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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 MGB Technical - Aluminum Heads

Are the aluminum heads (not xflow), such as advertised in Moss, prepared as far as porting, unshrouding etc. are concerned?

If anyone has purchased one, was there a spec sheet supplied re: chamber volume, port size etc.?

Can they be reworked per the same specs as the cast iron heads?
Fred Horstmeyer

Hi Fred,

The heads we have seen are ready to assemble. However, the heads we have tested flow less than the standard cast iron heads. It seems as if the seats are cut for smaller valves!
The heads can be reworked to improve flow to a level similar to a modified cast iron head.
The chamber volumes are around 42 cc's.
If you buy an 'ally' head don't forget to use half to one compression ratio higher than cast iron heads...eg 9.5 to 10.5 for standard/modified use. The reason for this is the thermal efficiency of aluminium...unfortunately the rapid heat removal ability reduces the combustion efficiency....hence the need for a higher CR.

Peter
Peter Burgess

Peter, The ads in Moss for the alum head claim "improved cyl head flow, and better porting and combustion chamber design."

Are you saying that an alum head out of the package doesn't flow as well as an unworked mgb head?

Have you tried working one of these heads?



Fred Horstmeyer

Fred,

Do you really think someone would write ad copy saying that their head would not perform as well as the stocker without modification?
Check the archives, there is lots of material on this. The consensus across the board is that the aluminum head takes as much or more work to make HP as a cast iron head.
There ARE some advantages; It's lighter, runs cooler (see Peter's comment on thermal efficiency), and tends to crack less than a cast iron head. But it does not make more power, regardless of any claims to the contrary.
Paul Konkle

I realize Mr. Burgess is of great reknown and I respect his knowledge. But I wonder if he is speaking of the same head that Moss USA sells. I have installed two and they both had 37cc combustion chambers from new. I cut them both about .045 after which they measured about 35cc. The engine I just finished a week ago is as follows. 76B bored .060 Crane 342-0010 cam. No mods to head other then cutting .045 and three angle seats. 1 1/2 HIF SUs with K&N tapered filters to clear booster. Peco header into stock exhaust. As I say the customer has been driveing it for a week as of today and has about 600 miles on the new engine. Neither he or I have put our foot in it but it is very strong. I am very impressed with these alum heads and recommend them to any one needing a new head. I don't doubt that further improvement could be achieved with some knowledge and a flow bench. By the way I checked cranking compression and it showed 185psi straight across. Runs great on our 93 octane. Curently have it set up with 10 degrees at idle and 32 degrees at full advance no vac. Used a multi keyway cam gear to degree in cam. Have a great day Bob Thompson/International Auto Service
Bob Thompson

I am begining to wonder if there are two different type of heads avaiable. I have a Pierce Manifold aluminum head that came from a source other than Moss, but it appears to be the same. The casting numbers are the same at least. My head measured 37cc chambers as new, I did open the chambers up to 42cc to avoid too high of a compression ratio. 18GB engine with 0.60 over HC pistons. It also came with the larger intake valves, hardened seats and phospor bronze valve guides. The port work was a little rough, but the exhaust ports were larger than my stock cast iron head. The intake ports seemed about the same. It also had the later style combustion chamber. My main reason for the aluminum head was its ability to handle unleaded gas. My cast iron head is a good core, but it was starting to pocket the valves. I looked at the cost to convert it to unleaded, and went with the aluminum head which I got for $500.00 with stainless valves. A swap meet deal from a know vendor. I did port and polish the head using Peter Burgess's specs as published in his book. Aluminum is easier to work with than cast iron. As I do not have a worked over cast head I can't say that the auluminum head is any better, but I am happy with what I have.

Ron
Ron Smith

Ron;Started to say your up late also but the three hours do make a difference. My question on your project is why did you lower your compression ratio? Do you run it on 87 octane gas? Again I have had no problems with the 10.5+ ratio that I have set these up with. No pinking or running on. Just curious as to your reason de Bob
Bob Thompson

With the early style pistons with the 6cc dish and a 0.60 overbore and 37cc chamber I came up with over 11 to 1. The crap we get for gas in CA had me concerned. An aluminum head should give 1 compression point but that would only back it off to over 10 to 1. Went with gross CR of about 10.25 to 1, letting the aluminum head back that off for the gas. Trying to remember the final TDCcc, if I remember right it was 54-55cc.

Ron
Ron Smith

Hi Bob,

Your compression readings of 185 seem a little on the low side for 10.5:1, wouldn't you expect to see 200 plus psi? Same as MG Metros at 10.2:1 which give around 210 psi?Is the Crane cam you use quite a long duration or plenty of overlap as this reduces the compression readings?

Did you say you took 45 thou off the head? Rule of thumb guesstimate for MGB heads is 10 thou per cc, so the skim should have taken around 4 cc from the volume.

When we work on heads we are given virgin heads so maybe the final chamber vol is different for the finalised US item...also the heads are already three angle seats.

Peter

PS degreeing in the cam is the way to go....I missed a thread re need to degree in cams.....did you get involved with that one?
Peter Burgess

Bob,
Where did you get the multi keyway cam sprocket? Moss has a timing sprocket set
but the multi keyways are in the crank sprocket, is that the one you used?

A note in the remarks section the Crane cam card states the cam is ground 1degree
retarded. Optimum performance will result from installing the cam 5 degrees advanced,
as is indicated on the card. Based on that note, if the cam is perfectly ground, you
need to move the timing 6 degrees. The Moss sproket set gives a + or - range of 4
degrees so you would need another 2 degrees unless the keyways are based on cam
degrees rather than crank degrees. I have found on US cars the multi keyway sprockets
are not always accurate so I always verify the timing with a degree wheel.

Peter,
You can see a Crane cam card at:
http://www.cranecams.com/master/apps/mg.htm#57-80
In short intake duration 260 degrees exhaust 270 degrees. Intake opens @ 24 BTDC.
Exhaust closes @ 21 ATDC at valve setting of .016. LSA 110 degrees.

Best Regards,

Clifton Gordon
Clifton Gordon

Peter & Others;
Here are specks on the crane cam which has little overlap. I call it an improved stock. .050 lift= 6btdc 36abdc 51 bbdc 115 btdc. I am familar with your comment about .010 = 1cc from your excellent book. I have found thou that cutting .045 with this chamber shape gives me about 2 less CCs. I just had my machinest cut my crossflow .025 yesterday as I was dubious about going more due to the oil cross drilling at the rear of the head limiting max cut to say 60k. I'm not "kissing up" in saying thanks for writing your book, You have done a service Bob Thompson
Bob Thompson

Cliff;
Looks like were up at the same time here! Yes that is the unit from Moss I'm speaking of and I have set no two cams the same! One I installed on a MGA I had to use a 4degree key in addition to the multi key gear. Have a fine day Bob
Bob Thompson

Hi again,

What gives with these multi degree gear wheels....the UK ones from Piper, Kent etc usually give a 9 degree swing so you can cover every degree.
If you had to use an offset key...why not buy just the offset key?...they are available to 9 degrees....its what we use for nearly all our engines....no slippage and any alterations are easy to perform.

I had an e-mail exchange some time ago from someone Stateside re the gears you are talking about...I think he had it machined to allow a wider spread....I haven't seen one of these wheels myself....how about someone sending me a smallish KB picture of one by e-mail?

From the overlap figures of the Crane cam I would still expect to see a figure of 200ish psi cranking on wide open throttle.

Peter
Peter Burgess

Gentleman;
I like the offset as well but they are not that available here. A set of Three 7 deg max is about $44. The gear sets I'm speaking of are brought in by Moss from Australia. Have thought of talking a machinist I know into making me a supply of the keys. Can you put me onto a resonable $ source for the keys? The kent adjustable is a bit dear on price$$$ By the way I just measured my crossflow head which was cut .025 yesterday and now it holds 34cc. Bob
Bob Thompson

Hi,

Thanks to Clifton Gordon for sending me a piccy of the timing gear from Moss....similar to the Cloye's setup we use for V8s.

Clifton mentioned he can get the offset keys mail order for $10 plus delivery....that is close to the £5 per key in the UK.

Peter
Peter Burgess

Peter,
Where can I get the offset keys in the UK?
Here in Norway they are impossible to find.
Thanks.

Morten
Morten

Thanks, Guys.

This is one of the more informative and useful motor-building threads I have seen in a while. Since we are talking about cam timing, why is it that the stated INO/INC/EXI/EXO numbers never seem to be consistantly attainable? I always use the lobe center angle ATC to time my cams, and when you check the duration, there is always a real discrepancy. Sometimes you can get, for example, the INO on target buy varying the checking clearance from spec., but then the INC mark might be off as much as 10 deg. as well as the exhaust timing marks.

It looks like poor cam manufacturing quality control, but is there another possible reason?

Drives me crazy.

Dave
Dave

Dave,
The Crane site has degreeing instructions and mentions their opinions for the
centerline timing method not being as accurate as using the .050 lift method.
You may want to read their article on degreeing a cam. It suggests that most
cam lobes are not symetrical and that is the reason readings may not be
accurate.
http://www.cranecams.com/master/degree.htm

Offset keys are available from APT for $9.48 each, but the numbers they supply
are 2, 4, 6 and 8 crankshaft degrees offset.
http://www.aptfast.com/Main_Index_Page.htm

I know everyone alyways suggests that we get," How to Power Tune MGB 4-
Cylinder Engines" by Peter Burgess if we plan to do engine work. I agree and
I do have that book. I would also like to suggest his book, " How to Build,
Modify & Power Tune Cylinder Heads" for anyone planning to work on their
engines. It has lots of very detailed information about all types of cylinder
repairs and modifications.

Regards, Clifton






Clifton Gordon

Hi Morten

You can buy the offset keys from Mini Spares ...(not Mini Sport) ....they are available in 1 degree increments.



Re the duration and full lift figure...if we are given a full lift figure for cam timing, we use the full lift method...say half a thou each side of full lift.
I do feel that cam grinding leaves something to be desired! Have you ever noticed that the 'rule of nine' for setting the tappets/lash doesn't always work? Usually caused by a poorly phased regrind!

Peter
Peter Burgess

Peter, You are correct about the rule of nine. Even with my new Crane cam, adjusting the tappets is more of an art than a science. My guess with Bob Thompson's engine is that either the rings are not yet seated, or the cam is degreed in wrong. I have readings in the 205 range on my fresh rebuild with total Seal rings.
Jeff.

Jeff Schlemmer

Hi Jeff,

What compression ratio are you working to?

We found that Total Seal rings improve the compression reading but lose out in terms of friction....

Chasing the loose point for setting the valve clearances can be annoying can't it?

Peter
Peter Burgess

Peter,
Does Mini Spares have a website?
I have tried several partstores with no success.

Thanks
Morten
Morten

Hi Morten,

I would expect Mini Spares to have a website.....when I find it I will let you know.

Peter
Peter Burgess

Hi Morten the address is http://www.minispares.com/home.cfm

Looks very cluttered but you should find the keys there.

Peter

Peter Burgess

Peter, if everything was calculated correctly, I am at 10.1:1. I was playing the balance game between friction and cylinder pressure when I made the decision to install the total seal top ring. I believe their oil control rings are WAY too loose and allow too much blow-by, so the rest of the ring set is factory. As for the accuracy of my pressure guage, I can only assume it's very close.
Jeff.


Jeff Schlemmer

Hi Jeff

As you say your readings are of the right magnitude for 10:1 and guage pretty close.

Peter
Peter Burgess

There's nothing quite like a pat on the back from the Mg performance king himself...
;-)
Jeff.

Jeff Schlemmer

Jeff......

LOL :)

Peter
Peter Burgess

This thread was discussed between 26/10/2001 and 02/11/2001

MG MGB Technical index

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