Hello everyone.

So after careful deliberation (many beers) I have come up with this idea to use an LS motor in a light weight japanese time attack car.
My first choice would be an RX7, but a 240 SX or an S2000 could work as well.
S2000 is nice because the entire engine sits behind the front shock towers and I have access to a caged roadrace car with a blown engine tomorrow.
RX7 is nice because it handling is telepathic, although its expensive.
240SX is nice because its cheap, plentiful and handles very well also

Ive looked at a bunch of different ways of powering it and keep coming back to the LS for its simplicity and ease of fitment.

Question is: which combo?

My requirement is that it revs to at least 7000. 7500 would be better, and 8000 would be ideal.

Due to the fact that I ill be using a light weight chassis, I wont need all the torque that thse engines are known for.

Ive looked at a bunch of different options: L33, LS3, LS7, 4.06 with a 3.27 crank, 3.62 crank, 4.125 with a 3.62 crank etc etc.

I dont have a specific power goal in mind, but would certainly hope to be over 600 at the wheels on race gas and 550ish with 93.

While I dont have an end power goal in mind, I do know that I would like a nice linear mid range that eases off at the top.
3000-7000 is what Im thinking.

Im pretty open as to how to get there, however, if I come up with 2 equal options, I will choose the factory/low cost/simple option over a super sexy aftermaket, billet etc..

For instance if someone can port 799 heads to be within 25hp of expensive aftermarket cnc ported ones, I will choose the 799.
If there is going to be a 150hp difference, then I would choose the more expnsive heads.

So, Im looking to hear what some of you have to say, any combo and opinion is more than welcomed.

Share your experience(s)!

D

 

Hi DK,

I have two LS based engine's built for true road racing applications, and agree with what you are looking for. There are two ways to get there one a lot less expensive than the other.

If you do a quick search you will see that I have posted on the exact same road racing application twice on this thread, one under "400ci Short Stroke, Big Bore", and the other generally under "Help water in my oil"

My short stroke 3.625" big bore 4.185" engine is a no expenses spared US$50K, 800 BHP plus, revving to 8200 RPM that is still in the build stage.

My affordable current 'mule' is an RSH block with a Callies 4" stroke forged Dragon Slayer crank, plus their 6.125" Ultra light billet rods, standard LSX-LS7 cylinder head's, custom Cam Motion camshaft, standard inlet manifold with a 92 mm cable operated throttle body. We also use Bill Dailey's custom V8ST spec integrated dry-sump system [limited to 10" of vacuum] and a set of very nice custom stainless steel headers.

This engine easily makes 700 BHP @ 7,000 at the flywheel and will run through 7,500 RPM all day long, from 3000 RPM up.

PM me if you want some specific detail happy to help you.

Cheers,

Mark.

 

I will happily do that, althought I must say - your 'cheap' mule is nto exactly cheap.....


Sounds great though and thanks for the reply!

D

 

A really simple 402ci LS2 with TFS heads would probably fit the bill pretty easily.

I would lean towards an aftermarket head rather than a ported factory casting of you plan to use a cathedral head. TFS As Cast 220cc heads are really inexpensive and already have larger seats if you ever want to go with larger valves. For example, I put 2.165" LS3 intake valves in my TFS heads which are probably as big as you want to go in the stock valve spacing. You also have a nicer port with a taller short turn which you can't really get in a ported fa forty head.

What do you have planned for the oiling system? Wet or dry sump?

 

I would certainly like to a dry sump, either as a hybrid setup or a complete system.

I have to peace meal it together since no system set up from the manufacturer would work for my application.
Im looking at all options.
Im pretty sure that high rpm like this would require external oiling....

As for cathedral vs square port - I wasnt really leaning towards one or the other - Ill take whichever flows the most at that rpm range that costs least (if that makes sense).

The critical element in this setup is that I cant have the instant sledgehammer of torque right off the idle.
It would kill the car.
I ned nice roll on and a strong rush of power from 3k to 7/7.5k and a little headroom for carrying the gear longer if I have to.


As I said in the original post - Im ok to try any combo and Im flexible in the overall power output.

D

 

Don't overcomplicate this. With your goals in mind, simple is going to be better.

Gen IV 5.3L
afm/dod delete kit with ls7 lifters
west coast racing stage 1.5 cnc heads with 1.94/1.575 valves
ls6 intake/tb/cam
heavy duty valve springs and pushrods
slp 1.85 rockers
80# injectors and supporting fuel system
single 80mm turbo
ARP hardware/studs
flycut stock pistons with ceramic coating
shot peened stock rods
cyro'ed stock crank
fine/.5g balance

You won't be in boost until 3k, so you will still have some semblance of traction in that lightweight of a car. It's a proven combination, nothing fancy, doesn't spend any money you don't need to.

 

Yes, as we all know, boosting is a lot cheaper way to make power than na.

My situation is that I dont have a lot of room on the exhaust side, and making all my own bespoke piping gets up there too.

Certainly something to think about, but I would like to stay na if possible.

 

id do an ls7 with ported heads and valve guides replaced and a katech 110 torquer cam. its a proven combo designed for road racing. lots of power and torque all over the powerband no crazy bottom end parts to mess with no custom work.. just a heads cam motor with supporting mods will suit you just fine and rev to 7000-7500 easily

 

Ls7 in a rx7? Because we hate tires, that's why...

N/a power is awesome, and commendable. But it doesn't help your traction issues. Stuff a bunch of ls6 bits in/on a 5.3L, pay for a little head work and a decent rotating assembly balance, and add 15psi to it via a single snail. It's a perfectly drivable 300rwhp vehicle until you get into it, 3000-7000rpms, exactly like you said.

The truck/vette manifolds with a simple 2.5 crossover pipe doesn't take too much real estate and can be done in some pretty tight engine bays.

You could use the stock truck intake/tb and even use the stock 5.3 cam. Just install a afm/dod delete kit with some ls7 lifters, good valve springs and pushrods, and the slp 1.85 rockers. The slp rockers have the trunion upgrade, and will give you some extra valve lift. The stock 5.3 cam is a reverse split design, begging for a turbo. You can retain the vvt for driveability.

You could get a reliable 500rwhp without opening the longblock or replacing the cam. The arp hardware and cyro/ balance and ported heads are all just peace of mind for the road course.

 

turbo is going to be wayyyy too violent and unpredictable for road racing IMHO. where as even tho an ls7 will make the power it is much more predictable to control going through corners.

 

Hi David,

I road race with this car and this engine, see photo's below, and this LS7 based NA engine does everything DK says he wants and its affordable in terms of what DK is after which is Time Attack track car.

Apart from the off the shelf V8ST spec Dailey Engineering Dry sump pan and pump, it is pretty much a standard LS7 with a really nice 665" lift Hydraulic roller camshaft, spec'd for me by Kip at CamMotion. It makes very smooth power from 3,000 and revs to 7,500 RPM. Peak power, 700BHP, is @7,000 RPM and peak torque 540 Ftlbs is @ 6,000 RPM.

It even use the stock Ls7 manifold and 90mm throttle body, so for a short duration "Time Attack" car its an awesome road race engine, with great throttle response at a very reasonable cost, less than $20K all new.

Cheers,

Mark.

 

Wow. Yes, do that. Screw the turbo 5.3 and forget I ever mentioned it.

 

LOL

Im sure both of these are good combos, but Im trying to stay away from boost.

Ive driven a few LS7's on track and the way they come on, feels like a drag engine or something.
For me, and my cause, it would be better if it came on slow and carried all the way up top.
I dont ned massive torque to get a 2600lb car moving.

I can be a lot faster when I get on the throttle and can stay there, than having to lift right at the corner exit because I get wheel spin.

Most of the guys Im going up against are on 4cyl turbo cars making 550-650 range and some V6 cars as well as a few LS cars. Just about all the LS cars are done wrong in my opinion.
The powerband doesnt play into the strength of the chassis and that leaves a lot of time on the table.

I would love to nail this thing and show that an LS can be done the right way and be a devastating weapon on the track....

Keep em coming!

 

Im sorry I cant hear you from the loud bang that was my jaw hitting the floor

 

I'm many levels of: **** me : behind the monstrosity that you are racing, but we did campaign an S2000 with crap power for a few years and filled a room full of trophies (roadracing, SCCA, NASA UTCC)



Great car but lacks power.



Currently campaigning this guy in street class:

Supercharged and over 500 at the crank but chassis is not as sweet as an RX7 for example.

In any case, studying the unlimitd class builds that are competing right now- I think I would have a very reasonable shot at winning.


20k might be a tad much, but you have to pay to play.
Im hoping to get stuff second hand to reduce the cost as much as possible.

 

Hi DK,

No question we run a serious race car at the top end of road racing here in New Zealand.

I guess my point is that you don't have to use anything more than a bog standard LS7 crate engine, which you can buy brand new from Chuck at Pace Performance for under 13K, then re-cam it, and stick some decent headers on it and go racing for about 15K, if you don't want to go the expense of the aftermarket top end dry sump system, which you will only need if you are cutting a lot of laps.

If you can buy a second hand LS7 from a really reliable source you may be able to do it for even less money. the Camshaft is only $375 and that and the headers are the key to what you need, believe me! I spent a lot more money on the exact same configuration and basic spec because we run for 3 hours and longer, so we have to go for reliability, and better parts cost, its that simple.

WE RACE CAR'S NOT DYNO'S

Cheers,

Mark.

 

http://www.superchevy.com/how-to/vem...oke-of-genius/

Here's a thought. Seems to meet your requirements.

 

Thanks!

If you read my original post, that was exactly one combinatin I was looking at.

Although Im wondering why they chose 1.7 rockers for this build??
Surely 1.8 or 1.85 would have been more in line of a high rpm build.

It didnt mention what compression, but I imagine a 13:1 on E85 would pick up close to 100 more?

E85 is a legitamate option for us because we dont have to carry fuel for many laps

Man, thats so much down my alley...

 

Hi DK,

Thats a 'half way house' engine to my own 3.625" short stroke engine, as it keeps the standard 4.125 bore which saves a bunch of money, so I understand the reasoning behind that build decision.

What I also don't understand [like yourself] is why use 1.7 expensive Jesel Mohawk rockers, instead of 1.8's, that's leaving very cheap BHP on the table.

The rod ratio could be improved further by using a 6.200" rod but then again that's more money, so staying with common components such as the 6.125" rod saves money, but it does mean the piston will be heavier that ideal because of the compression height needed unless they have decked the block.

In my opinion there is no point in upping the compression ratio, because that is going to increase the torque potential of the engine.

Its interesting that the engine also use the Dailey Engineering V8ST spec pump and pan that Bill Dailey and I designed, and I also use in my Mosler's present engine.

I dont see a price on that engine build but I think it will be mid $20's if not higher.

Cheers,

Mark.

 

Actually, wouldn't a more mild rocker arm ratio provide better high rpm stability? Same thing for milder cam lobe profiles. I have always heard it's best to let the cam do the work, not the rockers. If you want more lift, get a cam with more lift, don't compensate with wild rocker ratios.

Just my two cents, but I will be the first to tell you that I don't know ****.