The water pump was purchased from a local (Detroit area) "accumulator" of
Sunbeam parts 14 years ago. I believe he had them rebuilt locally.
But, the basics should be covered. The condition exists on both this
low mileage engine, and a similar previous low mileage 302, but not a
rebuilt 260. Even though I am running a Holley electric pump (in spare
tire well) and a pressure regulator near the carb, it can vapor lock when
the HOT engine is dropped to under 1500 RPM. It sometimes also boils the
gas in the carb after the engine is turned off! To date, I have installed:
a high density 3 row radiator core, wide 6 blade stainless flex fan (with
original shroud), electric pusher fan, blocked off horn holes in radiator
support, sealed bottom of shroud to crossmember to prevent hot air
recirculation, and tried 160 deg thermostats and plain thermostat restrictor
plates with various hole diameters. The engine won't actually boil over if
the electric fan (thermostatically controlled) is working, but will run to
230 deg after maybe 1/2 hour of running at all speeds. Engine RPM at 65 MPH
is about 2700 RPM. The cooling changes were put in place one at at time.
To help stop vapor lock, all the lines from the pump have been carefully routed
away from the exhaust and covered in a high tech insulating wrap. The carb
(Holly 4 bbl) has a 1/2" phenolic spacer under it, along with a GM carb heat
shield under it. The hood is a LAT with the exhaust vent in back. Also,
the heat crossover in the intake is blocked off.
Engine timing is set at 12 deg BTDC, with 36 degrees total. The only things
that I can guess that may still be causing the problem are that the flex fan
is actually flattening out at speed and blocking air flow, or that the rebuilt
radiator is defective or just plain inefficient. The questions about the
anti-cavitation water pump were a result of my trying to figure out what may
be different on my car as opposed to 95% of the other Tigers out there.
..... ANY IDEAS?
*** Forwarding note from I1922283--IBMMAIL 06/04/96 02:25 ***
Date: Mon, 3 Jun 1996 23:23:14 -0700 (PDT)
To: "STEPHEN SALATA USAET(UTC -04:00)" <usfmdgbj@ibmmail.com>
From: Tom Hall <Modtiger@engravers.com>
Subject: Re: Anti-cavitation Water Pump
Cc: tigers@autox.team.net
At 09:42 AM 6/3/96 EDT, you wrote:
>Does anyone have any experience with running the so called
"anti-cavitation"
>style water pump? It was used on the 302 Boss engine (among others). It
has
>curved impeller blades instead of the common straight blades. I'm running
>this pump on my 302 Mk.1, along with every cooling trick I can think of,
and
>it still runs 230 degrees and vapor locks the carburetor at 70 deg ambient
>temperatures. Maybe this style pump is contributing to this problem.
Stephen,
I've run this pump for years, and I'm curious, where did you find one to fit
a Tiger. I had to make mine from SVO parts, including pulling the old
impeller, changing the seal, and pressing the new impeller on to the shaft.
A lot of effort, but I consider it worth it to reduce the cavitation common
to straight blade pumps. This is particularly true with 3.54 and up gears.
It frequently takes a lot of effort to pin down why your Tiger runs so hot.
You must be sure that you have covered all of the basics to assure that your
system is operating at full efficiency. You also have to be sure that you
don't have problems like combustion leakage into the cooling system. The
problems are frequently overlapping, and this makes them hard to pin down.
We, on the net, may be able to help you if you can be specific, and tell us
what youv'e done to date.
Because of the electric fuel pump, vapor locking is not a common problem.
You will have to define your terms so that we can offer suggestions.
Tom Hall
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