Air, what CC runner size is the Edlebrock 6155 head? Is it a rectangle port head? Thanx in advance

Mark, Im pretty sure those are 315cc Rect port heads. I think those are the same heads my buddy Joey used on a set of 522ci procharger builds. He did over 1000HP with them with the big prochargers and chillers.

MT,how you been?...thanks, sounds like excellent results on both apps. It just shows that a blower can make good results of out of just about any head....especially right out of the box without any mods. I'm thinking a head with some porting mods should only help....???

Blowers just sound like the ticket for a while now---and with good reliability.

I think I'll be trying something out here soon with a pair of 557's, hyd rollers, some fully ported aluminum 335cc heads, and some root style 14-71's, big tube headers and 6000rpm.

Of course, the trick I want is smoooooth idle quality,---but heard it's a lot easier to do this with a blower vs NA. I don't know how much power I will kill with a smooth, mild idling cam and still make peak power up at 6000rpm. :snide:

Open for more comments. thanx

Ive been good Mark, and You?

I think you'll like the blowers. I could be way off on this, but, if you are seeking a mild cammed good idling setup, that will make big numbers without having to spin it real hard, you might wanna keep the duration conservative, 114 LSA, and maybe a 10-71. Reason i say 10-71, Im not sure you'd reap the benefits of the 14-71 if you were underdriving it alot and the rpm levels 6k rpm or below. Lets say you had a N/A 557CI that made its peak HP number at 6000RPM with the cam thats in it. Then you fully port the heads, and add a blower, with that same cam. I think the peak HP will come in a few hundred rpm higher, if not more.

I remember seeing a blower dyno test comparison a while back. They took a small 177 blower and ran it up against a 8-71 on a 489ci. Anyhow, the little 177 actually made about the same power if not more making 3psi, where the 8-71 was making almost 5psi. Of course the little blower was maxed out once you started to get around 6000RPM, and making more boost wasnt a option for the little blower.

It was interesting to see that the small blower actually made more power than the big one at lower RPM. Probably because of the HP required to drive the larger 8-71.

What I am getting at, is maybe the mild cammed 557CI at say 7psi chilled, would make more power at the flywheel from say 3000-6000RPM with the 10-71. Granted if we were talking 600+CI with some really large cams and 6000+rpm maybe the 14-71 would be the way to go.

I'd like to think that Roots blowers are application specific. Kind of like how a naturally aspirated mild 454 might make more power with a single 800 holley over a modified 1350 dominator. I'd like to think a 557CI even with a modest cam, good flowing heads, good exhaust, intercooled 10-71 with some 4150 850 or 950s, 7-8psi would make some REALLY nice power thruout the entire band. Like probably 900+.

Granted, Im still tryin to learn all this stuff. So i could be talkin out my A$$ on this lol

when you get ready to start gathering parts,pm me,i can give you some info that will help you achieve your goals.

only thing done to the heads was a little cleaning up around the bowls,they made 1175 at 6200,i almost hit the floor from a heart attack the day we dyno,d the first motor,i told joe to expect around 950hp,those m4 pro chargers are unbelievable.

Mike, thanks for your input/response....I'll shoot you a PM.


MT, funny you mention that about the 14-71 vs a 10-71 for a 557cid. A friend told me the other day that a 14-71 blower creates more heat than one expects even when they're underdriven on engines my size (557cid). And he was told this "off the cuff" by a well known marine engine building crew in person. He said he doesn't know if there is any merit to he was told that day, but they had nothing to gain by telling him that. Then you tell me about the 14-71 blower possibly being to large for my 557's and the app I am looking for. I guess I'll have to ask Dave W...my builder.

Of course, from what I have known in the past about roots blowers is that a larger blower doesn't neccessarily give an engine more power over a smaller blower, but that it will create LESS HEAT/HEAT SOAK.

I didn't know a larger blower could actually hurt or create LESS power on the same engine vs a smaller blower.

I plan on cruising most of the time anyway. Perhaps I would be willing to trade my 14-71's for some smaller 10-71's.

Anyone else want to chime in on this 14-71 vs 10-71 on a mild cammed 557cid engine making peak power at 6000rpm???

Mark, I also read that while turning a roots blower too slow, you can get "leakage" past the rotors, reducing its efficiency. Granted not as much heat produced, but...

I would imagine there has to be something to that theory, otherwise, why run a 6-71, 8-71, or 10-71? Why not just throw a 14-71 or 16-71 on a 454 and underdrive it 75%? I'd like to hear more on this subject too .

Hey Mike, do you remember what kind of boost he was seeing at 1175HP with that setup? I remember thinking they were pulling my leg with those numbers when i got that text!

Here's an interesting post made by Tyler Crockett back in 12-5-2006 regarding a 468cid big block chevey destined for a roots supercharger....