389 for a 71 lemans

Pontiacpower

Pontiacpower

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hello all. i have been looking for an engine for my lemans for a while now but a lot of these pontiac guys in michigan want 400 bucks for an engine in need of rebuild. i found a 389 for 70$ that is nearby and its in pieces but it seems everything is there except the carb and intake and manifolds. it just so happens that i have all three of these from a 400 that i intended to bolt onto my 350. my question is if this is a good idea for a rebuild? will the intake bolt up? will headers for a 400 fit on the different shaped heads of the 389? the story i was told is that the guys dad was going to rebuild it but got sick and abandoned the idea and later passed away. its a beleiveable story i suppose because theres two sets of pistons, rods and a bunch of pulleys and a couple cooling fans. the engine is a 65 according to the heads and it was in a gto. bore needs to be honed and the block is a little rusty but in decent shape. any input is appreciated.
 
you have to also look at the block code to determine what you are dealing with. An excellent source for what fits with what is Wallace Racing. The link below covers intake manifolds. The headers for Pontiacs cover all engine sizes 326 to 455, there is no special header for a 389.

http://www.wallaceracing.com/intakesearch.htm
 
if its a 65 block like the heads that come with it i should be fine right? i think it was wallace that i checked to see if anything fit but i cant remember now.
 
The purpose of checking the block code is to make sure you are not buying a 326 or a 350, etc.
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I see. I will get the code from him today and confirm the displacement. is a 389 a good foundation for a build when compared to a 400? I know the 400 is going to have more power but is a 389 a motor that compares to the 400? are those 11 cubes and different heads a deal breaker?
 
Not a deal breaker for a price of $70 but make sure you have the block and heads checked for cracks before putting any more money into it.
 
so the block number looks like 9778789 which would mean that the block is a 389 according to Wallace racing. correct me if I'm wrong as the picture is tough to read. I can not make out what the numbers under the casting say.
 

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that would be a 65 or 66 389. The engine code is on the pad on the block in front of the passenger side cylinder head.
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does it matter what the casting sais? I know that the 557 400 blocks are weaker than others. was there a 389 thinner cast?
 
those 400 blocks in 75 were thinner to reduce weight, they werent worried about that when making the 389
 
I knew that about the 400s. ive done a lot of research on the 350 400 and 455 but I have not done much on the 389. I know 2 things about the 389........tri power was really cool and stock 400 heads breath better.
 
one thing I have failed to mention is that I did find a few candidates at the junkyard. few 400s and 1 455 were still sitting there but the yard wants 325 for me to pull it. thoughts?
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Well the $70 price for the 389 tells me buyer beware, that price is awfully low. You will have to spend money at the machine shop to check the block and heads whether a 389 or a 455. Personally I would go for the extra bucks and seriously consider the 455. The torque a 455 can put out is truly awesome.
 
455 sounds like a lot of fun but would that even get above 10 mpg with one of those? I like to drive my car on the weekend so decent mileage would be nice
 
that depends on the rest of your build, using a spread bore carburetor a mild cam and gears no higher than 3:36 you will get high teens on the highway
 
thats pretty impressive haha. cant believe thats even possible. I going up to the junk yard today to see whats left up there
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