does anyone know of any upgrades to make the throttles bigger than the aj6 kit?

I thought I remembered.someone using xj40 throttle.discs but I don't really remember

 

Yep.

I used throttle discs from the 3.6 AJ6 engine.

Memory now, is 71mm, or was it 73mm, dunno, but standard AJ6 discs I robbed from a wrecker yard, and about as far as the housings will allow without exposing the mounting bolt holes.

The air cleaner backings required opening up to suit, and the air filter will need "tweaking", or when WOT is asked for, the discs will jam on the filters, and that is not as exciting as it might sound.

 

I was planning on runnng cold air intakes,

would you mind giving me a run down on what exactly you did so I can tell my machinist?

 

Calvin,
Have you considered running standard-sized quad throttle bodies? Here is a great article on how to make them: Quad Throttles
The only real problem I see in what Dick did when he made his, is that he plumbed the cold air through a single 3" opening in each air filter housing. That 3" opening represents only 7.065sq. inches of surface area, which is more than enough to feed either the stock V12 TB, a stock TB from the AJ6 engine, or the enlarged TB offered by AJ6 Engineering. However, I can't see it keeping up with the combined surface area of 9.8125 sq. inches represented by two stock TBs per side. Either a 5" opening would need to be plumbed into the stock air filter housing (I don't see that being even remotely possible), or an entirely new air filter scheme would need to be devised to keep up with the potential airflow demands of those quad TBs (which, in itself, is complete overkill unless you can also enlarge the valves and exhaust system to handle that much flow).

 

I think the Quad TB's are not a good idea, the distribution of air to each runner would be inconsistant with cylinders 2 and 5 possbly running lean as they are opposite the TB opening.

The stock TB with stock butterfly made over 500HP in the Group A XJS. It was profiled on the inlet and outlet but retained the 2.5" butterfly. So opening up the stock TB to 71mm (2.87") per side would flow enough air for over 600HP.

Cal if I were you I would port the stock TB profiling the inlet and adding a velocity stack to protrude into the airbox and sit about 1/2" off the wall of the airbox. This will increase both the volume and velocity of the air through the TB. I would also do some work on the inlet manifold, making sure the flow between each runner is the same (say within 1%) I think this will provide more power benefit than just increasing the TB opening.

 

calvin,

basically i got 2 discs and shafts from the 3.6 engines. Plenty here in the wreckers at the time, bit skinny now however.

Dismantled the throttle bodies.

Got it all clean, and the 3.6 shafts fit just fine.

CAREFULLY machined the housings in a lathe, and I mean CAREFULLY, as there is no going back if you enlarge that opening too much. It is machined until the new disc closes the opening just as the old discs did. If you go too far the disc "rolls over" and the housing is junk.

A lot of trial and fit and try again.

The discs are "angle cut" on the closing face, so watch that for fitment and testing.

I then set them at 0.002" and did further idle adjustments once fitted, as I dont run an AAV or a balance pipe, so very different to the "standard" engine.

 

thanks Greg, that's what I was wondering,

and how exactly did you mount them in the lathe? from the inside or the outside?

 

that's gonna be pretty hard to adjust thoes runners, because I have to.have the side cut off and welded back on. if I just welded it myself with the mig it'll look like a toddler welded it.

 

My very clever, now departed, man used his 4 jaw lathe, and gripped from the outside. Took some time to set them up, but it was a passion of his.

Others here have done it with a 3 jaw and gripped on the inside.

One guy with waaaaaay too much time on his hands, made a support dummy for the lathe head and drilled and tapped it so the throttle body could be bolted up to its face, and machined away.

 

Use a 4 jaw chuck on the outside and a dial indicator in the inside to center the TB in the lathe. Problem with the 3 jaw on the inside is you can not bore the TB in 1 go it needs to be turned around and I know my lathe is about 1/2 thou out so I would have very small step.

 

i did mine like warron,
Darn, i miss my lathe, when you have one,you just do things without any concern of not having a lathe, many,, many parts can be made, for almost nothing!

old machinist saying,( give me a lathe and a mill machine and i will build you the world)!

 

im still waiting for the funds to get a lathe myself. thank god for a good machinist

 

Great little toy, mine is a 9" Sheraton (Aussie made South Bend) only cost $500, has paid for itself over and over. Ron is right I just make parts as I need them. Like my front hub spacers to go between the inner and outer bearing to set hub end float. You can also do light milling with a mill attachment to turn the lathe into an end mill.