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MG TD TF 1500 - TD head questions

This first picture shows a standard TD head. Notice the size of the divider in the port. See picture below in second posting and notice it is the same area on a different head. It appears to have been modified. The area in all of the ports have been polished on the second picture. The modified one.

My question is that it appears to have been a race mode. Can I use the head in the second picture. By the way I do not have the first head. I only have a picture so that is not a option.

The second head has enlarged valves, bronze guides and the compression ratio is 8.3:1. It was used with high compression Pistons.

Thanks

Joe






JWP Policastro

Head with the issue.



JWP Policastro

You can certainly use that head on a stock motor. However, you are not going to get much advantage out of it without a higher performance cam, larger carbs, and higher compression.

The only downside I can think of to using that head on a bone stock motor is that you might have to do more work on the carbs to tune them properly and the "usual" needles might not appropriate.
David Littlefield

Joe what is the measurement from the valve cover to the head gasket surface?
Len Fanelli

Thanks Dave I should have. Included some background on why I was asking the question.

I it is is going to be used with a supercharger conversion. This head has been ported and polished, it has a 8.6 compression, larger valves conversion, bronze guides.

Based on the above I was hoping to increase the airflow like and performance of the car.

Joe
JWP Policastro

Len I need to go to the lower garage. I will get the measurement.

Joe
JWP Policastro

Len it is 2.954".

If I calculated correctly that is between 8.3 and 8.6 but closer to 8.6 compression ratio.

Joe
JWP Policastro

With standard bore that computes to 8.23:1 when run through the Hal Kramer formula. Bud
Bud Krueger

Thanks bud. I did not run the formula just looked at where it fell in the numbers in the Wood pamphlet.

Thanks so much for the precise number.

Joe
JWP Policastro

Bud i have sent Joe Hal Kramers article on tuning the XPAG cylinder head.
With a longer duration camshaft you can use a higher compression ratio
Len Fanelli

With todays fuel, I think having an 8.2 compression ratio is perfect for normal driving on regular grade gas with an otherwise stock engine. The original compression ratio was appropriate for the fuels they had in the day.
Jim Merz

Which ever one you use, spend some time matching the edges of the manifolds to the head, and check for gasket protrusion. The replacement head on my car had big steps/ledges in some areas. George
George Butz


Joe, I know you said it in your narrative, but I'm not totally sure others saw it. Be sure you tell all of the experts your going to run a Supercharger! I have been told It is an important factor in your decision about compression ratio. Too much can ruin a lot of good things.
Richard Cameron

8:1 compression ratio is recommended for a supercharged engine, you may go a little higher with custom supercharger pistons and or ceramic thermal coatings of the piston crowns. 1 bad tank of gas could ruin your day! I can ceramic coat the piston crowns.
Len Fanelli

Hi Joe,

If you want to reduce the compression ratio a bit AND improve gas flow you could do what I call "Laystalising". That is you can grind out the head near the inlet valve to improve the space where inlet mixture (especially when big valves are fitted) normally is impeded by the wall of the combustion chamber. Laying that area back and giving it a smooth curve MUST be good! The factory 8-port heads were like that. Of course you have to use a burette to ensure every chamber finishes up the same size. I have included a photo. Hopefully it shows the vertically curved aspect of the way I do it. Sorry this photo was aimed to show the dry decking process, not the Laystalising.

Re the carby settings etc needed, look in the factory tuning manual. It lists the needles to use with lots of variations of big valves, port mods and superchargers etc.

Bob Schapel

R L Schapel

Bob, I'm not sure exactly what you are doing (well, I get the gist of it, overall) but my question is what are you doing to the banana holes in the head? Are you plugging them for some reason?
Geoffrey M Baker

Hi Geoffrey,

The photo was the only one I could find to show the reshaped combustion chamber but it also shows the process I used recently on by brother's race car head to "dry-deck" it.

The dry deck process is to block all the holes between the block and the head and to re-route the water out the back of the block and into the back of the head. After doing it to my s/c race TC 20 years ago, I read that the factory had done it to some of their record breakers. It is mentioned in the book "Maintaining the Breed" by John Thornley.

The advantage is that if some gas leaks past the gasket it does not get into the water jacket and push the water out. I used to have that trouble with my race TC when I used lots of revs. I am limited in the head stud tension because the head is an Aluminium Laystal unit. It is easier to do on a round holed block/head. Don't try it unless you research the water flow in the XPAG engine or get advice! This is because the water channel on the right side of an XPAG ends at the rear head hole ONLY, and is not well connected to the other holes, you can block off flow badly if you don't cater for that! I also fit an air bleed high in the back of the block to prevent an air lock in the top of the block.

Cheers,
Bob Schapel
R L Schapel

An example of what Bob is talking about: http://www.mg-tabc.org/library/cooling-system.htm
Gene Gillam

See http://www.ttalk.info/XPAG_Cooling_System.htm for a view of the XPAG cooling passages put together by Gene. Bud
Bud Krueger

Thanks, got it! Interesting... learn something new every day. I just finished totally cleaning all the water passages out and making the modes suggested by Gene as part of my engine rebuild. I'd never heard of "dry-decking", however!
Geoffrey M Baker

Check in the archives for "EX176" which was the dry-decked prototype for the XPEG engine, as used at Bonneville for the successful Land Speed Record attempt, and by Ken Miles in R2.

Apprentices would spend a week matching heads and blocks by lapping with a fine abrasive.

Tom Lange
MGT Repair
t lange

The factory EX176 engines had a slightly different water route that what Bob describes - an elbow at the rear of the head routes water down and around the back of the block to the rear-most core plug hole, where the engines have a cast flat surface, drilled and tapped for another elbow. Radiator hose connects the two elbows.

Tom Lange
MGT Repair
t lange

This thread was discussed between 30/01/2016 and 03/02/2016

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