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gn or other roots experts

9K views 142 replies 20 participants last post by  sam805 
#1 ·
Was wondering if you think an 871 is enough blower for a 586" blower moter. 8.8:1, it has fully ported pro1 345's, two 1150's done by pro systems, bullet cam .750 lift cant remember duration exacly but like 290@ 050, lee intercooler. my problem is i cant get the rpms. took it out today 5900 at 5psi of boost. Use to run 6200 w 8psi of boost. boat has an agressor A. am i dreaming to think this thing should make 1100 to 1200 hp and i should see 6600 to 6800 rpms? My builder sid i should see about 6800 to 7000 rpm with an A cut.
 
#3 ·
something just don't sound right. my little old 468 w/ an agressor A (they
say is comp. to a berk AA) would turn 6400-6600 all day long with a 12-71
at I think 2% over , making 16lbs boost /of coarse 116oct. fuel. what
lobe I ran was a custom grind, but baby compared to yours- 112lc, 655/678 lift , 268/272 @.050 but it ran EXTREMELY WELL! turn up the
boost, put some good gas in it, and see what it it will do!
 
#7 · (Edited)
Whoa, whoa. What is all this about a 14-71. Is this a pump gas deal. I assume it is or you would be running the blower harder than that. Why the hell would you go to a 14-71? Just to slow it down to a crawl so it leaked more. He is already running the 8-71 butt slow.
Your at damn near 9 to 1 compression, and 5lbs of boost, your creeping up on the limits of pump gas now. I don't know your timing, but you MIGHT be able to get away with 5% on the blower, but its edgey.
I have no idea how much power it takes to turn your impellor. I wouldn't know a A from a AA if it hit me in the head. But that piece is cammed and headed for way more boost than 5lbs. When you run a motor a 5lbs, you almost have to treat it like its N/A. Too much head, too much cam.
Take the same piece, throw some 116 in the tank, crank 32 degrees in the dizzy, push the blower up to 20-22% over with 16lbs of boost and bring a change of underwear.

The thing wants to run 7000+ It just can't do it with the boost pressure. Its all miss matched. It will never run right till it sees at least 12 lbs.
But on pump gas, you'll be picking piston pieces out of the pan in less than 5 mins.

If your engine builder knew you were going to run this on pump, go kick his ass!



 
#8 ·
ok gn 7, yesterday i was running a 110/91 50-50 mix. Timing was set at 28 degrees. All i have access to is 110. Do you think I will be ok at 32 degrres and 12 psi of boost with 110 octane? With an A it would take around 1050 1100hp to turn 7000rpm the same hp to turn my impellor 6600-6700. Also without changing major components what kind of hp could i make on pump gas? I am willing to change pistons cam etc, but i would like to keep block, heads blower etc. What components should i change and to what to maximixe hp on pump gas? Can i make a 1000-1100hp on pump gas with the roots setup? Thanks guys.
 
#13 ·
One last question gn. on race gas and at 12-14 psi of boost is the intercooler doing that much or just restricting boost. I just have a lot more pulley options w out the intercooler w the pulleys i have. but if it is helping to make power or helping to prevent detonation even w race fuel than i am ok with it if it is killing a couple psi of boost. It is a lee intercooler.
 
#14 · (Edited)
It helping. With the setup your talking about running, I would be leary of any more than maybe 28* timing with out the cooler. Your compression/boost is pretty close to what I run most of the races. Its reliable at that setup. If you were running the drags, you might be able to take out the chiller and leave the same OD ratio. You never really said what it is you do with this boat. recreational, or drags, or....? With the pump gas set up I was assuming it is a recreational boat. If so, leave the chiller.



 
#15 ·
For the amount of air you need with those heads and cam you need a bigger blower. Once you get to a point of airflow with a given size blower, spinning it faster will only make more heat, and that gives a false high boost reading, but no more power. I run a similar setup with a stripped 14-71 and superchiller at 12 lbs. on a 565 on 87 to 91 pump gas depending on air temp. Discharge air is much cooler than with the 8-71 at 8 lbs. I found I could drop the overdrive from 28% to 12% and make more boost too. TIMINATOR
 
#19 · (Edited)
Not a single word on compression ration here. Guess thats a mute point in blower motors once you jump to a 14-71. :D So you run 12 lbs of boost on a 9 to 1 motor using pump gas. Your pretty good feat considering the final compression ratio is around 16 to 1, and 12.5 is about the upper limit for pump gas. He can hardly deal with the boost he can make now, and you think a 14 is the answer?

sam805, run what you have and see if it does what you want.
 
#16 · (Edited)
cam .750 lift cant remember duration exacly but like 290@ 050,

OK thats a insane big cam for what you are trying to do. 290 deg at .050 ??? and running 6 lbs /pump gas?? ummm try like 275 at .050,32 deg timing 100llav gas and 12-14 lbs boost.
remember you want to spin the blower at 15-20+ %, so to big is not good as well as 2 small. I think a well set up 10-71 at 20% od would work quite well on this.


yeah and tim's correct over 22% or therebouts its a fine line between od,boost,heat and power
 
#17 ·
I really appreciate all the help guys. GN, Right now i am just trying to get the motor to make hp (like my own personal drag racing). I will leave the cooler on it run on 110 at 32 degrees and 19% over and see what it will do. Quick cp i have a buddy at the airport so av gas is a strong possibility for recreational use. What final compression can i get away with on 100? I wont leave it at 19% over when using it recreationally. I am just frustrated. I have had this thing at two different builders and shame shit no power. First builder smaller cam, heads not ported, 8:1 compression and 8psi and same story 6-6200. Next builder ports the heads tells me i need more cam same story. He tells me 1200hp at 10 psi and good gas so in his defense thats what i will try we will see I am pretty sceptical. I have thrown a lot of money at this thing and been disappointed. Tminator i am very interested in your setup. Whats the static? What kind of hp you making? I wanna make 1000-1100hp on pump gas. Can you pm me your number so we can talk bout your setup? I obviously need help. Heck maybe you can build it? I have a lot of nice components.
 
#18 ·
One thing to keep in mind guys is this thing was built almost 5 years ago. But I literally only have like 3-4 trips on this thing since my second build. i got a divorce early 07 so this thing has been sitting since fall 06. I remember i was running 8 psi of boost but couldnt remember my pulley ratio. When i dragged it out of the garage a month ago it had a 49 on bottom and 42 on top. But i cant remember if i ran it like this or stepped the pulleys up and ran out of season. The thing that made me think i didnt run it like this was it was making 10psi of boost on the trailer when timing it when i revved it to 5k. So i just bought a 45 and 46 and ran it like that to see and got s whopping 5 psi. I went with the intention of bringing and swapping the pulleys i had on it, but I forgot them at home like a dumbass.
 
#21 ·
Yes. With 600 inches, you just don't need that much help making power in a unboosted condition. Then you could ramp up the boost on pump and get away with a little timing., and boost it even more on race gas. Your compression is what is limiting your options. Lower the CR and your options open up.



 
#22 ·
I have a question do you have access to e-85 where you boat or live, with e-85 you can run the higher static compression and blower boost. It seem to me with the parts comb you have it might be the cheaper way to go. While producing some real serious numbers. :)bulb
 
#25 ·
Ok so excuse my ignorance but is e85 the stuff at the pump? If so, Ive seen in it nocal but i havent seen it in central cali where i live. How much would I have to up jets in carbs? Any other changes? I know if its what i am thinking of if you get 10mpg on gas you will get 7 on it. Believe me impatient i am thinking of it. I work for my dads business and we drill water wells and do pump work. I am use to pumps just having a lot more stages than our jet boats. But we have detroits and jimmys lying around everywhere. Any of those AR turbos work?
 
#27 ·
575 inch, cam about 275 @.050, .750 lift, compression 8.75-1,timing at 30-32, run 100% av gas with 13-14 psi boost...built many of this combo, it will make 1200+ no sweat and should have no issues. Stick C-16 in it at 25-30 psi for race day.
I do not like "pump" gas in ANY high performance motor,period. The current 91-93 octane is CRAP (and yes we still draw samples and test it every year for our snowmobile blended fuel we use,last years stuff was the worst we have ever seen, exxon,shell,conoco and sinclair 91 non oxigenated..all garbage) I even run 25% av gas in my moomba stock ski boat..lol...:D
 
#28 ·
ok

well, i run about 8.5 to 1, with my 509. 100 ll av gas, and i was running a fresh 10-71. it worked best, about 12 lbs @ about 10.5% over. when i upped the boost to 14lbs @20.5%, it made a little more power, but the heat was really killing the gains. i tried 15lbs at 25% over and really felt like i was heading backwards again. good power changes up to 12 lbs, or 10.5 %, but the heat really started to kill things after going up and past 20%. im guessing 15% was about the end of the big increases, then started slowing down towards 20+. i do run a chiller too, but the heat change from 10.5 to 25% was HUGE.

got a call this morning from littlefield, and the new 14-71 shipped today. im gonna try 10.42% over 1st. that made 12lbs on the 10-71, it will prob make about 16lbs on the 14-71. i think with the drop in temp, and less hp loss to the blower, i should see a good increase in performance. if nothing else, i will feel better about cooling the blower down.

i was getting away with 15 lbs of boost on 100 ll while making a bunch of heat, and hopefully i can get away with 16 lbs now. i think i was running very close to the edge before with the 10-71. so hopefully i wont be pushing it any further with the 14-71 and the extra 1 lb of boost.

any thoughts on this set up? i have run the old combo in 100 to 115 deg weather without issues.
 
#33 ·
well, i run about 8.5 to 1, with my 509. 100 ll av gas, and i was running a fresh 10-71. it worked best, about 12 lbs @ about 10.5% over. when i upped the boost to 14lbs @20.5%, it made a little more power, but the heat was really killing the gains. i tried 15lbs at 25% over and really felt like i was heading backwards again. good power changes up to 12 lbs, or 10.5 %, but the heat really started to kill things after going up and past 20%. im guessing 15% was about the end of the big increases, then started slowing down towards 20+. i do run a chiller too, but the heat change from 10.5 to 25% was HUGE.

got a call this morning from littlefield, and the new 14-71 shipped today. im gonna try 10.42% over 1st. that made 12lbs on the 10-71, it will prob make about 16lbs on the 14-71. i think with the drop in temp, and less hp loss to the blower, i should see a good increase in performance. if nothing else, i will feel better about cooling the blower down.

i was getting away with 15 lbs of boost on 100 ll while making a bunch of heat, and hopefully i can get away with 16 lbs now. i think i was running very close to the edge before with the 10-71. so hopefully i wont be pushing it any further with the 14-71 and the extra 1 lb of boost.

any thoughts on this set up? i have run the old combo in 100 to 115 deg weather without issues.
Once you hit 20% your into an area were you really need to think about a diiferent blower. But you may not see any real gains at 16lbs with the 14 over the 8. and if you don't, it because your in a different area than Chris designed your cam for. You can tell him 10lbs and then run 16 and expect the same HP as someone who ordered a cam for 16lbs. Remember, the boost is a intication of the air the motor couldn't swallow. Throw a 225 at .050 with about .500 lift in that thing and you'll hit 16lbs at 15% on the 8-71. Toss on a set of peanut ports and you can get there with 12%. Won't make power, but it will make boost. Hopefully your new heads will help some also.



 
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