Re: Piston Questions

[n9ads@domain.elided (Howard R Pletcher)]

On Mon, 19 Jan 1998 18:21:20 -0500 (EST) "DENNIS L. PETTERSON II"
<dpetters@domain.elided> writes:
>Hi All!
> I was sitting with my Northern Auto Parts catalog and gave them a 
>call to see why they say "except scouts" on the 304/345 engine rebuild 
>kits.Turns out that  they include a new oil pump in the kits and the
pump will 
>not work on Scouts.The sales man said they would sell the kit without
the 
>pump and the price would be about $507.00 or so.The salesman also asked 
>"are the pistons flat top".I said they were and then said "why do you
>ask?".Turns out they show a domed piston that they can sell with the
>kit.Is this piston from the heavier duty trucks or is it from the LPG
>fueled trucks?If the LPG engines used a higher compression piston can 
>the gas engine use this piston or is the compression ratio too high for 
>gas?
>
>
The early IH V-8s had the domed pistons.  I don't know just when the
change was made to the flat-top pistons, but the change was made for
emissions reasons--the domed pistons have a greater surface area for a
given combustion chamber volume. The flame in the cylinder is quenched
when it contacts the cooler surface area, resulting in more undesirable
emissions.  The change to the flat-top piston gave lower emissions.  This
change occurred somewhere around 1970 and is probably connected with the
"E" engine designations (V-304E, etc.), although I don't have any
information here to verify this guess.  I don't believe the two types of
pistons were used at the same time and I believe different heads are
required for each type piston.

Howard Pletcher
Howteron Products Scout Parts