Moss Motors, Ltd

My Fellow Posters-

I dug up an old pre-emmision MGB head from the back of my garage and had it magnafluxed (No cracks!) and had a couple of broken studs removed and am thinking of doing a cost effective, performance enhancing rebuild that might include some mild porting, H.P. springs, etc. 

The head itself is solid but all other components are toast.

Thanks for ALL suggestions in advance.

LCJUTILA 

Is anybody out there?

I'm surprised that after all the responses I've given to other poster's questions, I haven't received a single response to something that should be of interest to all MGB owners who are doing a rebuild.

To clarify my question:

What kind of results, good and bad , have people gotten in the rebuilding and modifying of an MGB cylinder head? What was worth the $ and what wasn't? What was too much of a modification for a street driven car and what worked out great? Should you port the head mildly or is this a road to disaster? Do the big, "flowed valves" make a big difference? Are the heavy duty springs in the Moss catalog of significantly higher pressure and do they accelerate rocker arm wear? How high on compression can you go on pump gas? How much is too much to mill off the head? How about relieving the intake and exhaust valves in the chamber?

Let's hear it!

LCJUTILA 

LCJUTILA,

Hard to clarify exactly how to answer so sometimes it is easier to just say "How much do you want to spend?"  Bigger valves help quite a bit as does basic porting but "race" size porting will actually hurt streetability quite a bit.

My 64 MGB has a Dave Headley built engine that should put out about 120hp,,,,,,,now to get there it has a nicely ported head, nice "rally" grind cam with new followers, new pushrods, re-bushed rockers and a hardened rockershaft, adjustable cam gear, then there are the JAE forged pistons with the compression set at about 10.5:1 and,,,, it is breathing through a Weber DCOE45 on a TWM intake that is all port matched to the head. Ahem,,,, a few bucks

Relieving the valves in the chamber is a whole kettle of fish too but not really important for a street motor because that is typically a mod done for motors breathing upwards of 7500rpm, cool yes but not driveable for the street because the cam required to make power there would agravate the hell out of you around town.

If you search Classic Motorsports magazine there was a very nice article on doing a freshen up and cam change to an MGB. I believe it was a 73 or 72 MGBGT but the point was a fresh head with just some mild "cleanup" porting and a performance street cam produced 20-25 hp more and drastically reduced the 0-60 times for the car.

If it were my MGB that was a nice running example i would tear that head down and simply cleanup the porting, see Vizards book, have a machine shop do a nice three angle valve job and set it aside for the motor. Take the head off your motor, check your bores and pistons for wear and order correct rings, light hone the walls and re-install the pistons with new rings. Yank that stock cam and lifters out and intall a QUALITY cam and lifter kit like a Kent 276. learn how to time the cam correctly and set it per grinders spec either with offset keys or a vernier sprocket and timing chain set.

Obviously this is very abbreviated but the point is if the motor runs well but is perhaps a little tired, has decent oil pressure etc, just a freshen and new perf cam can really bring her back to life.

And,,,,,,

if you have a spare 5-6 grand laying around,,,,,

just do what i did and crazy,,,,, only live once right? 

 

 

 

      

   

 

Jayrz-

Thanks for the info. Very good indeed. One area in question for porting is relieving the exhaust valve guide boss in the head. I'm guessing it goes around the valve guide to remove heat from it through the cylinderhead water jacket but the thing sits right in the middle of everything when the exhaust is going out the port and has got to be killing the flow. If you install the improved bronze guides I wonder if they will hold up with this boss removed...or at least trimmed down some. 

Also, on the intake side the port has a nice 90 degree transition up to the cylinder, but once again, the valve guide sits right in the middle of everything and I'm thinking of slightly widening the bowl around it by half  the guide's diameter on each side to increase flow but not lose velocity.

I would get a three angle valve job, as suggested, and blend the transition from the port to the first angle, and from the combustion chamber to the last angle. I would polish the chambers to reduce surface area so that less heat of combustion would be lost to the head and would be used to move the car down the road.

I'm also going to improve the blending work where the intake manifold meets up with the cylinderhead and match my weber manifold to it.

The funny thing is I no longer have the rest of the car that attaches to this cylinderhead. It went to heaven years ago. I plan on selling this one when done....or maybe buying the rest of the car somewhere...

LCJUTILA 

Hi

   it depends what engine you will be using the head on. If it is going on to a late model B then you will have to fit high compression pistons as the early heads had a larger chamber than the later emissions heads so the early engines had higher compression pistons to match. The loss in compression will negate any porting advantage. If this head does not match your engine then there is bound to be someone who will swap a good early head for a good later one. Do not forget to get the head refaced as well to make sure of a good seal to the head gasket.

 

Mark

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1958 MGA coupe ( under restoration
1972 MGB GT
1995 Ford Bronco
2004 Pontiac GTO

Very good point Mark.

Thanks!

Anyone else out there have any ideas or observations?

LCJUTILA 

LCJUTILA.

If you don't have a copy of "How to Power Tune MGB 4-Cylinder Engines" by Peter Burgess, then you need to get a copy. It is currently the definitive work on building up the B Series motors and does give very good advice on home porting of a street engine.

Most of the performance oriented components such as heavy duty springs and rim-flow oversize valves are wasted on a street driven engine and will reduce engine life. Performance is all about making compromises. Even something as benign sounding as a three angle valve grind reduces the longevity of the head as the narrow seat faces created for increase flow will errode faster than the original wider seating surface.

Just something to think about.

There is a lot of performance left on the table due to the head manufacturing process, so it is very worthwhile doing a basic smoothing and cleanup. Above that the cost/benefit starts to decrease rapidly for an engine that will only be run up to the 5,000 rpm range on the street.   

 

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Kelvin Dodd
Global Sourcing Engineer
Moss Motors, Ltd.
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LC,

so after all this work it is highly likely you WILL rev it to above 5k. Mine now pulls hard to 7000 where I shift regardless because, although it is built with all quality ARP stuff, I'd just rather not actually TRY to break the thing.

Noticed you also own a Lotus, I also own a 69 Elan SE S4 and as great as the MGB runs now, yeah, still not as fast, maybe close, as the Elan and the Lotus is "fresh" but stock.

Had a early MGB when I was a teenager and couldn't afford to do anything to it so maybe I was just fulfilling an old fantasy to build the MGB I really wanted when i was a kid.

I'll say this though

It sure is fun isn't it?!!!!!! 

 

 

Hi  - Why don't you get a copye of Peter Burgess book called "How to power tune MGB 4- Cylinder Ehgines for Road & Track" Published by Veloce Publishing.

First Published in 1996, last in 2004 ( I Think)    Is a near A4 sized book with 112 pages in black & white.

ISBN No is - 903706-77-7/UPC 36847-00277-0.

He is UK based and also has a Web site.

One could say it's the bible in 4 pot tuning and development, all MGB owners should have one maybe, as covers Head/Block/Fuel/Broaes/Exhaust/Cooling/Tuning etc.

Hope the above helps a little.

Kind Regards

BillS 

 

 

 

 

 

Hi.jayrz,with all the details about cylinder head mods/for more power etc. i was amazed that you could spin your b engine to 7000 rpm.

my 73 b has warning start at 5500rpm  and red band max revs is 6000 rpm.

so i wondered if the export mgs could rev more than uk models,or have you done extensive work to the bottom end,to enable these revs safely.

there,s an old saying - there is no substitute for cc's    as i get older,i much prefer  torque or pulling power to high revs.my standard b seems to have loads of torque at fairly low revs.

You can get  4 cylinder b engines in uk  up to about 2200 cc and would think this a better route to more power.

phil

 

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phil wilkins

Thank you all for the great suggestions running from the "Don't overdo it" to the "How much money ya got" camp. The project has been temporarily shelved due to other obligations.

As to the question of how high you can rev a "B" engine without blowing it up. If I recall, on a stock MGB the power would start nosing over in the warning zone and there was nothing to gain by over revving so the issue would not come up.

In my youth I did blow up my Sprite engine by over revving. It didn't self destruct but it did break some rings and may have bent a valve.

As far as building a bigger engine for more power goes, "There's no replacement for displacement!" I'm putting together an engine for my Europa that will have a Cosworth 2 litre BDP aluminum block and a lot of other goodies. It's going to be scary fast! About as fast as a Type 47 (If I ever finish it.)

 

LCJUTILA