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Joined: Apr 2009
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I have an oppurtunity to buy a 1976 pontiac XY 400 stock bore engine with 6x heads (8,s) 98 CC'S, stock crank (N)cut 10/10, with rods and pistons for $250.00. Engine is torn down and has been kept oil down and sitting for about 20 years. I was think about buying this and swapping out my 350 (4 speed) in my 68 Bird that's been plagueing me with problems. This would give me the oppurtunity to build the engine myself and know all the specs. (Bought my 68 from Brother-in-law and don't know any of engine specs and neither does he lol).

Fair price for engine?

Should I swap to 400 engine?

Thanks for help and comments



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I would expand your list of qestions with another:

Should I buy THIS particular 400? Because it will probably not be a direct bolt-in unless all 5 engine mount bosses have been drilled and tapped.


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I "think" 76's had both mount patterns. Check to be sure.
As long as all it needs is assembly, thats a good price.


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"Just needs assembly" sounds like an urban legend to me. It's a good price for a complete motor. A solid platform to build a good running motor for your car. Just add water and about $3K and your good to go. If the bolt bosses are not drilled you can get them drilled or I think they make adapters for the mounts.

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I`d mill those heads to 88-90 CC before assembly....that might be another $300


FireBjorn http://FirstGenFirebird.org/show/closeup.mv?CarID=221
69 convertible 400 (was 350) Natalie, SOLD
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Depends on the pistons used. I have a set that would put the CR right at 9.3:1. Perfect for pump gas.

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excactly...I had heads milled to 88 CC, gets my CR at 9.2...perfect.


FireBjorn http://FirstGenFirebird.org/show/closeup.mv?CarID=221
69 convertible 400 (was 350) Natalie, SOLD
58 Alfa Romeo Giulietta Spider Veloce , Gina,(SOLD)
1974 Alfa Romeo Spider, Mrs Robinson
2011 Volvo C30 T5 , Victoria ,.....( or Vicky)
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Are you sure about the cc's on the heads? A little quick research indicated that the 6X-8 heads should measure about 114 cc's. The 98 cc number you use would be more accurate for 6X-4 heads. I have a perfectly good set of 6x-8's in my shop that I replaced with higher compression heads. If it were me buying it, I would not plan on using those heads. I don't think you will like them very much.


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If I end up parting out my car, my engine from carb. to pan for 3k would be the deal of the century. Drop it in, hook up your linkage and power, trun the key and away you go!




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Heck, for another $400 I'll leave the LBMs on there, and then for another $1200 take my M22 (new main shaft and all new harden steel gears, 2.56 1st gear), NOS shifter body & NOS 5325 round handle shifter and you are good to go! For $4600 you'd have one serious killer 400/M22 combo...





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