99VetteFRC

I am wanting to put a Holley Hi Ram on my Chevelle, which is essentially a 2003 Silverado with DBW. The intake only comes in four bolt TB flange only. I was looking for adapter plates but they are all for LS1 style TB and the truck TB is different and will have a vacuum leak even though it will bolt up.

Is there any jumper harnesses or any DBW 4 bolt TB that I can make work while still using the 2003 truck setup? Any help would be greatly appreciated.

garys 68

iTrader: (1)

Just curious, why will there be a vacuum leak with truck TB?

Broon72

Yeah I went with Holley high ram and my dbw set up was for the 3 bolt throttle body. I'm going to use 4 bolt ls2 throttle body and torquerush.com X link plug in adapter harness to run it.

oldecmech

Easy solution, CBM has the adapter plate that will let you bolt your 3 bolt TB to the 4 bolt manifold. I'm using it. Good fit and finish.

99VetteFRC

The gasket on the truck DBW TB is almost backward from the LS1 throttle body. The cavities on the TB do not line up. The adapter could be worked around if it had the stock style gasket, but since it is missing the extra part, I can't use it. I put the truck TB on the LS1 intake because the stock gasket has the correct perimeter size, I filled the breather hole in the TB with silicone. It kept vacuum/boost leaks at bay. With incomplete adapter gasket, it will have a spot for air to leak past.

garys 68

iTrader: (1)

Ah, I get it now!
The adapter is to put a 4 bolt TB on a 3 bolt intake, not the reverse.

99VetteFRC

No sir. I need to put a 3 bolt 2003 5.3L DBW TB on an intake with a 4 bolt flange. the truck TB has a different gasket and passage on the back than the LS1. I can't use the standard adapter. I can't find any that support the truck TB.

oldecmech

I am using a 2005 5.3 DBW TB (3 bolt) on a LS2 (4 bolt) manifold with CBM 10708 adapter plate. Fit and function is correct. No vac leaks, PCV system works properly, drives and runs great. Check out specs on CBM web site.
MikeH

CBM Motorsports

iTrader: (2)

oldecmech is correct. If you are using the same throttle body that is pictured below, our adapter will work fine. The provisions in the back of the throttle body don't go to anything and technically do not need to be sealed. Worst case, there is one 1/4" hole that will need to be drilled in the adapter for the air bypass hole (and a little silicone around the hole). CBM-10708 is the correct adapter for your needs.

99VetteFRC

So I bought a sheet metal intake with 102mm inlet. I also bought an x-link module. I now have to figure out what throttle body to use.