Valve Seat And Port Mismatch On S16 Head

[Anthony 1,003]

Got my standard S16 head back from being skimmed and the valve seats 3-angled and was going to reassemble it this weekend and finally get an engine ready for the driveway ornament that is my 205 Mi.

 

Checking over the head though reveals a fairly sizeable mismatch between the valve seat and the port on the short-side bend of the inlet ports. As the following (laughably bad) picture tries to show, the valve seat insert is intruding about 0.5-1mm or so, and I can't help but think that a sharp edge like that has to be ruining flow...

 

 

I guess the first obvious question is will that mismatch be messing up flow as I suspect, especially given how critical the short-side bend is to getting the head to flow properly by my understanding of various posts/articles?

 

Secondly, if it is going to make a mess of the flow, will my cack-handed efforts at trying to minimise the mismatch and make a smoother transition from port to seat insert make things better, or without a flow bench do a risk making something that looks nice but actually flows no better (or even worse)?

 

Thirdly, are the valve seats so hard that I'd be fighting a losing battle trying to cut back the lip with something like a dremel, given I don't have access to a set of proper port-cutters?

 

Any insight from the likes of Dave Baker, Mattsav, Petert or anyone else that is knowledgeable on porting and prepping heads would be much appreciated

[christopher 5 1 Cars]

Anthony,

 

I advise you ask Guy Croft on his forum.

 

Question is if you have just had a 3 angle set done why didtn't they blend it to the port at the same time? I would have thought that this is affecting some flow for sure...

[Beastie 1]

I seem to remember David Vizard writing words to the effect that "if it doesn't look like it wants to flow then it is worth investigation". You have seen something that doesn't look like it wants to flow and I'd say your question is very much justified. At the end of the day the only way that you can guarantee better flow is to use a flowbench. The condition which you have illustrated is not conducive to good flow and IMHO would be better corrected. This does not however ensure that the head will flow better as a result: A lock is as strong as its weakest pin therefore if your head has other more significant problems then correcting this lesser restriction won't make much difference. (Likely guess is that it will though) This error is very easy to correct if you have a die grinder. Judging by your posts on this forum then you are likely to have sufficient manual dexterity to carry out this job without "cack handedness" becoming an issue of any sort. I must admit that I have never used a Dremel because I have an Aro die grinder which turns at a healthy 80000 RPM I should have thought that a Dremel would be able to tackle this sort of job though providing you have a little patience! A good die grinder will power a tungsten carbide bit and make light work of an austenitic valve seat. If the Dremel won't then a suitable carborundum bit will do the job at a more leisurely pace! (Noli illegitemi carburundum and all that).

 

The main worry about removing a lot of metal from valve seats is reducing the strength of the seat and reducing the heat mass of the seat thereby making it more likely to come loose and "drop". In my own experienced removing metal in the area which you have indicated is unlikely to lead to this trouble. Nevertheless it is always wise to assess the amount of metal left after the operation in order to form some idea of the structural integrity of the seat / head interface.