Reply to "4V CC head porting with pressed bronze valve guides."

quote:

Originally posted by Jérémie:
Hi Doug, thanks for the feedback.

Can you show me this Ford picture about the port showing the modification ? blending means that I cut the remainin material arround the pressed guide, or remove the booster ring ?

For the porting I was following what was said here : http://www.351c.net/archive/te...ic-porting-4v-heads/

My car won't be a race car It will be for road, I live on country side, and I have shock towers, so the best for me is the geometry that will give the best power curve taking into account that I will leave with this unefficient exhaust port and I would like an engine that goes above 6500 rpm, I don't want a second diesel car even if it is a 400 hp one.

If I do not remove the ring and the material arround the guide, do you think I should smooth the walls ?

And one big question I have, I have new EPN stanless steel valves, which seat cut should I do ? I was think about a classic 3 cuts 60/45/30, this is the next step for my heads after having ported and pressed the guides.

Jérémie

The diagram shown there is the same one as was shown in the Ford Boss 302 book.

If you follow that, it is removing the ring.



60 degrees is going into the port. You will have to blend or smooth that into the port.

Some will use an additional cut there with a stone of about 75 degrees and just leave the edges alone.

I don't think it matters too much which way you go, that cut is ALMOST a matter of tuning the head with the rpm and the cam lift and durations?

You do not polish the inside of the intake ports on an iron head 4v. The rough as cast walls will "co-operate" more with keeping fuel vapor in suspension in the port.


You need to realize that some of the work done to these ports is for rpm use well above where you intend to run your engine and therefore is useless or even damaging in some respects.

The point of Ford on these ports originally was they needed NO porting on them as cast.

The ring is usually the area of discussion or controversy on them though.

I do not know at which rpm the cast in ring becomes restrictive or restrictive significantly?


With the exhausts there are at least two issues. 1) the angle turns down instead of exiting up 2) the header tubes turn down 3) the Mustang chassis will not allow the ports to exit up.

So the answer is the exhausts are what they are and ultimately are the rpm restrictors to your engine.

I do not know at what rpm that all transpires?


Let me just say though that it isn't unusual at all to have the Ford aluminum head engines showing around 700hp and the iron 4v head engines in the 450 to 500hp areas.

There are quite a few of them running around on the street to verify those numbers.

I can hear the differences in the exhaust sounds between the two. The aluminum head engines have a scream to them not unlike the Indy engines do and the iron heads have a drone to them?


In my experience that plays into the exhaust tuning of engines and is where you can gain 150 hp through the exhausts over another car?

That exhaust frequency is definitely an indication. The higher the frequency, the better.


The fastest cars on the track ALWAYS have that HIGHER FREQUENCY exhaust scream to them. It isn't a coincidence?

Also, we are talking about hand made headers (as if you could cast them up, right?) and here the cost starts about $3,500 for a set of them? These guys use a computer to calculate every tube along the way and match it to your gears and cam profile.

Change those and you need a new set of headers?