SoRRoW

Ok im lost as hell now..

Why not notch both front and rear housing?and shouldnt they be notched towards the center plate?

WackyRotary

Oh, you are afraid about low rpm sealing and you own a PP engine? What kind of seals are you running now?

I thought all the PP engines out there were using carbon seals. They are very lightweight and don't damage rotor housings over time like the others. I am unaware of them breaking due to very wide ports. IF they are very worn down thin, they will become more prone to failing that way I presume. I don't know, mine were still close to new thickness after the stationary gear failure, less then .05mm lost material from usage.

As for starting, I have no problems with starting the bridgeport..It has never flooded on me. Just pump the gas a bunch of times and pull the choke(if you have one, I don't)and start it. As for low rpm, I can't imagane how a PP feels like, so I won't even pretend to know how is the power feel at 2000rpm-4000rpm? I also can't imagane anyone spending much time down in the low rpm range with a PP except when letting off the gas or at stops.

peejay

Relieved rotor housings for both ports is fine IF you are using 1 piece apex seals.

I personally wouldn't use them, due to low-RPM sealing issues. I'd rather just build a half-bridge or a peripheral port engine and use stock seals, and hold the revs to below 8500 if the engine has 3mm seals (all 12A and '85-earlier 13B)

Rotortuner

Ya almost every one uses the carbons i guess. But i was using a set of steal ones. I didnt really care about the housings or anything, the steal ones really helped with the low and mid range pwr. But i was running the car yesterday and just sitting there stopped and i was showing a friend at my house. Of course i was revving it out and it was just off the header. The all of a sudden its running off one rotor and spitting fuel back up the IDA carb. Shut it down and pulled the intake off and shure enough 1 seal gone and another piece of one is too. This time around im forsure going to go with the carbons though. they sound like they are what i want. And i was driving it on the street so i was in that 2k - 5k range a lot when coming to stop signs and stuff. I hardly had any miles on it though. I had put probably 400 total driving miles on it befor it blew yesterday. I didnt have an air cleaner on it yesterday either. So th eonyl thing i can think of is that it ingested something or a small piece of the material i used to block th eold ports came off and blew it ??? Who knows. Im going to pull it and dissassemble it tomorrow so we will find out.

CJG

REVHED

Of course you notch both housings but you only need to flip the seals around on one. I guess it wouldn't matter too much whether you notch them towards the center or end plates as long as you're running a two barrel carby and the ports are the same size. But, it's usually done next to the secondary ports.

fatboy7

Isn't the port timing different on the primaries vs. the secondaries? Thats why I figured they did them on the secondaries, because they naturally close later....

SoRRoW

Ok I will be runnign the same carb my 600 double pumper,Why only flip the seals on 1 rotor?

Theres 4 intake ports
1 front plate
2 on the center plate
1 on the rear plate

If you notched both housings wouldnt you have to run both seals backwards? Cause the of the triangle corner?

I want to stay with my 4 bbl 600 double pumper and steel 2 peice seals to cut down on cost right now.

REVHED

The apex seals normally all face the same way... ie. the apex seal corner pieces all face the rear of the engine on both rotors. That means you only have to flip them around on one.

If you're running the Holley you'll definately want to notch the housings on the secondary side. That way you'll have more flow potential through the the larger secondary barrels of the carby.

XLR8

iTrader: (52)

Looking into a Bridge port myself Let me know what you guys think.

https://www.rx7club.com/forum/showth...73#post1377973

Happy rotaring

peejay

Very few Holleys have different sized secondaries than primaries. When they are different, it's only by a sixteenth of an inch or two. This is why they're known as "square-bore" carbs, as opposed to Carter AVS/Edelbrock/Quadrajet/Thermoquad/etc carbs which have very small primaries and huge secondaries, which are known as "spread-bore" carbs. The Nikki would qualify as a spread-bore carb since the secondaries are about twice as big as the primaries.

The port timing on primaries/secondaries is generally the same except for the 6-port engines.

REVHED

Rightio, in that case it probably won't make much difference whether he notches the primaries or secondaries. BTW, port timing is the same but do you think the different runner profiles will make any difference?

peejay

I'd imagine it might

SoRRoW

Ok so the secondary sides would be closer to the end plates right?

Do I bridge all 4 ports or just the centers or what?

This will be my FIRST Bridge port job..and it will be on mine...so I dont want ANY **** ups..lol

I heard people just porting the middle plates and what do they mean "the over lap' <<is one guy ask me liek a year ago when I was geting bridge porting quotes..

My friend came over last night and describe his port job..he said its bigger than a street port...and it dont have the slot cut out like a bridge but it has holes drilled in ...

I said it sounded like a hack job...has anyone heard of this back yards set up?

fatboy7

overlap refers to the timing in degrees when both the exhaust ports and intake ports are open. Naturally, bridgeports have a lot more overlap than stock ports, maybe this is what he was asking about?

The secondary ports are the ones on the outside housings.

REVHED

If I was you I'd probably just make it a secondary bridge-port. Cut a nice big street port for the primaries (center plate) and bridge-port the secondaries (end plates) with notched rotor housings to match. Then you just flip the seals around on the rear rotor. This setup will work very nicely with a Holley and should have a slightly better idle and low end.

Your friends "bridge-port" is a complete hack job if it's done like that. It's all about flow. The only thing that would accomplish is the bridge-port sound but with no performance gain. In fact it would probably run worse.

Like fatboy said overlap is the period when both exhaust and intake ports are open. This allows some exhaust gasses to escape into the intake cycle which gives us that rhythmic miss-firing at light load and characteristic bridge-port idle. brap brap brap

SoRRoW

Ok im understanding this better,

Cut the bridge on the secondaries
(front and rear plates)

Cut a oversized street port for the center plates..

Will this give me a better idle or how about lower rpm power?

How much HP is this set up good for?
The closer to 300 the better

It seems like this set up will have more streetablility,BUT has any one actuall y run this set up?

Sounds good,this sounds like it may be the one..

peejay

Plenty of people have run that way.

Low-end torque depends on many factors. Obviously if you hog out the runners and put a huge carb on it and a restrictive exhaust to quiet it down (overlap motors hate exhaust restriction) the low end torque is going to be damn near nonexistent, especially if you use one-piece seals.

spoolin

did i read you right up there peejay? who the **** is going to have a peripheral port and hold it to 8500 rpm's?

whoever... should be shot

peejay

Well.. the R26B engine that everyone so drools over had an effective redline of 8000rpm...

NSU engines were peripheral port and had peak HP and torque numbers about the same as where a stock 12A was, except they were smaller and made 30% more power...

WackyRotary

I don't know were you heard that. Its not as good as stock ofcourse. I don't care about 1000-2500rpm much, I have my bridgey idling at 2100rpm. 1st gens are so light you don't have to slip the clutch that much even with the lack of lowend the bridgeport makes. At least that is the case with mine. And as for lowend power, WHO FRICKEN CARES? It does not take long to pass 3000rpm in 1st gear and much quicker after 4000rpm on the bridge I did. Full bridgeport with 1piece seals and its quite drivable on the street. Maybe because I am used to driving it. But they rev so fast that if you simply give enough gas to get moving and wait till 3-4KRPM to go to WOT, it drives just fine? NOT HARD TO LEARN AT ALL!

peejay

Did you even read the rest of it? The porting and the exhaust configuration are important too.

Low-end torque is a nice thing to have. It's fun to pull out to pass a car from 30mph... in 5th.

SoRRoW

Ok I should at lease tell you guys my plans...

600 Holley DP/mechanical secondaries
RB intake

Rb road race header (Either keep my exhast set up now or re do it)

2.5in pipe to a presilencer,to a free flow muffler..my exhast is non restrictive now,and I dont want to spend the cash unless its needed but I know I need to look towards a 3 in exhast..

runnin FC T coil (Some one show me a draw out on stemtatics to run direct fire)

(I need to weld the dizzy..some one please show me welding points.)

E fan set up

I will be runing the 2 peice apex untill they take a ****..

REVHED

I don't know much about Holley's (**** all actually) but from what I've read a 600 might be a bit big for even a bridgey 12A. Maybe someone else knows.

The exhaust sounds pretty good. A long primary system would be better but the most be important thing on a bridge is to have non-restrictive mufflers. They need next to no backpressure to work properly with the increased overlap.

There's two ways to lock the dizzy. First you need to pull the guts out of it so you can get to the advance weights right at the bottom. This is done by pulling off the chopper gear, removing the vacuum advance pots as well as the bearing plate that holds the magnetic pickups. The next step is to lock it. The easiest way is to simply remove the springs from the advance weights. Removing the springs allows the weights to swing out to full advance as soon as the engine is running. The other way is to tack weld the weights into the fully advanced position. You'll see what I mean once you open it up.

peejay

The answer is, it depends!

If you're using a plenum manifold then the 600 would be too big! A 450 or even maybe a 390 would work better.

If you're using a RB (no plenum) manifold than a 600 would be OK if maybe a little small! But that's not the main problem, the main problem would be that you'd have to extensively modify the carburetor to work on the RB manifold.

Or you could modify the RB manifold to be a plenum manifold... but then the 600 would be big... ! It'd "work" but don't expect the engine to run or respond well at all in the lower rev ranges, because the engine would be still on the idle circuits until maybe 4000-4500rpm.

SoRRoW

You do NOT need to do big modifications t run a Holley on a RB intake thats whats they are made for...

Its a little big for stock ports..BUT I personally think its a little on the msall side for a bridge,My friend ran a 750 on a 12A bridgeport..and the bitch was fast..


With my listed set up right now..I run low 15s on stock ports

I pan to be in the 11s or 12s just with a port.



You will see a spacer Under the carb..its not needed but its just one of my tricks..

yeah it look ugly