Blazeracer

iTrader: (2)

Got me a new steel 5.7 built for my jet boat. Running twin turbos and last time out with the aluminum block it turned 7,200 rpm and leaned all over the rev limiter. Ended up cracking three of the sleeves and turn the block to scrap metal. My forged rotating assembly is fine and now in an iron 5.3 punched out to a 5.7 liter. I'm thinking before I reinstall the AFR Mongoose 210 heads I should change the valve springs to something that can handle 7,500 rpm or more. I got forged pistons and forged rods on a stock crank in an iron block. That should be able to turn real fast. Induction is twin GT-35's with a QFT E85 blow thru carb.

So yeah, AFR says the valve springs that come with the heads have a 6,500 to 6,700 limit. I can either impeller the boat down to slow the motor, or get the right valve spring and let it eat... I wanna let it eat. I would love to turn it close to 8,000......

Ideas?? Is Tony Mamo still on here???

gagliano7

Mamo is still on here.

farmington

iTrader: (14)

you need to contact a spring supplier and let them know how you plan to use the motor. Very few people with these motors run them at that kind of speed for long periods. Your spring requirements will be different from a car.

Fbodyjunkie06

iTrader: (10)

Anything in a boat is going to require very smooth lobe design with a very well matched valve train package.

Sustained RPM's, especially higher RPM's are hell on valve train components. I would be looking to make the weight over the valve as light as heavenly possible and ensure that the camshafts lobe design has longer duration seating ramps and isn't trying to push the .200" duration number. A lot of companies will push the .200" duration number to make the lobe look good on paper, but these lobes can sometimes be very aggressive. Especially when combined with shorter duration seating ramps.

What rocker arms are you running? What lifters? What diameter push rods? Do you know what lobes your current camshaft has?

Blazeracer

iTrader: (2)

It's a drag boat so it only sees the WOT rpm for like 10 seconds at a time. Lake cruising is at around 4k RPM or so.

Running stock rockers with the trunion upgrade, LS7 lifters, and Manley chomemoly 5/16" push rods.

My cam is an LG G5X3 - 24x duration with .600/.610 lift on a 114 stright up.

Fbodyjunkie06

iTrader: (10)

Although that cam is a great N/A cam, it's not what I would have in mind for boost.

Blazeracer

iTrader: (2)

While I would love to get a solid roller cam, I don't have a handfull of available cash at the moment, so I'm running with what I got. I think I need new valve springs a lot more than a cam. Might could get another cam later, but for right now, valve springs are my weak point.

Brian Tooley Racing

iTrader: (13)

Like Martin said, that's not a stable camshaft with boost past 7000 rpm, ever, you need a different cam and spring kit.

We have hydraulic roller cam packages that turn 8,000 rpm with over 20 lbs of boost, no problem.

RQSGTO

PSI can help you with your valve spring selection: http://www.psisprings.com/index.php?...ured&Itemid=35

Blazeracer

iTrader: (2)

Might just do that. What's a used LG G5X3 cam worth? Ain't nothing wrong with it. Makes a **** ton of power. LOVES nitrous.

redbird555

iTrader: (14)

200-250 i'd say is a fair price. i agree go with a grind made for what you want

Martin Smallwood

iTrader: (2)

If Brian doesn't get you squared away with a cam and spring package, I'd be glad to offer my recommendation as well. I sell his spring kit along with my own spring kit and can custom grind you a camshaft on a 8620 Cam Motion core.

As RedBird said, you should be able to get 200-250 for it as that is what a used stick usually goes for nowadays.