MILD THUNDER

Lets also not forget, when talking about " how much boost" what role the camshaft plays into the equation.

I wouldnt try running 7lbs of boost with a towing cam coupled with a moderate compression ratio.

donzi matt

Very true, which starts the discussion about dynamic compression ratio vs. static compression ratio and the role that plays in cam selection, especially when forced induction is involved.

MILD THUNDER

Yes sir. Thats why I kinda have taken the general "compression chart guidelines" with a grain of salt. There are so many variables.

Supercharged engines, especially for marine, have such a bad wrap. Guys will always say "I dont want blowers, too many problems", based on a cousins buddy's, brother who melted a piston after installing a blower on his 454.

The entire package must be though out thoroughly.

donzi matt

I've always felt that camshaft selection does not get nearly enough attention in a roots blower application because of the lack of lag as opposed to something like a turbo motor where cam profile can make a huge difference in how an engine behaves. That certainly goes to your point of the entire package being considered.

The other misnomer is how people look at boost as the end all be all of power production. An engine could care less about how much of an inlet side restriction (AKA Boost) is going on, it is much more interested in mass airflow as it is nothing more than a giant air pump. This is where simply knowing what your intake air temperatures are in the manifold can give you major insight into what is going on with combustion temperatures.

MILD THUNDER

Totally agree Matt. I've seen or heard guys look at me or my buddy's like we are CRAZY for not having an intercooler. Heard things at the bar like, "No intercooler, better keep the boost at 4lbs". Alot of us have been running without them for years with no issues.

Icdedppl is turning a 10-71 at 3% underdriven. Makings 6lbs of boost right now. At wot his intake temp is 130ish. Now, take that 10-71 off his engine, and bolt a 256 blower on there, and make 6lbs. Intake temps will likely exceed 200*. I'd rather run the 10-71 at 8lbs, than the 256 at 6lbs.

My buddy is building a similar build this year, with 10-71s. But he will have a blower shop intercooler. I am anxious to see the intake temps on his. All these years intercoolers been out for roots blowers, I have not seen 1 legit test, of measuring intake air temps before and after the install. For what some of these units cost, I need some data before I write a check, or trust adding more boost safely.

SFOcean

Brad (Smith Power) related a story to me about a dyno session where the power output just kept slowly dropping. He finally went outside and found the hose feeding cold water to the intercooler had been turned off. Turned it back on and the engine's power came right back. On race gas, so no engine damage was done due to the mild heat buildup. This was on an over-driven roots deal. Not really big pressure, big heads and cam though. 1000+HP

blue thunder

You really need an O2 sensor to get the af dialed in. If you have a bung in your exhaust you could use my Innovate af meter and sensor to get a read on whats happening fuel wise in your engine. We appear to be in the same area. Ive also been running 454s on 177s for a number of years and have some knowledge in that area.

nonstop

Thanks for the offer Blue. I just may take you up on that. As MT said I'm at the end of my line with my set up but if I keep it, having it run at its best would be the way to go.