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 MGB Technical - Racing Mod to Water Flow

I saw this on a car at silverstone a few years back.

Can someone tell me what the pro's and con's are of doing this to a racing engine ?


http://uk.pg.photos.yahoo.com/ph/yd3801/detail?.dir=/c6cf&.dnm=14c2re2.jpg&.src=ph

Diverting the water flow front the centre of the head (Heater outlet) back into the radiator.

I've seen mga twin cam engines with this mod also.

Cheers <MARK>
Mark Hester

An interesting mod. I have not seen it before. As you may know highly tuned Bs can suffer with the rear cylinder getting too hot. So this may be to improve the water flow from the rear of the head. There is another mod people use to improve rear cylinder cooling and that is to increase the diameter of one of the holes between the block and the head at the rear.

I have a late north american spec head, air pump style, it has a water outlet at the rear. I don't know where these were plumbed to. Perhaps it was manifold warming for emmisions reasons.
David Witham

I'd be interested to see a picture of that head.

I've had a few head gaskets leak or blow, so anything that helps I guess is a good thing.

Any Drawbacks ?
Mark Hester

Provided the air pump style head is ok for you, I don't no of any drawbacks. I compete in standard class in the MGCC speed championship so I am going to change to a 12H2709 head. One of the head modifiers such as Peter Burgess may be able to tell you if an air pump head is ok for modifying.
David Witham

David,

The rear water outlet was plumbed to the automatic choke on the Zenith carb.
S Rechter

Obviously with the time and effort expended creating my existing racing head, swapping now would be expensive.

So the heat build up is mostly at the rear and not the middle then?

So a extra hole at the rear is better then?
Is that possible with an early head?

Cheers <MARK>
Mark Hester

I can see no advantage to the water flow mod.

If the engine is fitted with a thermostat then the engine will be slow in reaching operating temp since a restricted flow of water will bypass the thermostat.

If the engine is fitted with a blanking sleeve and no thermostat then very little water will flow throught the heater tapping - there bing more resistance to flow in the narrow pipe than the large thermostat housing and top hose.

For best cooling of the rear cylinder the mod is to block some of the forward drillings between the head and block and to open the rear drillings to around 1/2 inch.

The water is then forced to flow from the front of the block to the back and then up into the head before flowing forward again to the top hose.

Some drillings are left on the head/block interface to allow cooler water to mix with the hot water flowing forward in the head to reduce the temperature gradient in the head.
Chris at Octarine Services

David. About 80% of those North American specification head having the water outlet for the Z-S water choke have been cracked when I have tested them. I do not know if this is, as some have said, due to inferior quality castings or if the flow of water out of the rear of the head is part of the problem. People I have spoken to, professional MG mechanics, seem to feel the later style "US" head tends to crack more frequently than the ones not having the rear water port.

Unfortunately, they did not keep records of the heads which they found to be cracked and the type of head. I do know that, here in the US, a cylinder head which has been tested and proven to be uncracked is worth as much as a used, running engine.

Here in the US, where MGBs are the main source of used cylinder heads, good, used cylinder heads are almost as expensive as new cylinder heads.

Les
Les Bengtson

A modification highly used to the type A engine (in racing), dry deck, the coolant circulate by a big hose between the block and the cylinder head.
The engine to the shot is built by Delta Garage in Japan, type A engine with KAD dohc cylinder head, sixteen valves, Keihin racing carburettors.
regards
http://membres.lycos.fr/mgcontact/fileupload/uploads/mini1.jpg
http://www.kad-uk.com
http://www.delta-mini.com
michel

Guess I'm old, hard of seeing, and so forth.
But I need a better explanation of this modification.
Would you?
SF
Dwight
DCM McCullough

Swight,

Its for racing only really.
But water flow around the back of the cylinder has always been a problem, as the temperature of the head is not even all over and I guess can increase the likelihood of cracking or head gasket failure.

From the S/T books example here

http://freespace.virgin.net/marka.hester/RaceStuff.htm

It's always been recommended for racing to make the mods Chris suggests above. Also shown on page ?? above.

My question though is, how many people have tried taking another pickup from the heater outlet back to the radiator return pipe.

Is this likely to keep the head cooler and prevent cracking under race conditions?

I guess if only one person has tried it, then it's a risky thing to try.

Cheers <MARK>
Mark Hester

Chris-

Any chance of a picture or a marked puicture of a block deck identifying the passagese opend and closed?

Thanks
greg fast

Mark Hester, Perth, Australia OR London UK
Swight,

Its for racing only really.

Swight?
What's up wid dat?
Oh, you've got the same problem as me, 'Fat Fingers'
Alright Nark, [LOL] I auto cross my 'B' and it might be helpful.
Thanks
SF
Dwight
DCM McCullough

See here - http://www.octarine-services.co.uk/blockmods.jpg - the cylinder head centre core holes should also be blocked.

The holes should be tapped and a brass or aluminium threaded plug screwed in and faced off flush with the block / head surface.

Note that the rear holes were opened up on the late production engines anyway - so not just a mod for track use.

Sealing the centre holes also prevents water loss if the head lifts at high revs!
Chris at Octarine Services

Chris,
Great picture.
Do you know if an 18V581 block would have the larger 1/2 holes already?

What to you think of the heater outlet bypas pipe back to the radiator ?

Cheers <MARK>
Mark Hester

Mark,

Yes they have, I've checked it on mine of 18V581.
You also add "as the temperature of the head is not even all over and I guess can increase the likelihood of cracking or head ...". I agree with you too.
Chris' s modification was strongly suggested by the factory for a high tuning level and high power output.
Renou

They were opened up on all the 18Vs as far as I know.

I see no point in routing the heater take off back to the rad - it won't increase cooling - in fact, I reckon it will reduce the cooling of the head as the water flowing out of the heater fitting will reduce the flow through the forward part of the head.

For better cooling in high performance engines it is the rad that needs uprating to be able to dissipate the extra heat produced at high revs and power.
Chris at Octarine Services

Yes Chris, you are right, It won't increase cooling, but this mod will reduce the head internal temperature gradiant. Acting so avoids to have to improve thermal dissipation capacities for a given cooling system .
Renou

Heya Chris- Thanks for the picture
greg fast

This thread was discussed between 27/02/2006 and 05/03/2006

MG MGB Technical index

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