[QUOTE=wyomingoutlaw]okay, I'm sorry, I know this is an old thread but I gotta ask...
Originally Posted by firstname.lastname@example.org
Small carbs are important but the real killer in tunnel rams is the big plenum between the carbs and the runners. Once the air and fuel are mixed in the carb, the worst thing you can do is slow the mixture velocity down which allows the liquid fuel to drop out of the mixture and puddle, flow to one or two runners and not others, etc. The purpose of the tunnel design is to use the 'organ pipe' effect to super charge the cylinders at a narrow design RPM range and divorce the dynamics of weird pressure pulses thru a carb from the intake valve. Exactly the same technology of tuned exhaust headers. This design RPM is usually @ WOT at max power in a drag machine so low velocity isn't a problem. Try to idle one though and all bets are off.
If you want to run one of these things on the street and you want streetability, consider filling the majority of the plenum with something that will reduce the size to that equivalent to a standard hi-rise manifold. /QUOTE]
now I kinda understand the theory here, but if this holds true, why does edelbrock recommend using a 2" spacer on their victor intakes? or doesn't a spacer increase the plenum? I just measured the runner length on a victor for a pontiac and it's within 1/2" of a wenzler tunnel ram. doesn't that make it more similar to a tunnel ram than a regular intake? seems tunnel rams are getting alot of bad press, but from what I can see the victor intake is using the same priciples as a tunnel ram, and it doesn't fit under my hood either, with or without the 2" spacer.
If I understand your question, the 2" spacer you refer to is acting as an intake runner extender more than a bigger plenum. As long as the area of the added passage doesn't increase substantially it adds to the length of the duct from the carb to the intake valve which changes the tuned rpm range of the system. The longer the intake runner, the lower rpm the engine power band kicks in. Tunnel rams are intended to shorten the intake runner length so the engine has a higher rpm power band. The problem is that the tunnel increase the area as well as the length. The area is so big, it effectively eliminates the distance from the point the intake runners enter the plenum to the carb. The organ pipe pressure waves operate only in the relatively short intake runners. Great for high speed tuning and performance but deadly to low speed performance.