Swapping a 3500 Plenum onto a 3400 Engine

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Product Information

The 3500 upper intake is great for the larger plenum volume and stock 65mm TB opening, but presents some issues when used on a 3400 lower intake. This is a work in progress article though anything not pictured and fully explained will at least be mentioned.

Stock fuel pressure regulator and bracket interfere with the fitment of the 3500 upper intake.
Here you can see how far off the manifold is from bolting to the lower.
FPR Bracket ModificationCheck this link for information on making the 3100/3400 fuel pressure regulator work
The 3500 upper intake uses a different MAP sensor setup than the 3400.
The easiest option is to have this tapped and plugged.
Or you can run an adapter pigtail and get the MAP used for a 3500 (and other newer engines)
The 3500 is missing some vacuum ports compared to the 3400. The 3500 CCP (charcoal cannister purge) location is excellent for tapping a new 1/4 vacuum line to be used for the FPR and 3400 CCP setup.


And now for the parts that aren't pictured. The 3400 CCP will no longer have a place to bolt down to, unless you find a mid 90s grand am or equivalent with the 3100 and take the CCP bracket off it. These were mounted onto the same bolts as the ignition coils. It will not hurt anything to let it hang off of the vacuum line however. Also, the 3500 upper changes the ignition coil bracket bolt locations. You can either bolt the bracket to the studs on the rear head, or the manifold itself. The throttle body we use is off the GM LX5 engine, with our throttle body adapter plate. The original 2000+ 3400 EGR needs to be swapped as the 3500 EGR is slightly different on its EGR tube to manifold setup.


Product CodeArticle35Plenum

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