Jeff,
There's a lot of thought out there on what things need to be done on the
1500 block.
But there are several things that really should be done to increase the life
of the engine.
First, have the main oil galleries drilled out to allow for more oil flow.
Add to that an oversized oil pump. APT has one. Getting oil throughout
this engine is extremely important. And keeping it cool is just as
important. So add an oil cooler kit.
The thrust washers on the 1500 blocks have a nasty habit of falling into the
oil pan when they wear out. To prevent this, have the machine shop pin
them in. Once they fall out and the crank rides on the block, you might as
well get a new block 'cause that old one just became a big, heavy paper
weight.
One idea is to also use the cam to a Spitfire 1300 and have the 1500 block
machined to accept cam bearings. Yes, the 1500 does not use bearings on
the cam. Yet another reason why good oil flow is imperative. I didn't
machine for cam bearings.
As for the head. I used a 285 cam with the vernier gear set to a TR6 (twin
chain) and advanced the cam 4 degrees to bring the power range down. I
didn't open up the intake or exhaust valves, but I made some nice DEEP D
shaped pockets behind the valves (for good puffing action) and did a
_little_ opening of the intake and exhaust ports, mainly to smooth them
down. Too smooth apparently isn't good either. Twin springs to complete
the head. Also, the machine shop shaved a hair off the head and the block
to ensure a good seal. MGTs (where I had my engine done) uses a real good
head gasket set, rather than the one from Moss. And the ARP head studs are
3/8" too short. I had to use Moss studs (9) and one original stud. Yes,
one of the Moss studs stripped (no, not the nut) at 40lbs on the torque
wrench. Yes, the torque wrench was calibrated correctly.
For carbs, Dan Dwelley and I opted for the UK spec SU HS4's, which have the
1 1/2 inch venturi. Opinions vary on which are better, the Weber or the
SU's. The DGV isn't a performance carb. I think Dan has an extra set
complete with linkage and intake manifold. Dan? I used a set of stock MGB
Ram pipes in conjunction with K&N 6" round filters.
Cooling is an issue as well. The '75 uses a smaller radiator than the later
cars. You may want to upgrade to a later radiator, or think about the GEO
aluminum radiator conversion. I don't know much about it. I used my stock
radiator (which is about 3" longer than yours), but recored with a 3 row
louvered fin core. Three row staggered cores are better, but they are
really to wide for our engine compartment. Some list members use a 10 or 12
inch electric fan for better cooling, but since the motor was peppier, I
went with the mechanical water pump and fan from a '74 Spitfire. No clutch,
and a much higher CFM. We did have to cut and reweld both the shroud and
mounting brackets in the car to bring the radiator forward 3/4 of an inch to
prevent fan contact at high RPM, which moves those fan blades quite a bit
forward. If you get the larger radiator, you also need to find a later
mounting bracket for the overflow tank as the stock bracket mounts too far
forward.
For exhaust, I used Moss' 4-2-1 header and a Monza. It's really loud, and
I'm contemplating adding something in-line to quiet it down.
If you're changing the pistons, go with the high compression ones (non
dished) which are 9:1 vs. 7.5:1. Available in standard, 10, 20, 30, and 40
over. I used the hepolite 030 over pistons.
And make sure the rotating mass is balanced. From front pulley, to crank,
rods, pistons, flywheel, and clutch pressure plate.
As my car was completed yesterday, and I only have 96 miles on it, I can
only say that it's extremely peppy, that cold oil pressure with 20w50 is
80lbs and 50 hot, and that the engine temp remains at 165/170 in 80 degree
weather. I haven't stepped hard on it yet b/c of break-in, but it REALLY
looks to go. We shimmed the oil pressure relief valve to get that oil
pressure up. I'm changing to synthethic at 2 to 3K miles, after everything
has had a chance to settle in.
Good luck with the rebuild. Ted Schumacher at TS Imports in Ohio is worth
giving a phone call as he is excellent with the triumph motors. He helped
Dan and I out quite a bit when we had questions. He's where I got the
Vernier gear set. Not an easy thing to locate. Rob Medynski at MGTs has
them fresh on the brain as I bombarded him with opinions on what we needed
to do to get the best compromise of power and durability from a 1500. He's
very helpful on the phone as well. And I know he has a few overflow bracket
on parts cars, as well as a radiator. I have a spare radiator that needs to
be recored that you can have for shipping if you want. Otherwise, to the
trash it goes.
Hope this helps.
Michael
'78 Midget (amongst the living once again)
'87 300ZX
-----Original Message-----
From owner-spridgets at autox.team.net
[mailto:owner-spridgets@autox.team.net]On Behalf Of Jeff Wilson
Sent: Sunday, July 30, 2000 1:56 PM
To: spridgets@autox.team.net
Subject: 1975 1500 Engine Rebuild
Head Work,
Thoughts on Head milling (amount) and increasing the Size of exhaust
valves (size - type),
I have already secured a higher performance cam and Webber down draft
and would like to hear of any other engine performance feedback.
Jeff
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