Met a friend when I was running at the Victoria (BC) hill climb one year. He was running a 1500 with 1800 head and was wondering why he was so slow. I told him that having something around 7.8:1 compression probably had a lot to do with it......

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (350 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

Actually I have an 18v engine laying around but (a) it requires a full restoration and (b) if opting for an 1800 engine then the 3 main seems to be a much more convenient option ... so I might just see if I can tune the 1500 engine a bit instead.

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1959 MGA 1500 Coupe

If you want to use a 1800 head on the 1500 go for the "O" head, i am running that with an MGA exhaust manifold and 1 3/4" system, runs very nice with good low speed torque (still running the 5/45 50/10 std camshaft,
I cut valve reliefs in the block to suit future cam updates.

Forgot to mention engine is in Magnette ZB.

Erik,

1800 engine with 5 speed and 3.9 diff. You can cruise all day at 65mph, and revs about 3000.

Peter.

Hey Peter,

That is indeed the dream ... But to get there is a bit pricey so I was hoping to first try tuning the 1500 engine and fitting a 3.9 diff.

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1959 MGA 1500 Coupe

What years of early B heads? With the 74 B heads that have the larger valves be used on the 1500 and the 1622 engine?

The tuning capabilities of the 1500 engine are limited and whatever you'd gain would be thrown away again when you put the 3.9 in it.

Frankly I would do what Peter said even if it means waiting awhile. Keep an eye out for a 3 main MGB engine you can pick up and work on rebuilding it to suit your needs. And reconside the 3.9.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (350 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

Erik,

Had the 3.9 fitted with my original 1500 engine and it was fine to drive.

But my wife complained when we went to Reno Nevada, as I was not keeping up with her in her coupe with 1622 engine, 5 speed, and 3.9 diff. She said I had to upgrade, and I do not argue with my wife!!

Peter.

Hey Bill,

You have a good point there. As I have a 3.9 I'll fit it this winter and see how the car runs, so that is definitely happening.

The thing is that I have a pretty rough looking 18v engine (US low compression version) which I could restore and rebuild, changing the cylinder head, pistons, flywheel, timing chain, and many other little things to make it a performance engine. However, even that would be pricey and in the end, it would have been much easier to buy a 3-main engine ... Might just wait and keep my eyes open for a 3-main engine ...

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1959 MGA 1500 Coupe

So where did the factory find the extra power gains with the 1622 engine compared to the 1500?

I'm guessing its in the head.

I have a new head sitting in my shed for my B and the original still on the motor.


Looks like a head swap is on the cards.

Rob

Larger valves, better porting and IIRC higher compression. Same cam.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (350 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

So if I want to put my 18 head on the 1500 what cc's should I be looking at achieving in the combustion chambers to get the same compression ratio as the 1600?

The same chamber volume as the 1500 stock head has - 39 cc. Or better yet, put in some flat top pistons and raise the compression higher than stock - and machine the head to suit the new ratio you want.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (350 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

Hi Rob,
You need the 1800 :O: head ( it has "O" cast into the rear top face where they had"1800", the only problem is you will need cutouts for the valve travel cut into the top of the block, i have one on my 1622cc (1500 bored out to 3" in the Magnette and am very happy with it.