Baibro,
sorry late reply as I haven't been on this forum in six years.
I have my reasons.
On your intake to trumpet base I found out there is no gasket.
Been told by Rover mechanics, later also personal friends they applied a light coating of "High Tack" to both parts before assembly.
Later years back inside I machined out a 1 1/2" thick aluminum intake extension but went with "The Right Stuff" in a can like cheese wiz. Applied lightly then smoothed out a lightly buttered coating now dealing with three mating surfaces vs stock two surfaces.
Wipe off exterior excess with rag soaked with lacquer thinner.
Balled up cloth material on a dropped parts grabber lightly soaked with lacquer swabbing out the internal trumpets across both mating joints removing any Right Stuff that may have squished out.
Same with the plenum cover to trumpet base mating surfaces.
No vacuum leaks good to go.
BTW, purchased 1 1/2" longer allen bolts allowing for the intake extension length plus milled the plenum top allen bolt pockets 1/4" deeper compensating for the plenum spacer looking factory stock for Kalifornia smog tests.
Added 1/4" spacer between trumpet base and plenum cover for better and smoother airflow for the end trumpet bells under the sloping plenum cover.
I recall 96's still had trumpets vs the longer cast aluminum intake runners on later 4.0 engines.
My design lowered max torque to 2,715 rpm's vs 3,100 stock on a 4.6 litre engine transplant. NASCAR engine friend ran on their engine computer program entering all my intake runner lengths. All different BTW.
Pulls like a mule considering how tall the D1 is geared with 5 speed without hurting top end still pulling hard to 5,900 with RPI Tornado chip.
Your up north 93 miles from me, i'm in the S.F. bay area.
Prost, Carl
