deep is your wallet (not asking for a specific figure but some idea of how far you are planning on going and over what time period).

Also do you or your friends have the necessary fabrication, sanding, painting, upholstery, electrical, blah blah blah skills necessary to keep your costs down or do you know that some things will have to be farmed out to professionals?

Edited by Frosty

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Mostly original restoration aside from the motor. I have just about everything I need or within reach to complete 90% myself. I can swap engine parts but have never rebuilt a compete engine. Nor do I want to put 5K into it if not completely necessary.  Like to keep the engine cost to about $1500 max, so I realize it's probably just a good street tune on it.  Intake ,Carb Headers, maybe a cam.  I am able to lap the valves once I get the heads off.  I don't need a beast just a bit better than the original I suppose.  My biggest hang up is the paint. I haven't painted any auto's since the late 80's. And really don't want to blow money away learning again for one or two cars. Body work is not a problem, ( just time consuming). So that is were the bulk of the budget will go, Paint job.  Most everything as far as restoration parts are already  bought. door panels, wire harness, trim & hardware. I even had the tranny rebuilt. Getting ready to start the engine and rearend. Just a Sunday cruiser with a few extra ponies.  Any Tips for engine  tunes?

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Posted (edited)

Well I do recommend that you tear it down to the short block and thoroughly inspect it. Check the state of the rod and crank bearings. Check to see if there is metal in the bottom of the oil pan. Check for damage to pistons, valves, pushrods, etc. All that will tell you if you need a rebuild.

I would keep the original factory iron 4-barrel intake or find a '68-72 4-bbl manifold (non-EGR) from a swap meet for dirt cheap. Stock Pontiac intakes are surprising as good or better than most aftermarket intakes. No sense in wasting money on a shiny aluminum intake you don't really need. A properly re-built Rochester 4-bbl is fine.

Stock rods can be re-used so long as they aren't cracked. Use ARP studs and bolts through out. Don't assume the old bolts are any good. This is just cheap insurance. Chase all threads with a thread chaser/tap.

If the stock crank is no good, Eagle carries them.

Inspect the timing chain, look for play. I would probably just replace it with a double-roller chain set - just for insurance and reliability purposes.

Assume the water pump needs to be replaced. I recommend using a wide-mouth Mr. Gasket thermostat for better water flow. Mine is a 190 unit.

BOP Engineering has a new rear main seal that replaces the old rope seal. Rope seals were original from Pontiac and come in virtually every engine re-build gasket kit. The new BOP seals are suppose to be leak free when installed properly.

I would probably plan to replace the oil pump with a new one - just for insurance purposes. Mine is a Melling.

You can re-use the distributor or get a new one. If you are reusing the old factory distributor I do recommend eliminating any points or dwell with a Pertronix breakerless ignition kit. New cap, rotor, plugs and plug wires are a given. Be sure to properly gap the plugs. 

Triple angle valve job, port and polish, and match the intake and exhaust ports on the heads. Install/re-install harden valve seats if necessary (6X heads should already have them but they could be damaged by now too).

For exhaust you have choices: You can go with your favorite set of headers or get a set of Ram Air Restoration reproductions.  Ran Air is  pricey compared to headers but they do give a factory correct look.

https://www.ramairrestoration.com/lb-1-long-branch-d-port-factory-headers.html

As for a cam, that's up to you. I would probably go with a factory Ram Air II, III, or IV profile with matching springs, pushrods, and rocker arms from the cam manufacturer of your choice. For a stock build, the factory stamped rocker is fine, however, I upgraded to a stamped roller rocker arm for a few extra bucks, for better precision and reliability.

Did I miss anything? Obviously my fellow FPers are welcome to chip in with their recommendations as well.

 

Edited by Frosty

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Frosty, thanks for taking the time to walk through this. Good stuff here and a good place to get started on each. I appreciate your help.

I'll keep you posted. If this weather ever warms up enough to keep the toy garage heated.  Central Pa mountains, gotta love em.

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