I've been toying with the idea of putting together a blower motor at the next rebuild... this will be a while off (at least a year), so there's still plenty of research to do. This will be a summer-only weekend street car with fairly regular open track time, not a drag-oriented setup. I'm not too crazy about making anything over 550 rwhp.

I've noticed that several places, like Speed Inc, sell 355 LT1 and 348 LS1 shortblocks for about the same price.

Given that the prices are close, I'm wondering if it wouldn't be worth it to part out my current powertrain, buy a junk LS1 bottom end and start from there.

Here's the obvious question... A Gen III motor is obviously superior to an LT1 when it comes to making naturally aspirated power. If I was staying NA, the switch would be no-brainer. But does the difference still exist when boost comes into the picture?

Thanks for the info.

 

At the power lever you're talking about you'd be better off with the ls1. The listed lt1 shortblock only uses 2 bolt mains that aren't even studed, i wouldn't want to run that with boost. The ls1 will make more power for a given boost level and also has 6 bolt mains. There's a guy right now running a forged/rod piston ls1 right now with stock caps and crank and hes pulling off mid to low 8 quarter mile times. You'll also have to remember though that you'll need an ls1 k-member, pcm, intake, heads, wiring harness, sensors and accessories on top of what just the ls1 is gonna cost to convert it. It wouldn't be a simple swap but imo if you have the money and time it'd be worth it.

 

I would agree, an LS1 will make more HP per psi of boost - but the cost of upgrades - including getting all the new parts (as listed above) will negate it. Not to mention I know the hood on an lt1 car with an ls1 under it doesnt fit too well (though it is possible I think)... Anyway, assuming the bodywork fit, everything else would add up a bit. Also if you're talking of 550rwhp, you're talking something that could be done on a single in-tank walbro and stock fuel lines. In fact, the stock lt1 heads with a port job will get you there with everything else being good. I'd say stick with the lt1 and go from there. You'd have less to buy, fewer headaches, and you'll get power either way.

You cant go wrong either way - it just depends on what you want and how complicated it'll get.

 

It'd make a lot more sense to sell the LT1 car and get an LS1 car. The LT1 would be much cheaper in the short-term, but with as much work as you are looking to put into it, you'd probably be better off upgrading. I don't agree about the two-bolt mains vs. 6 bolt-mains. I think at the power level you're talking about, it'd be a wash. (even though I had splayed 4 bolt mains put on my 355 LT1... )

 

I just checked out what you've already done to your car and I want to change my answer...

You've already got a really nice car there, just rebuild with some lower compression pistons and throw a P1SC kit and a Walbro fuel pump on there. It'll get you where you want to be.

 

I just want to say for a forced induction LS1, the aluminum block is a liablility. They now sell cast iron (truck) blocks which are built to handle it. SLP sells a built shortblock, it's like $3500 bucks (not too bad!)

I agree with what the other guy said. If you decide to switch to the LS1, just get the car with that motor already in it. It makes much more economic sense

 

Not sure what your looking for, but you can get as much streetable hp out of an lt1 as you want. As said above just buy a 98+ and go from there if your bent on a ls1. Its your $$$$$....

 

Buying a new car would be difficult since my car is at that point where bringing it back to stock would be a PITA... the HVAC is gone, the rear seat brackets have been drilled out and removed, it's a T56 conversion, coilovers, suspension, yadda yadda.

 

Not sure how much more power you can get.... If you guys have been following Big Rick's formula build up .... LT1 block and stock suspension.... is running 8.30s on shake down passes at nearly 170mph. He'll be in the 7s soon with that kind of trap speed. Can't see how switching engines is an "upgrade" when the one you have is already proven.

When talking FI, the LS1 loses much of it's head advantages since port volume and valve size is more important than port configuration and valve angle. Yes those last two qualities still play a part but a little more boost can make up for it. Ports under vaccum and ports under pressure act in very different ways... and comparing an average 215cc LS1 port to a 215cc LT1 port with similar valve sizes, the power differences won't be very much. The larger AFRs will take you way farther than you may think with the LT. 550-600rwhp will be relatively easy with a moderate built LT1 and ported stock heads, blower or turbo. With either engine you're gonna spend the majority of your money on the FI parts, fuel system, and chassis/trans/rear mods. With that idea in mind, spending the money on the LS1 swap is not the best way to go IMO.

For the situation you describe, you're better off keeping the LT1, get a good forged rotating assembly (for 35_ or 383, forged crank prices are pretty close for both), have 4-bolt STRAIGHT caps installed (search the advanced tech section.... you'll see why to do this on LT blocks), well ported stock heads or AFRs (if you ever plan to max it out)... and let the boost do the talking for you. I say "if you max it out" b/c what you say now and what you might want to do later can be different things. Boost is addictive.

I did see the LQ4 build up that made 1500 crank hp. Very impressive indeed. Doubt we'll see an LT1 block make it that far.... but that's why the gen1 SBC is there.

My $.02

 

LS1 swap is a bit of work.

I'd just do a budget LT1 and find a solution for ditching the stock opti.

 

LT1 block is more sturdy than it generally gets credit for.

All things considered; you should either sell this car and get an LS1, or just do an LT1 buildup.

As a veteran of many totally custom projects, many not even automotive; I can tell you that when you do something "different" you "get nickle & dime'd" to death like you wouldn't believe.

If I were going to run a lot of boost on an LT1 block, I'd blueprint it completely and fill the block to the bottom of the freeze plug holes.
That would be a lot more cost effective than changing your powerplant completely.