tech question: DIY 4age cut n shut inlet manifold?PICS

[Aust162]

Hi everyone, i have a bigport 4age fwd inlet manifold that i have cut each ends off in an attempt to make it work in rwd configuration.

I have read witzl's write up :http://www.toymods.net/forums/showthread.php?t=88

I have gone about it in a slightly different way. I cut the T/B flange off and have cut the opposite end off too. I'm going to try and weld each end on the opposite ends. (refer pic)



My question is: re' the valve cover breather. To avoid pressuring the crankcase, can the oil vapour/air blow directly back into the plenum? Or does air have to go through the specially designed pipe that goes directly through the T/Body, then out into the intake pipe?

Sorry, i cant explain it better, so here a picture.

[Cuzzo]

Are you going to turbo charge this beast or is it going to be NA?.

If turbo charged you will not need to vent the crankcase gases directly into the manifold, instead you will need to vent them on the inlet of the turbo.

If NA someone else may have an idea. But if it enters the inlet pre-throttle body flap, you could plumb it into the inlet pipe.

BTW on my smallport rwd setup i purchased a fwd smallport manifold which was cut and flipped on the runners therefore not having any of these issues.

[Hen]

You can't tap the PCV line directly into the plenum. Otherwise if the manifold is under vacuum it will suck out oily air from your crankcase.

You can just run it to somewhere before the throttle.

Hen

EDIT - Good point from Cuzzo. If FI then tap it in before throttle AND turbo.

[Aust162]

Thanks for that guys. The car is staying N/A.

I would like to get it running as per factory. I'm pretty sure a catch can would solve the problem, but i'd like to be able to run it without one.

[Aust162]

So would it be best to run it like this:


Blue line is the new design. red is the factory setup.

But do i need to block off the hole that goes through T/B?

(I will block off where the Breather hose use to joint to the plenum.)

[LeeRoy]

As mentioned above it will need to be before the throttle body in either scenario but if you turbo it then block it off and put it before the turbo. To do this your probably better off pulling out the fitting from the manifold that the pcv originally joined to and then weld up the hole that is left behind. Alternatively you could weld up the hole in the manifold where it went to the TB or just but a blocked off hose on the fitting. Pulling it out will look better though.

Your best bet is probably to just get an intake pipe made up of alloy and tap the pcv return into that or if turbo do the same but before turbo.

Cutting the runners to flip the manifold - havent heard of that being done before. Seems like a good solution but wouldnt re welding the runners be a bit of work?

- LeeRoy

[TA-022]

If you wanna retain factory runnig etc im thinking tap a hole and thread on the bum piece that is now where the throtle flange used to be and run a hose to the throtle?

[The Real Roadrunner]

make sure to block the hole in the tb and mani as the idle will be around 3000rpm if you dont. been caught out once with that and it shat me
cheers
linden

[Aust162]

Thanks for the replies everyone. I will weld up the hole that goes into the T/B and probably blank off the original PCV inlet just incase.

I have a 3" mild steel intake pipe, so i'll just weld a barb onto that so i can then vent the pcv vapour/air into that.

[briney]

just my 2 cents, this pipe looks suspiciously like the engine breather. i think it would be best for it to go into the intake piping where it will see only atmospheric pressure. that or a catch can. this doesn't look like the pcv pipe to me.

[TA-022]

maybe drill the hole into the new back and pop a bolt in or rubber bung to block it just incase it is needed later?

[takai]

just my 2 cents, this pipe looks suspiciously like the engine breather. i think it would be best for it to go into the intake piping where it will see only atmospheric pressure. that or a catch can. this doesn't look like the pcv pipe to me.

Uh, engine breather is PCV. PCV stands for Positive Crankcase Vent, i.e. the engine breather.

They should see atmospheric/slightly under atmospheric.

[stidnam]

so for a turbo setup why do you have to vent this before the turbo?

[takai]

Because if you vent it post turbo (i.e. in the compressed tract) you are feeding Xpsi into your crank case when you get on boost. Where X is normally a high number like 15psi and you blow out your seals.

[YLD-16L]

so for a turbo setup why do you have to vent this before the turbo?

If you plumb in the crank case ventilation post turbo then you will pressurise your crank case when the car is on boost, the results of which would not be good for your seals etc. You can't just use a one way valve either as the crank case can't vent whilst on boost which is when they tend to breath the heaviest.

Dang Chris beat me to it