MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - 1500 Head vs. 1600 Head

Is there any difference between a 1500 cylinder head and a 1600 cylinder head? I was under the impression that the only difference between the 1500 and 1600 was the size of the pistons and the bore in the block. I know that the carb needles are different, but I assumed (incorrectly?) that the rest was the same. Can a 1500 head be used on a 1600 block???

Dennis, Az
Dennis

Hi Dennis. I believe that the 1600 cc valves are slightly larger than the 1500 cc ones. Yes a 1500 CC cylinder head will work on a 1600 block, but performance is decreased a bit. Cheers! Glenn
Glenn

I am a new owner of an 1960 MGA. The previous owner had the engine rebuilt and of course the shop lost the engine tag. He did though record the number as 16GA/U/3445. According to this it is a 1600 engine but looking at the head the other day I noticed 1500 cast into the head. Did they use 1500 heads on the 1600 engine? Could I possibly have a 1500 engine installed? how else can I verify the engine size other than a teardown? Thanks
Charles O'Brien

Dennis,

You say that the head has 1500 cast on it. Do you mean 15? The 1500 and 1600 heads have 15 cast at the rear of the head. Only the MK11 1622 had 16 cast on it.
The engine size is cast on the block just below the front cam follower cover, 1500 or 1600 or 1622.
The 1500 and 1600 have the same size valves. They are larger on the 1622 engine.

Mick

Mick Anderson

Hi Charles. Your 1600 engine block has a 1500 head transplanted onto it. The 1500 head is not the proper head for your engine. However the 1500 head does fit and work fine. I believe the proper 1600 head has slightly bigger valves and slightly better performance. Cheers! Glenn
Glenn

Sorry, the message was meant for Charles.

Mick
Mick Anderson

Hi Charles. Sorry, Mick is indeed correct. MGA 1500 and 1600 valves are the same size. It is the 1622 that has the larger valves. My apologies. The engine Block has the displacement sizes cast into them as described by Mick. Cheers Glenn
Glenn

Charles - what Glenn says is the general rule but some very early 1622 engines had heads that while stamped with a "15" were actually machined to the 16 specs. There is a thread somewhere in the archives about this.
- Ken
Ken Doris

Here's the link to that thread - look for Frank Graham's post: http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=6&subjectar=6&thread=200006260159412647
- Ken
Ken Doris

Mick, Glenn, Yes it is 15 that is cast into the head not 1500 sorry, and upon searching around I was able to find the 1600 cast into the block. Now I am sure it is a 1600 engine. I can't wait to get this baby on the road. I love everthing about this car well almost getting the winsheild wiper motor out for a rebuild was quit a chore. Thanks Chuck
Charles O'Brien

Thank you all for your help. I thought that the 1500 and 1600 heads were interchangable. I did not know there was a 1622 block, however. This is good to know. My current head has 15 in raised letters on the front. The block says 1600. They worked well for several years together. I did something to the engine and now it overheats all the time. I am going to have to spend some time cleaning it up, but now I know I can replace the head with one I know I can get.

Thanks again.

Dennis.
Dennis

So a 1500 and 1600 are not interchangeable?
And the 1622?
what about a 1798 cc MGB head?
Safety Fast
Dwight
Dwight McCullough

All heads have a number cast into them, from memory the MGA head is 984, the 'B' heads are 4184? and 2709, you can fit MGB heads onto a 1600, I'm not sure about a 1500, the 'B' heads have bigger valves and are shaped in the combustion chamber for better performance etc. If you want to know the numbers please reply and I will check my spare heads
Terry Drinkwater

One of the best heads is an austin maxi -this has enormous valves and needs 'eyebrows' or 'cutouts' taken from the block to stop the valve hitting.
J H Cole

Forgive my ignorance JH but are you just saying that the Austin Maxi E-Series engine cylinder head is a better design in general than the B-Series engines head?

Or do you mean it that it can be made to fit the B-Series engine?

I dont know much about the E-Series engine except that I believe it is an overhead cam design.

Cheers
Colyn
Colyn Firth

Yes the Maxi probably was a better design as it was designed a lot later and yes it had the advantage of being single overhead cam. It would be quite a challenge to fit one to an A.

Interestingly 2 policemen once arrived on our doorstep at 6.30am returning our banger of a Maxi that had been stolen only 4 hours earlier while we slept. Rather than commenting on the elderly state of the car they just said that goes really, so head design was perhaps good.

Paul
Paul Dean

Colyn, I'm not an expert on the various availible heads for an A but about 5 years ago I read everything that was going and came to the conclusion that the maxi head was about the best BUT not everyone wants to cut 'eyebrows' from their block (Barney helps) and you need to do some maths on the likely comression ratio change depending what engine you have. Mine is a 1622cc. I can't remember the figures now but I think the maxi head came out better than the MGB (the MGB does not need eyebrows I believe). The maths is to work out the volume of the compression chamber and requires filling the cylinder head with a fluid. I'm rapidly getting out of my depth now so I better give way to more experienced owners.
John
J H Cole

It is not the valve size which determines the need to cut eyebrows. It is the valve lift, and only if the inlet valve OD goes outside the cylinder bore. With standard MGA cam and rockers there is no need. I have a B head on a 1622 block and no cutouts.
Of course if the head has been skimmed, then need to check.
Art Pearse

Seem to be a bit all over the place here.

There is an early MGA 1500 head that was slightly different and inferior to later ones, but they could be opened up and modified to match the later 1500 and 1600 heads.

The 1622 and early 1798 heads are functionally identical although the cast numbers are different.

You do NOT want to use one on a 1500/1600 or you'll end up with bout 7.5:1 compression.
Bill Spohn

The 16 and 18 heads can be used on the 1500/1600 engines, if you shave the head down 0.047" from 3.187" to 3.140" thickness to reduce chamber volume from 43cc to 38cc. That will give stock compression ratio of 8.3:1. I've been running the 18 heads on my 1500/1600 engines for 400,000 miles since 1987. Works good with larger valves and better porting. you may need to add eyebrows to the block, depending on valve lift, but grinding the eyebrows is pretty easy.
barneymg

Only thing to add is that it is the exhaust valve clearance that poses the problem and needs cutouts not the inlet
The later 1800's had the cutouts from new with std cam lift
William Revit

With the larger valves of the 16 or 18 heads, and near standard bore of the 1500 engine, the inlet valves also need eyebrows (only the 1500 engine). 1600 or larger bore does not need eyebrows on the inlet side, only for the exhaust valves.
Cutting eyebrows: http://mgaguru.com/mgtech/power/cm202a.htm
Valve layout: http://mgaguru.com/mgtech/power/cm203.htm

If you want to use the "L" head from 1972-1974 MGB (or later issue European cars), that one has one size larger intake valves, but comes original with 38cc chamber (pre-shaved). Those engines had intake eyebrows standard on the 1800 block, and need slightly larger intake eyebrows.
barneymg

exhaust
William Revit

Doh. Yeah, exhaust eyebrows. The only ones needing inlet eyebrows are 1500 with shaved large valve head.
barneymg

This thread was discussed between 21/12/2004 and 01/03/2018

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.