need to port

[cameljockey]

hey guys its me again,

i blew a head gasket between cyl #3&4 on my 200 ci six. :x

any way I've now got the head off the car and I figure while its off I could get some work done to it. hardened valveseats, over size valves, and unshrouding the valves, but most importantly porting. however I'm being told by several machinists in my locale that this is not a good Idea ofrd the six and it will cause the engine to run hotter and the head to warp, and several structural problems with the head will ensue especially cracking. but how can this be? hot rodders have been doing this to cylinder heads since before I even knew what porting was and only those who over did it were the ones who complained of cracking warpage and all manner structural and performance problems.

 

[cameljockey]

sorry my hand slipped and hit the enter key

I only want to open things up on the intake and port match the runners on the exhaustside of things. not a full race treatment , maybe even extrude hone the log and mod it for two one bbl carbs as opposed to cutting it off or switching to an oz 250 head.

are these machinists fears valid or are they wanton grey beards who just think it can't and shouldn't be done?

keep six'n guys

Dan

 

[MustangSix]

Sounds like someone who has never ported one of these six cylinder head before.

The majority of the gains come from blending the pockets under the vavle seats, blending the vavle guide area, and removing any lumps and bumps in the exhaust port. The exhaust is very restrictive, but you don't have a lot of metal in the ports, so just smooth it out, and make it a little taller at the port opening to get rid of that slight downward turn. If in doubt, less is better than more.

A little valve unshrouding also helps. Find Mustang Geezer's website for some photos.

 

[80broncoman]

I have always belived when doing port work, especally around and in the bowls that more than half your gains are in the first hour of work. Even if you don't git rid of the sharp edges directly under the seats if you just smooth out the sharp edge, you have done a lot.

 

[Anonymous]

When I ported my 200 (Oct., 2003), I just opened up the bowls on cylinders 1,2,5 & 6, then matched up the (new) hardened seats to the profile of the tract on all intakes. Then I narrowed the sides of the valve bosses (left the front & back sides alone), and smoothed out all the tracts to make them less 'bumpy', like Jack said.

On the exhausts, I just matched the outlets to the manifold (and installed the 3-4 port divider).

The difference was immediately apparent when I drove down the street! I get beter gas mileage AND better power, all across the range. The top speed went up from 86 MPH to 94 MPH, mileage went from 14 MPG (in town) to 16+ MPG.

I also raised the compression ratio: the new CR is not quite 9.1:1.

If I take the head off again, I'll go a little deeper in the bowls and take Jack's advise and raise the exhausts a little taller. Even though I have to run into a catalytic converter, it still made a nice difference.