simpson36

I did a search to find Lionsden's new lids @ $150 (in year 2003) to mount Crossfire TBIs on aftermarket crossram type manifold.


I am just wondering if there is any interest in a new lid to mount a 454 (7.4L) or bored 350 (5.7) 2 bbl TBI on the stock CrossFIRE manifold.

It is very doable, but if there is no interest, it makes no sense to do.

The 2bbl TBI would be mounted at an skewed angle in the center of a new plate . . . I haven't worked it out, but in the 30 degree neigborhood perhaps.
Stock throttle/cruise/trans (with new brackets) and wire harness would hook up.

coolram62

iTrader: (2)

It's an interesting idea and it has been done(also I've seen a plate to mount a 4 bbl carb).I'm sorry but I don'r remember an exact link for them.There have been a couple people on the Crossfire Forum that have converted and there's also the X-ram manifold.
But the 400 series single TBIs can be bored to 2" each that will outflow the 2bbl TBIs.And as you probably know it's usless unless you port match the CFI base and modify the runners.

Ronny

iTrader: (1)

The 7.4L TBI unit will outflow the CF manifold by 20-25%. Would make more sense to use a traditional manifold of choice unless you chose to use the smaller 350 TBI unit then they should be comperable in flow #s.

simpson36

Thanks for the comments.

Actually I was thinking more along the lines of helping out the people who give up on Crossfire and go to a carb.

A better alternative I think would be to keep the crossfire, but go to something less cantankerous like the 2bbl TBI while keeping the computer . . . especially important for the '84 Vette guys who have a computer controlled dash. Then if they wanted to do some performance mods, they can easily go with a bigger (bored or 454) TB and port the CF manifold (I am doing a CF port on a milling machine).

I have also modified a stock Truck/Camero 87-94 TBI dual plane manifold to go on pre '87 engines and I will be making an adapter plate to rotate the 2bbl TBI 180 degrees to line up with the CrossFire linkage and wiring harness. I will be making brackets for the throttle/cruise/trans also. So that will be a plug and play Crossfire to 2bbl TBI swap . . hopefully.

Again, the performance mods can follow . . . and aftermarket TBI dual planes are available for 5500 RPM, so that should satisfy most street needs.

coolram62

iTrader: (2)

I'm one of the ones that decided to stay with CFI and I've port matched(head)and opened the runners but I've kept the EGR tunnel.The CFI top plate ports are already 2" for the TBIs even the the units themselves are 1.480"(I think that's correct).The TBIs can be opened to 2" and the only hard part is having the units in synch(using a manometer).And a big thing is having the TBI's throttle shafts rebushed.Removing the noise restrictors on the lower air cleaner lid helps air flow a bit also.And remember CFI motors hate ANY vacuum leaks.

The other big problem with the LU5 is the exhaust.It shared everything with the LG4.Just switching to a L69/TPI manifolds/y-pipe/catback will give you 15-30hp.And even more can be gained with a good set of headers.

simpson36

This is what how a 2bbl would fit on a crossfire manifold:
Below that is the profile to port the Crossfire. Stock dual plane TBI for comparison:

This is the first pics I've posted. Can't seem to type in between the pics??

simpson36

Sorry, I can't quite figure out the pictures.

I'm very aware of the shaft issue. A problem with bushing a Crossfire TB is that GM took the clearance out of the shaft (.371" unworn,.370"-.369" worn) and available bushings (at least to my knowledge) assume a full 3/8" (.375") carb shaft and allows for the clearance in the bushing (.378") so there ends up being too much slop in a Crossfire TB using standard carb bushings.