Vortec port question for you flow Guru's!

[James Thomas]

I have never not one time used stock exhaust let alone cast manifolds so this and Vortec heads are a first. That with the fact that it's a turbo mani's, I just want to be sure before I send these off to Jet Hot.

If using Felpro gaskets Pn MS90746 as a template, all the stock manifold ports are almost right on the money (see the scribe line in pic 1).

The Vortec ports are another story and these heads are supposed to have been ported by McCoy Motorsports. The top and most of the sides of all 6 ex. ports are real close, the floor of the ports is way high compared to the Felpro gasket and the stock manifold ports (see pic 2, 3 & 4)!

So do I..... leave them alone and let the smaller cyl. port "dump" into the larger manifold port or match them to the gasket / manifold size? Like I said, never done Vortec's just L-35's and the stock manifolds are a new thing to me also?

Thanks fellas!


Pic 1 - Stock Manifold ports


Pic 2 - Vortec port #6


Pic 3 - Vortec port #4


Pic 4 - Vortec port #4 & #6

 

[Luke]

Re: Vortec port question for you flow Guru's!

I would at least gasket match them, doesnt look like it would take a whole lot

 

[blk00z28]

Re: Vortec port question for you flow Guru's!

The only thing porting is going to do is free up some back pressure. Its not like air is going into the engine at this point. Its going into the turbo to spool, and then out the downpipe.

Whats the difference between stockers and headers? Because I wouldnt port the exhaust manifold's, I'd do the heads if I wasnt planning on going to headers. (I only say this because if you port the heads to match headers, they might not match up. But if you never plan on going with headers, it doesnt matter and the heads can be ported away.) But I guess if you plan on porting them yourself. Have at it, lol. But I wouldnt spend money on having someone port either or just for that little bit.:2cents:


(btw, thanks for this post and pointing this out. Because I plan on using stock exhaust manifold's on my truck when I rebuild and go vortecs :tup: )

 

[bezerk]

Re: Vortec port question for you flow Guru's!

what exhaust gaskets are those? they look pretty easy to install, with that i mean you don't have to take the manifolds off to install those

 

[blk00z28]

Re: Vortec port question for you flow Guru's!

Can't you read Bez..

If using Felpro gaskets Pn MS90746 as a template, all the stock manifold ports are almost right on the money (see the scribe line in pic 1)

 

[Quickstop [UK]]

Re: Vortec port question for you flow Guru's!

he is dutch.

 

[James Thomas]

Re: Vortec port question for you flow Guru's!

what exhaust gaskets are those? they look pretty easy to install, with that i mean you don't have to take the manifolds off to install those

Pn is posted above but trust me, you don't want to use gaskets! I'm just using them as a template to clean up / port match. Use no gasket, only high temp R.T.V.

_____________
James

 

[James Thomas]

Re: Vortec port question for you flow Guru's!

I would at least gasket match them, doesnt look like it would take a whole lot

Yea I agree but I was wondering about the ex. port on these Vortec heads being smaller than the port on the manifolds? The manifolds damn near match and I think about two minutes per port will match each one two the gasket template but that is a lot of material on the port floor of the head, 3/16 - 1/4 in or so.

Are you guys doing a complete port match of the head to the exhaust on the Vortec's or not?


___________
James

 

[Wikid 1]

Re: Vortec port question for you flow Guru's!

When you Port heads, on the exhausts, the floor is supposed to be approx 1/16 higher than the floor of the manifold/header to prevent reversion, or the back flow of exhaust. leave it there, however on a turbo car i'm not sure if it'd be as usefull as on a N/A car seeing as how there's plenty of backpressure to fight anyhow, but it's certainly not hurting anything seeing as most flow is along the celing of the port, and outside walls.

 

[CKEITH]

Re: Vortec port question for you flow Guru's!

:2cents: james i would gasket match them.you are probably not gonna notice a diff either way but if it were me i would do it. wether it be a lil more or a lot more...speeding up the exhaust velocity can only help...again :2cents:

 

[myclone]

Re: Vortec port question for you flow Guru's!

what exhaust gaskets are those?

Those gaskets or very similar gaskets come in all the gasket sets that you can get from the convenience store parts outlets. You can make your own by just cutting out the bottom of the gasket at each bolt hole too.

 

[James Thomas]

Re: Vortec port question for you flow Guru's!

When you Port heads, on the exhausts, the floor is supposed to be approx 1/16 higher than the floor of the manifold/header to prevent reversion, or the back flow of exhaust. leave it there, however on a turbo car i'm not sure if it'd be as usefull as on a N/A car seeing as how there's plenty of backpressure to fight anyhow, but it's certainly not hurting anything seeing as most flow is along the celing of the port, and outside walls.

Wikid 1 & CKEITH,
Thanks for the info. As you said the forced induction builds don't need to worry about the step in general as far a flow or prevent reversion. I am wanting to know if McCoy or who ever ported these heads left this in for a reason such as BAD FLOW or Vortec castings are thin to the water jacket in this area etc. If these were L-35's I know exactly what to do but I have never done the Votec head castings before and they are a little different.

ANY ONE KNOW OR HAVE PICS OF THE PORTS WITH MEASURMENTS?

Thanks!

__________________
James

 

[dgoodhue]

Re: Vortec port question for you flow Guru's!

I was planning on doing some light porting clean up to a set of vortecs next week. I will take some pictures of the gasket & manifold as I go along.

 

[turbodig]

Re: Vortec port question for you flow Guru's!

Get a smooth radius on the top inlet of the manifold.... slightly larger than the exit of the port

Don't mess with the floor of the exhaust port. You'll lose flow/port efficiency unless you really know what you're doing in there; If you do decide to grind, make the port floor radius as sweeping as you can, which means you'll have to grind a fair amount out of the knee of the short side turn before you touch the port exit. You'll want a wider cross section down in the port than at the exit.

The slight mismatch helps deter reversion, as long as the port is smaller than the manifold, so personally I wouldn't mess with it. The potential to booger it up is far greater than the potential gain.

The big gains are around the first 1/2" near the seat.

 

[James Thomas]

Re: Vortec port question for you flow Guru's!

Ok so still pretty simular to the L-35 then. I can deal with that if so. Been doing the L-35 for seems like ever and can get real decent flow out of them.

Thanks!

_________________
James

 

[dgoodhue]

Re: Vortec port question for you flow Guru's!

Get a smooth radius on the top inlet of the manifold.... slightly larger than the exit of the port

Don't mess with the floor of the exhaust port. You'll lose flow/port efficiency unless you really know what you're doing in there; If you do decide to grind, make the port floor radius as sweeping as you can, which means you'll have to grind a fair amount out of the knee of the short side turn before you touch the port exit. You'll want a wider cross section down in the port than at the exit.

The slight mismatch helps deter reversion, as long as the port is smaller than the manifold, so personally I wouldn't mess with it. The potential to booger it up is far greater than the potential gain.

The big gains are around the first 1/2" near the seat.

Sorry to hijack this thread, I was just planning on following this article and port matching the intake mistake.
http://www.carcraft.com/techarticles/116_0306_porting_gm_iron_vortec_cylinder_heads/index1.html

 

[turbodig]

Re: Vortec port question for you flow Guru's!

Sorry to hijack this thread, I was just planning on following this article and port matching the intake mistake.
http://www.carcraft.com/techarticles/116_0306_porting_gm_iron_vortec_cylinder_heads/index1.html

If you plan on running 6500+ RPMs, it'd be great.

The gains in our typical RPM range weren't particularly large; what he says is true - the base head is good, you don't need to change it much. Much of what you do will be in the seat and throat area.

Keep things simple, and you'll be fine.

 

[dgoodhue]

Re: Vortec port question for you flow Guru's!

I dragged out my stock Vortecs and Victor Reinz exhuast gaskets (They came 4.3 top end gasket set). The look almost the same as your pictures, so I didn't bother downloading them.

 

[It's just a six]

Re: Vortec port question for you flow Guru's!

I agree, do not lower the exhaust floor, unless you want it to flow worse?

 

[James Thomas]

Re: Vortec port question for you flow Guru's!

Well I have decided to send them to Racing Head Service / Pro Heads in Ca. and let Richard flow bench them as is (along with a several other things) and see where they are as far as flow. If the Ex. aren't 200 or over then it's grind time. I'll keep the thread up dated and let everyone know as I find out. After the heads are back to me, I will post pic's with port diminsions so we don't have to guess anymore along with the flow sheet results.

____________
James