ali123

Hey guys, I purchased a whole forged bottom end and cams from a person who had them spec'd out to be able to handle and make power up to 9000rpm in a LS3. Thing is from what I understand is getting heads that are able to handle that reliably is going to be real expensive so I'm looking at something
that can handle 8000-8500 RPM. What would you guys recommend? My budget would be around 4k.

Thank you

Tuskyz28

I recommend you calling Chris Frank at Frankenstein Racing Heads.

Vito.a

Tusky has a good recommendation. Brodix BR7 heads with titanium valves and Jesel rockers are about as rugged as you can get, but 9k is going to be tough. You are going to be changing valve springs quite often.
Suggest you post the components in the 9000rpm short block?

ali123

Ya I don't think I'll be doing 9k as that seems like it's on a different level maintenance wise. This is going into my street driven Rx-7. I see that good valve springs generally max out at 8300-8500 RPMS so I'll stick within that range. Preferably 8500 lol. It's a short stroked setup with lightweight forged internals and a roller cam that's spec'd for mid to high rpm's. Don't have the exact specs with me now as I'm outside.

Thank you

Tuskyz28

What size motor is the heads going on ?

KW Baraka

iTrader: (7)

How short?

Less than 3.3" stroke??

KW

ali123

It's a 3.0 stroke.


Thank you

ali123

It's going into a LS3 Block. Man I got a reply from AFR saying that I should rethink when it comes to reliability at 8000-9000 rpms lol. I hope that doesn't mean between 8000-8500 as well.

Vito.a

Sorry, but I think they mean anything over 7000rpm is going to be expensive with heavy maintenance.

NAVYBLUE210

310"X 8000 RPM I would call Kip @ CAMMOTION for a LLSR, if NA
340 CFM enough airflow for 680+ FWHP I would look at MMS 235,
From MAMOMOTORSPORTS reason being enough airflow, smaller & LIGHTER
valves, and less shrouding for bore size, also 20 CC port size between
235 vs 255+ for LS3 heads = HUGE difference below 6000 RPM with 310"
Cam,Springs,Rockers,Pushrods ~$2500.00+
MMS 235s with Light Valves ~$2500.00+ (springs already counted)
Maybe $5K, but reliable to 8K RPM with moderate Maint.
Good Luck!

ali123

oooh that sounds awesome 5g's would actually not be bad so almost 4g without cams. Will def contact mamo. This is a NA build. Thanks

Oh I know it's not going to be cheap def. I am worried about the maintenance though. Which is why I'm trying to go for between 8000-8500. I've seen plenty of built engines that can do that. Reliably who knows.... I was talking to AFR and they forwarded me to Mamo as well because an out of the box will not suit my needs.

gnx7

iTrader: (28)

We had a stock 3.62" stroke cast crank in a 4.065" bore block spin to 7800rpm on occassion and mainly 7000-7500rpm shift points for 4 years making well over 900rwhp all the time. Sometimes 1200rwhp. Morel linkbar lifters, hydraulic cam, MAST LS3 heads, turbo'd.

The best way to go about it is with a solid roller. Your stroke is super short.... it is the valvetrain that is expensive when trying to make it reliable above 7500rpm as stated. Springs can vary from $300-650 alone. Keep the lift under .750" and you can run reasonably priced springs.

A 416ci motor would make that 310ci motor look slow even if you only rev'd it to 7000rpm (the bigger one). It makes well over 100rwhp/100rwtq more... cubic inches is key unless you have to fit in a class restricting engine size.

Not only do you need heads that flow.... but the intake manifold is critical. Any production polymer intake stalls out at around 7000rpm and becomes a bottleneck. Only a single plane or custom intake will be able to support those RPMs...

lil john

So true GNX on all points, on the intake choice he only has Ma$t or Edelbrock *Holley High Ram for Cathedral ports, and or a Cu$tom sheet metal intake. The FAST or MSD just wouldn't work to 8grand. Just build a bigger engine it's easier on parts and will make more HP...if the class will allow it. Win -Win situation 4 you and your engine.

Me24seven

Those rpms arr hard on valvetrain

ali123

For the intake I was thinking of picking up a used ITB. I understand that bigger is always the way to go for more power but I'm not a person who's going for 1/4 mile times. Just want something cool to go into my RX-7 and the previous owner shares a similar passion which is why I decided to go with this method. Plus I got a good deal :p. These are the cam specs "240@.050 intake and 248@.050 exhaust roller lifter .381 lift with 1.7 rocker so .648 lift total". I was looking at titanium valves but I think Ferrea hollow stems are the way to go. Looks like it's less maintenance, cost, and can handle high rpm's without valvetrain float. My budget can go up all I want is to not worry about something breaking. Periodic maintenance is ok as long as it's not too often...

Thank you

Tony @ Mamo Motorsports

Was alerted to this thread recently....finally found the time to hop in here

First off, I'm glad the subject of manifolds came up recently in this thread as its just as important as the heads. So this deal is kind of strange in the sense the OP owns a cam for a combination and an unknown set of heads which is the main component that dictates cam events. Cart before the horse type of thing.

OP....the ITB intake you already have, I assume its an LS3 based manifold or is it possibly an LS7? (they look very similar).

If its an LS3 based deal I could port a set of TFS LS3 castings for you with hollow stem valves and probaby come in very close to your initial budget. You would have more than enough airflow to hit any RPM you wanted within reason and to reiterate whats already been said....an 8-8500 RPM engine with be alot less reliable than a 7 - 7500 RPM engine....its the nature of the beast. I would recommend an 8000 RPM max shiftpoint if you really only want to deal with routine maintenance which is how it sounds to me and even that would be an impressive feat but one that's perhaps actually doable with the right set-up.....an SR is the only way to go so you will have some occasional valve adjustments and I would recommend springs be replaced at the end of every season if you drive the car alot.....the end of every second season if its only a few thousand miles a year. Springs in a high RPM engine are simply wear items and you need to toss them and go fresh for that ultimate reliability your in search of. High quality springs are a must also.....I would look into a 1200 series PAC at a minimum

OP.....all my contact info is below....get in touch with me at your convenience

Regards,
Tony

speedtigger

iTrader: (16)

Definitely. You will not find anyone with more experience making high RPM power than Kip. He has been there, done that and won the championships.

Jason 98 TA

iTrader: (4)

That's going to be awesome rpm. I think its definitely a doable project, just spend a lot of time on the camshaft & intake manifold selection as well!

The PRC 260 head is available with hollow stems standard. From there we just need to line out a spring configuration to meet your needs. I have no doubt that a PRC 260 head combined with a PAC spring spec'd for your lift & rpm is no problem.

What rocker arm are you thinking about running?

427 zeo6

You want a 9000RPM V8?.........sell your LS stuff and go on Ebay to find a used NASCAR motor......you probably don't have enough $$$$ to build a high RPM LS motor......it would probably run $45K.......the used cup motor is the cheapest/easiest way to get to your goal of making a V8 run like a rotary motor.

NAVYBLUE210

I think the OP has reset to 8K RPM
Beyond that, 8.5K+ you are right, used NASCAR Engine!