[ihc] Ted's under pressure

["Jim Grammer" <jgrammer@xxxxxxxxxx>]

Date: Thu, 5 Feb 2004 18:43:42 -0500 (EST)
From: Ted Borck <tborck@domain.elided>
Subject: [ihc] Re: SII 345 compression test

Looking at a SII with a low mileage rebuilt 345.

Compression varies from 90 - 98 - 100 - 110.

I don't remember what is considered to be OK.

I RTFM and was unable to find compression specs.

Anyone know?

Thanks

Ted -

I've compression tested *lots*(like a couple dozen at least) of IH SV-8's
over the years. I write the #'s on the valve cover in Marks-a-lot or paint
pen so I don't have a piece of paper to go missing years later. Consistent
with the other responses, engines in reasonably good running order(whether
266/304/345/392) clocked 125-160PSI. All tests warm, throttle/choke plates
blocked fully open, and a freshly charged known good battery. 4-6
compression strokes to make sure the #'s have peaked. A little lower than
125 I don't worry too much as long as the #'s are within 10%, the engine's
not smoking excessively and has good HOT idle oil pressure. These last 2 are
usually *not* the case when the compression is low, and I know I'm messing
with a tired motor.

The point may be moot, but you need a wet/dry compression comparison to
isolate whether it's rings or valves causing the low #'s and high variation.
'Rebuilt' means a lot of things to a lot of people, starting at just
replacing some gaskets :( Others will just do a re-ring(with or without
touching the heads), or a head job alone and call it a rebuild. A fresh set
of rings in an otherwise untouched IH SV bore is practically guaranteed to
be a 'no-seat' disaster.

To me, the hot oil pressure is even more important than the actual
compression. The engine needs to run for 20-30 minutes on a fresh oil
change(spec is 30W)so that the pressure stabilizes as low as it's gonna go.
Much less than 10PSI and I'll park the engine as not worth putting in, even
if the compression's great. Beats pulling it back out in a year or 2 when
the valve train starts making noise that won't go away ;)

Jim