what size vavles to buy

[black_ss_blazer]

wanna go with 2.02 ....whats the biggest ex valve we can put in the head...????what kind of vavles are you running.....???...??
is it just a stock smallblock chevy valve....((valve stem length, etc etc....

[ZR1 S10]

I beleive mine are 2.02 intake & 1.60 exhaust.

[Maximus]

Im having a set of vortec heads cut out to 2.02/1.60.

[biglouie_underpressure]

i run 2.02/1.60 i would do that combo on vortec heads again.If i were you i would keep the stock intake valve and go 1.65 exhaust.

[Sparky2263]

I'm with Louie. If you're not going over 6000 rpm's Keep the 1.94 intake and open the exhaust up. I'd use 1.6 though.

[ZR1-S10]

2.02/1.60 is the most commen setup. Howerver I think the heads will suport up to 2.08/1.65, dempending on your needs will make a big differentice. For the street I'd go with the 2.02/1.60

[Maximus]

The purpose this engine is gonna be used for should be looked at before deciding on what size valves to get.

[biglouie_underpressure]

it's been proven 2.02 valves on vortec heads don't do jack!

[bvr775]

it's been proven 2.02 valves on vortec heads don't do jack!

yeap..... I was wondering when someone would bring that out.The stock vortek head is good for 300hp (400 with minor work). The intake ports are too small on the GM heads,but you can't really do much tooling to them without messing them up and the GM bowties and dash heads are for non-vortek blocks so I don't know if they will bolt up to a vortek block. I know there is an aftermarket head out there that will bolt up to bolt-up vortec 90* v6 block that will flow at least 76cc(not sure of the exact spec), but that's more than you will ever need for a V6 street engine.

I don't what your planing to bolt on to the engine so this is just in genrale, but before you start you need to thinck about if you going N/A or bolting up some power. a blown or charged engine builds a little differnt than an N/A engine to maximize the power added and make it last longer.
a 3 angle valve job(you go farther with it but it woun't do you any good) will open them up a little more and you can tool the bowls a little to even them out. Haveing some very slight machine work done on the topend (heads shaved, block decked and of course you have to give the manifold machined as well to match)will give you a little more top end. you can't go to much though.

[ZR1 S10]

Vortec block?!! I mean I know theres differences but the way the head bolted to the block has always been the same.

Why do you think theres so many syty's with vortec heads?

[biglouie_underpressure]

yea bvr i know this from my engine builder he's done countless test with heads,valves and cam combos. I'm looking at the brodix 23* Aluminum from some of the old bush series nascars MOST of the new ones run 18*.

[Maximus]

Well if I see no gaines from the larger intake valves no worry they didn't cost me a thing.But I still am not convinced that 2.02's do nothing for the vortec heads,I have heard it before but have yet to see concrete proof.Any way you look at it your getting more air in with the larger area.

[biglouie_underpressure]

sure go ahead and prove it to yourself! i'm still trying to figure why ppl spend all the money on porting the intake side also, a little blow work is all you need.

[Sparky2263]

The 2.02 valve shrouds so much area you have to grind in the combustion chamber area to unshroud the valve opening just to allow the valve to work. This takes away from the intent of the chamber to create a swirl flow.

i.e., the head will show better flow on a bench but will not work as intended. You actually back up from the intended result.

[biglouie_underpressure]

frosty don't for get about our run

[Sparky2263]

http://www.sicgmtrucks.com/forum/showthread.php?t=1241&page=2

You musta' missed this.........;)

[Maximus]

I might need to look in to this a little further.I don't have a lot of experience with the vortec head.As of today they still hadn't started on them except cleaning them up and checked for cracks.There is a local speed shop that deals with a lot of late model Chevy truck engines I'm gonna give him a call and see what he does with his.

[Sparky2263]

Max, either Hot Rod or PHR did a test on the 350. Found the 1.6 exhaust did a bunch but the 2.02 intake results were mixed. Seemed to balance a lot on the camshaft used. Basically came to the conclusion that they're best suited for a 6000 rpm max engine.

Don't remember the year engine though. dammit.......

[Maximus]

Beside the valves I was gonna do a gasket match on the exhaust side and maybe some clean up behind the valves and a 3 angle valve job.I wonder what 1.65 exhaust valves would perform.

[ZR1-S10]

With 1.65 vavles my engine sim shows +3hp/1tq after 3500rpms compared to 1.60 valves. Thats with any combo.

[Sparky2263]

Dunno. Headwork is still such a damn "black art" what with wet-flow head benches and guys coming out with out of this world chamber shapes.

My last big myth buster was watching a pair of 195cc intake Canfields outperform a set of 210cc Brodix on a 383 turning damn near 7000 rpm's.

I've got a machinist I can trust that keeps up with all the "latest, greatest" and has the means and ability to test it out. They're getting fewer and further by the day.....

[biglouie_underpressure]

lol 12.4's on stock bottom end nice. i'll run ya 10 psi w/no nitrous.(i have two stage 30/30 that i haven't used yet :)

[black_ss_blazer]

it's been proven 2.02 valves on vortec heads don't do jack!

Just trying to learn more about the heads, not trying to bust anyones BaLLz.......Where was it proven so I can do some reading up on them.......Has anyone on here ever done a real world dyno comparison........??...engine out of the truck on the dyno, 2 sets of heads same port work 2.02 intakes VS. 1.94's ........?

[Maximus]

Oh man there are tons of tests out there comparing one head to another.There are articles it seems about every few months comparing heads with certain combos and applications and so forth.Just do a google search on a certain head in a comparison test and you will get all kinds of different subjects on them.There is no head that's a one size fits all.It's like anything in the performance arena it's a constant journey to find that extra edge.

[black_ss_blazer]

anybody have a link to one of the comparison tests.....
Did a google search for chevy 4.3 2.02 vs 1.94
only came up with 3 pages and none had the info I was LQQKING for...

[Maximus]

Here you go read this article.I found it last night to get some more background info on vortec heads and what works and what don't.I found it pretty interesting.
http://www.carcraft.com/techarticles/116_0306_vort/index.html

[Maximus]

Oh click on grind time and the numbers link at the bottom.

[Sparky2263]

http://carcraft.com/techarticles/116_0306_vort_dyno_z.jpg

Very good article Max. The proof is in the pudding!

[Maximus]

Look at this dyno print out with the port work done.Also look at the hp/tq numbers above 5000 rpm.Especially between 5500 and 5600.Almost no change ported or unported.Shows were the vortecs really start falling off and why a cam selection for vortecs should be looked at closely.http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1215&stc=1

[ZR1-S10]

Can't see!

[Sparky2263]

Yup, 5500-5700 HP practically the same. But we kinda knew that ;).

[03 Rado]

http://www.chevymania.com/tech/vortec.htm
http://www.2quicknovas.com/vortecheads.html
http://www.chevyhiperformance.com/techarticles/46364/

[black_ss_blazer]

Thanx everyone for ALL the info..........Learned alot in the past few days......thanx again..!!!!!!!!!