Ideal engine specs?
Turbo Mini Forums

Hi, from the USA,
I have a 1960 mini highly modified, with a 1430 mill after much consulting with David Vizard over here and many tuners over there. It has been fun for about 8 years. The other day it coughed the oil pump and the level of internal damage is unknown (it just lost power and I noted the low pressure).
At this point I have been trying to decide between a turbo and a supercharger. I think the Turbo is winning out because I don't like the quality ofthe kits I've seen and I would like to intercool it which might be difficult.
I have done both in the past and fabrication is easy and enjoyable for me as I have a mill, mig and tig welders, a metal lathe and a lift.
Now for my questions.... I have a doner A series motor with the big journal crank and some race prepped cooper S rods so we can stroke the motor if we choose. I would also harden the crank (Nitride) and can obtain pistons with almost any pin height as well as dish, from J&E Pistons. I have both an aluminum head, ported with big valves (rimflow), and a Mini Sport ported head with big valves, and some roller rockers I have a Kent Cam 286sp but assume that thats too much camshaft.
What is the ideal bore and stroke for a Fast road motor? How about CR? I figure I wont run more than 8-10lbs of boost.
As far as the Turbo goes, Garrett Turbo's engineers are working up a couple of options for me, but we are working on getting boost at a very low RPM (around 1800-2200). I'm guessing it will be in the GT15-GT20 range and they are working on the compressor and turbine trims and A/R's. Also, I don't want to butcher the bulkhead on this nice old car so I will run the Hif44. Do you need throttle shaft seals with this carb on a blow through?
I also want to fabricate a plenum because I will be running an intercooler, but I still have never found the definitive answer on design or size of the reducer, and if it should be like a stub stack, as I would imagine. Where can I find a used LSD or maybe just a crosspin diff for a remote gearbox, and maybe some straight cut primary dropdown gears?
Despite how it may appear, cost is a factor--hey we have It rough over here these days!
Help with these questions would be appreciated,
Russ

Welcome!
I would imagine the 286sp is indeed to much cam if you want power low down. A simple option would be an MG Metro NA cam or an SW-5.

If the rockers are 1.5:1 then they wouldn't be advisable for a torque monster either.

Bore and stroke are fairly well debated issues for turbo motors. There was a time when people stuck with +20 bore as they thought bore flex would be an issue. Nowadays people are running 73.5mm without issues.

You could keep the car driveable with a CR of ~ 9:1 if you're not going overboard on boost.

The best way to size a turbo is doing the airflow calcs and comparing with compressor maps. Maybe VNT would be an option if you are looking for quick spooling. Check out Mini13s work on the subject.

There is a turbo specific HIF44 which most people use for turbo motors. However, there are also guides on here to help to convert a standard HIF44 to turbo use. You are right about throttle spindle seals. They are installed the opposite way around on turbo carbs.

You may not have to fabricate a plenum as the MG Metro Turbo plenum is used with the HIF44. I don't know how available they would be in the States though. I believe it was Iain(?) who has a guide on restrictor plate findings on here somewhere. From memory it's a 38mm hole in flat plate.

EDIT: Made it slightly more readable

Edited by GaryOS on 10th Sep, 2009.

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

Sorry to here about your 1430, but the turbo plans sound interesting.

Here is some information on the restrictor ring which might be of some use to you:

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=513

Without cutting the bulkhead you will have clearance problems fitting the turbo in it traditional location and you might want to think about relocating it over the clutch.