Exhaust scavenging

When tuning for tailpipe length for proper exhaust scavenging, is it possible to measure a intake manifold vacuum improvement? Also is the cast iron tri-yi manifold worth the hp/weight over the ranger tube manifold? ? 84Dave/JBV/Rob

TIA

Measuring intake manifold vacuum? To be precise in the measurement, because induction character 'pulses', your standard $20 vacuum gauge won't do the job. It essentially 'averages' everything. It would require high sample-speed instrumentation for precise measurements. However....... if you switched or tested exhaust manifolds and there was a measurable/moderate difference in vacuum with your $20 gauge, something would be amiss between exhaust manifolds. Good or bad.

For those on this forum that may not know........... if you're working with exhaust systems, I HIGHLY recommend Larry Meaux's PipeMax software program. About $35 + shipping on a CD. Some of the cheapest/best $$$ you'll ever spend on your race engine. Check it out @ www.maxracesoftware.com . And if you have upfront questions, larrymeaux@cox.net. Some of you may remember when I started a thread on this Forum entitled 'Induction/Exhaust Tuning'. The formuli I used in that screed belonged to Dr. Gordon Blair of Blair & Associates out of PA. With all of the right inputs to Larry's PipeMax software, the recommended length/diameter results were very close to identical between my formuli & Larry's software. And Larry's software obviously does all the 'heavy lifting' calculations in milli-seconds! Versus my pad of legal paper, a calculator, & pen. BTW...... whether you use Blair's formuli or Meaux's software, be prepared to measure the INDUCTION tract lengths. Get the measurements wrong between the induction and calculated exhaust dimensions, & it'll cost you 27#torque/25HP in a heartbeat on a 262HP 2344cc Ford! Make you think I've been there....... done that?? -Dave-

To answer the question about whether a tri-y or a ranger tube manifold would be better I would bet 3 out of 4 times the tri-y would win that battle if not always. For the money though there are better headers out there. Not sure where any more but there is a guy on here who designs em and sells em from up north. He has a website you might try googling something to find him if he doesn't speak up.

Here is one supplier......

http://www.powerbyace.com/

X2 with PipeMax.You won't believe how much capability there is for the price.This is no cheap crap software deal. Well worth the $$.

I can't use a header. I do own pipemax. Collector length of 38.1" on my set up. It's that the measuring starting point on the collector is iffy on a stock manifold, and measuring a bent piece of piping (from manifold to muffler) is questionable at best. I was just thinking of a way to get closer without a trip to a dyno. Not easy or cost effective to keep testing pipe lengths on a chassis dyno.