5/11/04
James et all,
A 10.4 to 1 C R is all fine to talk about, but how does one stop
the dieseling after shutoff when using carburetors???? I have several cast
iron engines (Volvo & Morris) with CR of about 8.75 which diesel furiously
even on the highest octane fuel I can buy here in Northern California. I
assume that fuel injection systems cut the fuel supply completely at
shutdown so no dieseling is possible. Is this the case??? Is that 10.4
supposed to be with the sheet metal head gaskets? There are not many
choices of head gaskets for these engines as far as I know. So many
questions---------.
The answer I have heard for the "ovality" question is to get your
pistons +.030" and bore the cylinders, not just hone. Then you have
complete control. The required bore size should be about +.010" compared
to the original 3.9 size.
Cheers,
David Kernbeerger
-----------------------------------------------
>Dave,
> W/out any machining, the C/R is about 10.4, which is fine w/pump gas
>and aluminum heads. A thicker gasket will lower that some. As far as I
>know, no machining is required to pistons or head to make this combo
>work 'out-of-the-box', so to speak. Depending on my rocker ratio, I'm
>gonna' make sure there is clearance between the valves and pistons, but
>that's it. Hope to be there next month.
> If I recall, some 3.9 and later blocks had some ovality to the
>bores, so D&D recommends that you hone the bores to take the 255 pistons
>in +0.020. That's what I did, for insurance, but individual engines may
>vary. It's just too bad that these pistons can't be gotten
>off-the-shelf as hypereutectic castings. There are other piston options
>if you are willing to re-sleeve the block. Ford 2300 pistons come in
>around 3.75" if my memory serves me. One person reported a non-fatal
>block crack when re-sleeved to 4.0" inches, so Chevy LS1 pistons at 3.9"
>might work if the deck-height is OK. Wildcat, in the UK, makes a
>special 4.00" bore block (new casting, I believe) and cranks to take the
>vererable BOPR up to 6.0L if you can afford the price of admission (I
>can't).
> That Chevy LS1 looks mighty fine if you want to push the limit over
>4.9L, as does the Northstar, but you've all heard me drool over those
>before........
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