Inlet manifold+Cylinder head rattle noise

[dom14]

Hi guys,
I've been noticing a rattling noise from the carby, inlet manifold and that area of the cylinder head for few days now.
It's an RB30 Patrol.

I used a "screwdriver stethoscope" to localize the noise and then decided to pull the carby out and have a look.

What I found has shocked me(pictures).

How could this happen? As you can see in the previous pictures it was in very good condition with no cracks, etc.
You can't install that cup thing the wrong way on that carby base heater plate. It's keyed.

Any ideas how could this happen?
Is this cup thing is critical for the performance?!

I tried vacuum cleaner with the hope of getting the piece out.
It wont 'budge.
Apparently it's stuck inside the manifold passages or inside the cylinder head inlet ports.

I'm thinking on pulling the manifold out tomorrow and have a look inside it as well as cylinder head inlet ports.

Any chance of getting it out without having to pull the inlet manifold out?!

It may be in pieces, I have no clue.
It's aluminium or something, so magnet won't work.

[Patrol'n]

Have you thought of using one of those flexible retractable claw tools to try and grab the bit that snapped off? Not sure if it would have enough bite on the metal of the broken piece, but perhaps worth a try. Having said that, I think I'd want to pull the inlet manifold off to check for any bits stuck in the manifold, and check the inlet ports too. If it failed like that, no guarantee it stayed in one piece.

I wouldn't want bits of broken metal getting into the cylinders....

I'm not an expert so only IMO, but when I recently spoke to a Carbie bloke about rebuilding my carb, I told him about removing the heater element and said I left that cup bit in, and he said it wouldn't have mattered if I had removed it. Having said that, I imagine the factory put it there for a reason, I just don't know what it was although I think I remember reading it is for improving the fuel distribution to some cylinders, so perhaps without it some cylinders run leaner / richer than others? If that is the case, then it might affect tuning, power or longevity of the engine but I am guessing at that, so again just my opinion, I haven't personally driven one without that cup piece so can't offer any info on that sorry mate.

[dom14]

I wouldn't want bits of broken metal getting into the cylinders....

That's my fear too. The problem is that the noise has been there for quite a few days, or could've been lot longer than that.


I'm not an expert so only IMO, but when I recently spoke to a Carbie bloke about rebuilding my carb, I told him about removing the heater element and said I left that cup bit in, and he said it wouldn't have mattered if I had removed it. Having said that, I imagine the factory put it there for a reason, I just don't know what it was although I think I remember reading it is for improving the fuel distribution to some cylinders, so perhaps without it some cylinders run leaner / richer than others? If that is the case, then it might affect tuning, power or longevity of the engine but I am guessing at that, so again just my opinion, I haven't personally driven one without that cup piece so can't offer any info on that sorry mate.

I prefer to have it there the way it was intended. And I don't think it's there for any emission related reasons(like egr, pcv systems). I think it is as what you described above.
So, I prefer to have it there. But, breaking like that and getting sucked into inlet is bad news.
I need to investigate how something so tough can break like that. I reckon it's bad news, even though it's intended to make the engine run better. It's not even typical aluminium either.
Not easy to bend. Backfires couldn't have done that(Or can they?!). Sudden heat and cold cycles can weaken metal, but all the other metal parts have been coping pretty well, so why not this little piece? closely examining the pieces, it has some scoring on the edges, which looks like from friction scores from moving and rubbing. That could've happened after the protruding part has broken off. So, it's a big mystery atm.
I have a theory why it's there though. I think the heater grill bit is inhibiting the air fuel mixture equally getting into each one of the directions of the inlet manifold. The directional cup is probably there in the other side to compensate for that. If that theory is correct, then all I have to do is to remove the grill bit in the smaller hole. I've been advised to do that long time ago, while at the same time advised not to do it as well. So, I left it alone, and decided to make a base plate of aluminium of the same dimensions. I still haven't got around to do that.

One thing is clear though. For that piece being able break off like that is bad news, regardless of it's good engine design intentions.
So, after all, I think the general idea of removing it(as well as the grill bit) is probably better for the engine.
Now I have a mess to clean up and I hope it hasn't gotten that far enough for me to have to pull the cylinder head out as well.

Thanx mate.

[threedogs]

Ive had venturi's melt off a 4 barrel and make a racket but eventually they passed through the system

[garett]

metal fatigue ?

[Patrol'n]

I would definitely remove the heater grid if it was me, (unless perhaps you live somewhere where it is super cold regularly), I did mine a while back and the difference was huge, plus when I examined it closely bits had already begun to break off... so I'd suggest having a close look at it.

I found the driveability improved noticeably and my fuel consumption improved heaps too, (as long as I didn't use my new found power all the time). The biggest thing I felt while driving is it didn't feel laboured keeping up in traffic, whereas it did beforehand. I have read somewhere that the heater grid is for super cold temps, which we don't get here in WA, so I am super happy with it out.

I still have the cup piece, but after your experience, I may have to consider ripping it out.

You mentioned about backfires, I suppose combined with metal fatigue over 20 odd years of operation that is a reasonable possibility, years ago I saw a couple of cars blow inlet tracts apart from backfires, so there's a bit of pressure there I reckon, plus once when trying to tune a custom Webber installation up with the air cleaner off I made the mistake of looking down the throat of the carb to check fuel delivery (young and inexperienced... I won't do that again!!!), the backfire almost singed my eyebrows and face, flame actually shot back out the carb, scared the s*#t out of me!

If you do remove the cup piece, and it improves performance then I'd love to know about it, I'd definitely do that mod then too. Good luck with the the repairs, hopefully it's just one piece in the inlet and it comes out easily😀

[dom14]

metal fatigue ?

Yeah, I guess so, combined with the violent back fires, may be? Metal fatigue fractures are apparently not too uncommon with aeroplane fuselages.
Apparently one of the reason they get decommissioned while still running good. I'm not ready to decommission my Patrol, not yet. :D

[dom14]

Ive had venturi's melt off a 4 barrel and make a racket but eventually they passed through the system

I found a 5mm x 5mm metal(aluminium) round piece inside carby float bowl when I was first time rebuilding it couple of years ago.
I never could explain that.

[dom14]

I would definitely remove the heater grid if it was me, (unless perhaps you live somewhere where it is super cold regularly), I did mine a while back and the difference was huge, plus when I examined it closely bits had already begun to break off... so I'd suggest having a close look at it.

The grill bit is still in good condition in mine. But, I remember you posted your experience of removing the grill bit while ago. Even if I did remove the grill bit back then, I would've still left the cup bit as it is. So, I'm beginning to believe now, whatever the reason this grill bit and the cup thing was designed and put there, it's not a great design and obviously born with only little bit of hang time. So, it's better out than left as it is.


I found the driveability improved noticeably and my fuel consumption improved heaps too, (as long as I didn't use my new found power all the time). The biggest thing I felt while driving is it didn't feel laboured keeping up in traffic, whereas it did beforehand. I have read somewhere that the heater grid is for super cold temps, which we don't get here in WA, so I am super happy with it out.

Yes, the heater grid was put there preheat the combustion fuel, air mixture to improve the cold engine performance in very cold weather. It's a good thing in theory, but bad if the related directional cup & the grid deteriorates over time and get sucked into the inlet. So, it's better to have a separate aluminium or copper plate put in there with no heater grid or directional cups. I'm putting that project on steroids right now. I already have the plate, just couldn't have bothered to get it done before, now I am.


I still have the cup piece, but after your experience, I may have to consider ripping it out.

Rip it out asap. Mine is a 25 year old vehicle. Your can't be heaps younger than mine. Or get the base heater place out and have another plate fabricated, which what I'm about to do.


You mentioned about backfires, I suppose combined with metal fatigue over 20 odd years of operation that is a reasonable possibility, years ago I saw a couple of cars blow inlet tracts apart from backfires,

Yeah but if it breaks like that, fatigue or not, it's better out than in. Such breakages can ruin the hole engine if it get sucked into the cylinder bore and score the walls and damage the pistons as well. That might be the case in mine, I'm yet to find out. I may pull the head out and do the head gasket as well. I was going to do that while ago, just to be safe with longer trips.



so there's a bit of pressure there I reckon, plus once when trying to tune a custom Webber installation up with the air cleaner off I made the mistake of looking down the throat of the carb to check fuel delivery (young and inexperienced... I won't do that again!!!), the backfire almost singed my eyebrows and face, flame actually shot back out the carb, scared the s*#t out of me!

I always avoided that, 'cos I had a late start with backyard car work, so read enough to see and hear the horrible accidents caused by backfires in that way, including blindness & disfigurement. I still do carby work in that way, but always wear a full face cover when I do that. Consider yourself lucky, 'cos some fellas haven't been. I've seen half blind, half fingered mechanics from work place and backyard accidents.


If you do remove the cup piece, and it improves performance then I'd love to know about it, I'd definitely do that mod then too. Good luck with the the repairs, hopefully it's just one piece in the inlet and it comes out easily��

Thanx mate. Yeah, and have the directional cup piece removed in yours asap. It's nothing but trouble to have it there.

Don't forget to pray(prey?!!) for me, asking not to have any pieces sucked into the cylinder bore and stuffed up the engine for good. :D

Cheers
Dom

P.S. Pls let me know your experience after removing the cup thingy.