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I've got an engine out of a 1966 thunderbird, the 5th letter in the vin code is z which is supposed to be a 'special' 390, 10.5:1 compression, 4v, etc.
Anyone know if this is a good motor to build up?
Is that 10.5:1 compression gonna be too much?
thanks
 

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I don't think there is anything too "special" about that motor,just sounds like a basic 390 4 barrel engine...10.5 compression should be ok with premium octane gas.Is the engine still all original? You might want to think about freshening it up before you start building it up if it is.Yes it is a good engine to build depending on what you want to put it in and what you want it to do.
 

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There may be some argument over fine points, but my opinion on 390's is listed below.

Your question has an answer that is based on what you mean by "build up".

If the engine is going to need pistons rings, bearings...in other words a full rebuild. Then it doesn't really matter which 390 engine you start out with. Except for a very few, very rare, solid lifter High performance 352/390's from early '59 to 60-61 and to a lesser degree 66-68 Mustang/FairLanes, most 390's are pretty much the same. Even those that were in pickup trucks and Mom 'n Pop grocery getters...by the time you change cams, manifolds and put headers on them...it really doesn't matter whether it started out as a 2-v, 4-v or better...you are going to throw away most of that stuff anyway.

So, when it comes down to push or shove, unless you are building a restored car, or freshening up an original; it doesn't matter. bottom line ... "Z" 390 motors are OK for something to swap in and keep for a while, but not anything extra special.
 

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I have a 65 Gal with a Z code 390 4v. It has detonation problems at WOT but I have yet to try anythng to relieve that problem, ie better cooling, serious additives, and or a good drain of all gas and a fill up with ALL high octane gas.
 

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with 10.5 to 1 with iron heads you will detonate with a full timing curve unless you have race gas. Modern cams can still make great power even if you bump down the compression.
 

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I ran a 429 thunderjet with 10.5 compression and it ran fine on premium gas.I used to even run it on regular and it was fine unless I really got on it hard but for everyday around town driving it was fine.If I wanted to play I filled it with premium.
 
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