Datsun Roadster Forum-311s.org

I was just looking at the factory special tuning guide for the MGB and the different stages of modification they have for the 1800 B series motor. With the most radical setup, they say to expect 129 BHP @ 6000 RPM. This is with a shaved head, flat-top pistons (dished standard) hot cam, bog-bore SUs (Webber DCOE didn't add any grunt over SUs) etc, etc. Displacement is right between the R-16 and U-20, of course, and the stock MG motor makes 95 HP and 105 ft/lb torque. What do you 1600 racers get out of your motors, any ideas?

This is just thiunking out loud but I would think a R motor has the potential to make more peak HP than a MG engine. Two things lead me to think this, but it has been a long (relatively speaking) time since I was in one of those engines.

1) Bore to stroke ratio: The MG engines have small bores in relation to the stroke (long rods). This limits max engine speed due to piston speeds. Good for torque, not for horsepower. The Datsun has a better ratio and can spin faster, potentially producing more peak power.

2) Cylinder head design : Some of the MG heads I have seen actually have paired intakes or exhausts (like I said, been a while) which is not good if all out performance is what your after. Maybe this is why the Webers didn't outperform the SU's? Also, because of the small bore, smaller valves must be used, restricting max flow.

I hope my recollection is correct for the above. I would have to think, dollar for dollar, the Datsun would have better performance than a MG. A R16 in race trim may be able to put 120-130 to the wheels or about 150 at the crank, but I'm just guesstimating.

Mark

This is from the Roadster Racing board by Mark Coffin discussing the power output of Bill Wessels 1600 racer with Solex carbs:

Mark Coffin wrote:I was just teasing Bill, I already know that in GP trim he was making almost 200hp! Wink Probably up around 230 hp in FP trim.

Laughing Laughing Laughing Laughing Laughing

See you at the Prod Fest, Mike?

Mark C.

Not too shabby...

datsunrides wrote:
2) Cylinder head design : Some of the MG heads I have seen actually have paired intakes or exhausts (like I said, been a while) which is not good if all out performance is what your after. Maybe this is why the Webers didn't outperform the SU's? Also, because of the small bore, smaller valves must be used, restricting max flow.
Mark

THe head looks identical to the head on a Datsun E-1 or J-13. Cylinders 1&2 and 3&4 share intake ports, and 2&3 share an exhaust port. 1&4 get their own exhaust. The pistons look tiny in comparison to the 1600, but the rods, as you say, are longer.

MTyler wrote:

datsunrides wrote:
THe head looks identical to the head on a Datsun E-1 or J-13. Cylinders 1&2 and 3&4 share intake ports, and 2&3 share an exhaust port. 1&4 get their own exhaust. The pistons look tiny in comparison to the 1600, but the rods, as you say, are longer.

I would say there is why those engines will not make the same power as a Datsun engine of a similar size. Didn't someone like cosworth make aftermarket heads to address that issue?

Mark Coffin wrote:I was just teasing Bill, I already know that in GP trim he was making almost 200hp! Wink Probably up around 230 hp in FP trim.

Laughing Laughing Laughing Laughing Laughing

See you at the Prod Fest, Mike?

Mark C.

200 at the crank is pretty impressive naturally aspirated!

Mark

OK, everyone TIME OUT! I was just TEASING Bill about his Roadster and its horsepower. He and I race against each other and he always has a little more power than I do (in my VW Scirocco 1600cc SCCA racer). My car makes around 155hp @ 7500 RPM at the flywheel, so I'd guess a top level SCCA 1600 Roadster would make in the 165-170 hp range (at the flywheel). The difference is due to a couple of factors: 1) The Datsun is allowed bigger carbs than the VW (to allow for the newer OHC technology on my VW), 2) my VW is lighter by about 100 lbs. (Weird huh? The metal on my little Scirocco is a lot thinner than on the Roadsters and the Scirocco doesn't have a frame) and 3) the intake valves on my VW are a LOT smaller than the Roadsters (the intake valve on a VW is only 34mm vs 42 mm for a Roadster in race trim). This severely restricts the horsepower potential in a race engine.

I just didn't want anyone to get TOO excited about the (false) numbers I was throwing out there.

Mark C.

Well, that is still respectable power in my book. I was only reporting what I read...

MTyler wrote:

datsunrides wrote:
2) Cylinder head design : Some of the MG heads I have seen actually have paired intakes or exhausts (like I said, been a while) which is not good if all out performance is what your after. Maybe this is why the Webers didn't outperform the SU's? Also, because of the small bore, smaller valves must be used, restricting max flow.
Mark

The head looks identical to the head on a Datsun E-1 or J-13. Cylinders 1&2 and 3&4 share intake ports, and 2&3 share an exhaust port. 1&4 get their own exhaust. The pistons look tiny in comparison to the 1600, but the rods, as you say, are longer.

IIRC, several folks have put the MG head on their J motors; it's almost a straight bolt-on, which isn't surprising considering Nissan had licensed Austin technology. I'd have to dig up the why though I'm guessing the 1800 head on a 1300 motor would help the breathing.

srl311-04425 wrote:I just didn't want anyone to get TOO excited about the (false) numbers I was throwing out there.

Mark C.

False numbers rule!
I heard those U20s make 250hp at the wheels on C16

Alvin wrote:

srl311-04425 wrote:I just didn't want anyone to get TOO excited about the (false) numbers I was throwing out there.

Mark C.

False numbers rule!
I heard those U20s make 250hp at the wheels on C16

I recall an old Peanuts cartoon saying 87-percent of all statistics are made up.

Alvin wrote: False numbers rule!
I heard those U20s make 250hp at the wheels on C16

I sure wish that was true .

Roadsterx wrote:

Alvin wrote: False numbers rule!
I heard those U20s make 250hp at the wheels on C16

I sure wish that was true .

I've seen a dyno sheet of one that makes pretty darn close to that. It lives on the East coast, it will hold off a Speed world Challenge Porsche GT3 at VIR. I'm not going to name names (I was asked not to) but it does exist. Its dry sumped, and very very trick. Races SCCA.

Will

SLOroadster wrote:

Roadsterx wrote:

Alvin wrote: False numbers rule!
I heard those U20s make 250hp at the wheels on C16

I sure wish that was true .

I've seen a dyno sheet of one that makes pretty darn close to that. It lives on the East coast, it will hold off a Speed world Challenge Porsche GT3 at VIR. I'm not going to name names (I was asked not to) but it does exist. Its dry sumped, and very very trick. Races SCCA.

Will

I know of another that wasn't to far off of the 200 plus HP at the wheels, but it wasn't cheap .

BTW... The VIR hint was to easy

Roadsterx wrote:

I know of another that wasn't to far off of the 200 plus HP at the wheels, but it wasn't cheap .
BTW... The VIR hint was to easy

The head on my car is a near clone (valves are different, port work is the same. My cam was ground for this engine, but it made its power too early to work really well with the rest of his engine, so they went with something bigger.) of the one on the car in question. Yes, I'm thinking of a blue and yellow car.

Will

ppeters914 wrote: IIRC, several folks have put the MG head on their J motors; it's almost a straight bolt-on, which isn't surprising considering Nissan had licensed Austin technology. I'd have to dig up the why though I'm guessing the 1800 head on a 1300 motor would help the breathing.

If that's the case, they make a big valve crossflow head for an MG...Victoria British sells it.

I have a friend who built drag race and speedboat motors for 25 years. He swears he can get me 180 -190 HP out of an H20 and make it streetable, without making me broke. I have extra heads, so I may take him up on that. 100 shot of nitrous might be fun too...