Okay, suppose you had some spare heads lying around. What modifications would you do to them?

From what I can tell, there's no way to get larger valves in, the intake and exhaust valves are too close to each other.

About the only thing I can think of is to port them to match the intake and exhaust manifold gaskets, and to remove casting lines. The valve guide bosses are already pretty well recessed and don't look to impede flow much at all.

 

Cams, clean up the ports, and SwainTech coat to deter detonation.

 

Smooth out the combustion chamber. Gasket matching is good to a point, but make sure the headers/manifolds are matched to them aswell (you dont want a 'wall' there). Same with the intake, but generally it is more of a problem with the exhaust side.

You've probably noticed you aren't going to have to do much to smooth everything out lol. The most time consuming part is just making sure everything lines up.

Swaintech is nice but $$$$$$

I just wish all the work netted more gains

 

Okay, how about this. In the pictures below, you see how close the valves are to the cylinder walls? This results in shrouding - impeded flow along the backside of the valves. By backside I mean the side opposite the spark plug hole.



What about milling into the quench area behind the exhaust valves just enough to unshroud the exhaust valves, maybe about .050-.060"? That would improve flow out of the cylinder and also lower the compression a bit as well.

Or would it screw up detonation suppression of quenching flow in the combustion chamber?

Here's some pictures with the exhaust valve at maximum lift:

 

$190 for SwainTech coating vs. rebuild is cheaper.

If I went through all the work of pulling the heads, I'd go for broke, ie port/polish, SW coat heads/valves/ports, stuff with lighter valves and stiffer springs, and most of all cams.

If you don't put in cams, might as well not bother, RIGHT Stephen?

 

With boost, I think a coating is recommended and is a good idea. As for messing with the combustion chamber, anything more than very minor grinding, I think you would need to cc each chamber to insure all the bowls measure out to the same cc.

 

I've got some VQ35 cams for a little extra lift, but the other stuff gets expensive quick. Unfortunately, the valves from these heads are in very good condition so I don't have an excuse to get $600 worth of titanium VQ45 valves. I might do the Swaincoating, though.

 

You can go slightly larger valves. There are 1mm oversize valves availabe as we speak. It is tight, though. You're right about that...

 

How much improvement do you expect from that? It looks like there's enough room for flow there, if blocked the smallest bit. Anyone care to guesstimate what kind of help it would do to open it up a little bit in that tight spot?

 

Those heads are in pristine condition. How did you clean them so well?

 

oh, woah, I thought it was still in the $600-800 price range :eek3:

I dont remember enough about the effects of messing with quench area to really comment on it. I'll have to start researching it again

 

They were low mileage heads to begin with, so they weren't too dirty when I got them. I cleaned up the end combustion chamber with scotchbrite and a dremel and flapper wheel in the ports.

 

Not much probably, but I have a goal I'm trying to reach.

 

I'm a firm believer in not screwing up a good thing. The VQ heads are fantastic from the factory. All I would do is just polish up (skip the porting) the imperfections and perform a valve job. Install valves, springs, retainers and big cams. The reason I would skip the porting is unless you have a reputable source that solely does VQ's, it could actually hurt performance. A poor port job could decrease velocity much in the same essence as having a 3' exhaust on a naturally aspirated SOHC Street Honda. Overkill.

Sam

 

but he is boosted. So he is just trying to shove as much air as possiable into the combustion chamber.

 

Stephen,

You might want to reread Corky Bells' Maximum Boost. He definitely warns about messing with the CC area and changing the squish area around the perimeter of the CC.

IIRC, he states that OEMs design the piston face/CC to force the combustion front towards the center to ward off detonation and if you mess with that, you're more likely to cause detonation.

I'd leave good enough alone and just clean up the ports, then Swain Tech coat them.

 

the swain tech is a good invest. Maybe having a higher lift exhaust cam (in comparison to intake cam) reduce effects of scavenging since the exhaust valves are so much smaller?

 

Not sure if this helps any, but here is SGPs examples on CC work:

 

are those larger valves? looks purty anyway

 

No kidding. It seems a shame to hide it away inside where you can't see it.

I've never seen valves that dished before. Is that to lighten them up, or maybe lower compression ratio a few tenths perhaps?

 

Any progress Stephen...what's the plan man?

 

Haven't done much since posting the pictures. I've got a big project review I have been putting a lot of overtime on (I'm at work right now) and haven't been able to do much.

I'm waiting on some VQ30 cams so I can figure out what dimensions to make the spacer rings for the VQ35 cams. I also need a set of cam timing gears so I can drill new dowel holes for the intake cams. I thought I had a set coming from an org member but nothing's showed up yet.

 

Okay, no progress on the intake manifold idea then. I liked your version of the idea, but have a concern or two. I'll email ya, since my PM box is full and I don't care to clean it.

 

i have a set of port and polished heads that were originally for a turbo max. they ended up in my hands due to a non paying customer and a shop that we would hang out at before. i can take pictures tonight so you guys can take a look at the port job im not sure if it will be worht it to install anymore.

one problem is the heads did not have the the first cam bridge. and they cannot be order alone. plus it does not have a valve train in it. sooooo im not sure if it would be worth its weight in gold. i ve been sitting on the heads for the past year or so.

 

Definitely post some pics of the combustion chamber and intake/exhaust ports. Thanks.

 

will do

unfortunatly it will have to be after 8pm here cause stupid parts dept at the dealer i work at decide to extend the hours till 8pm.

 

here are some pics

 

 

 

I will probably spend a small fortune before i get these heads ready to go.