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MG MGA - 1800 GB or 1600

Gent's, I had the mis-fortune to loose my 1500 engine this weekend. It appears the PO never replaced the bearings as he said he did. I have two spare blocks. An 1800 3 main and a 1600. I want to get on the road ASAP. I plan to send one of them out to the machine shop. I figure the advantage with the 1600 is I can swap most everything over from the 1500 to the 1600. But will the distributer, carbs, waterpump, etc. (Which were all replaced with new or rebuilt) be able to be used on the 1800 ?

WMR Bill

Bill, Everything from the 1500 will fit on either engine, ie the waterpump, intake, exhaust, carbs, distributor. Use your 1500 back plate. I would go for the 1800.
James Johanski

Thanks Jim, Will the head from the 1500 also fit the 1800?
WMR Bill

Yes, but the valves are smaller and would be resrictive. Use a B head as the valves are bigger. Good luck.
Bill Haglan

I not sure the water pump will fit the 1800.

dominic clancy

Bill, if your 1800 is an 18GB as the thread title indictaes, it is a 5 main not a 3 main.
Andy Bounsall

Andy, I stand corrected it is a 18-G-U-H5422. If any body can add some insight to the year or any other info i wouls appreicate it. I just dissassembled it today to save on cost at the machine shop. All the pistons, bearings, crank , appear in good shape. I am hoping to just have to replace bearings and rings and have the crank and rods checked and hardened. any othe suggestions whil I am in there?
WMR Bill

Hi Bill, I will be interested to see what you decide. My original 1600 untouched engine is running fine at the moment but running lower than average oil pressures ( 20 tickover, 40 at 3000rpm when hot)and dripping lots of oil- mainly from the front cover. I have had the offer of a 3 main bearing 1800 from a '64 MGB - possibly for free so may have to make the same decision as you - engine will have to come out anyway when I eventually do the gearbox 5 speed upgrade . cheers Cam
Cam Cunningham

I had a 64 MGB with low oil pressure at idle and speed. A local mechanic friend came over one day after I had pulled the pan off and he replaced the main bearings while the engine was still in the car. He simply removed each bearing cap and pushed out the old bearing and slipped in a new bearing. After each one was installed he turned the crank to check for any tightness with the new bearings. I believed I also changed the oil pump at the same time. I remember when I called Moss to get the new bearings, they questioned me about getting the stock size bearings. They must not sell too many of those. Mostly oversized I would suspect. It brought the oil presssure back up to acceptable numbers.
BTW...If you have access to a early 3 bearing 1800. You can swap the timing chain cover from it to your engine. The early 3 main bearing timing chain cover has a neoprene seal rather than the felt seal. The timing marks/indicators are in the same place.

Ray Ammeter

Maybe run over to the MG gathering with a homemade tee shirt wanted good motor might be your quickest fix you never know what cash will do these days . Bring some fliers or a sign for the windshield . Even if you don't find anything great excuse to run over :)
Karl LaFollette

Thanks for the info Ray - might try that as a quick fix - cheers Cam
Cam Cunningham

Concerning low oil pressure, my 1600 idle pressure would drop below 10psi after a "good run." I replaced the rod, main, and cam bearings plus the rocker shaft. I measured the oil pump gap and it was borderline serviceable. This work gave me 5 more psi.

At first I blamed the shop who installed the cam bearings. A few months later I replaced the oil pump- problem solved. I didn't do this at first because I thought a worn original was a better bet than an aftermarket. Not the case here.

Have fun,
Bill Eastman

Well guy's, because of time constraints I have elected to hold off on the 1800 rebuild and just try to get the 1500 going to salvage the summer. I took the crankshaft out of my 1600 extra block and will have it polished. I will remove the engine from the car and replace the crankshaft and damaged rod. I will then replace all the bearings with new as well. I am hoping to get this done for under $300 and be back on the road in two weeks. Suggestions welcome!
WMR Bill

Are the 1500 and 1600 cranks the same dimensions?
Russ Carnes

From what I have been told here fom fellow memmbers, the two cranks are the same. Since I will be replacing all the bearings with new, all I needed to do was confirm weather the replacement crank was previously cut and to match the new bearings to it.
WMR Bill

This thread was discussed between 13/07/2008 and 17/07/2008

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