Ultimagt4

Hi people. i am a newbie from sunny UK and trying to get my head around which gen 4 LS engine to go with for my kit car project.

The car in question will be an Ultima GTR which will be mainly a track weapon and occasional GT car so my focus is on low weight, bullet reliability, revability(7K rpm minimum), streetability, emissions compliance and bang for buck

If money was no object then i would go for the LS7 but my thinking is i can also hit NA 500-600HP with a drysumped forged LS2 or LS3 with the right specced parts like heads, cams/valvetrain and forged bottom end. I know the intake and exhaust are important too and take care of by a good system available from the Ultima factory which give very good results(eg >40HP gains when paired with the LS7 engines) so i should expect good gains with either LS2-3.

My idea is to go with the LS2 and on top of my head :
-ported stock heads or AFR 205
-Comp cams ? which
-Uprated valvetrain parts to enable high rpm? which
-Forged blueprinted bottom end
- Forged high CR pistons(we have 99 octane pump gas here)
-ARP fastenners
- Bigger injectors? size/which
-ARE dry sump system to name a few things that will be needed.

I would appreciate any recommendation to which is the best starting point eg LS2 or LS3 or other and a spec list of the best/major parts required to achieve my goals while being under LS7 money(a turnkey LS7 will set me back by $25K delivered in the UK ) I look to spend 10K less ideally.

Please any other input will be welcome including recommending good tunning shops and parts store or if my goals are unrealistic. i know 500-600hp with stroking is easy prefered option by my tuning shop but i feel thats its just a lazy way out! (they have been tuning SBC for years and only getting to grips with LS engines now!).
Thanks

nysbadmk8

Do a LS2 based 402 stroker

Top it with TFS TEA 225/235cc heads Or AFR equivalent

Cam, have it custom spec'ed

Valvetrain- stock rocker w/ upgrade, YT's, Or jesel

With 99 octane go 12 to 1 or 12.5 For CR

Injector size should be 42lb's

Ultimagt4

Thanks chap but I rather not go the stroker route as already mentioned. Yes you get nice Hp and tq gain but the trade off is revs limitation for reliability inherent with strokers.

Out of interest what did your build set you back?

nysbadmk8

Roughly 8,000 and I put it together.

You can get a 550-575 flywheel out of a high strung ls2/ls3 Ls3 leaving you a bit more potential due to the extra displacement.

Ls motors dont really enjoy being much over 7k... and the added expense to build one that makes power over 6700 and does it reliably is wayyy over your 10k limit.

You wouldn't have any issues spinning a 402 to 7200

Ultimagt4

Anyway maybe if i rephrase: Is it possible to build an NA non-stroked drysumped forged LS2/3 engine with 500-600HP @ 7k rpm(or more) that will be bulletproof and streetable for about $15 ($20k max)? The other consideration is torque. The ultima weighs only about 2000lbs so i am not after a torque monster just useable top end power decent torque range to haul it along and be nice to the transmission.

My rationale for is that because the crate LS2/3 cost half as much as the LS7 therefore if I can build a spec with similar performance and even more durability/reliability and for my application for less $$, it is a no brainer!
If this is unrealistic then i will bite the bullet and go for the LS7 which will cost me more than 25K as it would need uprated drysump to a proper 3/4 stage system and it would be rude not to shoot for 600-650hp with such a great lump or use the Audi 5.2l V10 or BMW 5l V10 but this requires alot of work but may cost less overall.
Thanks

kmracer

iTrader: (1)

question, when you say 500hp do you mean flywheel or rear wheel?

Ultimagt4

I meant fwhp though i reckon 600fwhp should be close to 500rwhp so it will be nice to be in that ballpark

On a different note i am surprised that there has been no real nudge in the right direction so far though nysbadmk8 was helpful. where are all the tuners and engine builders? i am happy to communicate by pm, email or telephone if necessary.

casper383

iTrader: (8)

Im almost done building my 364" LS2, its "suppose" to make around 600fwhp. Im running TFS 235s, Super Vic w/4barrel TB, 42lb injectors, 1 7/8 headers, 13.5-1 compression, agressive hydraulic cam spinning to 7500. Just giving u an idea of what it will probly take...

Ultimagt4

Thanks casper383.
Would you be runing on race gas or pump gas with that CR? I will keep an eye on your results and experience.

casper383

iTrader: (8)

Ill be running leaded race gas, i will be posting dyno results in the near future

COPO9560

I would recommend you reconsider using a stroked engine for NA application. A 402 stroker, with ported LS3 heads, can easily achieve your 600 hp desires in a very reliable and cost effective package. Going smaller in displacement will require spinning higher to get the same power - not what you want for a bullet proof set-up.

Pwebbz28

iTrader: (31)

My stroker has no problem hitting 8k+ RPM

Made WELL over 600fwhp

Ultimagt4

That is not necessarily true. By increasing stroke there is more piston travel but the time is unchanged so with increasing piston speed more distance is covered in the same time hence more wear and potential for failure. However this is just in theory and most strokers are of better construct(forged) and tend to be more durable than cast stock parts.

WRT to making 500rwhp power at 7-8k rpm the major limiting factor is the cam selection and valvetrain i believe. higher CR also helps.
By doing the right spec and match cam/valvetrain with a fully forged bottom and dry sumping(which appart from providing reliable oiling, it would reduce parasitic windage HP losses!) I think there is enough displacement in the 6.2L LS3 lump to achieve 500rwhp. I just need someone to spec/build this for me.

I never said you can achieve this level of power and rpm stroked. I am just a purist and will prefer pure NA and good old fashion tuning.......see how the Nascar engines can rev freely up to 9.5k with <6L displacement!

Anyway, I am interested in your build specs in case i change my mind and some dynographs will be nice too

airforcemanss

iTrader: (23)

ls3 427

COPO9560

Your original post mentioned bang for the buck. I believe you will find building a 600 hp stroker will be less expensive and more reliable than a 7500 rpm 6 liter version. Either can hit the results you want, just a matter of how much you want to spend.

I think of an engine as a positive displacement air pump. The larger engine turns does not need to turn as fast to move the same amount of air. Take a look at the latest BBC concepts and street motors. No one in their right mind would build a new 396/427 or even 454 anymore unless going into a numbers matching ride. 496, 540, 582 are becoming very common and put down stupid high numbers with single 4 barrel carb and good heads - all with same external dimentions. Tall deck guys are even bigger.

Its your money - build what you want.

merim123

iTrader: (11)

I love your project, would love to build a Ultima here in the states, but the cost is too prohibitive at the moment.

if you're going to have an engine built for that car, you're going to need everything, sensors, accessories, oil pan etc...not sure how much of what has been posted above is that inclusive.

my vote is go for the easy solution and spend 6k on the ls3 e rod engine direct from GM. Comes complete intake to oil pan and with all sensors accessories wiring harness, catalytic converters and programmed ecu. you can then swap out the cam and put in whatever you want to give you the top end profile you desire. but this way you'll get a 'complete' engine not just a longblock. you can get that engine from SDPC on here.

Mast performance also a sponsor here can give you turnkey engines.

Did you talk to schartzperformance dot com? they have built a bunch of LS powered ultima's and have been featured in magazines here too. they are about 45 min away from where I live.

Ultimagt4

Thanks chap. you have the same thoughts as me and all i need is to find the right person to do spec and build to my desired targets.

Jeff schwartz has a good reputation and i had some quotes but i want a bespoke build not just a package of the shelf.

There is an almost complete US ultima for sale on www.pistonheads.com and the price is very very good. have a look!

nodrok

Call john scoggin at SDPC

He can spec the motor and have it built. Alot of times he can have it built with upgrades from the stock GM crate engines for little to no more money.

merim123

iTrader: (11)

you are right, that is a killer deal! I emailed with him, if I can't buy it, at least I can help with where he can post it in the US to get it sold

Irish350

iTrader: (14)

thats what im doin