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MG MGA - 1800 MGA

Putting an 18V engine into an MGA, are there any problems with using the later 18V crank pulley and associated water pump?

Thanks

Colin
Colin Parkinson

mmmmm
Something I've never done, and don't have an MGA here for a look
The crank pulley, as you know, is a fair bit larger diameter and I'm not sure how much clearance there is there for the crossmember-
With the MGB with the 18V engine ,the engine was in the same position as early B's (different style mountings though) but the crossmember was mounted 'around' an inch lower giving truckloads of clearance so can't tell from that
Fwd and aft isn't an issue as the overall thickness of the pulley is the same as early B and fits A's ok it's just that dia thing that I'm unsure of
Sorry I can't help, maybe find an MGA and have a look under the front , I think the pulley half hangs over the front of the crossmember from memory and should be ok but not 100% sure
Other option if it won't fit would be to poke an early 5 bearing B balancer on it, They clear on an A ,--the water pump would spin a little slower but I can't see that being an issue really
willy
William Revit

The 18V is 5 bearing, and has the harmonic balancer on it..fits the MGA fine. Only thing is you lose the ability to crank the car. No problem with water pump, but there are a couple of different sizes.
Gary Lock

The pulley on my 1976 18V is 6" diameter and gives about 3/4" clearance over the cross member. Are you also fitting a 5 speed gearbox?

I used the crankshaft nut from the 1600 and can crank the engine.

Cheers

Dave
Bolney Coupe

Colin. I have the same as Dave - standard pulley, no thrills. It's been working just fine for 18 years. I also used a short nosed pump giving the front of the fan about an inch clearance with the radiator. I also use the Moss 7-blade asymmetric fan with the standard core radiator. In my opinion it maintains excellent cooling under all conditions with no add on extra cooling aids.

Steve
Steve Gyles

Thanks guys, I was concerned about the clearance between the crossmember and the damper.
Dave, yes 5 speed conversion as well. Mazda kit!

Not my car, helping a friend.

Colin
Colin Parkinson

Chris Betson once brought me an engine with a later 18V crank pulley fitted. I took it off to fit the engine (makes ckearing the chassis much easier) and found it was too big to refit in situ as it fouled the chassis, so I fitted the earlier harmonic damper pulley which works fine. I gave him the other pulley back when he next came with a delivery.

There is a big difference in the diameter of that 18V pulley and the earlier one.
Dominic Clancy

Hi Colin
I switched my 3-bearing 1850cc MGB engine for an 18v 1950cc 5-bearing MGB engine about 18 months ago.
The new engine has the MGB harmonic balanced front pulley and it didn't really pose any problems during installation.

I removed the 3 brg engine and fitted the 5 brg engine on my own without any help and it went really well with no clearance problems.
It is better if you fit new engine mountings as the old ones may have squashed down a little.

Like Garry said, you have to make sure the water pump is the correct one that doesn't project too far forward into the radiator.

I had to put 1/4" spacers under the radiator mounting setscrews to move it forwards away from the fan.

If you check the archive you may find that the biggest challenge could be getting the Mazda gearbox conversion to fit the MGA.

Cheers
Colyn
Colyn Firth

Colin
I just looked back at the MG Experience Forum comments about the Vitesse 5-speed conversion and I have posted a link to the discussion.

Ken Klay in London posted his experiences of fitting this conversion.
Hope it helps
Colyn

https://www.mgexp.com/phorum/read.php?2,3727676
Colyn Firth

Colin
The earlier MGB 1800 damper is 5" dia
Later18V MGB 1800 is 6" dia

The early 5: definately fits in an A chassis

Bonley Coupe-above says-
"The pulley on my 1976 18V is 6" diameter and gives about 3/4" clearance over the cross member."
BUT
on the other hand Dominic-
"----- once brought me an engine with a later 18V crank pulley fitted. I took it off to fit the engine (makes ckearing the chassis much easier) and found it was too big to refit in situ as it fouled the chassis,"

Maybe fit the motor to the car and try the pulley, if it fouls get the smaller one they both have the same belt offset just different shape/size
Whatever you do don't fit the original-non dampered MGA pully--It needs to be a damper pulley
willy
William Revit

Why not Willy? Mine is non damped and has been in situ without issue for 18 years.

Steve
Steve Gyles

The 18V with original 6" pully fits easily into the MGA..have done it twice now.
Gary Lock

Steve
I'm a bit rusty on this, but
Smaller capacity 4 cyl engines don't need one to dampen harmonics but 1800s do
A lot of even larger-4cyl engines have a secondary balance(out of balance)shaft to trick the harmonics
From memory 4cyl engine harmonics go up in 1875 rpm steps
At 1875 rpm mostly because of the shortness/stiffness of a 4cyl. crank it's not enough to cause an issue but at 3750 there's enough going on and if driven dead on this rev for long enough without a damper there will be damage to all sorts of things like oil pump drives vibrating,engine bolts coming loose, main bearing wear increased and possible broken crankshafts
At 5625rpm it's even more of an issue but rarely would you be sitting on that for long periods
Don't quote me on the exact revs but I think it's around there somewhere
If you're not sitting on these harmonic points and don't have a damper, you have probably dodged an issue

Safer to run a damper
William Revit

Thanks for the explanation Willy. The engine has always been exceedingly smooth at all the rpms in my operating range. I run the T9 box with a 3.9 diff so I rarely get to the higher revs you note on day to day driving. Not fallen apart yet after 18 years.

Steve
Steve Gyles

Colyn thanks for the article on the Vitesse gearbox conversion. Makes interesting reading........!

Colin
Colin Parkinson

This thread was discussed between 06/08/2018 and 08/08/2018

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