Rb30 carbie question

[Patrol'n]

Hi all, having come back from a country drive with hills today with my rb30, I find myself (sure I'm not the first), wanting more power... As in I was unable to get past about 80-90 ks per hour up some hills with no trailer.... Soooo slowwww

I bought the car with extractors already, it runs really well, so although the beast has a few k's on her, (320,000 or so), I don't think it's too far down through age, given no oil leaks, no smoke whatsoever, no oil in the air cleaner or any of the usual signs of a tired engine.

I plan to go through the usual things, plugs, points, fuel filter, maybe a carb clean etc to try and make sure it has the best chance at power it can, but I have read a few times about the plate that can restrict air flow through the carb, my car has what appears to be a black spacer between the manifold and carb, can anyone tell me if this is the plate I've read about, and does pulling it out cause any problems with stud / bolt length etc when I try and bolt the carb back on the manifold?

While I'm at it, are there any known issues with the rb30 setup that might have made it feel slower than it used to?

Thanks as always.

[mudnut]

G'day, Patrol'n. Have a look at this thread:

http://www.nissanpatrol.com.au/forums/showthread.php?28517-RB30-Facts-Figures-and-Helpful-Hints

There is a bit about not achieving revs. Some forum members cut the heating grid out at the bottom of the carby, to make it breath better.

[dom14]

G'day, Patrol'n. Have a look at this thread:

http://www.nissanpatrol.com.au/forums/showthread.php?28517-RB30-Facts-Figures-and-Helpful-Hints

There is a bit about not achieving revs. Some forum members cut the heating grid out at the bottom of the carby, to make it breath better.

Altis007(George) advised me last year that may be not a good thing to do.
I'm planning to leave the original sandwich heating plate between the carby and manifold and make my own. It's exactly 1cm thick.
Only hard part of it is to cut the two large holes in the middle. But, that's achievable with some grinding bits attached to an electric drill.
If I can find a hard plastic piece like the original one or a aluminium, copper or steel piece, I can cut a and drill that plate.

Original one has a heater attached to it, which apparently preheats the intake gas mixture before it enters the manifold to aid the combustion.
I"m not too sure that's necessary on warm weather season. However, I'm reluctant to modify the original as some members suggested. That because there's no going back.
It's better to make another one, i reckon.
I'm onto it.

[dom14]

Hi all, having come back from a country drive with hills today with my rb30, I find myself (sure I'm not the first), wanting more power... As in I was unable to get past about 80-90 ks per hour up some hills with no trailer.... Soooo slowwww

I bought the car with extractors already, it runs really well, so although the beast has a few k's on her, (320,000 or so), I don't think it's too far down through age, given no oil leaks, no smoke whatsoever, no oil in the air cleaner or any of the usual signs of a tired engine.

I plan to go through the usual things, plugs, points, fuel filter, maybe a carb clean etc to try and make sure it has the best chance at power it can, but I have read a few times about the plate that can restrict air flow through the carb, my car has what appears to be a black spacer between the manifold and carb, can anyone tell me if this is the plate I've read about, and does pulling it out cause any problems with stud / bolt length etc when I try and bolt the carb back on the manifold?

While I'm at it, are there any known issues with the rb30 setup that might have made it feel slower than it used to?

Thanks as always.

Are you saying you can't rev the motor above 3000rpm or so?
Can you try on lower gears and rev it bit higher(It's been said that the RB30 can be safely revved higher than average 3 litre 6 cylinder inline engine)
Or are you saying there's no power at all even if you rev higher?

RB30 is no power horse, especially on LPG. I've just learnt to live with it, until I go for a turbo conversion or so.

I'm not sure how high the hill that you were doing. For an average up hill driving, 80-90km/h isn't that bad from the experience with my RB30 Patrol.

The "black spacer" is a heater core(and perhaps a mixture flow controller/dispersing mechanism). If you break the heating grid bit of it, there's no going back, if that doesn't work.

I decided to make my own black spacer with a compatible material and see whether it improves the performance and smooth running of the engine.

[dom14]

I suggest you tune the carby or even rebuild it with a kit and then tune it. I had significant power improvement last year(on petrol) after I put the rebuild kti through it and tuned it.

[mudnut]

I had to get rid of the grid, any way as about a quarter of it has crumbled and dropped into the engine .

[dom14]

I had to get rid of the grid, any way as about a quarter of it has crumbled and dropped into the engine .

How did that happen??!!

The grid is metal in mine(either aluminium or steel). It's metal ring grid kinda thing in my carby.
It's fixed into the hole. Not something I can take off and put back in, so I decided to make my own plate to experiment.

What material was it in yours?

[Irish]

You could always p**s the carbie off and go efi from an R31 skyline...... then add the turbo and manifold from a VL. There's more power right there.

[mudnut]

Same, but it looked as if it was somehow burnt. I should have got a photo before I binned it.

[dom14]

Pardon me, I don't mean to hijack the thread.

Another thing I wonder is that whether the 1cm thick gap created by the "black spacer" is necessary.

Can the carby be bolted onto the manifold without the "black spacer" for the sake of an experiment and see whether any performance improvement?

[mudnut]

You will find that the studs will be too long. As it is now, I have to lift the carby up a little bit to get the nuts closest to the engine on.

[dom14]

You could always p**s the carbie off and go efi from an R31 skyline...... then add the turbo and manifold from a VL. There's more power right there.

Yep, totally agree. I got two carbies now to p**s away.
I'm onto it. First I need to source a R31 with a good motor.
I read somewhere if I'm to go for turbo, then I need the EFI computer, manifold, etc from a VL, not from R31( from a Altis007 thread I think)
If that's right, I may choose VL over R31, just to save time and work.
If the Wikipedia is correct, will I get a lot of performance enhancement from 250Nm to 296Nm by going turbo?
I'm not too sure.

[dom14]

Same, but it looked as if it was somehow burnt. I should have got a photo before I binned it.

In mine, it's pretty tough grid ring built into the "black spacer".
In your one, probably, it was a left over from a previous attempt to break it, perhaps by the owner before you.

[mudnut]

If you want to get rid of two carbies, sling 'em to me and I'll jet them down and set up a triple carb manifold, like the old Hemi used to have. LOL.

[dom14]

You will find that the studs will be too long. As it is now, I have to lift the carby up a little bit to get the nuts closest to the engine on.

In mine, it's true with front nut near the engine side. Others go in fine without having to lift or fiddle.

I can remedy the stud too long issue by taking them out and putting in shorter studs
I reckon that exercise is easier than having to build a new "black spacer"!

I reckon it's an experiment worth trying.
Only thing I'm concerned about that the carby being too close to the manifold, it may get hotter than without the "black spacer"?!!

You just gave me an idea. Man you're a genius.:animierte-smilies-t

[dom14]

If you want to get rid of two carbies, sling 'em to me and I'll jet them down and set up a triple carb manifold, like the old Hemi used to have. LOL.

You may find it's a pain in the ass to balance them. LOL.

[mudnut]

I would think that having a slightly longer inlet would be benificial as the air/fuel mixture will get swirled around that little bit more. The steel ring that holds the grid in mine is till there, at a guess it may create a little bit of turbulence.

[Irish]

^Hence why guys chasing power in old V8's tend to go with higher rise manifolds.

[dom14]

^Hence why guys chasing power in old V8's tend to go with higher rise manifolds.

Ok, cool I get it now.

[dom14]

I would think that having a slightly longer inlet would be benificial as the air/fuel mixture will get swirled around that little bit more. The steel ring that holds the grid in mine is till there, at a guess it may create a little bit of turbulence.

That makes sense. There's also a directional pipe/cup that's attached to the other hole next to the grid(see the picture attached).
This goes into the manifold hole and directs the air flow of one hole more towards one side of the manifold.
I don't completely understand it's purpose, but i'm sure one of your guys know it's purpose there.

I'm guessing it's a performance enhancement. It prevents (the way the cup/pipe is angled) the heated mixture from the grid side getting into the other side of the manifold, or rather limits it and vice versa.

[mudnut]

I asked the bloke who did my carbie kit, if it would be beneficial to drill some holes into that to create more mixing effect. His answer was a definite no as it could create problems. I wonder, if you made your spacer thicker (taking into account the bonnet height) and roughened the walls of the throat whether you would gain a tiny amount of power?

[dom14]

I asked the bloke who did my carbie kit, if it would be beneficial to drill some holes into that to create more mixing effect. His answer was a definite no as it could create problems. I wonder, if you made your spacer thicker (taking into account the bonnet height) and roughened the walls of the throat whether you would gain a tiny amount of power?

Yep, I'm already into the idea of experimenting with different size spacers. I'll keep you guys updated with my experiment in another thread .

I'm uncertain about the difference between having a smooth and rough throat.
I like to think a smoother throat allows a more steady air flow. But, as you suggested it may not help.
To create a useful artificial turbulence, I reckon it's a good idea to cut a spiral inside the throat(like the thread inside a nut). But, that's beyond my abilities at the moment

[Patrol'n]

Are you saying you can't rev the motor above 3000rpm or so?
Can you try on lower gears and rev it bit higher(It's been said that the RB30 can be safely revved higher than average 3 litre 6 cylinder inline engine)
Or are you saying there's no power at all even if you rev higher?

RB30 is no power horse, especially on LPG. I've just learnt to live with it, until I go for a turbo conversion or so.

I'm not sure how high the hill that you were doing. For an average up hill driving, 80-90km/h isn't that bad from the experience with my RB30 Patrol.

The "black spacer" is a heater core(and perhaps a mixture flow controller/dispersing mechanism). If you break the heating grid bit of it, there's no going back, if that doesn't work.

I decided to make my own black spacer with a compatible material and see whether it improves the performance and smooth running of the engine.

Engine will rev past 3000, I've had it up to about 4200, just that the last time i did the same hill, I got up to 110 ok, (the speed limit on that road), albeit it wouldn't have had too much left after that.

Mine doesn't have LPG fitted, so that won't be the issue, but revving harder doesn't seem to translate to more speed, just noise. Dropped to 4th, more revs and yet no more forward speed.

I like the idea of making a new plate, so I don't wreck mine, I might even see if I can find one out of a wrecker and cut that up instead. Tried pulling the carb off this arvo, but the nuts were stuck fast, I'll have to hit them with wd40 next weekend and have a look.

Cheers

[Patrol'n]

I suggest you tune the carby or even rebuild it with a kit and then tune it. I had significant power improvement last year(on petrol) after I put the rebuild kti through it and tuned it.

I just bought a kit, so I'll do this as well :-)

[Patrol'n]

I had to get rid of the grid, any way as about a quarter of it has crumbled and dropped into the engine .

Did you find a noticeable improvement after getting rid of the grid?

[mudnut]

It takes a little longer for the engine to heat up, but I have also disabled the Pre- heat flap for the warmer weather so that must also be taken into account. When warmed up the engine is far and more responsive. Upon putting the boot in it goes harder and I can really feel the second stage open up.

[Patrol'n]

It takes a little longer for the engine to heat up, but I have also disabled the Pre- heat flap for the warmer weather so that must also be taken into account. When warmed up the engine is far and more responsive. Upon putting the boot in it goes harder and I can really feel the second stage open up.

Did you take out the insert on the other side as well or just the grid?

[mudnut]

I left the insert in as the mechanic was adamant it would be there for a reason. have you made sure your second stage butterfly is operating correctly?

[Patrol'n]

I left the insert in as the mechanic was adamant it would be there for a reason. have you made sure your second stage butterfly is operating correctly?

I haven't had a good look yet to see if the carb is operating optimally, although I have to admit, it looks a bit dirty in the primary and clean in the secondary throat, not sure if that's a good thing yet, and whether it's due to less use of the secondary or if it isn't working... I just picked up a carby kit for it, so that's on my jobs list, hopefully this weekend

[mudnut]

As posted in the RB30 facts and figures thread, the second stage had worn a groove in its bore and was sticking shut so the engine couldn't achieve high revs. I had to disassemble the second stage butterfly and use a fine wet'n'dry sand paper to smooth the bore. I also had to smooth the butterfly edge. It took a few goes to reassemble it and adjust it to get it to operate properly and not bind anywhere.

[mudnut]

I have had to re-connect the Pre-heat flap as the carby was taking too long to heat up. The next step is to fit a solenoid valve so I can control the flap so there is no chance of it being open when crossing deep water.

[Patrol'n]

I'll leave my pre heat flap alone then, how are you going to control the solenoid activation, a manual switch?

[mudnut]

I was thinking of using a manual switch in parallel with a relay powered when the 4wd light comes on, so If I forget it will do automatically shut the flap.