puff of blue smoke at higher rpm decel

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Belgian1979
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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Sun Jan 28, 2018 5:25 pm

Newold1 wrote:
Sun Jan 28, 2018 4:34 pm
Absolutely!
A manifold vacuum even in your vacuum chamber under the manifold if it is leaking under vacuum will pull oil up from the lifter valley area and send it through those individual ports into the ITB inlet runners and burn it. When you are decelerating you will have maximum vacuum and thats when it would happen the strongest.

Is there a way to plug temporarily 7 of the 8 holes and then put some slight air pressure into that chamber with a hose and just pressure when you blow on it to see if it holds any pressure. If it has a leak into the valley it should bleed of and you might even hear the leak if its quiet enough.
Hi Newold, thanks for replying.

That is rather difficult as the hole is some distance down the intake tract and hard to reach. On top of that i need something that would stay in place against any air pressure.

As far as what has happened I'm still speculating. but the intake flange where it bolts to the heads and in the front and rear has a machined ridge where the plate is bolted on. It's not a thick plate, maybe 1-1.5mm thick. Thinking out loud here, but under vacuum the plate might try to bend inward (towards the runners, which would then stress the silicone seal and break it. This means it is probably leaking all around the edges.

It will have to come apart to fix. Not sure what I'm going to do against this bending. Maybe weld on some angular pieces or so.

On the other hand it might be better to completely delete the chamber and make a vacuum can of sorts with take off fittings in each runner.

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Re: puff of blue smoke at higher rpm decel

Post by Newold1 » Mon Jan 29, 2018 7:38 am

Understand the design precludes testing for a leak.

It's going to have to come apart. Is it possible to fabricate that chamber cover plate out of aluminum and weld it to seal it all around the bottom of the manifold and eliminate any chance for a leak? Welding a new cover would also eliminate the need to have it extend over the china rails on each end of the block.

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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Mon Jan 29, 2018 2:29 pm

I'm a bit worried that welding it would make the weld crack under the flexing of the plate.

I took out the cam sensor unit and one of the barb fittings for the chamber at the rear of the engine. I stuck a camera in the hole for the distributor and into the vacuum chamber. It's difficult to see certainly from the valley side. Bolts on the bottom seem ok. I did see some oil shining along the silicone bead.
Had the impression it was sweating some at the rear china wall as well. The block was a little wet on the pad below.

For informational purposes some pictures so you know what I mean :

Image
Image

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Re: puff of blue smoke at higher rpm decel

Post by Newold1 » Mon Jan 29, 2018 2:47 pm

Yep, I see the manifold you are working with and I understand your concern, but if a decent thickness plate of 6061 aluminum is properly welded to the bottom by someone good with a TIG welder, with an extremely well cleaned surfaces, correct rod and preheating the manifold casting to about 250 degrees there should be no problem making a correctly sealed chamber. I also don't like using blue silicone sealer around oil and using Permatex black or GM gray # 88863486 sealant will do a much better job of staying sealed provided the surfaces have been nicely cleaned with alcohol.

This type of manifold component welding is done all the time in fabricated intake manifolds and when done well those welds hold and don't leak. JMO

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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Mon Jan 29, 2018 3:43 pm

Yes, someone else also suggested to install some ribbing.
I'm also a bit afraid to warp the manifold when welding things in it.

I'm still a bit baffled that it would be able to draw that much oil through there.

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Re: puff of blue smoke at higher rpm decel

Post by Newold1 » Mon Jan 29, 2018 6:20 pm

It does not take much oil burning to make smoke out the exhaust of a good clean running engine, especially under high vacuum on decel.

As for warping the manifold, three points. One, a good knowledgeable aluminum TIG welder will not just start laying long continuous welds along open areas but should and will move around to different places on the total weld areas to minimize raising excessive temps in small areas of the manifold and causing warping. Second, he should and will use some gases with the welding and know how to keep his temps and flow even and under control. Third, this manifold because it tends to be a big centrally located hunk of aluminum without thin sections or long separate runners the possible warpage at the head faces or china rails should be nominal and easy to eliminate.

Ribs on the bottom plate would control shape some and also eliminate the plates chance to ring or resonate. Not a bad idea.

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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Tue Jan 30, 2018 11:03 am

hmm, you've got me wondering if it would not be worthwile to just epoxy it in place with some supports. However I'm unsure about the heat in this location as I do know that epoxy doesn't like heat.

I'm also considering making ports with vacuum lines to a seperate vacuum reservoir which might be a better solution. As this is also used to control idle speed. What lines would I want to use per intake channel ? I have had experience with the main IAC line that it doesn't provide enough air if not 1/2'" rubber line. This is however a central line for all 8 cyls.

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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Sat Feb 03, 2018 11:18 am

I took the manifold out. Couple of pictures

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I found the outer bolts of the manifold not really thight. The ones in the center were. Not sure if it's related but it could be.

I forgot but the plate doesn't have bolts along the short sides. I could move it upward with a screwdriver.

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Re: puff of blue smoke at higher rpm decel

Post by mk e » Sun Feb 04, 2018 5:42 am

That is a TERRIBLE design.

Maybe tap the holes and plumb tubing that can't leak? I'd use metal lines. This is probably the easiest fix. Or maybe better yet tap and plug the holes (or weld) and drill new holes on the outside that you can plumb with vacuum line or whatever you thing looks nice and hide a little canister somewhere that is not inside the engine. On mine setup I have a little board with 12 separate MAP sensors that feeds the ECU the signal from the lowest pressure cylinder....I was seeing 35-40kPa at idle which absolutely shocked me as my cams are anything but tame so the setup is working much better than I expected.

The other option is a LOT more screws. I'd be taper to weld on a bunch of bosses but small screws down the flange might work. I like loctite 518 for assembling stuff like that, basically the same stuff as red loctite but thick so it also helps retain the screws pretty well. As someone mentioned it could be fully welded...but that's going to warp the snot out of the manifold I think....I'd just double the number of bosses you have and it will probably be good.
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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Sun Feb 04, 2018 7:11 am

What size tube for each cyl ?

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Re: puff of blue smoke at higher rpm decel

Post by mk e » Sun Feb 04, 2018 7:34 am

Mine are 5/32" but they just go to the individual MAP sensors. That is about the size i've seen on sportbike setups that are Tee'd together and go to a common MAP.

If you are doing IAC thought the lines they will probably need to be much bigger, 1/4" or 5/16" I'd think but I've not personally done a setup like that so I could be wrong....i guess it will largely depend on where the idle is set with the iac plugged, if you need basically no air warm a small hose will probably be fine to get you cold idle speed....some experimentation will be needed unless you can find a similar setup to copy.
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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Sun Feb 04, 2018 9:30 am

What I have here is alu tubing with associated fittings inside diameter .18". This equals .025 sqin X 8 or about 0.2 sqin total. The feed tube of my IAC is 10 mm inside, or .12 sqin. Not sure but looks ok to me.

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Re: puff of blue smoke at higher rpm decel

Post by mk e » Sun Feb 04, 2018 12:36 pm

If its been working then its good...just T the MAP to it and call it done.

Math wise you can't really just add all the tubes up like that because only 2 will be flowing at any 1 time, the other 6 will probably be back flowing. It should held to keep them all similar length so the pressure drops are similar if you haven't already though of that.
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Re: puff of blue smoke at higher rpm decel

Post by Belgian1979 » Sun Feb 04, 2018 12:51 pm

Keeping lengths the same will be very hard to do. Current holes were 6mm diameter (about 1/4)

Air distribution was never good with the air entry in the back as it gave a 12% VE difference front to back.

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Re: puff of blue smoke at higher rpm decel

Post by mk e » Sun Feb 04, 2018 1:03 pm

A 1/4" hole is very different than a 3/16 hose/tube....it will flow a LOT more, but the hose might be fine, not sure. One way to find out :)
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