silvertop port work

[alltracfreak]

Hey everyone my silvertop turbo build is about to begin and I was curious about port work. They say bigger isn't always better and I've seen higher flowing heads make less power than lower flowing heads on an identical build. So what do you guys recommend that will yeild the best results. I'm probably going to be using factory valves with aftermarket springs and cams.

[burdickjp]

Make sure your guides are good! These like to eat guides.

For the intake side, silvertop bowls and short side radii are notoriously bad, and much can be improved there without the fear of screwing things up too terribly. Similar improvements can be made around the valve guides.

The exhaust is similar enough to the 16v to be able to follow Oldeskewltoy's posts on the matter.

Do a good valve job.

[yoshimitsuspeed]

I don't know enough about the port geometry to agree or disagree with burdickjp on what could benefit from work but I can tell you this.
Boost increases density, not velocity.
Velocity increasing mods are the ones that benefit the most from port work. This includes VE mods like intake and exhaust and especially cams and also includes increasing the RPM. All of which increase volumetric airflow.
Turbo increases volumetric airflow before the turbo but after the turbo the volume and velocity is roughly the same as it would be in NA and the gains would be similar to NA. There are gains to be had but you have to ask if they are worth the effort. You also have to weigh the gains to cost. For example if a perfect port and polish will gain you a 2% gain in power would it be worth paying a skilled professional to get you that gain? Or if a home hack job could gain you 0%-.5% gain in power is it worth that gain for the time? Or is it easier to raise the boost by .5 PSI to get the same result?
The ratio changes much more at higher levels. If you were running 304 cams with a 12k RPM redline there would be no more low hanging fruit. Well before that it would be worth a good P&P because at that point the gains to the cost would be better than many other mods you would be looking at.

[burdickjp]

The silvertop head could be the best example for beginning porting due to the pretty atrocious machining left over by the manufacturing process. If you feel like trying, the silvertop is a good start.

Be careful. Go slow. Work small.

[alltracfreak]

Thanks guys I will consider both.

[oldeskewltoy]

for a turbo build I'd build a ping proof chamber... or as ping proof as possible. the exhaust ports need re-shaping and for a turbo build I'd push the ports a bit larger than I normally do... the intakes need blending as burdickjp recommeds.

[yoshimitsuspeed]

the exhaust ports need re-shaping and for a turbo build I'd push the ports a bit larger than I normally do.

The general rule of thumb is to keep the header diameter smaller on a turbo build to keep the velocity up going into the turbo. I would consider this and factor the primary size before deciding on how big to go on the ports.

[burdickjp]

for a turbo build I'd build a ping proof chamber... or as ping proof as possible. the exhaust ports need re-shaping and for a turbo build I'd push the ports a bit larger than I normally do... the intakes need blending as burdickjp recommeds.

The edges of the chamber around the squish could probably be rounded a small amount.
I wouldn't expect them to be too much of a problem, as the squish there is very good around TDC. rounding too much may actually cause problems rather than curing them by slowing down the flame front instead of completely eliminating flame propagation.

If junk valves are available a chamber polish could be advantageous. Work small. Go slow.

[oldeskewltoy]

the exhaust ports need re-shaping and for a turbo build I'd push the ports a bit larger than I normally do.

The general rule of thumb is to keep the header diameter smaller on a turbo build to keep the velocity up going into the turbo. I would consider this and factor the primary size before deciding on how big to go on the ports.

I don't work from general rules....

I KNOW what works in a 4AGE head.... The problem (insufficient exhaust velocity) occurs because most turbo manifolds use piping that is misplaced, and is too large.

You make a turbo manifold... what size piping do you use? Is your flange slotted to allow for proper fitment - adjustable to fit the exhaust ports?

Stock 4AGE exhaust ports(except blacktop) are marginally 30mm... My typical port work has a finished diameter around 31mm... In a turbo build, I'd push this to 33 mm.

Most turbo manifolds I've seen use 42mm OD pipe, that is a bit larger then 38mm ID, going from a 30mm port dumping into a 38mm pipe slows down the air speed... it doesn't speed things up! Now if I have a 33mm port, and I KNOW the velocity hasn't been reduced, the flow into that 38mm pipe is not going to slow as much....

IDEALLY... for a stock valved head the manifold is built to the head, it uses 38mm OD, 35mm ID piping for improved exhaust velocity....

[yoshimitsuspeed]

Damn OST there's no need to be so snarky all the time. You didn't mention diameters in your first post. I was just saying that as a rule of thumb you would want a turbo manifold to be on the smaller side. Therefore I would expect you would want the runner to be on the smaller side as well. I don't see how a bigger step from port to primary would be better in an NA build.
Whatever the case my main point was that the OP should pay attention to the primary diameter before deciding on port diameter.
My manifolds are 35mm ID BTW.

I use the SV3 power flanges because they are a tight fit and don't eclipse the port. They fit well. They don't need to be adjustable. If They weren't as good or as cheap as they are I would make my own.

[burdickjp]

I don't see how a bigger step from port to primary would be better in an NA build.

I'll posit that steps reduce the amplitude of reversion waves, which have a large impact on naturally aspirated power production, but I'd have to dig into some literature to have any citations for that.

[yoshimitsuspeed]

I don't see how a bigger step from port to primary would be better in an NA build.

I'll posit that steps reduce the amplitude of reversion waves, which have a large impact on naturally aspirated power production, but I'd have to dig into some literature to have any citations for that.

Definitely let me know if you find anything.
I doubt it though. The dynamics of a boosted engine are much the same as an NA. The differences I can think of if anything cause more and more chaotic reversion waves. The manifold is usually shorter. Because of this it can be very hard or impossible to make a collector as good.
The initial pulse leaving the head will be operating under the same principles as NA but then it will travel down the short runner, get funneled into the turbine and slam into the turbine wheel.

[burdickjp]

I doubt it though. The dynamics of a boosted engine are much the same as an NA. The differences I can think of if anything cause more and more chaotic reversion waves. The manifold is usually shorter. Because of this it can be very hard or impossible to make a collector as good.
The initial pulse leaving the head will be operating under the same principles as NA but then it will travel down the short runner, get funneled into the turbine and slam into the turbine wheel.

While the problem may be larger in forced induction applications, it does not affect overall power production as much as in naturally aspirated applications. Probably due to the substantial pressure differential across the intake port preventing much reversion during overlap.

[oldeskewltoy]

I don't see how a bigger step from port to primary would be better in an NA build.

where did i mention it would be???


Again from knowledge I've gained working these heads....

because of bolt hole slop, even as small as a 1 mm MIGHT cause hang over and cause serious eddy interference. Let me explain... as I mentioned the port outlet is marginally 30mm. A porter NEVER lowers a port floor on a 4AGE, they always, or should always work the roof. In my case, I work the ports to 31mm, this is the typical hang point for an OEM Toyota exhaust gasket... meaning the OEM exhaust gasket just sits at the top of a 31mm ported port. The exhaust gasket is 33mm, so it is possible to open an exhaust port to 33mm and still use the stock gasket if properly aligned... IF not properly aligned, the gasket will interfere. The same can occur with the exhaust header flange.

[alltracfreak]

Speaking of headers will 16v header fit on my 20v?

[Rogue-AE95]

Speaking of headers will 16v header fit on my 20v?

Not exactly. The bolts at the ends of the exhaust ports are slightly off. See this flange, which has accommodations for 16v and 20v.

http://www.matrixgarage.com/products/4a ... mild-steel

[alltracfreak]

Just read about your turbo manifold with the flange. Is their an option of external wastegate.

[yoshimitsuspeed]

where did i mention it would be???

It would have to be.
Let's say even if the primary diameter stays the same 35mm then if you ported to 31mm for an NA build then the step from port to primary would be 2mm.
If you ported it to 33mm for a turbo head then the step would be 1mm.
Why would it be better to go from 31 to 35 on an NA and 33 to 35 on a turbo?
Then if you actually did a smaller primary for the turbo then the difference in diameter from port to primary would be even greater.

because of bolt hole slop, even as small as a 1 mm MIGHT cause hang over and cause serious eddy interference. Let me explain... as I mentioned the port outlet is marginally 30mm. A porter NEVER lowers a port floor on a 4AGE, they always, or should always work the roof. In my case, I work the ports to 31mm, this is the typical hang point for an OEM Toyota exhaust gasket... meaning the OEM exhaust gasket just sits at the top of a 31mm ported port. The exhaust gasket is 33mm, so it is possible to open an exhaust port to 33mm and still use the stock gasket if properly aligned... IF not properly aligned, the gasket will interfere. The same can occur with the exhaust header flange.

If you have even a 33mm port and 35mm primary 1mm of slop would at the most put a section of the flange flush with the port. This may not be ideal but for your average build shouldn't be a problem.
Aaron was smart when he drew his flanges so they sit damn close to centered when resting on the studs. If you tried to push the exhaust up when you bolted it down it would be a little off but still wouldn't eclipse the port. If you just let it hang while you tighten it then it will be very close.
If someone is paying enough for a professionally ported head I wouldn't expect them to just slap a cheap mani on without mentioning it. I can always modify the flange to an application or could even add adjustment but personally to me that is using band-aids to fix sloppy work. Even if they didn't think of it before ordering a mani they could still taper the flange 1mm to make the top flush. 1mm of taper blended over the 11mm flange and then blended into the primary may not be ideal but again the kind of issue that only would only be important at very high levels of performance and at that point it would be the fault of the buyer for thinking a cheap shelf part would bolt right up optimally for their extreme build.

[yoshimitsuspeed]

Just read about your turbo manifold with the flange. Is their an option of external wastegate.

Yeah, the price on my website is for a bare bones mani. Modifications like O2 bungs, external WG etc can all be done but it will cost more.

[oldeskewltoy]

Why would it be better to go from 31 to 35 on an NA and 33 to 35 on a turbo?

You are always happy to note that a turbo (intake side) doesn't change the VE, and so the volume doesn't change, but the pressure has increased.......

Once ignition takes place, the volumes going out are DIFFERENT! There is more volume in the burnt boosted charge then there is in the burnt n/a charge. THAT is why I'd run a bit more size on the exhaust port on a turbo build

[oldeskewltoy]

If someone is paying enough for a professionally ported head I wouldn't expect them to just slap a cheap mani on without mentioning it.

the kind of issue that only would only be important at very high levels of performance and at that point it would be the fault of the buyer for thinking a cheap shelf part would bolt right up optimally for their extreme build.

How many build advice threads do you and I respond too?? How many of them are unrealistic, or have some stereotypical fallacy? In my near 40 years in the automotive industry... I've learned you really can't ASSUME.......

edit - apologies... I too ASSUME.... as in that you would be using the incorrect pipe diameter, or that your flange would be "run of the mill".