Blow Through Carbs Holley vs Edelbrock

[SPARKY]

The fuel pressure regular must be boost referenced.

[Dynoroom]

The fuel pressure regular must be boost referenced.

Some carbs need the power enrichment port boost referenced too........ 

[Buickguy3]

   Here's another thought about a draw thru carb. When you use a draw-thru system with an intercooler, and the 5-6 feet of piping and associated stuff, you are providing a perfect charge in the entire system. Should you break an intake valve or valve spring,------------- well, we've all seen what happens to a top fuel engine when that happens. The other thing is that when you shut off the engine all of that fuel settles out in the manifold, piping and intercooler which really confuses things on restart. Buick got away with this system in the 70's because the carb was mounted on the side of the turbo, and the turbo was mounted on the manifold directly. Total distance about 12". Incidentally, the fuel rich environment on these cars destroyed the center section bearings and seals and diluted the oil to the point that they lost the bottom ends on a majority of the cars. Most dealers were reluctant to even trade them in because they knew the problems. Hope this helps your decision. The Salt Cat 1 car was a blow thru system and would have worked fine had we had more education on what we were doing. It was a very steep learning curve. If you can't use EFI, go with a blow thru.
   Doug 

[Dynoroom]

Yep, this draw-thru twin turbo, chargeair cooled engine still holds the record in D/BGMS set back in 1988. Ran it for years until EFI came along......

[JustaRacer]

   Here's another thought about a draw thru carb. When you use a draw-thru system with an intercooler, and the 5-6 feet of piping and associated stuff, you are providing a perfect charge in the entire system. Should you break an intake valve or valve spring,------------- well, we've all seen what happens to a top fuel engine when that happens. The other thing is that when you shut off the engine all of that fuel settles out in the manifold, piping and intercooler which really confuses things on restart. Buick got away with this system in the 70's because the carb was mounted on the side of the turbo, and the turbo was mounted on the manifold directly. Total distance about 12". Incidentally, the fuel rich environment on these cars destroyed the center section bearings and seals and diluted the oil to the point that they lost the bottom ends on a majority of the cars. Most dealers were reluctant to even trade them in because they knew the problems. Hope this helps your decision. The Salt Cat 1 car was a blow thru system and would have worked fine had we had more education on what we were doing. It was a very steep learning curve. If you can't use EFI, go with a blow thru.
   Doug 

Interesting.  You'd think the fuel could not breach the turbo seals because the oil pressure normally exceeds boost for most spark engines.  What killed a lot of various turbo cars was owners who did not know that you must let the turbo cool down prior to shutting off the engine.  The turbine shaft is very hot, and can coke the engine oil.  As of late, GM got around this by using watercooled center sections.   

[Buickguy3]

   Justaracer,
   You are correct on the reasons for center section failures. Lack of oil changes and owner error. I don't think the dealership sales force in general should have been selling them as they were no more educated on turbos than the owners.
  Doug 

[barrybill]

The Turbotech forum has a 6 page discussion on AFB blow through Carb set up. Scroll down quite a few titles till you see something about blow through. Lots of good info.  Barry

[redhotracing]

A fellow forum member (greenjunk) ran a SBC a couple years ago blowing twin
70's into a carb box... He was running a standard Holley 950 carb, presumably
jetted rich, using a referenced fuel pressure regulator to handle delivery. Made
great power, enough to crack several 4 bolt main blocks...