HIGH COMPRESSION normally assperated
 

Has anybody ran high compression reguarly! I have a 572 and am looking at around 13 /1. I understand i need to run racing fuel, But is this a reliable set up

Wette Vette is OSO's naturally aspirated HIGH COMPRESSION KING!!! Sit tight, he will see your thread and jump in here to help you so fast he will look like a hungry trout chasing a worm! :D

Does the word "hang grenade" sound familiar. Never done it myself but I have a friend who regularily blew up high compression engines in his boat. Takes all the best parts and then its a crap shoot. And what ae you gonna do when you want to go on a poker run, have drums of racing fuel waiting for you in places and a siphon hose? You are better off putting blower on it. Just my opinion of course. Best of Luck.

Most of my time(all of my time) is spent at one lake where i have my own dock fuels not a problem

High Compression King!!
 

:D You're killing me KAAMA! I do run a high compression (13.2:1) BBC and in my opinion it is very reliable. I have yet to have a problem with about 75 HRS logged on 6000 plus RPM high compression engines. The key to making a high compression motor live is fuel (I run 110 octane leaded Union 76) and cam selection. The fuel is pretty obvious, but the cam takes some real expertise to make reliable high compression HP in a marine engine. I can't give you cam numbers since your combo is quite a bit different than mine, but I can offer some assistance. My motor is a 498" Chevy with fully ported 325 Pro 1 heads. The cam is a comp grind with 272/280 duration at .050" with .714" gross lift on a 112 + 4 installation. It seems if you keep your net lift at .700 or less with durations @ .050" in the high 270 on intake to mid 280 on exhaust you can expect to get 75 hrs. out of springs and lifters. You will need springs that come in at 225 to 240 on the seat installed at about 2". Isky makes a good spring and I am running comp 951 springs. High compression ratios are designed to give big cams enough cylinder pressure to continue to run at low RPM with some efficiency. High compression with to small of cam on the wrong LSA is a detonation failure waiting to happen. (I suspect this is what happened to Formula 31's buddy) Cylinder pressure control is the key!!!! Shoot for 180 to 200 PSI. Less than 180 will be a little sluggins and not idle well and more than 200 will tend to get into detonation easlily.
It works and is initially cheaper than the blower route. But in the long run the blower will let you do more boating and on pump gas. High compression isn't for everyone!!
Good luck- Hope this helps.

thanks for your input sounds to me like you have be there done that. What kind of power in your opinion do you think it sould make? lunati crank oliver rods dart grumppy jenkins heads310cc dart intake 1050dominator Thanks this really helps. any one else out there done this!!!!

With the right combo, you should be able to get 800 to 850 HP out of a 13:1 572!! With the right combo is the key!!

second Wette Vette's comments..Only thing I'll add is "OR MORE";) :D

ps..I think that motor is going to want more head....

VETTE SOUNDS LIKE YOU NEED SPRING OILERS AND COATED SPRINGS IT REALLY MAKES THEM LIVE . I RUN THEM ON EVERTHING WE BUILD WITH 650 PLUS LIFT AND IT DOUBLES THE HOURS ,THE CAM YOU DISCRIBE SOUNDS PERFECT ,BLEEDS OF ENOUGH CYLINDER PRESSURE AND WITH KILLER GAS SHOULD BE A TERROR,HAVE A GOOD ONE

IS there a good starting point for a cam that you might recommend for this app.

572;

I run a 280/[email protected] 115CL with .730 lift in a 10.5:1 632. The problem you'll have if you try to run much more duration than this is it will be very difficult to make the motor idle below 1000. I would also not recommend trying any more lift than .730 ish because coupled with the spring pressures necessary, the lifters won't live (speaking from vast experience here) I would talk with Steve Tanzy @Erson for a cam recommendation, he nailed Wette Vette's and mine. I had so many lifter problems I recently switched to the Schubeck "radius lifters" (basically a high tech very hard material solid flat tappet with a radius to run on a roller cam lobe) My guess is your durations and lifts will be very similar to mine, but your CL might move to a 112. How hard do you plan on turning the motor? I have an Erson 276/284 @.050 with .730" lift on a 114 brand new in the box that would probably work perfect, it has the "pro-stock" firing order 1-8-7-3-6-5-4-2. I had this cam ground before I decided to go with the Schubeck program. I just about bet that is the Cam Steve will recommend you.

JDNCA1/

You have some wild ramps on your cam. How hard do you turn the motor? I would be interested in hearing how your Schubecks work out. Merry Xmas.

Bob;

One thing to keep in mind about big inch motors is they like A LOT of cam. My previous cam had the same duration with lift approaching .800"...very, very aggressive ramps. (AKA lifter killers) Had to run triple springs that were 340# on the seat and around 950# opening. 280/288 is definately a big cam, but not like it would be in a 502. My motor will idle at 900-1000 and drops to about 650 in gear. Most of the reason I can make it idle is I run small carbs 2X775 race demons, a pair of 1050 Dominators would never work. The 115 CL helps the idle a lot as well. The motor actually wants more cam, I have it installed 2 degrees retarded. Any more duration though and the idle qualities would not be compatable with shifting a bravo. I turn around 6200 natural and around 6700 on NOS. The Schubeck stuff has been trouble free to date and makes BIG power. I took .050" lift out of the the Schubeck cam and left everything else alone, still made the same power. The lifters weigh half of a traditional roller lifter, you can run less spring, and there are NO moving parts to break. ;) To run the Schubeck program you have to run a custom grind cam thats coated (different base circle, 1" vs a 3/4") tap the lifter valley to install the link bars (similar to Jesel lifters) and get new pushrods (shorter) which helps with deflection issues. I changed springs as well, now 270# on the seat with 750# opening.

Merry X-Mas to you as well.

JDNCA1/

I spoke to Joe last year and almost ran his stuff. There were some questions on durability and what would happen to the lifter coating in the event a spring broke and the lifter started bouncing around on the lobe. I would be interested in hearing of people who have experienced 200+ hours with his lifters/hardened lobes. How many hours do you feel you will get before you have to address the lifter lobes or cam coating? Is it an expensive proposition to have the cams ground to a 1" base circle"? In your application, do you do much idling? No doubt, if you can run the inches and the cam profiles you have, your going to make some power! Thanx, Bob

With this set up will my bravo be able to handle this as far as in & out of gear. I was planning on around 6000 to 6500 RPM.I am not sure of the RPM that it needs to be at.This high comp is a idea we are tossing around .My engine builder says we can do this! I belive him, He has built some pretty wid stuff. I just wanted to here some other opinions Thanxs Guys!!!!

Bob;

Believe me I was skeptical as hell and still need to see a lot more time before I am a complete believer. So far, everything Joe has claimed has turned out to be true. Ther is no power loss at all over a roller lifter and if anything a slight gain. My last set of roller lifters lasted 7 hrs, so anything beyond that is a positive.;) The first set went about 40 hrs on a slightly smaller cam and I think 50hrs is all I would expect with my combo. Joe claims he has circle track racers with 2 seasons on sets. I don't think the lifters will be an issue from a wear standpoint due to the rockwell being a 95, the cam would wear first. I will be happy with 100hrs, Joe thinks 200 before a cam change...Who knows? A cam and lifters runs around $1300. In my opinion if a spring breaks you have problems with either set up. I guarentee a standard roller lifter will self destruct in very short order taking the cam with it. The Schubeck could live (if it doesn't shatter) which would be my worry. If you look at your springs regularlly and check seat pressures every 30-50 hrs you should catch anything starting to sag. One spring to stay away from (at least in my application) are the Manleys, more often than not they will break before they sag.

572;
You should be fine on the shifting issue if you have the right combo; heads, cam, intake and carb. The Rpm band you are looking at is exactly where I try to run and will work great for a high CR motor. Feel free to PM me if you want some ideas and/or experiences. Wette Vette is a great source as well, his high CR 496 is nastier than many blower motors I've seen. :cool: :D

The cam JDNCA1 mentioned!!!
 

I bet he would give you a good price too. That would be a real good starting point and with .025 to .030 valve lash you will be right at that .700" max lift for durability, and the duration is about right as well. Set your heads up with about 230 to 240 seat pressure and run a double spring like the comp 951 or the Isky. You will have great power to 6500 RPM and decent durability. That cam was designed by Erson to be easy on valve train components with gentle lash ramps for endurance and still put out the killer power of a solid roller. Make sure if you are going to do this to run enough head. 325 fully ported for max flow would be the smallest I would go. A fully ported 345 or cnc 355 Dart Pro 1 would be ideal. To crank a large pitch prop 6500 RPM with the 572 will require some healthy flow capacity. Keep in mind the high compression does a pretty good job keeping adequate torque down low, but to make big HP on top end you need cam and flow capacity which also includes good headers!!
Good luck!!

wette vette.. check your PM box..


Travis :D

Hello Guys!
Hope you all had a great Christmas!!!
I have the discussion about compression motors vs blower motors or nos all the time! When you are trying to make the power you are talking about here with a normally aspirated engine, you must have some very good and EXPENSIVE components. A blower motor makes this level of power with much less stress on all the parts. You can use a smaller cam-by a lot-the heads don't have to be as good, idle is much better, engine life can be much longer, and many other positive factors.
If room is a factor, consider different blowers like Pro Charger. They can be put in some pretty small bays. If you must have a normally aspirated engine, make it as big as you can with less compression and use lower RPM-consider something like Sonny Leonard's 704. The initial cost of the blower will almost certainly be offset quickly by fuel economy and breakage costs. You can pm your phone number and I'll give you a call and we can discuss this at your convinence!
Have a great day!!