LSnoobee

Has anyone here ran the 5.7L LS7 Sneak Attack by Katech? This is a 4.125 bore x 3.267 stroke = 5.7L (349 ci)

I'm really interested in the dyno charts of this build. Although quite expensive (I think Katech MSRP was $25,000), this engine might have some significant advantages over many LS engines (especially on boost).

gnx7

iTrader: (28)

I have a Callies 3.27" stroke Magnum crank and Howards billet rods that match if you plan to go that way. Resleeving an alum 5.3 is pretty common practice these days....

Unless you have some heads flowing some serious air with an intake that can support high RPM's (no stock intakes or MSD/FAST etc are going to support high RPMs) plus a solid roller cam setup and nice rocker arms this isn't even worth attempting. Dry sump also for oiling safety.

LSnoobee

Thanks for the feedback!


Unless I'm wrong, the LS7 heads and intake would work at high rpm's considering the 5.7L displacement. Now running 7.0L displacement would be a different story...Plus, I would be running boost so stuffing that air in shouldn't be a problem.

I would be running premium valve train with Cadillac CTS-VR lifters.

Am I missing something?


BTW Nice vids/car!!

gnx7

iTrader: (28)

Reliably those lifters shouldn't be pushed past about 7200rpm... Going with a shorter stroke gives up torque.... Giving up overall power unless you rev it higher.

Plenty of people have pushed stock stroke 3.622" cranks to 8000rpm. Unless you are shooting for more than that you are giving up low end power. Also solid roller lifters $700 and rocker arms are needed to take advantage of high rpms in conjunction with an intake manifold that can flow up there vs. hitting a bottleneck shortly after 6600rpm which most intakes do.

Katech_Jason

iTrader: (19)

The Sneak Attack engine he is referring to is the 2005 CTS-V.R 5.7L that developed the Cadillac Racing lifters. The redline was 8000rpm and valvetrain was proven to 8400rpm. It had a stock LS7 intake back in that day with a minor modification.

LSnoobee

Thanks Katech Jason for the clarification on the Sneak Attack LS7.

GNX7, please consider this and correct me if I'm wrong (this is from one of my other threads). In short, shorter stroke doesn't ALWAYS give up torque...Also please consider the volume of air pumped through a 7.0L LS7 @ 7000 rpm vs. volume through 5.7L LS7 @ 8000 rpm.

"So I've been doing some 'back of the napkin' calculations.

Normally, a longer stroke gives a mechanical leverage advantage (well, it ALWAYS does if the force on the crank's rod journals doesn't vary when comparing different stroke lengths).

However, cubic inches being equal, a larger bore can produce more torque on the crank if the bore is large enough. However, it would not be very cost effective.

Using an LS7 block with 4.125 bore, you could build a 349 ci using a 4.8L 3.267" crank.

Assuming compression ratios are equal between this theoretical engine and an LS1 (therefore peak cylinder pressure at detonation is equal), the theoretical engine would place more force and rotational torque on the crank even while having a shorter torque arm (shorter stroke).

Again, I doubt that anyone would want to build this due to the cost, but imagine how that engine might perform if you were constricted to 350 ci!! More torque and way more rpms/high end HP! Also, this engine would likely see improved fuel economy over an LS1 due to longer rods causing more dwell at TDC and more complete efficient combustion of air/fuel mixture.

Please correct me if I'm wrong.

(Peak cylinder pressure)x(piston surface area)x(crank stroke)=rotational torque"

Katech Jason, I discovered the Sneak Attack after coming to this conclusion...therefore my interest. Thanks for your reply to my email! However, I don't think I could justify the expense unless it was on scale with other LS engine builds.

KCS

iTrader: (20)

You're not really going to see much RPM advantage with a shorter stroke. Even a 4" stroke crank will rev high enough to find the limitations of the LS valvetrain. On the other hand, the 4" stroke cranks aren't really very nice to the main bearings with higher RPM without the crank being fully counterweighted.

LSnoobee

Exactly. The 4"+ stroke is not nice to the cylinder bore or main bearings.

I'm not following you when you say that a shorter stroke won't allow an RPM advantage. Could you please elaborate? I would greatly appreciate it and don't worry if the discussion becomes very technical...that's not a problem.

KCS

iTrader: (20)

The 4" stroke really isn't a big deal on the cylinder bores, especially on the LS7 which came with the 4" crank from GM. The piston design and block prep are critical to longevity though.

The 4" cranks have no problem turning RPM. Joe Honeycutt was turning over 10k RPM with an 6 counterweight crank years ago. The shorter strokes may be able to turn higher, but you will never be able to turn that high. You will be limited by the valvetrain before the crank.

LSnoobee

Thanks KCS, I appreciate the feedback.

But, I would be running the same valvetrain that Jason Katech described...with Cadillac Racing CTS-VR lifters (good for 8000-8400 rpm's). This has been done before with the 5.7L LS7 Katech Sneak Attack.

I would just need to figure out how to do it without spending big bucks. The shorter stroke and longer rods would lend to longevity.

gnx7

iTrader: (28)

High rpms and budget don't belong in the same sentence. If you think $200 lifters and a hydraulic cam/stock rockers will reliably go 8400rpm I would love to see it.... Especially on any composite intake under $1k.

What kind of budget are you working with? What application is the engine going to be used for? What chassis?

Katech_Jason

iTrader: (19)

Here you go:

gnx7

iTrader: (28)

I feel like CiA hq just released data from the vault. Thx for sharing Jason. Are these 100% stock or have they been shimmed?

LSnoobee

Man, I don't want to argue with you. You obviously have a lot of experience.

If you compare the air volume passing through a 7.0L LS7 stock composite intake @ 7000 rpm and the volume at 8000 rpm with 5.7L LS7, you will find that the port velocity is LOWER with the 5.7 @ 8000 rpm (I can provide the calcs if you want).

I would like to place all of this in a 4th gen Camaro just for the hell of it.

Maybe I could beat the 4th gen Camaro that set the Texas Mile record (for any Camaro) of 263 mph!

slogo

I remembered this video after reading this. Just because

KCS

iTrader: (20)

Using a 4" or larger crank and turning less RPM also lends to longevity.

uxojerry

If you could get a forged rotating assy at a good price, it would make for an interesting build. To save money, you could move your red line down to say 7500. At 7500 you won't need big money heads or valve train components. When it is all said and done, you will have paid more for a little less.

I know because I recently built a short stroke bbc and paid a little more for a little less. It still made 810hp so who cares, lol.