Enlarged Plenum Issue

[Belle427]

I had my plenum enlarged and without wishing to name names at the moment I'm a bit concerned on the quality of the work.
Could anyone advise if they think this is the norm when the bottom breaks through, the black substance is some sort of epoxy or similar, which the throttle is binding on slightly.
I would have thought this should have been filled with weld and then machined?
Any advice is much appreciated.

[blitzracing]

If the epoxy is something like JB weld it will be up to the job as the plenum does not get that hot. I've used the stuff to hold a home made aluminium inlet manifold on an air cooled and it was fine at well over 100'c.

[Dungman]

I was similarly concerned when I found the same on my old 4.6. I posted about it as well and was reassured that it is quite common apparently

[Penelope Stopit]

As you have commented, the plenum should have been welded and then re-machined

[Sardonicus]

I had mine welded up underneath in the pre-heater area to avoid this in fact the guy that done mine insisted on it before sending it to him for the enlarging treatment

[Boosted LS1]

Is there really an issue? If so, is it something that can be fettled with a bit of wet and dry? It's not pretty but would seem to work. I wouldn't want somebody welding inside a TB in case of distortion.

[Sardonicus]

Boosted LS1 said:

Is there really an issue? If so, is it something that can be fettled with a bit of wet and dry? It's not pretty but would seem to work. I wouldn't want somebody welding inside a TB in case of distortion.

You dont weld inside you weld the lower outer void underneath to stop breakthrough ... I wizzed over grained area with a burr and my local engineers filled flush for £20 no brainer IMO looked like the 2nd pic after


.....

Edited by Sardonicus on Sunday 8th April 22:01

[Boosted LS1]

^ Ok thanks but I see nothing wrong with using resin instead of weld/heat. We used to use resin inside out 2 stroke engines and it was very up to the job.

All the OP needs to do is rub it down with some wet and dry where there's some stiction and all should be fine.

[anonymous-user]

Resin is fine, we used to stuff crankcases all the time, well up to the job.

[Belle427]

Sardonicus said:

You dont weld inside you weld the lower outer void underneath to stop breakthrough ... I wizzed over grained area with a burr and my local engineers filled flush for £20 no brainer IMO looked like the 2nd pic after


.....

Edited by Sardonicus on Sunday 8th April 22:01

Nice work. I was just curious to see what is done when it breaks through.
Im a bit pissed off that i should have to start messing around with wet and dry, i would have expected better.

[anonymous-user]

Resin is fine, we used to stuff crankcases all the time, well up to the job.

[Classic Chim]

There’d be a lot more scrap parts about if JBWeld and similar didn’t exist.
I don’t see any problem with the stuff personally either.

[blitzracing]

I think a bit of careful work tapering the step where the plenum meets the inlet pipe should produce some gains if it reduces turbulence.

[Belle427]

Is there a specific adjustment procedure for setting up a small amount of clearance on the throttle disc to body?

[Boosted LS1]

Iirc there's a little tiny screw which will open the throttle butterfly slightly. Your revs will increase so obviously you want to adjust it to the point where you get a nice stable idle but not 4000 rpm's :-)

[Sardonicus]

You want just enough air gap so the butterfly dont snag/jam/bind in its bore the base idle you can set with the air base idle screw the stepper motor takes care of the rest

[Boosted LS1]

^ Is the screw sometimes hidden under a blanking plug? It's been a very long time since I looked.

[Sardonicus]

Boosted LS1 said:

^ Is the screw sometimes hidden under a blanking plug? It's been a very long time since I looked.

Boosted Its in a formed tube/recess and a long T10 torx fitted like a glove, although it maybe some old imperial hex/Allen head and originally possibly had a tamper proof bung like you say

[Hedgehopper]

[Sardonicus]

Not that one thats an air bleed bypass screw the one that does the butterfly is a sort of adjust and forget affair in fact in normal usage should never need attention, the one thats upside down under this throttle stop

Edited by Sardonicus on Tuesday 10th April 10:53