I was talking to a guy that said gasket matching is only effetive at higher rpms,is this true and what rpm range are we looking at.thanx

 

A given engine can only consume so much air/fuel at a given RPM. This amount varies widely based on many factors of which displacement is the biggest.

There is a point which air velocity suffers from ports being too big and you will loose low RPM fuel atomization and power.

Porting your heads can make more power starting at 2,000rpm or starting at 5,000rpm depending on the application.

 

Here is my meager understanding:
I agree with whomever advised you.
What RPM range? I couldn't begin to guess. Flow rates will be more uniform the further from the valve seat it is observed; therefore, some minor offsets will mean relatively little upstream, IMHO. The area near the valve seat is incomparably more critical to getting the charge moving and filling the cylinder as quickly as possible, in comparison. Personally, for an moderate performace street V8, I wouldn't bother, as I don't think anyone could tell the difference, even on a dyno. Am I reading your mind? BTW, "gasket matching" would be a much better heading and might get some answers smarter than mine. (OMG, that last sentence sounded like Eric!)
(No offence intended to you or Eric.)

 

I would have to say that gasket matching can improve the performance at even a lower RPM. This is due to differences in sizes from port to port from core shift and casting imperfections. Gasket matching basically will get rid of some of the possible flow imbalances and possible turbulance issues. This has been proven many times with a flow bench. The performance gains that can be obtained from porting are very substantial.

 

so gasket matching and porting and polishing are two differant things things right,one takes out factory inperfections and the other increases flow and the CCs of heads or intake does this sound right,I'm not totaly clear on the subject,but if I don't ask I'm bound to do somthing stupid.

 

gasket matching is a part of porting and polishing. In doing a gasket match, this does help increase the flow potential of that head. This is not enoght work to increase the velocity to a point where your low end torque might suffer. Quite the contrary is true, you should have better torque and power across the board. In doing a gasket match, you could also do work beneath the valve in what is referred to as the bowl area and the short turn radius where the transition is made into the port beneath the valve also. These two areas are both beneficial to perform work on in all engine applications as they are going to improve your performance across the board.
I would highly recommend a thourough understanding of the process before any work is done. You can do a search on this web site on porting, you will find there are some very good links to porting tutorials with photos also. There are also links to machine shops that will perform this service for a fee.
A full port, race port or stage 3 porting would be the type of porting that would not be used in most truck engine applications as this type of port work will be for increases in flow at the higher rpms and higher valve lifts assosiated with a racing engine.

 

I think the above replies nailed it. Something to mention is if your talking stock heads on a 351w, the logic is, these are small heads on a 302. Being most 302/351 heads after 70/75 are about the same, they are restrictive. I spoke with some folks about stock heads and porting on a 351w motor, the general idea was if I ported the heads right before break through, which is max, you would still end up with a restrictive head.


Here is a thought, say your thinking the DO or E7/ E5 heads on a 351w. It takes experience and a three angle valve job to get these to flow like the gt-40p heads. With that said and to back up 94F150-408's post, not that he needs it, when ratsmoker did some cam comparisons using stock heads vs. gt-40p (which would be the equivalent of ported stockers) the low end torque actually improved. Being your thinking gasket match, which is minimal porting, your not gonna have a problem. This is all given your thinking stock heads or the introductory aftermarket heads, such as, world or performer, which again the gt-40p flow real close too. Just a thought, later

 

Hey JW,

can you post some of the references to sites that have the porting tutorials for this guy? Also, how about some of the shops that do port work? I believe Capone had posted several choices on this. I dont know how to post the links or I would do it. Computers and me dont get along very well on alot of issues.
Thanks!
Kevin

 

thanks for all of the replys guys,the help is appreciated.

 

Standard abrasives has a website that has a basic and easy to understand procedure for a basic port and polish job. They sell a kit which can be bought at Summit etc. The kit is ok for the finish work but if you do it yourself you really need to get at least one eggshaped double cut carbide burr. If I were doing it again I would probably also get a smalle or more pointed burr, especially if your heads have some deep crevices like around the plug ares or guide boss. "www.sa-motorsports.com/diyport.htm"

 

yes, you definitly want to do any major metal removal with a egg shape crosscut carbide burr for iron. The smaller ones are good for "corners" but I would practice on something other than my good head if you havent used one before, the reason is that its alot easier than you might think to dig a hole with one of the smaller ones. Just be careful.

 

I'll practice first ,I have a set of chevy heads kicking around somewhere.

 

Here is the links 94F150-408 requested I post.


Just in case the above link didn't work:

http://www.sa-motorsports.com/diyport.htm

Here is another very indepth one:

http://www.cmc.net/~xero/Mousesporting.html

http://www.carbdford.com/tech/headporting/porting.htm

another real good one:

http://www.workmonster.com/id17.htm

places for porting kits:

www.eastwoodcompany.com

www.summitracing.com

www.harborfreight.com they also carry an electric die grinder for $30 you will need the $20 router speed controller, but a couple of people have used this will good results.

places for carbide burrs and/or sanding rolls:

www.carbidebur.com this company offers 1/4" carbide burr heads on hardened 1/8" shanks, so you can use a dremel and have the cutting head of a larger die grinder.

www.tavers.com

www.ruffstuff.com

These companies will port your heads for a decent price:

http://www.jlmcylinderheads.com

http://www.xsrcylinderheads.com contact this company direct, the website is confusing but the prices aren't bad if you contact them direct.

This one is fairly well known for doing port work:

http://www.hunterstyle.com/thumper/combos.php

also there is this company they actually use a cnc program:

www.powerheads.com

So as you can see you have options, later

 

Dang, good listings JW! Thats a pretty comprehensive list...thanks for sending that along. Theres a few I'm going to save myself!

 

tastyklair...you mention using a small burr around tight areas such as around the spark plug? Never use a burr in the combustion chamber. Only use a stone and sading discs if your going to polish the combustion chambers. You will end up taking out too much metal if you use a carbide burr. This will lower your compression and you could end up with an imbalance in the sizes from chamber to chamber. If yu have done this, you will need to cc your chambers to get them all back to the same size, allbeit a lower compression motor now. When using the stones or flat sanding discs in the chamber you will need to install old, unneeded valves in the head to keep you from ruining the valve seat while you polish the chambers.