Ok, I have a set of vortec heads, and am looking to get them ported and polished. What kind of HP gain am I looking at in doing this, and is it really that benneficial? Also, i want to put 1.6 roller rockers on and i know that in order to do that I need to have the valve seats ground out and I need bigger springs. Anything else I need to do other than that, and can anyone reccomend good springs with a comp cams XE cam .487 - .490 cam? Anyone have any suggestions to anything else? Thanks

 

I've got a scan of a flow chart by David Vizard somewhere. I think if you click on the link for my exhaust clip, you'll find it in the folders somewhere.

I'll try and find it first.

 

If you want to use that XE274 with 1.6 rockers, you need at least 986 springs, and it might not be a bad idea to step up to 987s, especially if you're going to be running it past 6000 RPM. Same price, a little better spring.

 

OK...... here it is. I had to upload it. I must have removed it from Yahoo.

BTW, you gotta be a member of Yahoo to see it.


Vortec

 

I would leave the intake port as is and port and polish the exhaust port for this motor.
The stock vortec port and 1.94" valve is hard to beat as it comes.
porting will only help at real high lift. which you don't have.

Just do the exhaust ports and set the springs, guides and
studs up for your new cam.

Use a thin head gasket to help maximize your final cr with your "base crate motor" (dished pistons)

 

Porting or other mods to the bowls and runners has been shown to hurt flow!

 

If you look at that chart I showed (or buy the book) you'll see that just doing pocket porting (bowl blending) does very little to the Vortec heads.

IMHO, I'd agree with ME Leigh that you'd be better off not messing with them due to chancing amature mistakes, like nicking the valve seats, or hitting a water passage. But that's me.

The ONLY thing I'd do is back cut that valves 30*. That's been shown to help. Although word around the water cooler is GM now sells them that way. You'd have to ask (Scoggin-Dickey or Jim Pace Performance Parts) if the ones you're buying are that way.

 

with the xe 274h and the re done vortecs it should make peak right around 5900....go to the car craft website and look for a backissue on this buildup called "400hp vortec engine"



this is the same motor i am building and it made 442hp@5900 and 452ft lbs at 4400rpms

 

Hey AJ_92RS,
Do you have a bigger version of that article? I can't read any of it. Or if you know what issue of mag it came form, I could look it up on the net.

Thanks,

 

Once you click on the link, you can click on the pic also. That'll bring it up to full size.

Doing that fills my 17" flat screen. Granted it's a bit fuzzy, but legible.