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MG TD TF 1500 - Cylinder Head Mods
|Has anyone ever seen a mod like this? It came on a car with a race history, but I am puzzled why only the middle two combustion chambers would be so crudely ground out.|
|I'm assuming NFG means No f'ing good so probably not a great idea.|
|Seems like it would eliminate all the squish and remove the turbulence in the chamber. The attached image illustrates the desired area.
|Jim - that was MY (disgusted) editorial comment on the usefulness of the head...|
|Grind .100 off it, notch the pistons, and use avgas? :-)|
|It's a pity because the intakes have been nicely profiled to a knife edge; it is, after all, a TD race car driven on the airport using airport transfers sevenoaks circuits in the 50's. It still puzzles me, but it must be so imbalanced that I just can't bring myself to use it.|
Could someone have tried to decrease the compression ratio by enlarging the head volume? Possibly decreasing the compression because they are fitted a supercharger after the head had already been skimmed? It looks like the shape follows the gasket marks so it is still inside the cylinder profile. Just looks like a butcher job though. Not the kind of thing a craftsman would settle for!
|R D Jones|
|Certainly possible, but why ONLY on nos. 2-3? 1 and 4 are untouched.|
|It seems a pity to waste it. Seriously, have you determined how much you would have to grind? In the two dimensional photo it looks like a lot.|
|Unfortunately, the grinding is about 1/8" deep...|
As I see it, my only two options are to use it as is, or trash it. Used as is the central two cylinders will have a wildly different compression ratio, CC size, etc., and the engine will be considerably uneven because of it.
Anyone disagree before I throw it away?
Why not grind 1 and 4 to match 2 and 3? Maybe, just maybe, there is some genious hiding behind what looks like a hack job. You cold have an XPAG HEMI.
Just a thought
|Have Dremel will travel?|
If I do that I will set it up on a milling machine and do all 4 nicely...
I just don't know.
|I'd grind the other 2 to match and use it as a low compression supercharged head. Don't pitch it. I'll take it if you plan to scrap it.|
|It's a puzzler, all right. I'll add it to my Wall o' Speed for now.|
Thanks for all the help.
|According to the Wood tuning book you can remove 1/8" or to a head thickness of 2.898 (73.58mm) with the result on a stock bore of 9.3 to 1, doable on premium gas. A little relief around the valves and some chamber polishing would bring that down a bit.|
A .60 overbore brings the compression to 9.6:1 which should still be fine on hi-test. We routinely ran 12.5:1 in SBCs on the street and I went as high as 14:1 on Sunoco 260 or avgas. That was a relatively light car with 4.88 gears. It was easy to get some detonation in the wrong gear.
Don't consign that head to the trash yet! At the minor expense of premium gas it may soldier on for quite a while. I would not consider grinding the rest to match as that will surely make it scrap.
A performance shop can do some valve relief and chamber polishing that will lower the compression ratio slightly without destroying the desired combustion chamber characteristics. That would be helpful if you had to go slightly beyond .125, assuming the casting core allow it. I have no idea how much you have to work with.
This thread was discussed between 08/05/2014 and 11/05/2014
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