Hey gang,
I have been thinking about my car's powerplant and the impending upgrades in power. I think I want to do a single turbo application and build the motor accordingly. Initially, I had thought about building a turbo setup for the LT1 that is in the car now with modest boost levels, then rebuilding the motor for some serious power once it was time for a rebuild. I then did some shopping around, and it appears that there are some deals to be had on tired LS1 motors. Would the LS1 be a better choice for this application? I could buy the LS1 and rebuild it with a turbo in mind at my own pace, then drop it in the car once it is complete and pull the LT1. I am not looking for astronomical power, say under 700 hp when all is said and done. I don't really like the idea of rebuilding the LT1 right now as it has only around 18,000 miles on it and runs well. What do you guys (or gals) think?

 

Obviously the LS1's can be built for pretty decent forced induction application, but they do have some concerns when you decide to really push it. The main problem with the LS1 engine related to forced induction is that they use fewer cylinder head bolts/studs than SBC/LT1/LT4 engines, and are more apt to have cylinder gasket failure problems as a result. That's the limitiation right now with them. Otherwise they make a good platform because the cylinder heads and intake are very efficient for a production engine, and the bottom end is pretty solid for an aluminum block.

 

Monty--
Glad you chimed in on this one. ;) I know the LS1 heads and intake are really good, even more so when ported. But when you say, "The bottom end is pretty solid for an aluminum block," I take that to mean that an iron block might be better in this instance?!? I just don't want to have the downtime on the car while I do fitting, etc. I guess I could always buy another LT1 and do the same thing as I mentioned above with the LS1. What about the heads and intake of the LT1? I was thinking that the LTx stock heads would be good for up to 500 naturally aspirated hp, but might be marginal over that. Would they support more hp with a forced induction setup such as a turbo? I know the LT1 route would still be the less expensive way to go as I already have the setup in my car. Well, I guess I will just go back to reading my Maximum Boost now and keep these ideas rolling around. :cheers:

 

It all depends on what you really want. LPE and others have proven the LS1/6 to be reliable for 700+hp, however, it does seem that if your goals are substantially above that level, that the LS truck block (iron) or C5R block is preferred by most elite shops. I'm no expert on LS engines, just relaying what I have heard from others in the aftermarket/custom turbo crowd.

The simple fact is that as the rpms and power increase, the cylinder bores and mains move around alot more in aluminum blocks compared to iron. The reduces the piston ring seal and creates varying main clearances as the rotating assembly swings around. Of course this is all very minimal, but over thousands of miles it can become more pronounced in terms of piston ring and main bearing service.

It's cool to say you've got an aluminum block, and most people would consider it the foundation of a 'dream' engine, but in the real world, on the street, it's not necessarily the best choice when it comes to producing big power reliably on the street. The virtues of an aluminum block are more inline with competitive racing where weight is a primary concern, as well as with production vehicles where fuel economy is a primary concern and weight savings play a big role in that. I was really tempted to go with an aluminum block myself. I've read a couple of remarks from people regarding my engine, questioning why I would spend almost $40k to build my engine, yet still use the iron Rocket Block. The decision was based on research and what provided the best solution to meet my needs, not what was the most 'trick' in this case. Although admittedly, I am a sucker for 'trick' ;).


Alot of people are under the impression that in forced induction applications, cylinder head/intake efficiency is not as critical as in NA applications. This is not necessarily true. A forced induction applicaiton still benefits from intake/head efficiency and allows the engine to make more power with less boost. Remember that boost is simply a measure of backed up compressed air in the manifold, not in the cylinders. A more efficient top end will allow more of that intake charge to actually fill the cylinder rather than being stacked up in the manifold. You'll end up making more power with less boost, with increases reliability due to decreased risk of detonation.

On the issue of whether to go with an LS or LT block, keep in mind that the LS block is the future for GM V8's as far as most of us know. While the LT series of engines featured some nice, but sometimes questionable enhancements to the original SBC, it is readilty appearant that supprt for them is waning as people get more comfortable with the LS engines and more of them are produced. No offense to the LT crowd, but I think that in the future, they'll be viewed upon as a transitional engine and support/parts availability will become limited for them. I'd either go with the SBC (lower cost, proven, and incomparable support and parts selection) or the LS (the future of GM V8's). Of course the fact that you've already got an LT engine shouldn't be overlooked. An LS engine retrofit present several challanges not present with an SBC/LT engine swap/build up.


[Modified by Monty, 2:43 PM 11/4/2002]

 

Monty--
The LS would be the route to go if cost was no concern. I think the Iron block looks more attractive simply because of cost, power potential, and the fact that it wouldn't weigh more than the LT1 in the car now. I wonder how easy the 6.0 motors are to come by. Most the the LS engines I have seen are still over $3000 for a tired motor. I suppose that isn't bad, but the less I can spend now, the faster I can get started on the R&R! I understand what you mean by the LT-motors becoming the bastard child. I guess I will keep researching! :cheers:

 

Lat time I noticed, the 6.0L iron LS truck block was retailing for around $600-700, which is a darned good price in my opinion.

 

So, do you recommend buying the block and just piecing the thing together from there? I would need the complete motor, but if I bought a truck motor, most of the things would probably be out the window (i.e. heads, intake, internals, etc.) I suppose it might be better to start with a block and go from there....

 

That's the approach I would take, that way you have control over everything that comprises the engine. However, it depends on your own needs, goals, budget, etc. I don't see the point in buying a complete engine if you're going to end up replacing a significant number of parts, and modifying many of the others. I haven't really priced out all of the individual components for an LS engine, so I don't know if you can apply the same logic to it that you would/could an SBC.

 

Last Ride-Keep us informed what you decide with especially if you go with the LT1. I've been thinking of installing a blower or turbo on my LT1. I wonder if the C4 blower kits will fit in c3 compartment?

Monty- Very impressive set-up you have. I really have a lot of respect for those who do everything themselves.
Dan

 

Vettedan--
Not sure about the fitment of the C4supercharger kits in the C3 compartment, but just eyeballing it, there appears to be MORE room in the C3. I talked with a shop in Saint Louis today about the prospect of building a single turbo kit for the LT1 custom fit for my application. They seemed to think that they could do a single turbo, knock down the boost, and use the stock motor (for now) for $4000-5000 complete! I twin would be about $800-1200 more. Eventually, the motor will need to be rebuilt, and then you could go crazy with the boost. Doing it in stages like this would allow you to break up some of the cost of doing it all at once. The prospect seems very inviting, however. They agreed with the 321 stainless being the only logical choice for the headers. I will let you know if and when I find out more.