Blower size?
 

If I wanted to bolt a roots style blowers on top of my 600hp 509's. What are the pro's and con's of let's say an 8-71, 10-71, and a 14-71. Does it take more power to turn the bigger blower? I don't won't to run intercoolers, can I run more boost with the bigger blowers and keep charge temps down? The goal is 850hp. Bottom end's are ready for it, 8:1 comp ratio, 93 pump fuel.

the bigger blower makes less heat,really important if you are not useing a innercooler,but 8.71 at 7 lbs will really wake up a 509,been there,done that,run 34 total timing,with a locked out distributor.

So with out running an inner cooler, I should run the 14-71 cause it will allow me to run more boost with less heat, and ultimately make more power? Any negatives to running a 14-71, compared to an 8-71?

a 14.71 wont clear the distributor,8.71 clears easily,a 10,71 might clear,if you use a bds intake manifold.

14-71 for big boys!!
 

If you want the blower to clear the distributor you would have to buy a intercooler and you're done... its only $$$$$$:eek::

I believe if you were to run a 14-71, on a 509, it might be too much. Granted turning a large blower slow, can reduce heat, but if you turn it too slow, I believe they can be inefficient, especially at lower rpm, due to leakage past the rotors. Im no blower expert, but I think turning the blower around 1:1 ratio, give or take a little, would be best for marine rpm/boost levels. With a 14-71 on your 509, i would guess you would be underdriving it 25-30% or something like that. A 871 around 1:1 or maybe 10% over should get you the boost you want. Alot of that depends on cam selection and overall engine package. I have found the blower charts to suggest more boost than i see. Boost drops when you have the right cam, good heads and exhaust. Bolting a 871 on a 454/330HP engine might net 12psi at 1:1. But bolting it on a 454/500HP might net 7psi at 1:1. Im no blower expert by anymeans, so it would be best consulting with someone who is more knowledgeable with blowers.

I would think a 8-71 or 10-71 would be more than enough for you. 7-8psi 800+hp should not be a problem. A proper selected blower cam is important too.

Few guidlines to keeping a marine roots blower engine alive
Low Static Compression
Proper Timing
Big fuel System
Aluminum Heads are a bonus for heat dissapation
Cool water temps
I like running dumps off the back of the intake water jackets to cool rear cylinders
intercoolers
A/F ratio set safe, but don't flood with fuel to where your cylinder walls get a bath, and crankcase gets diluted with fuel after a a few runs.
Big Carbs are ok (within reason). Most will tell you its very hard to overcarb a roots blower setup. Its unrestricted airflow on top of the blowers what your seeking.

Two blower motors : 60 grand.
Two intercoolers : 4 grand
Simple math says 4 grand can save 60 grand.

Thanks for the help so far everyone! One of the reasons I do not want to run the intercooler is space. It's not so much a money issue as a space issue. Also will be running highly modified and ported steel heads by JimV, which was another concern with heat, and no intercooler. I thought by spinning a bigger blower I may be able run more boost even though there would not be an innercooler or aluminum heads. But yes motors where built with the plan to throw boost at them in a season or two. Pistons, cranks, cams, lifters, springs, have all been addressed.

If your at 8:1, with the iron heads, I dont think 5-6psi out of a 871 will be a problem without the chiller. The 600SC, was a 502 with a 420 B&M Blower. They were low compression, 7.5:1, with iron heads. I believe stock they ran 5psi, and were very reliable. No chillers on them.

At 5-6psi, I think you will be grinning from the power increase. Like Mike Tkach said, most 10-71's wont work without the chiller.

Is 5-6 psi going to get me to my 800-850hp goals though? Remember I am already making 600hp right now, but that's on 9.5:1. When we make the upgrade, heads will be coming back off for more extensive work and dropping comp ratio down into the 8:1 range. Would I be better off to run chillers, and then I can crank them on up to 8-9 pounds of boost, and Know I can achieve the hp goals?

For head work i suggest goodwinn cmpetition in WI

I have 14-71's on 572's, and they are not working very hard to make 1000 hp (6-7 psi). This is 9:1 compression with chillers though.

I think getting to 850 hp without chillers on a 509 block is pushing your luck. 10-71 would probably be the best blower for it, if you can make it fit.

If you haven't torn down the motors yet, maybe don't drop the CR all the way down to 8:1. What block do you have? Can you punch it out for more cubes? If you could build a 540 or 572, you'd stand a better chance of getting 850 hp sans chiller. Like others said before, definitely aluminum heads.

Have you looked at using a Whipple intake manifold/cooler. I'm not sure if you can bolt a regular roots up to it, but it might be low profile enough. If the bolt pattern isn't the same, there are NC shops everywhere that can make anything.

buy a 3.3L whipple with carb set up and intercooler and set your comp ratio at 8.5:1......run 7 lbs boost(steel heads) or 8-9lbs(alum heads)

With the chillers could I run 8-9 pounds boost and keep the steel heads, and make the 800-850 range? If I did run the chillers, I will be able to fit the 10-71's, and given the choice to run either 8-71's or 10-71's is the 10-71 the one to run with?

if the chillers wil fit under the hatch,run them,my 548,s with 8.71 and chillers at8 lbs boost made 950 hp on dyno,if i didn,t have chillers,id run them at 7 lbs boost.hope this helps.also.i had a 509 with ported iorn heads,8.1 comp,8.71 with no chiller,made 770 hp at 7 lbs boost.

That does help, thanks Mike. Look at that, my post counter does not seem to be working!

Rob , there is a set of 10-71's with everthing you need in the swap shop form at not a bad price . Jeff

Did some 509's with 8.5:1 comp, Canfield aluminum 350 cc runner out of the box head, not a real agressive solid roller, 8:71's, 4150 carbs, 7# and made 848 hp at 6000 on Zul's dyno for what it's worth. Never had any detonation issues.

The 10-71's with chillers should get you the numbers your looking at, and also be very reliable with low heat build up, and not spinning the blowers very hard.
My motors started life as 600SC's. They had cams installed, chillers, PFM blower drives, and 10 lbs of boost on 91 octane(only junk we have in Socal.) The motors make 800hp and i have put over 200hrs on them. The 10-71's will be able to do this with even less heat produced.



Darrell.

my 509 recipe was fairly simple. 8.2 to 1, 741 grind but double firing order swap roller cam, box stock edlebrock 6155 heads, chiller and a 420 blower at 8% overdrive. 902hp at 6000 after Crocket put a tune in the mefi.

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....

lets talk,i have a pair of 10.71, and i need 14.71,,my new combination is 588 cu in.

21 lbs,sounds crazy,but the intake charge was cold

Had a little chat with my engine builder today about the blower apps, etc.

I aquired these 14-71's a few years ago---but not thru my builder.

In a nutshell, he told me that if he thought the 14-71's would not work on 557's that he would have said something to me a long time ago. I told him some of things I was hearing/reading and he just quietly shook his head and looked at me and said point blank--- "Mark, it's no problem---they will work on 557's."

I don't know what he does to them if anything as he said he has to check "something" on them,---but Dave is not the type of guy who wears his knowledge out on his sleeve and I didn't pry too much. Someone else or some other builder might think Dave is feeding me a line of BS, but I DO know he is one extremely intelligent and successful dude and I trust him.

Finally, he told me that if he wanted to be dishonest or if he was ignorant with the subject he would have convinced me to trade them with him for some 10-71's he has sitting on the shelf. Then he said to me; "I'll still take your 14-71's in on trade for some 10-71's if you want---I wouldn't if I were you, but if you really want to I will" :D

By the way, I am thankful and greatly appreciate everyone's input...I am not here to discredit anyone. I would not have known to ask had it not been for some of you guys bringing up the subject to begin with.

Besides, I really enjoy discussing all of this stuff---it is all very interesting to me and I am learning more about this blower stuff as I have always been a NA man in the past.

However, if I have to take anyone's words to bed with me, then it should probably be the words of my builder.

Anyway, Bob Madara is doing the cam profiles, JimV did the full port work on the heads, and Dave Wesseldyk is doing the machine work, balancing, assembly and dyno testing.

If the 14-71's don't work as efficiently as expected, etc, then I will let ya'll know. I am always learning---that's what makes it all fun and interesting to me.

At least, that's how I try to look at the whole thing---not trying to set any world records. I'm no expert on this stuff....just a weekend warrior that kills bugs for a living.

nes.i totally agree with your builder,14.71 will work good on a 557,buy the way,from what i have heard,dave is as sharp as they come,and honest,good luck with your engines.

Hey Mark, No worries man! If anyone would know the answers to these questions its definitly Dave W.

Sounds like you are on the right path, a cylinder head guru doing your heads, a cam specialist doing your cams, and engine master doing your machine and assembly. Sounds like a winning combination there!!

As noted earlier, yes they are 315cc

As another option, I did a 8.0 to 1 540 for a buddy this past summer. AFR 357 heads out of the box, crane 268741 hydraulic roller, morel,jessel etc and a 4.0 whipple. It made 1102 at 6000 and over 1000lbf.
Starts and idles smooth as silk, no surge, no anything really except smooth, solid power.

No reason to go any larger than 8-71's on a 509. Innercooling not necessary. Never mentioned was the the driveline, what drives are on this boat?
With todays fuel diluted with ethanol i wouldnt go past 32* and dual 750 carbs are plenty big.

Huber 1350 transmissions, and big shaft #4's. Can I turn up the boost enough to make 850 with iron heads and no chiller though? It is sounding like I need to either run aluminum heads or run the chillers to get the boost high enough to get the HP results I am seeking?

Rov V, man I am sorry for "hi-jacking" your thread---I truely appologize. It is very easy to get caught up in the back and forth banter of questions and responses, but I think it has been a very helpful "blower" thread to most of us who are students......like me. :)