Jump to content
dave88sw

4.6 inlet on a 3.5?

Recommended Posts

Hi,

I'm in the process of converting my dads V8 defender to megasquirt.  The engine was a 3.5 flapper from an early range rover so we sourced another inlet manifold with the later injectors.  The manifold is from a 4.6 gems V8 P38 Range Rover.  I'm at the stage now where the loom is made and i can fit the plenum but I'm not sure about the trumpets.  Is there any reason why I shouldn't use the 4.6 trumpets on a 3.5?  I understand they're different lengths depending on the engine size but what are the upsides/downsides of each?  I still have the 3.5 inlet i can take the trumpets and base plate off if necessary.

Many thanks

Dave

Share this post


Link to post
Share on other sites

I doubt it will make much/any difference, but you can pretty much mix & match it all barring minor details that should be obvious with a bit of squinting at it.

The flapper bottom section will have different drillings/tappings for sensors, the base plate with trumpets will have different ports for the brake servo etc. and the plenum has a different idle valve etc. although the basics are about the same.

Biggest pain really is just making sure you have a one-way valve takeoff screwed into the base-plate for the servo, the flapper will have this, can't remember if the P38 does.

Share this post


Link to post
Share on other sites

I have a 4.6 plenum and manifold on my 3.5 because I like the neater stepper valve arrangement. Pretty sure I kept the flapper ram housing because I was being lazy and didn't want to swap all the threaded connections over for vacuum takeoffs for map sensor, fuel rail, brake servo etc when I performed the swap from full flapper arrangement.


I *think* I read somewhere that the 4.6 trumpets are closer to the top of the plenum to cause faster airflow at lower engine speeds and increase torque, but I could be wrong about that, and have never compared myself to validate this.

Share this post


Link to post
Share on other sites

The bunch-of-bananas manifold fitted to the last of 4.6's adds ~20 torques low down but I've not heard any claims about the Rover-style plenum until this thread.

Share this post


Link to post
Share on other sites
On 3/3/2019 at 10:17 PM, FridgeFreezer said:

Biggest pain really is just making sure you have a one-way valve takeoff screwed into the base-plate for the servo, the flapper will have this, can't remember if the P38 does.

The P38 uses an hydraulic booster instead of a vacuum operated brake servo. So o take-off or one-way valve present in the base plate. But should be easy enough to swap over.

I agree with above it probably wont make a noticeable difference which one you use.

Filip

Share this post


Link to post
Share on other sites

I hadn't considered the servo take off - which is stupid really, as i owned a P38 not long ago...

Thanks for all your replies, i'll mix and match the bits to end up with everything i need, but it sounds like i can't go far wrong with it.

Thanks

Dave

Share this post


Link to post
Share on other sites

Inline non-return valves work just fine for a servo.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy