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Tomzern

Used the wrong block for 89mm overbore. What to do?

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Hi!

 

Sooo, I have an ongoing stroker build and just AFTER I got my F54 block resurfaced and bored to 89mm I found out that the best block for an 89mm overbore is the N42 and the F54 is a rather terrible choice for this. Wish I would have found this out before I bored it, but it's already done :(

 

Now I am stuck with a finished F54 89mm block and I am unsure of what to do next.

 

This engine is going to be a street engine and not a 10000rpm race engine.

 

Is there anyone here who is running an F54 based stroker?

 

Will it almost certainly fail?

 

Any constructive input is appreciated here:)

 

 

-Tomzern

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Were the bores Sonic tested before it was bored?
Or were you just a cowboy and bored it on the original bore centreline?

 

FWIW I went through 4 blocks - both N42 & F54 - before I found a my current F54 block that could take a 89mm bore safely - while retaining 120 thou wall thickness.

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Were the bores Sonic tested before it was bored? Or were you just a cowboy and bored it on the original bore centreline?

 

Well I guess I am a cowboy then I just handed my engine mechanic the block and one of the pistons and told him to make it fit. It's my stupid fault of course. Should have done more research, but now it's done.

 

At least it's good to know that there are F54 blocks that are thick enough.

 

I will get it sonic tested and just take it from there. Thanks guys!

Edited by Tomzern

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My engine builder had a F54 block with a crack in the deck along its length that was un-repairable,

so he milled the top of the deck off to see where the bore core shift was.
Notice how non-concentric the bore castings are - this make sonic testing and off-set boring a must! 

post-3435-0-90692200-1454444303_thumb.jpg

Edited by Lurcher

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They are offset exactly the wrong direction there lurch---woulda been great if the core was the other way round, wouldn't it!

 

Coulda had a killer thrust side thickness to bore into, and moving the bore that direction helps with valve shrouding too.

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Hi!

 

Sooo, I have an ongoing stroker build and just AFTER I got my F54 block resurfaced and bored to 89mm I found out that the best block for an 89mm overbore is the N42 and the F54 is a rather terrible choice for this. Wish I would have found this out before I bored it, but it's already done :(

 

Now I am stuck with a finished F54 89mm block and I am unsure of what to do next.

 

This engine is going to be a street engine and not a 10000rpm race engine.

 

Is there anyone here who is running an F54 based stroker?

 

Will it almost certainly fail?

 

Any constructive input is appreciated here:)

 

 

-Tomzern

I ran (and still have) an F54 block 3.1L from when I was 17 until I was 21 when I took the car apart. It ran fine. I doubt it's an issue unless you start revving high, making a lot of power, or just got a really bad block with thin walls.

 

I didn't bother with sonic testing. I feel like this is a matter of what's best and what will work and you're at the point where you can spend extra time and cash to do whats best but really... really, what you have will probably do just fine for your intents and purposes.

 

But that's just me. :bonk:

Edited by josh817

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My engine builder had a F54 block with a crack in the deck along its length that was un-repairable,

so he milled the top of the deck off to see where the bore core shift was.

Notice how non-concentric the bore castings are - this make sonic testing and off-set boring a must!

 

I don't think this is an F54 block as it doesn't have the siamesed cylinders between 1-2,3-4,5-6.

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I don't think this is an F54 block as it doesn't have the siamesed cylinders between 1-2,3-4,5-6.

 

Common misunderstanding. It's the coolant passages that are 'siamesed' on the F54, for more even cylinder cooling. It means less metal, not more.

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Actually I enlarged that picture and you can see the metal between 1-2,3-4,5-6.

 

The point is that the cooling passages are siamesed on the F54. That means less metal, but not none.

 

An N42 cut in the same way would look quite different. You'd see less coolant passage space and more metal.

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Actually I enlarged that picture and you can see the metal between 1-2,3-4,5-6.

 

You can see metal, yes, but if we cut that block down another inch you'll see an open gap. That open gap is what we're talking about, the N42 block does not have it. The webs are solid all the way down on the N42, and the F-54 block is only solid at the top and bottom of the bores.

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