While I agree that you want to watch what you remove from the combution chamber, there are a a couple of spots where the burr may be the item of choice although you must be very delicate. I found areas of flash in the narrow areas aroung the spark plug that I just could not get at with the discs and drums. Also the exhaust valves were shrouded to within 1/16 of an inch which I think warrants a little opening up for flow sake at the price of some CR. I should still be over 9:1. I'll have to wait till I finish the ccing to find out. The closeness of the exhaust valve to the side of the chamber surprised me once I got into it. Really after opening the area up to the scribe mark for the head gasket it is still well under the recomended 3/16 of an inch shroud. I guess the question is one of trade off of flow vs CR and trying to make a compromise that works. I'd be interested in any other thoughts about this.

 

yes, unshrouding the valves can help, but doing work such as that should always be done with the use of a flow bench to assure that what you are doing is beneficial...I was surprised to find some of the things that would appear to be good would actually reduce the flow when you tested it out on the bench. Just dont go overboard if you dont have any way to test your work is all. I found that using a new, coarse disc without any folds in it yet was always the best way to remove all of that flashing your refering to, just use the outside edge of the disc holding it at a slight angle from your work. Are you using a air die grinder to do your work? If you are, a disc at 25K can remove more than enough metal, it just wont last very long! In many years of doing porting and polishing in a racing machine shop we never once used a burr in the chamber, so if you do....be careful!! Another thing to consider is if you widen out that flat spot around the spark plug with a burr, you have probably just changed the flame pattern also, maybe good or maybe not good.

 

thanks for all the great info ,if I mess up now it won't be for lack of information.

 

personally for a day to day/kinda a fun type of truck I would do a gasket match (on a more fun oriented truck i would do so on 351 heads) a 3 angle valve job, unshroud the valves, and cc match the combustion chambers, finishing off w/ a 9.0:1 to 10.0:1 comperession ratio

if anybody knows how much cfm a three angle job and unshrounding the valves will do for a head i can run two different setups on dyno2000(about 15 cfm i think)

and remember: the boss 302 proved that bigger isn't always better, you may have the torque and hp, but that doesn't mean that it will be where you want it.

HAH! you just explained me!

 

I'm doing this work on a set of d8oe heads,i'm not sure what the specs are on these heads from what I can remember they werenot a great flowing head at all ,but I have two sets of them so I thought I would give them a try,and where would I get a flow bench thanx ,you guys realy know your stuff.

 

You need to be very clear in your own mind what you want to achieve with your engine before you go investing in having a set of heads ported. Simply put, the more heads flow the larger the runners are and the higher you will have to rev it to make horsepower. If you are just interested in a strong street engine with a fairly mild cam heads that flow in the 240-250 cfm range will be fine.

 

does anybodie know what the flow rate on the d8oe heads is

 

i have numbers for c5 heads, not sure how different they would be. and a head that flows 240-250cfm on a flow bench sounds like a dragster head to me (no offense, i might just be confused cause i also have numbers for a ported 351 head w/bigger valves and it only hits 222cfm)

 

Anything you do to aintake port in general only brodens the torque curve.

 

not true, full porting and enlarging your intake runners will slow the velocity and you will loose your low end torque.

 

WOw....looks like alot has been taking place....having all the fun without me??

Looks like someone wants to try and make their heads flow better....

I'm all for that...Stick to the basics when it comes to truck engines...

"Gasket match" the cylinder heads to the intake gaskets using a carbide bit...
blending it into the port 1.25 inches into the port from the opening....(it should be a gradual transition)

Then....the valve bowl....the area behind the seats should be
smoothed/blended....lightly using the carbide bit....

The valve guide boss needs to be tear drop shaped....with the pointy side facing the intake port opening.... and the blunt side facing the valve opening.

Be sure that the upper radius breaks up into two smooth channels around the valve....and have a gradual transition into the valve bowl walls...

here is a before picture:
http://www.replikamaschinen.com/Web_...%20chamber.jpg

here is what it should look like after:
http://www.replikamaschinen.com/Web_...%20chamber.jpg

here is a 351w exhaust port before:
http://www.replikamaschinen.com/Web_...st%20stock.jpg

here it is after:
http://www.replikamaschinen.com/Web_...%20exhaust.jpg

The exhaust ports should be opened up to within 1 mm of a performance exhaust gasket...(if using headers)....if not then gasket match the stock exhaust manifold gaskets...and smooth the EGR bumps...smooth the valve guide boss....and most of the work is going to be here....the most restrictive part of the ford windsor heads...

So in a nutshell.....gasket match the intakes....sand smooth with abrasive bit....without taking too much material off....(focus on flashing)
then get the intakes bead blasted...(very important) Do open up the exhaust ports and sand them smooth.....polish them and leave as is....

get a 3 angle valve job for both intake and exhaust....get the heads machined for larger valves...if better flow is desired....get heads machined for screw in studs...(adjustable valvetrain) and the rest of the machining like surfacing etc....

Be prepared to port the exhaust manifolds for better flow....
the heads will only exhaust as mush as the manifolds allow them to...

in this case headers are the best option.......

keep in mind....removing too much material on the intake side can enlarge the ports too much and slow port velocity down....this will kill low end torque...

The key here is to remove cast flashing and casting core shifts...and smoothing them....

The riser (the part on the intake port where it is smallest...is there for a reason.....using the gas laws...and bernoulli's principle....the smaller the port gets....the higher the gas velocity will be....this means more effective cylinder filling.....(the better the engine is at filling cylinders...the higher its volumetric efficiency) Where you want this V.E. is going to determine where you develop your power....larger ports are akin to high revving engines....
smaller ports are best for street where high revvs are impractical...

just think of an engine as a thermodynamically controlled air pump....
the larger the ports...the faster the smaller displacement engine will have to spin in order to get that port velocity up there where it needs to be....

The larger displacment engines make better use of the large ports because one rev of that engine will displace more air....so it moves the air through the ports at higher velocities with ease.

Ratsmoker nailed it right on the nose.

Keep us posted and take pics of your progress...

 

Check my gallery for pictures of recent portwork done to Gt40X cylinder heads

pics include combustion chambers and finished deck mating surface machining...., finished intake port and closeup of polished combustion chamber.

regards
R

 

.