Flat top pistons will give you a theoretical 9:1 compression ratio. I
have heard that you can go up to 9.75:1 and still use pump gas. CR will
change a little bit depending on how much your head is milled (if at
all), and how big of an oversize piston you will need. You will probably
want to cc the combustion chamber (measure the volume in the head, in
other words) and use that together with the stroke to calculate CR.
There should be some info in the arhives on how to do this. Or someone
else can chime in.
The TSI-275-4 is a pretty good cam. It is a little lumpy, but not overly
so, and it's a good all-around cam. Expect to idle about 1000 rpm or so.
Larry Macy runs one in his 1500 Midget. If you're having a machine shop
do the head, a good port and polish is not a bad idea.
You'll want richer needles for the SU's I have AAB's in mine, and I'll
let you know how they do when I'm finally on the road.
You mentioned a header. TSI sells the Maniflow 4-2-1 for the 1500
Midget. That's where I got mine.
http://www.totallytriumph.net/spitfire/engine_building.shtml is a good
read.
HTH!
-=Chris
Chris King
http://home.comcast.net/~kvcbk/
<-----Original Message----->
From William M. Gilroy
Sent: 4/25/2004 7:12:24 PM
To: spitfires@autox.team.net;spridgets@autox.team.net
Subject: Re: Questions about engine rebuild and machine shop work
Hi,
I am about to rebuild the engine in my 77 MG Midget with a Triumph
1500cc
engine. That is the reason for posting to both lists.
The engine in question was a low compression smogged engine. It will
have
twin 1.5 SUs and headers. This car is used for driving in NJ, 0 to
seventy
back to 0 between traffic lights :-) I would like to make it a bit
higher
compression and change the cam, but I don't want a really lumpy idle and
a
power band that starts high up. This is what I plan to do:
1) Send to machine shop and have the head done if required
2) Have the block hot tanked.
3) Cylinders checked for roundness and size. How far can you bore one of
these engines out or do they need to be lined then bored.
4) Should I have the block line bored?
5) Thrust washers pinned in place. Any pointers on what the looks like?
6) Higher compression UK spec pistons. What is a a reasonable
compression
ratio, and I am not worried about using premium gas.
7) I am thinking of a Ted Shumacher has a TS1275 cam.
8) Replace the valve springs
9) Do I need umbrella seals on the intakes valves?
10) New pistons and rings.
11) New oil pump
12) I have heard of having the oil passages bored out. Any thoughts?
Anything that I have missed? Any thoughts? What would you do, or what
would
you do differently?
This is my first time doing this so I have a few questions. Thanks for
any
help or input.
--
William M. Gilroy
wm.gilroy@verizon.net
When those who make the law
Break the law
In order to enforce the law
There is no law
.
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