Ultima engine choice...help
Discussion
Some specialists will certainly be on here soon with some advice, but personally I would choose the LS3 with EFI over a carb engine any time. No more spitting and fuel smells. LS3 is a more modern engine too which will keep going for ages before any worries (hopefully), plus they say it is easy to get around 480 horses with a bit of tune and a decent exhaust system. All in all a simple solution IMO
LS3 makes a great all-round package as does LS2 (they are still lurking around new and quite cheap)
But do consider you will be stuck with the new engine emissions levels on a new build so if you do go stock LS and then decide to cam and tune etc its going to be more difficult to fix at recurrent MOT time both for yourself or a later owner.
I still think getting an initial smog check (early sbc) gives the car great all round flexibility for future development, engine upgrades, swaps etc without having tight emissions hanging over your choices.
Despite what is posted here lots of background hassles on emissions and registration do take place.... seems its just not correct to discuss them ... although the few specialist rectification companies will confirm.
G luck.
But do consider you will be stuck with the new engine emissions levels on a new build so if you do go stock LS and then decide to cam and tune etc its going to be more difficult to fix at recurrent MOT time both for yourself or a later owner.
I still think getting an initial smog check (early sbc) gives the car great all round flexibility for future development, engine upgrades, swaps etc without having tight emissions hanging over your choices.
Despite what is posted here lots of background hassles on emissions and registration do take place.... seems its just not correct to discuss them ... although the few specialist rectification companies will confirm.
G luck.
738 driver said:
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But do consider you will be stuck with the new engine emissions levels on a new build so if you do go stock LS and then decide to cam and tune etc its going to be more difficult to fix at recurrent MOT time both for yourself or a later owner..................
.
Ok don't have that problem as I have kept it standard and I still go on my original emissions test of 'if it doesn't smoke its passed' , but yes that might be a problem if you go too much with cam and tune, unless you find a friendly MOT tester But do consider you will be stuck with the new engine emissions levels on a new build so if you do go stock LS and then decide to cam and tune etc its going to be more difficult to fix at recurrent MOT time both for yourself or a later owner..................
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Okay you need to establish this a little further .... the accepted gases must be at or below the current registration authorities regs which usually encompass current manufacturers offerings in stock form .
If the PWP engine will be guaranteed to pass a new vehicle UK emission standard then fine.... but a stock output 420Hp LS 3 (mild cam etc) on a half decent exhaust system can be a pain to get through .... The GM LS performance cams are considerably more lumpy at the bottom and this affects idle gases.
The LS's are very good but not perfect and can need work...
Whatever the stock legal motor and regs at time of IVA are will have to be met at later MOT's... unless you have a bent tester who blows up the hose for a reading!!
If you chose an older block, pre 75 from memory, the test is far more loose and leaves plenty to play with .
The easy option is to buy all factory LS kit and allow them to sort any registration issues, be stuck with a tight emissions figure for the life of the vehicle and be quite green in the process.
If the PWP engine will be guaranteed to pass a new vehicle UK emission standard then fine.... but a stock output 420Hp LS 3 (mild cam etc) on a half decent exhaust system can be a pain to get through .... The GM LS performance cams are considerably more lumpy at the bottom and this affects idle gases.
The LS's are very good but not perfect and can need work...
Whatever the stock legal motor and regs at time of IVA are will have to be met at later MOT's... unless you have a bent tester who blows up the hose for a reading!!
If you chose an older block, pre 75 from memory, the test is far more loose and leaves plenty to play with .
The easy option is to buy all factory LS kit and allow them to sort any registration issues, be stuck with a tight emissions figure for the life of the vehicle and be quite green in the process.
Edited by 738 driver on Wednesday 2nd January 18:14
Chevy didn't spend several 10's of millions of dollars to replace the SBC because there wasn't room for improvment. I realize that being outside of the U.S. you don't get to see L.S. motors disassembled on a frequent basis. A very limited overview of the block would include chages in rear main oil seal, Oil pump, ignition trigger on the crankshaft, Materail changed to aluminum. Main bearing location, the crank is up inside the block and the main bearing caps have 6 bolts 4 verticle and two from the sides, the list goes on. Its a very different motor than a SBC. Lee
You won't get 500 from a standard LS3. The uprated LS3 PWP offer has proved to be difficult to get through emissions.
For a solid real 500hp you will need a standard LS7.
Unless you plan to sell soon after completion it is likely you will be tempted into more HP at a later date so emissions could be a problem after modifications.
It is not cheap to swap from and old SBC to and LS (as I am sure others will confirm) after the car is complete.
The Factory engine supplier will be able to offer an engine that is guaranteed to pass emissions (especially if the Factory get it through IVA for you) so you can have the power you want in either SBC or LS. If you want 500 British HP then you may need to specify 550 American HP!!
Paul
For a solid real 500hp you will need a standard LS7.
Unless you plan to sell soon after completion it is likely you will be tempted into more HP at a later date so emissions could be a problem after modifications.
It is not cheap to swap from and old SBC to and LS (as I am sure others will confirm) after the car is complete.
The Factory engine supplier will be able to offer an engine that is guaranteed to pass emissions (especially if the Factory get it through IVA for you) so you can have the power you want in either SBC or LS. If you want 500 British HP then you may need to specify 550 American HP!!
Paul
I don't know how old you are. Can you remember engines before ECU and EFI? Do you have a drip tray for your garage? Can you put up with an engine that stalls at roundabouts/junctions?
The SBC is a very old design and, yes, you can get EFI and electronic ignition for them now but it will still leak and be worth quite a bit less when you sell it.
With my LS7 there are no oil leaks. It starts first turn of the key with no action from me required to keep it ticking over. It adjusts to fuel grade (if I can't get super unleaded). You can tune it with a laptop. It doesn't miss a beat. Better fuel miles. FBW throttle. How many more reasons do you want?
Paul
The SBC is a very old design and, yes, you can get EFI and electronic ignition for them now but it will still leak and be worth quite a bit less when you sell it.
With my LS7 there are no oil leaks. It starts first turn of the key with no action from me required to keep it ticking over. It adjusts to fuel grade (if I can't get super unleaded). You can tune it with a laptop. It doesn't miss a beat. Better fuel miles. FBW throttle. How many more reasons do you want?
Paul
LSX block is a good high power basis FC but is Iron and a bit heavy for some (although I would use one and put the few grand difference between it and aftermarket ally into a great valvetrain).
The difference between efi LS and carb SBC is worlds in terms of all round running, manners, MPG and general user friendly.. although if you can live with a high HP SBC and their usual traits .. smelly, oil leaks... usually a bit cammy and occasionally street unfriendly then you will be fine and initially save a few quid (but the V power pump will eat that away slowly)
A well specced and built SBC can work out fine but choose the builder and power level carefully. With the old SBC its better to lose 20 peak hp but improve low and mid manners for this car. This can be as simple as a swap from a single to a dual plane intake... all been done. The hard part is getting the owners to appreciate they would enjoy the slightly lower peak HP version and actually be a bit quicker too in most instances.
If you decide to go SBC look at 406-434's .... easier power on a more mundane cam /broader range and can still take the occasional 7K blat. 383's are OK but for an endurance motor (remember many US builders are drag race and only need to get 250 miles between teardowns) Id look to keep it around 460-480 HP max unless you start to spend seriously on valvetrain.
All sounds complex !..... the LS motors have near the best of both worlds out the box.... just that nasty restrictive emissions limit.
G luck.
The difference between efi LS and carb SBC is worlds in terms of all round running, manners, MPG and general user friendly.. although if you can live with a high HP SBC and their usual traits .. smelly, oil leaks... usually a bit cammy and occasionally street unfriendly then you will be fine and initially save a few quid (but the V power pump will eat that away slowly)
A well specced and built SBC can work out fine but choose the builder and power level carefully. With the old SBC its better to lose 20 peak hp but improve low and mid manners for this car. This can be as simple as a swap from a single to a dual plane intake... all been done. The hard part is getting the owners to appreciate they would enjoy the slightly lower peak HP version and actually be a bit quicker too in most instances.
If you decide to go SBC look at 406-434's .... easier power on a more mundane cam /broader range and can still take the occasional 7K blat. 383's are OK but for an endurance motor (remember many US builders are drag race and only need to get 250 miles between teardowns) Id look to keep it around 460-480 HP max unless you start to spend seriously on valvetrain.
All sounds complex !..... the LS motors have near the best of both worlds out the box.... just that nasty restrictive emissions limit.
G luck.
Storer said:
You won't get 500 from a standard LS3. The uprated LS3 PWP offer has proved to be difficult to get through emissions.
For a solid real 500hp you will need a standard LS7.
Agree.... and disagree For a solid real 500hp you will need a standard LS7.
Agree that the PWP motor has been tricky to get IVA compliant in the past (do a search on here), might be worth asking them if they've since sorted this.
I've got a stock (internally) crate LS3, with a custom AB exhaust & intake, which has been rolling roaded to produce better power and to be IVA compliant. It's 480bhp and cost a helluva lot less than an LS7. On our Great British roads, I suspect it'll be more than enough for me and any mods I do will be minor.
Using the £/bhp scale and the all important IVA compliance check, I found the above setup to be the best compromise.
I think SBC is one for the nostalgic. It's probably more inkeeping with the aura of the Ultima, but I wanted a good reliable package that won't overheat in a traffic jam or stall at a junction if you forget to keep on top of it's tuning. Each to their own, but 480bhp LS3 was my choice once all options were weighed up.
To help avoid the HP claim debate here ... we can all expect higher than designed readings of late engine designs on aftermarket test equipment... The calculation used was recently refined yet most of the aftermarket dyno software out there uses the older method of deriving HP .
SO a modern bone-stock LS of 420(minimum) GM HP will demonstrate a higher output on the older software... dont be too swallowed in by dyno magicians big figures claims.
A good efi programmer who achieves great all round running with faultless on-road transitions is worth 10 of the peak HP merchants !!
SO a modern bone-stock LS of 420(minimum) GM HP will demonstrate a higher output on the older software... dont be too swallowed in by dyno magicians big figures claims.
A good efi programmer who achieves great all round running with faultless on-road transitions is worth 10 of the peak HP merchants !!
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