Need some opinions on a mile smog legal engine build
04-22-2013, 02:48 AM
#1
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Need some opinions on a mile smog legal engine build I have been struggling with the idea of swapping an ls1 or building an lt1 lately. I have a 99' trans am donor car that has everything I need for the swap if I choose too.
Pro's of ls1. More hp stock. Aluminum block, 6 bolt main, better ignition, stronger crank, better flowing heads stock, a little easier to work on/simpler design that makes more sense, better fuel economy than lt1. That's about it.
Cons of ls1, poor oiling system (oil gets trapped in the heads while taking high G corners, I am going to be using the car for road racing.) Would need some custom wiring done to use the ls1 computer with 96' lt1 dash. Would need to run custom fuel lines for ls1, not sure if my racetronix walborrow 255 ltx pump works with ls1.
Pro's of lt1 Already in the car. Has decent potential to make power. Sounds really good, can be bored or stroked. Better oiling system, sbc don't have the issues ls1's have, more cams to choose from than ls1, lower emissions standards (I'm in CA so the engine needs to be smog legal.)
Con's of lt1, heads and intake don't flow as good as ls1. TB selection is a pain, why cant there be a FAST intake manifold made for lt1's... lol. Some say stick the the stock 48mm tb others say go 58mm some say go 52... etc. I don't want my mpg to drop a bunch with a 58mm tb. Lt1's are more expensive to mod than ls1's. Head porting is expensive and flow numbers are worse.
Some other things to consider, rear mount sts turbo, or 383 stroker. I can't decide which is better. Both would need to be smog legal so that means no ls6 intake or 243 heads for the ls1, which kinda defeats the purpose of the ls1, but at the same time a stock engine would probably respond better to bolt-ons.
So now, the main question. I'm forced into building a mild engine regardless because whichever I choose the engine must be smog legal. So what cams are available for the lt1 that are smog legal? I can not find if the cc503 passes smog or not, I've heard it does and that it doesn't... so I have no idea. lt4 hot cam is really appealing cause its cheap, passes smog sounds good has low lift and gets me into the 12's. In fact I almost just ordered the kit until I found le1 heads are only $700. So now I have a problem because a smaller cam+ported heads might be better etc etc. So yeah I seem some opinions for a non max effort smog legal daily driver engine build. I don't want it to be super slow but I am not expecting 400whp. but it has to have at least 300whp and 350rwtq I mean, anything less is just embarassing. I would like to see a 12.5 timesilp. Thanks for the advice in advance!
Ls1 options are basically 224r with 114lsa, cheatr cam from thunder racing, ls6 cam, custom pat g cam, like a 218/230 115lsa or w/e it is for stock manifolds.
My biggest thing is that smog legal ls1's and lt1's make around the same hp, 320-370whp so really, to me, there isn't any difference in the two engines to begin with at least when they are both smog legalm btw I am willing to swap long tubes every two years, so by smog legal I just mean h/c/i not exhaust
not sure if this is the right section or not but here it goes anyway. ls1 would need to keep the 853 heads and ls1 intake to get past the state ref. for a smog legal engine swap in ca. After that I might be able to swap heads, but honestly probably wouldn't want to unless 243's would improve the oiling of the engine.
Pro's of ls1. More hp stock. Aluminum block, 6 bolt main, better ignition, stronger crank, better flowing heads stock, a little easier to work on/simpler design that makes more sense, better fuel economy than lt1. That's about it.
Cons of ls1, poor oiling system (oil gets trapped in the heads while taking high G corners, I am going to be using the car for road racing.) Would need some custom wiring done to use the ls1 computer with 96' lt1 dash. Would need to run custom fuel lines for ls1, not sure if my racetronix walborrow 255 ltx pump works with ls1.
Pro's of lt1 Already in the car. Has decent potential to make power. Sounds really good, can be bored or stroked. Better oiling system, sbc don't have the issues ls1's have, more cams to choose from than ls1, lower emissions standards (I'm in CA so the engine needs to be smog legal.)
Con's of lt1, heads and intake don't flow as good as ls1. TB selection is a pain, why cant there be a FAST intake manifold made for lt1's... lol. Some say stick the the stock 48mm tb others say go 58mm some say go 52... etc. I don't want my mpg to drop a bunch with a 58mm tb. Lt1's are more expensive to mod than ls1's. Head porting is expensive and flow numbers are worse.
Some other things to consider, rear mount sts turbo, or 383 stroker. I can't decide which is better. Both would need to be smog legal so that means no ls6 intake or 243 heads for the ls1, which kinda defeats the purpose of the ls1, but at the same time a stock engine would probably respond better to bolt-ons.
So now, the main question. I'm forced into building a mild engine regardless because whichever I choose the engine must be smog legal. So what cams are available for the lt1 that are smog legal? I can not find if the cc503 passes smog or not, I've heard it does and that it doesn't... so I have no idea. lt4 hot cam is really appealing cause its cheap, passes smog sounds good has low lift and gets me into the 12's. In fact I almost just ordered the kit until I found le1 heads are only $700. So now I have a problem because a smaller cam+ported heads might be better etc etc. So yeah I seem some opinions for a non max effort smog legal daily driver engine build. I don't want it to be super slow but I am not expecting 400whp. but it has to have at least 300whp and 350rwtq I mean, anything less is just embarassing. I would like to see a 12.5 timesilp. Thanks for the advice in advance!
Ls1 options are basically 224r with 114lsa, cheatr cam from thunder racing, ls6 cam, custom pat g cam, like a 218/230 115lsa or w/e it is for stock manifolds.
My biggest thing is that smog legal ls1's and lt1's make around the same hp, 320-370whp so really, to me, there isn't any difference in the two engines to begin with at least when they are both smog legalm btw I am willing to swap long tubes every two years, so by smog legal I just mean h/c/i not exhaust
not sure if this is the right section or not but here it goes anyway. ls1 would need to keep the 853 heads and ls1 intake to get past the state ref. for a smog legal engine swap in ca. After that I might be able to swap heads, but honestly probably wouldn't want to unless 243's would improve the oiling of the engine.
11-20-2014, 06:24 AM
#4
Launching!
Keep the LT stroke it (sniffer cant tell cubes) real good head thats efficient a reasonable cam & tune;work the intake over, it will still look bone stock
Not sure on F body headers but Dougs makes a smog legal shortie for the LTx they are decent used them on LT4 vettes in Ca before have an EO #.
It will be plenty fast driveable and reliable while being legit where you arent sweating the sniffer bs we deal with out here .
Hide a kit of spray in case you get bored hehe. Dont let the men in blue see it!
Not sure on F body headers but Dougs makes a smog legal shortie for the LTx they are decent used them on LT4 vettes in Ca before have an EO #.
It will be plenty fast driveable and reliable while being legit where you arent sweating the sniffer bs we deal with out here .
Hide a kit of spray in case you get bored hehe. Dont let the men in blue see it!
11-20-2014, 06:10 PM
#5
As far as LS1 engine options a FAST 92 intake manifold is smog legal in California, but I believe you would still need to run the factory 78mm TB with it. FAST and CBM both offer adapters for it. For a cam you'll need to run a split duration with at least 8*(aftermarket or factory cnc ported heads) up to 12*(un touch factory heads) more exhaust duration(@.05") because of the more restrictive exhaust. You want at least -4* valve overlap, but I'd run at least -6* valve overlap to offset possible variations in the actual vs. advertised (.05") duration. I'd also have the factory heads(what came on the engine) milled and professionally cnc ported from a company like AI or TEA, or if you budget permits a set a CARB legal AFR210's. For a older LT1 engine I'm fairly sure you should stick with a cam having at least -4* valve overlap (like the LS1).
