sydneyACE

Hey everyone!

I'm brainstorming a silly build, and am trying to figure-out about how much it would cost. I want to plan a short-stroke/large-bore, high-reving, forced-induction motor. I want to build it as inexpensive as possible. My plan for the bottom-end is as follows:

LS3 block (stock bore)
LS3 pistons
4.8l crank and rods
This combo should net 339ci displacement.

Like I said, I want to keep it simple and cheap.

I would like to have a valve-train capable of 7500rpm. (Wouldn't rev it that high regularly and peak power would most-likely be between 6500-7000 anyway, but I do road-race a couple times a year, so want I'd want it to be reliable.)
Lift would most-likely be no more than .575, but I would like to be able to run around 10psi of boost.

What would you guys recomend as far as base heads and springs, rockers, lifters, etc.? The reason I said cathedral ports is because I'm planning on using them in conjunction with a cathedral Maggie manifold. If it makes more sense to use a rectangle-port head, I think it's possible to swap the manifold to a rectangle-style without it costing too much.

Long-story short:
I'm planning on putting a TVS2300 or Whipple 2.9 on my LS1 C5 soon.
I would like to put this set-up underneath it eventually.
Ultimate goal is a 650rwhp motor that's less than 350ci and comfortable reving to 7500.

I'll leave-it at that for now, if you guys need any more info, let me know. I'm sure I left something out or overlooked some details.

96 Comp T/A

iTrader: (8)

A stable, reliable, 7500 RPM capable valvetrain does not come cheap. You are going to need serious springs, retainers, pushrods, rockers, lifters and a camshaft. Light weight valves would help here as well. I really don't think you need all that to make 650HP with forced induction. If this is a track only car, then go solid roller, if it it's a daily driver I would stick with the stock crank lower my RPM expectations.

Hard Core Z28

Solid roller cam and spring with jesel rockers.

Gray86hatch

iTrader: (83)

Nothing really trick is needed..

Proper cam lobe hyd roller. Big PR, Lunati spring kit and Lunati street link bars 7500 looks great on my motor.

Tim

BigRich954RR

iTrader: (1)

for long times at 7k plus go soild lifters

wildcamaro

iTrader: (15)

yea solid lifter valvetrain would be less worrisome than trying to keep the hydraulic valves from floating when revved that high

JPH

iTrader: (2)

The motor should peak way before then, but you will need a camshaft profile that will atleast carry it to 7k and lifters/valvesprings that will control both that and boost.

Whistler

iTrader: (46)

I stopped reading after I saw -high revving, forced induction, and inexpensive- all in the same paragraph

JPH

iTrader: (2)

Some have odder combos then others, but are willing to give it a try. NO harm there.

sydneyACE

This is the kinda info I'm after. I've deffinately seen quite a few threads around here with people running high rpms. I would like to hear from more people that are acrually doing-it. Basically what I'm after is specific parts used, (Lunati springs, link bars) and what kind of price to expect to pay on that. How long have people been running these set-ups without problems, etc.?

I don't plan to run-it at high RPM very often. Just once in a while when I want to haul down a back-road. There's really nobody to race around here, and no 1/4 mile strips anywhere close. The only time it would spend a significant amount of time above 6000rpm is when I take it to the track (road-racing) in Lewistown. I like to go out there a couple times a year and play with the Porsche boys. I don't know if solid is the way to go for me. My car is my DD and gets a lot of miles on it. I've heard that solid can be a PITA to adjust and maintain. Basically I would like to get close to the limit of what is safe with Hydraulic.

Thanks for the support. "New" ideas are always met with a lot of resistance. Although, I don't really think this idea is all that new. I like posting/reading posts over-here because you guys seem to be more open-minded and inovative than the Corvette guys.

The FI portion isn't going to be inexpensive. That I know. I DO however think a high-reving engine, by default, doesn't have to be "way" more expensive than normal. The bottom-end doesn't need to be anything special. The short-stroke will help for sure. By my thinking, the only-thing that is going to be critical is the valvetrain, and that's why I'm here posting, gathering information. I don't think a quality valvetrain will be overly expensive. The cam is the same $ as any other. If it can be done by simply using aftermarket springs and linked lifters, then we can't be talking about too much $ can we?

1lejohn

iTrader: (9)

You shoudln't need all the revs if going FI. If you still want to let her rip. A hyd roller will be fine with good lifters 400-600, shaft rocker arms 1000-1200 , springs 300-500, pushrods 100-250, cam 300-500. Your at 2k plus and haven't bought valves or a timing set. Stock valves won't like 7k plus rpm's

The bottom end does matter when turning rpm's.. Thats what kills rods or the bolts holding them together.

3pedals

iTrader: (3)

depends what you mean by "hi rpm"
stock lifters and rockers are good to 7000-7500, you just need a good cam spec with lobes designed to turn revs and be reliable, good springs, and good pushrods.

sydneyACE

I seem to be getting a lot of mixed feed-back.

One thing that does seem consistent is springs, which makes good sense.
I think some good dual springs are in the "Mandatory" column for sure.

Katech's site says they used "modified LS7 hydraulic lifters" on thier "Sneek attack" which turns 7500. I realy want to stay with hydraulic. Thoughts on where to look for good, linked, hydraulic lifters.

Obviously, the lighter the valves, the better.
It seems in the factory stuff, LS6 valves are hollow and LS2 valves are solid.

Might as well do performance push rods too because thier not too expensive.

Who thinks the factory rockers are fine?

I would love to hear some more input from people who are spinning thier motors this fast. Please...

Thanks for all the constructive feedback thusfar!

1lejohn

iTrader: (9)

Morel makes a nice link type lifter. They are $$. The stock rockers with a trunnion upgrade should be fine, it depends on the amount of lift. If you stay with a hyd. roller they should be ok. You are talking about running on a road course correct. How long will your engine be at say 7500? If you just bump it a few times a lap no problem. If it stays there for minutes at a time I wouldn't trust stock parts.

The stock GM parts are all nice pieces. You would be pushing the limits of their design with your build IMOP.

sydneyACE

I will most-likely be shifting @ 7000 while on the track.
There are a couple spots that I'm running-into the rev-limmiter right now.
On the back straight, I'm hitting the limmiter in 5th (I'm running 3.90s in the rear), and it's pointless to use 6th. Then on the front straight, I need like 1 more second in 4th. The extra 500-1000rpm would make it just perfect.

This ISN'T the entire reason I'm wanting to rev-it higher. After-all, with the super-charger, power will be up so much that I plan to go back to 3.42s anyway. It's just something I think would be lots of fun to do.

If the power-curve was just-right, I would make peak power around 6250-6500rpm, shift @ 7000, but have the option to run-out to 7500 once in a while if I needed to brake soon after. Idealy, the average hp would be about the same whether you shifted @ 7k or 7.5k.

From my understanding (I'm still learing about valvtrain stuff), I need to figure-out what cam profile fits my requirements, then match-up which components will provide stability with that profile.
As far as high-RPM stability is concerned, it seems the "accelleration" of the cam is critical.
So I think a long-ish duration coupled with mid-height lift should keep the valve-speeds down while still allowing enough flow for high-rpm.

Like I said, I'm still learning, and that's why I'm here.
Looking for more info!!
Thanks to all thusfar!

Jason 98 TA

iTrader: (4)

We've run the PRC aftermarket castings to 8000rpm with a solid. The PRC .675" spring will do 7500rpm in the correct hyd. application no problem.

driver56

I've had my 402 to 7500 lap after lap in a circle track dirt late model. Using COMP solid roller valvetrain, Ferrea valves, Manton pushrods, Yella Terra adjustable shaft rockers. No problems what-so-ever. Use good parts and you get good results.

DirtyDirk

Have you looked at the GM performance lifters? They claim they are light weight and have sustained 8000 rpm abuse and around $250.

1lejohn

iTrader: (9)

They have also had a run of failures. The plastic buckets also present a problem at high rpms and or lifts. The lifters have been known to pop up out of the bucket and spin causing failures. The link bars are cheap ins. against this happening.

1lejohn

iTrader: (9)

Good advice ,and a good selection of parts.

far as high-RPM stability is concerned, it seems the "accelleration" of the cam is critical.
So I think a long-ish duration coupled with mid-height lift should keep the valve-speeds down while still allowing enough flow for high-rpm.

If you stay with a hyd. roller it will be designed like that.