Old Timey Stroker

[Twentyover]

In addition to the Pro-Touring cars on this website, I have an interest in old English sports cars. Many years ago, when I lived in SoCal, I vintage raced an MGB. Water over the dam... but I still have the car and am making incremental improvements. But that's not the point of this query.

I have owned an MGC-GT for a number of years. Not my picture, mine's buried in a barn

189430

It's been parked gathering dust since I blew the engine up a couple years ago. Many people are aware of the MGB- the MGC was the much less common six cylinder variant. Basically, everything under the hood and inside the front fenders from firewall forward was different.

189431189432

The engines are externally huge and heavy, while being small displacement on undersquare based on then current UK tax laws. Displacement is 2.9L, 3.28 bore x 3.50 stroke. The engine will never be an RPM monster because you can't get enough valve in it. It was supposed to be a long distance tourer, so torque production was targeted.

So I'm here 50 years on with a spare block thinking- this thing is supposed to have long legs, how about getting more displacement in it? A friend has a similar idea, but you can only bore the deal to a little over 3.2. So I'm thinking there are two other ways to add displacement - stroke and cylinder count. Adding cylinders is out, so I'm starting to investigate building a stroker. Unlike US engines where stroker cranks are readily available, there is a limited supply of cranks available for this engine (it went out of production circa 1970), and essentially no aftermarket support.

In stock form, the motor is very lazy, the rods weigh about 1100 grams, and the piston iskit is 4" long w/ a 2" compression height They come in about 450 grams. And it has a 32lb flywheel. Did I mention the engine was lazy? The deck height is 10,25", so there is room for more stroke. there appears to be significant cam clearance, and the crancase is fairly wide. I've actually looked at aftermarket flathead Ford rods as a weight reduction to get this deal to spin up a little faster (they are .400" longer then stock, use the same bearing diameter, albiet a narrower bearing. And weigh almost 400 grams each less.)


What I am asking the group is, do you know of any old time crank shops that still weld strokers like they did to old, small displacement motors like Flathead V8's? Need to talk to them to see if this is as stupid an idea as some of my friends think.

Thanks

[mikedc]

I dunno anybody who does welded strokers anymore.

Welded stroker cranks got a reputation for not surviving in the muscle car hobby. But V8 guys break everything as a matter of course so take that for what it's worth.

Your intended application sounds like a decent place to try a welded stroker. I'm assuming that the stock crank is forged rather than cast.


If the rod journals are decent sized, and the rest of the rods are suitable for an aftermarket replacement, then you might consider offset-grinding the stock crank for extra stroke. That probably won't deliver much displacement gains though.

[Twentyover]

I contacted Castillo in SoCal. The guy that would weld it is out until next week.

I'm checking to see if the MGC crank is cast or forged- based on then current B series engine (smaller brother of the C series) using a forging, and the expected (but never delivered) volumes this engine was to be built in, it is probable this crank is also a forging.

Current rod journals are 2", so even offset grinding down to the Honda 1.88 bearings doesn't buy much, not enough to justify a set of custom rods (the last custom rods I had made for an MGC were on the north side of $1500-

More later

[andrewb70]

What about a current, high tech 4 cylinder engine? Honda K-series? 2.3L turbo Ford Mustang engine?

Andrew

[Twentyover]

There were 8998 MGC's produced between 1967 and 1969, when it was cancelled. The one feature that gave the MGC it's character, and made it significantly different from and MGB, was the engine. I'm reminded of the AMX or Javelin commercial from the 60's where a kid brings home a new car modified with a blower- "Its' a good car- I just made it better'" Well, the MGC wasn't a great car, but many have spent the last 50 years trying stuff to make them better. For the most part, all have kept the original engine. My vision for the car retains the original engine. Just not as originally configured. At a minumum, I believe the car should have an L6 to be consistent with it's original character

If the car was an MGB, I'd be all over a swap (most common are 2153.5 BOPR aluminum V8's, 302 Fords, and 2.8/3.1/3.4 V6 GM's. Ztec Fords, some are dabbling w/ ecotech 4's, oddly there doesn't appear to be significant interest is Oriental engines.)

[JustJohn]

Another option you might have is offset grinding the crank to a smaller, but available, big end bearing size and then ordering custom connecting rods. I did that to a Jag V-12 many years ago using Ford big end bearings, Crower rods, and dished OE pistons.