ive read too many threads and the i havnt found a straight answer.

i know 6port irons can be bridged, but can i get the same power as a 4port? everytime i hear some1 doing a 6port bridge theyre keeping the stock manifolds. im going with a jtech manifold with a 650 holley. does anybody have any numbers on full bridge ports on 4 n 6 irons? the reason im concerned with this is that i have 3 sets of 6port irons that i can use but i was told to get 4port irons being that they will yeild more power but they were using stock manifolds. it would be cheaper to go with 6port irons (being i already have them) if they yeild the same power advantages or similar.

i know bridgeported has done these 6port bridges. but does anybody have any experience with them on a carb?

thanx

 

Seems to work just as well. Since you're porting, it really doesn't matter which irons you start with. The intermediate castings are the same, but the end plates are not. The 6 port irons will allow you to make the port higher for a later closing, if you're into that kind of thing.

Don't use the stock NA manifold if you do a bridgeport. It doesn't work very well. If you really want to do that, then go into the dynamic chamber and grind out the internal passages so it just becomes a plenum.

Why would you ever want to use a carburetor?!

 

later closing alot of revs, right? isnt the middle plate primarys from a 6port a lil higher than the 4port?

y carb? simplicity, cheaper, less restriction and good horsepower

 

Maybe it's just me, but I don't find any truth in that statement.

 

^ except for the fact that he can just buy a well engineered manifold from racing beat and not have to spend all the time and effort trying to source one or fabricate it. I understand the advantages of fuel injection, but after personally looking into it it's just easier to find ready-made systems for a carb. Now Kahren might someday sell custom 6 port manifolds that will bolt on without any bullshit, but not everybody wants to spend all of their time doing completely custom work.

Fuel injection is superior, but going carb is going to be a much easier and quicker job.

 

Later closings generally mean that the engine will make power higher then an engine with earlier closings.

The port shape on the TII housing is different, but the casting is the same. So since you are porting it doesn't matter.

No, no and no.

 

also we recommend the growing of a mullet

 

don't knock mullets now, I rocked one for 2 years.

 

you do not have to go carb. get an IDA LIM and a fuel injected ITB setup, which will cost as much as the carb manifold and whole deal, if not less. unless you are really not wanting to mess around with electronic engine management stuff. and you will probably have to do some fabbing if you want to keep cost down.
example though:
manifold: http://www.tweakit.net/shop/product_...roducts_id=105
TB (expensive one): http://www.tweakit.net/shop/product_...roducts_id=117

there have been less people out there who have done a 6-port bridge compared to 4-port.
the 4-port seems to be pretty standard for this sort of thing since it is used lots in race cars and is just more common (i don't know any place selling 6-port bridge porting templates). really there is not going to be much seperating the two, and each has its own characteristics. i have a bunch of junk 6-port irons lying around that i have been meaning to start practicing porting on, and i have been thinking about this every now and then...
i'm going to assume you don't really care about low-throttle driveability, etc.
based on what i have looked at so far, leaving the primary ports either unported or mildly ported, and then doing a bridge on the secondary and auxilary ports would be my preference. a large bridge on the secondary, that notches into the rotor housing, is even better.
but, that is just opinion. i don't know anyone who has actually done that sort of thing on a 6-port non-turbo and documented results.

 

Same template.

Honestly, a bridge is a bridge is a bridge. If you are going to do half-bridge, you might as well do full bridge. You're going to have the same "issues" either way. Most of these issues are tuned out when you use EFI...

Judge ITO.

 

yeah, i meant the aux port templates, no one sells those.

well, a bridge is a bridge, but a half bridge is not a full bridge. maybe there's not much seperation between the two in terms of driveability and what not, but everyone would be running around with full bridges instead of halfs if there was no difference.
but you make a good point in that, if you are willing to do a half bridge, why not do full?
i guess you could same thing when it comes to notching the housings, and why people don't do that more often.

Judge ITO? interesting...has he posted that somewhere? i remember reading a thread of his on another forum. but i believe the 6-port bridge he built was running nitrous.

 

so i can use 4-port bridge templates on a 6-port?

This is jackpot for me ive been looking for the same info

 

The only problem I see with with that TB is that it looks like you might as well just run 2 large injectors instead of 4. The secondaries look like they are in the same place as the primaries, just on the other side.

 

No.

I have a full bridge NA 6 port. It is a stupid loud, peaky motor with no torque. It is fun though.

 

* A bit off topic *I'm going to be building a 4 port 13b, how does the water jacket seal hold up with the section of the housing cut out to match the port???? Hope the question makes sense.

 

For good reason. Bridging the aux ports only means you miss out on a lot of timing. I probably set a bad example with mine since I did mine as an experiment in trying to get more top end flow while minimizing overlap...I should have just continued the bridge down and then done the intermediate iron!

Exactly. The difference between a full and half bridge isn't that great with good tuning, so you might as well go all the way.

In my case anyway, I didn't want to go "ruining" a set of housings that I might want to use for another project (ie. semi peripheral port). Most people are probably a little concerned about cutting into the housings...

It was on NOPISTONs several years ago. I can't find it now because I don't have an account and they have restrited their forums...Also a bunch of other people if you look in the "Engine Building and Porting" section.

Yes. The bridge is exactly the same. Of course you don't really need a template to make a bridge anyway...

That's going to be true of any wildly ported NA. If you want a flat powerband, go turbo...or peripheral port NA as long as you can deal with the noise and lackluster low end.

 

That's the plan and I should be able to spool anything.

 

Aaron, are you saying nothing good comes from bridging that high (the aux port)? not too much research done on aux bridges, so just wondering what your thoughts are on it...

"flat" is relative.
a turbo will never have as flat of a torque curve as an NA rotary, but it will have a lot more torque and peak torque.
horsepower on the other hand, well, a big turbo car might be just as peaky as a heavily ported NA, but most likely it will make a lot more power.

anyways, about housing notching reducing engine life, i have heard if done properly it's not a big deal. but i mean, i don't think anyone has built one of these engines to see how long it will last...

 

[QUOTE=coldfire]Aaron, are you saying nothing good comes from bridging that high (the aux port)? not too much research done on aux bridges, so just wondering what your thoughts are on it...[/qutoe]

If you look at a "regular" bridgeport, it opens like 40 degrees or more before the aux port. At higher RPMs this means you can take great advantage of the scavenging effect of exhaust flow. With an aux bridge, this overlap is minimized so you don't get much of that effect. Sure, you get more port flow due to more area and it does open a lot earlier then stock, but it doesn't have the advantages of a larger bridge. However, it also doesn't have the disadvantages as I suspect the idle quality is much improved.

With a properly sized turbo you can put the torque almost anywhere you want. Especailly in these days of electronic boost controllers.

If you are putting on a massive turbo for huge HP numbers, peak power is generally the concern so the turbo is sized all wrong for low end and midrange. People seem to be in the habit of trying to build an engine for a specific turbo when you should be building the turbo to suite the engine.