Porting e7's...would you recommend unshrouding the valves?

[redterror302]

I am about to get started on my heads, just have a few questions before hand though. I am just wondering if any of you who port your own heads(preferably e7's) unshroud the valves. It seems as if there is both a benefit to it, but it does lower the compression ratio a little bit. Check out this info, http://www.geocities.com/jjonibones/Shrouding.html That is the process of how to do it, but if you go to the main page, and on the left side click head tune-up, it shows the flow test for it. Unshrouding the valves created a few more cfm at low lift, and then it stayed pretty much equal at higher lifts. So it would give more power at lower lifts.

Question though, is it worth it to do it? How much would it lower the compression? I wouldn't think it would lower it very much, but I wanted to check to find out. What would you guys recommend for this?

Thanks,
Chris

 

[bit]

It usually only add about 1/4 on a CC to the combustion chamber, but the thing about unshrouding is do you have the room. When I was porting mine I put blue on the head surface and used a head gasket to mark the cylinder wall boundary. When I looked at my heads I had less then a 1/8" to play with. That is not enough room to unshroud anything. Someone like thumper460 or Tmoss might be able to offer some better insight but that is my experience with the E7's.

It's a little hard to see in that pic but but it you look close you can see the line.

 

[sleeper89]

hopefully thumper will see this and give you a little input, but until then i offer the following info (not to be taken as gospel as i make no claims to being an expert):

when porting my e7's my "informant" (aka mechanic) said he was originally going to install larger valves, remove the shroud, port work, valve job and mill it down for compression. well, after some digging he said that when removing the shroud the combination of lower compression and less swirl wasn't worth the minimal gains from unshrouding. likewise he said that it was not advantagous (sp?) to go to a larger valve because it would be shrouded by the cylinder wall.

anyhow, we ended up milling the deck surface to bring the piston to the top (KB notched hypereutectic pistons) for the added compression, hogged out the ports, and did a nice valve job. i'm fairly happy with the results and cant wait to get a ported stock upper to let the heads breathe. so to answer your question: No, i wouldn't unshroud the valves. but again, you should wait for an expert opinion.

-steve

 

[redterror302]

Thanks for the replies. See that is what I was thinking, I didn't know whether it would even be worth anything to do it. One, because it only added a few cfm(not sure how much power that would give), and two, it would lower the compression a bit. I hope thumper sees this so he could put in some input, but input from others is still helpful.

Thanks,
Chris

 

[thumper460]

the shroud.....

Unshrouding in the heads is good... but with anything less than a 1.90 dia valve the HP increase will be almost nothing, and then when you have a big valve the block needs to be notched also . Try not to become a "Master Porter" on the first set of heads...cool?? do the basics.. gasket match, cross section between the push rods and just smoothing the sharp edges in the bowls!!

The Power will be there ( jsut doing that).. and IF you go TOO far... you will loose a lot of that precious bottom end!! Anyone can "HOG" out the ports.. and have good top end.. it is the low end and velocity that makes the heads work!!SOOooo... yes!! unshroud is cool> NO, you dont need to do it!! Read the "mouse " and do what you think you can do... dont get too deep!! Just a good gasket match on the intake and getting rid of the egr bump will amaze you!! esp for the first time that you have donr it!! Cool?

Hey this color is cool... Oh ****!! chevy orange....oops!!

AHhhhhh... thats better...
Just me...............................


Thumper

 

[redterror302]

Thats the answer I was looking for. Thumper: I read over mouse's page so many times its ridiculous. I went over the lift/cfm chart, and decided what I would be working on to get the most top end while keeping the low lift flow too. So no need to unshroud huh? Cool, one less thing to worry about.

Thanks,
Chris