First foray into porting

[abowie]

Armed with Des Hamill's XK Engine tuning book and a sense of trepidation I have embarked on the head for my MK2.

Brenton my machinist's comment "Nah mate you can't stuff it up."

So I made a brass mandrel punch, heated the head up with the oxy torch and knocked the valve guides back to give some room.

After 3 hours:

inlet and exhaust guide bosses gone
exhaust roof lip relieved
inlet port side waist flattened and opened up a smidge


Exhaust post exit.


Exhaust port throat.


Inlet port entrance.


Inlet port throat.

[Simonpfhc]

Hi Andrew,

Very neat work, well done. Will be interesting to hear what difference it makes.

Presume this is part of of un upgrade that includes other aspects of the engine - what other mods are you planning and do you have a target power figure you are after?

Cheers,

[abowie]

No specific HP figure, but want to make my MK2 "sprightly" rather than the current "sluggish" with its stock 3.4 and a 5 speed Toyota Supra box.

Spec is 4.2L short stud block relined back to standard and blueprinted. Stock flywheel judiciously lightened. My mild head work. D type cams. Twin 2" SUs mounted on the stock inlet manifold. 9.5:1 compression.

And I'm fitting big inlet valves.

I reckon I currently have maybe 150Hp. Looking for maybe 70 to 80 more.

[abowie]

I was surprised at how easy this was.

As always, 9/10ths of the job is overcoming the trepidation and just getting on with it.

Plan is to get it flow tested and then there's inevitable blending and fine work to do, but as a total beginner it was not difficult to get to this point.

[max-it-out]

One could argue that the main factor in limiting the flow of gases is the size of the valve openings , and the shape of the ports / manifolds is less important . However , porting should be a lot cheaper than fitting a new big valve head , so it will be interesting to see the results .

[mark10337]

As always, 9/10ths of the job is overcoming the trepidation and just getting on with it.

I know that feeling! Hat's off to you or should that be valve guides out?

I remember reading, not sure if it was Des Hamill's book or not, that the inlet passages should not be totally smooth. Some turbulence from the walls is desirable in order to ensure a good mixture of air and fuel.

Good on you. I need to bite the bullet and do my valve timings.

[steve3.8]

You don't mention valves Andrew ,so i guess you are maybe using standard as supplied ?.
Having gone to the trouble of doing a port flow, buying better quality valves are worthwhile as part of the port flow process.
Look up Race Engineering Components - G&S Valves - they stand alone when put alongside standard valves , it's a company most race engine builders use.

http://www.gsvalves.co.uk/

[abowie]

http://www.gsvalves.co.uk/

I'm going to fit the big inlet valves out of the S3 XJ6. 1.8715".

[christopher storey]

I don't know whether this applies on XK engines , but on A and B series BMC engines one of the mods which can assist flow greatly is to use 3 angle valve seats and valves

[steve3.8]

This photo may explain better , these are 1.875" inlets . The REC on the left and a commonly supplied on the right.

[abowie]

I don't know whether this applies on XK engines , but on A and B series BMC engines one of the mods which can assist flow greatly is to use 3 angle valve seats and valves

Yes I will be doing that. Has a surprisingly large impact on valve flow early in the opening period.