It seems like the biggest mystery on the board is cylinder heads and what exactly people do to heads to make them flow better. I have a bunch of pictures of LS1/Truck heads stock and unported that I thought I would share. After all, ported heads are expensive and it's probably a good idea for people that know little about heads to understand what they're paying for and how much work is involved.

Also, I have pictures of several of the aftermarket 8mm LS1 valves compared to stock and pictures of what we are talking about by valve shrouding. So hopefully the pictures will assist in educating people about modifying cylinder heads and help them make more informed buying decisions.

The first few pics are the 5.3 heads that I recently finished porting for a good friend of mine. You can see what they look like compared to stock and why porting is an art. Before you ask, they're not milled yet, don't have a fresh valve job, and have not been flowed tested yet.

Ported vs Stock Exaust
Ported Intake
Ported Intake 2
Ported Exaust 1
Ported Exaust 2
Ported Exaust 3

The next couple pictures are the chambers of the ported 5.3 head, a stock 5.3 head, and an LS1 head with 2.02 1.57 valves hung open at about .400" lift. Valves tend to be shrouded, thus a flow loss, when the chamber wall or the cylinder wall in the bore is too close to the valve. The polished chamber with the aftermarket valves is about how much clearance you want around the valves to avoid shrouding them. And the chamber wall has been widened all the way to the gasket line for an LS1 so opening them up anymore on a stock bore won't do you anygood. This probably makes you wonder why people go bigger than 2.02 and 1.57 huh?

Polished 5.3 Chamber
Polished 5.3 w/2.02 1.57 Valves
Stock 5.3 w/2.02 1.57 Valves
Stock 5.7 w/2.02 1.57 Valves

Notice how the valves almost touch the chamber wall in the stock 5.3 heads. You can see how much the chamber wall needs widened to prevent shrouding. That's why the "X" option or whatever each shop calls it, costs more. But in my opinion, it is worth it for the increased compression.

You can also see in the pics how the 5.3 chamber is shaped differently than the 5.7 chamber. Compare the polished 5.3 chamber to the stock 5.7, on the exaust side and you can see how the exaust side is more closed and how dramatic the tumble ramp is on the 5.3 heads.

Also notice in the polished 5.3 chamber how I rounded the spark plug guide boss which should reduce turbulence.

I would have posted pictures of stock intake and exaust ports etc. but they didn't come out very good on my camera. It's pretty tough to see anything in those dark ports.

The next two pictures are 8mm LS1 valves. From left to right, they are Ferrea, Rev, a Manley version, and a stock 98/99 and then 00+. It's pretty amazing how different the valves really are. In factory form I like the Ferrea's because of the smaller seat width and gentle radius below the seat. They also have a larger margin which will produce a little higher compression compared to the others. Notice how all three aftermarket valves have undercut stems. My opinion is that the aftermarket valves increase flow, not because of their larger size, but because of their better shape. Look at how pathetic the 98/99 exaust valve is. The stem is fat just above the tulip and it leaves a lot to be desired for a good radius from the seat. Look closely and you can see how the valves are tuliped more/less than the others. I think it would take a lot of flow bench time to figure out which valve is better for the port. And there are so many combinations of back cuts that are possible....who knows which valve could be the best.

LS1 Intake Valves
LS1 Exaust Valves

Well I just thought I would share these pictures. Maybe a light bulb came on for a few people that finally understood what somebody else was talking about.

Questions or Comments?

[ January 26, 2002: Message edited by: Jantzer98SS ]</p>

 

LORD! How many hours, or should I say weeks, did you spend porting/polishing those? They look HOT! Any solid HP/TQ numbers from them yet?

Ryan

[ January 26, 2002: Message edited by: The Underdog ]</p>

 

Man they look sweet!!!! I don't really know crap about porting heads, but on the intake isn't good to glass-bead the chambers and bowl area? I was told that the air likes to have something to stck to. But, like i said, i don't really know that much about porting heads. I love that exhaust runner.

 

nice info

 

Port job looks great. Just makes ya think why GM doesnt put better valves in there heads. I dont know how many stock valves I have thrown away and replaced with aftermarket ones.

Doug

 

Nice work, Let us know what they produce
<img src="graemlins/gr_hail.gif" border="0" alt="[hail]" />

 

Jantzer98ss, your post is the first thing ive ever downloaded on my hard drive from this site, congratulations, and you are the BOMB! <img src="graemlins/fluffy.gif" border="0" alt="[Fluffy]" />

 

Hi thanks guys. The heads aren't done yet, but they will be flow tested in the next week or so. I'm not big on flow numbers coming off a bench because their are so many other factors when the heads are on the engine. But, considering my stage I heads worked so well on my car, and I know my latest design is a whole lot better, I'm thinking they'll put down around 420RWHP with all the boltons and a good cam.

02BlackWS6:

Generally you don't want to polish the intake ports because the tendancy is for gas to pool up in the ports and get suspended from the air, but it's not so much a problem with a fuel injector that is pointed straight at the back of the valve.

ProModTA:

Actually the LS1 valves aren't THAT bad. I've seen a lot worse. But, GM does make some great valves too. LS6 Sodium Filled!

Scott

 

Are the links broke now? I wanted to see the valve comparison pics again. If someone has them can they repost or email them to me?

Thanks,
Dan

 

Right click on the link, chose properties, and copy and paste the address in the window above. That should work for you.

 

Scott you better get those heads on before bfield. I just read the rules and they didn't say anything about me having to run a rear hatch. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />