Iron Pukes & Chebbys

["Bruce Hevner" <scramblr@xxxxxxxxxxx>]

>original chevy 153 - 3.875"b x 3.25"s, same as 230 six, 90hp with 1bbl.
>chevy marine 181 - 4.00"b x 3.60"s, 140hp with 2bbl.
>pontiac 'iron duke' - 4.00"b x 3.00"s.

>it was the poncho that had all the gm speed equipt.  it has similarities
with the chevy four but a >lot of things are changed.
>stock blocks are significantly lighter than chevy 153/181, things like
bearings and wristpins are >smaller.

>they all - chevy six included - have gear driven cams.  that's why the amc
six hei swap needs an >amc gear - cams spin opposite directions,
distributors don't.

>also, the 153 and 230 use 283 sbc pistons.  rods are similar too, but wider
on the big end just >like amc 258 vs. 304/360 rods.

Kinda right and kinda wrong.
I have owned AND worked on all three of those engines.
The original ChevyII 4cyl (which is what I traded in to buy my new Javelin
in 1968) was not a very good engine although you COULD use SBC pistons AND a
SBC head (with heavy mods). They ALSO had a "Marine" head for this motor
which had better ports than the street version. They were used a good bit in
Midget racing back then.

The "Chevy Marine" (they were known under several different "Marine Brands")
and "Iron Duke" are the SAME motor with a few differences. They are ALL
Pontiacs actually. These engines underwent a LOT of changes over the years.
I know of at LEAST five different piston changes and MANY cyl head & head
gasket changes. SOME of the heads will interchange & some will not
(different head bolt pattern). They are TOTALLY different from the earlier
"Chevy" 4 cyl.

When I had my shop a local marina approached me with a problem. The
"Mercruiser" 181's were galling piston skirts left and right. These were new
boats with just a few hours on them. The factory had assembled them WITHOUT
torque plate honing the blocks. The cylinder bores were SO far out of round
they were cocking the pistons in the bore and under load would gall a skirt.
In one instance it had cocked the piston so bad it spun a bearing! I was
torque plate honing them for the marina which would then put them back
together. Normally I leave .003 (heavy weight block) to .005 (light weight
block) to finish hone with a torque plate. I had to leave at LEAST .007 to
have enough meat to hone on the "Pukes". I had to buy 2 different torque
plates, different bolt patterns and bolt sizes. That cured THAT problem,,
and then there were the head gaskets,,,,
Oh don't get me started!!!
Bruce Hevner



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