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Bakerlite/phenolic Manifold Spacers Rb26


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This is still in the thought process. The only thing set in stone is the material used.

The main reasons im doing this is to reduce some of the heat soak from the engine and to make a slight alteration to the intake runner length.

Looking for better low to Mid range without effecting top end

Here are the links to wiki



The RB26 and its ITB's make it a little different from most cars where they run a plenum- runner- throttle- runner again

and most cars run a throttle- plenum- runners so adding spacers between the head and intake manifold also effect

runner length and crosses over to plenum volume slightly.

So we know a few things.

Longer Runner length can aid in low/mid power but this isnt necessarily at partial throttle since that is more effected by velocity at low flow

Increasing plenum volume can give more mid to top end power

Actual heat reduction of the intake manifold etc will only help when in heavy traffic in low flow situations. I.e under 2k rpm. There are guys

who have had heat soak issues on the dyno and once an ice bag was left on it for a while power returned.

Pic's borrowed from google

Stock intake set up fitted to an engine


Plenum and throttle bodies. Increasing the plenum and the first part of the runner volume will need to be between the plenum and throttle bodies

however this will require adjustment of the linkages and throttle cable. TPS voltage would need to be checked and could even be used to adjust throttle position

back to whereI had it before. Initially I was thinking of a 6mm spacer here, but I think 3mm will work out better. More later


This is the manifold showing where the ITB's bolt to. It has the radiator neck incorperated into it so I will want to run a 3mm spacer here. Looks like

the studs will be just long enough. Was going to just run 6mm spacer here and forget the 3mm spacer above. I have a feeling that 3mm spacers

on either side will work better then just a 6mm spacer after the ITB's for partial throttle responce. (unsure as I have a cold and head hurts)


I'm not sure if I will bother running a spacer here. It looks like a pain to cut and is heated by coolant anyways. The only reason why I can think of running one is

for additional runner length. Running a 3mm spacer here as well will give a total of 9mm which might put the intake pipe out of alignment


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i had a customer come in and this was all he had done to his motor (holden v6) and he said he had made gains on the dyno.

i would just do the 3mm either side of the ITBs and leave it at that

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i believe gizmo make these already well sort of they are manly to reduce heat soak and only a few mm thick

one other problem you will have is the brake booster ther is almost no clearnce as it is

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  • 2 weeks later...

gizzmo do make these already - I have one on my RB26 and have found it has reduced intake temps when heat soak was an issue (when it was driven on the road). As far as making more hp, it can only help, I do not have back to back figures but the intake temps are down by around 5 degrees over what they used to be.

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